Glossary of technical terms for the use of metallurgical engineers Terms starting with alphabet ‘D’
Glossary of technical terms for the use of metallurgical engineers
Terms starting with alphabet ‘D’
Dalton (Da) – It is also known as unified atomic mass unit (u). It is a unit of mass defined as 1/12 of the mass of a free unexcited atom of carbon-12 at rest. It is approximately equal to the mass of one nucleon.
Dalton’s law of partial pressures – It is a law which states that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases. It is closely related to the ideal gas laws.
Dam – It is a structure built across a liquid stream for the control of its flow. It is flow control device which is used in continuous casting tundishes. It is also the boundary support or ridge used to prevent excessive edge bleeding or resin runout of a laminate and to prevent crowning of the bag during cure.
Damage – It is the impairment of the useful life of a part.
Damage tolerance – It is a design measure of crack growth rate. Cracks in damage-tolerant designed structures are not permitted to grow to critical size during expected service life. It is also the ability of a part component to resist failure because of the presence of flaws, cracks, or other damage for a specified period of usage. The damage tolerance approach is used extensively in the several industries.
Damped vibrations – These are periodic vibrations with a continuously diminishing amplitude in the presence of a resistive force. The frictional forces (or resistive forces) act in the direction opposite to vibration.
Damper – It is a mechanical device in a duct or chimney which regulates the gas flow.
Damping – It is the loss in energy, as dissipated heat, which results when a material or material system is subjected to an oscillatory load or displacement. Damping is the result of frictional forces working in that system.
Damping capacity – It is the ability of a material to absorb vibration (cyclical stresses) by internal friction, converting the mechanical energy into heat.
Damping ratio – It is a parameter which indicates how rapidly oscillations in a system die out, if ever.
Damp proofing – In construction, it is a type of moisture control applied to building walls and floors to prevent moisture from passing into the interior spaces. Dampness problems are among the most frequent problems encountered in building constructions.
Danger – It is a state or condition in which personal injury and / or asset damage is reasonably foreseeable. It is the presence of a hazard.
Dangerous occurrence – It is a near miss with serious injury potential.
Dangling – It consists of disconnect of an activity before the completion of all activities in a network diagram.
Dark-field illumination – It is the illumination of an object such that it appears bright and the surrounding field dark. This results from illuminating the object with rays of sufficient obliquity so that none can enter the objective directly. In electron microscopy, the image is formed using only electrons scattered by the object.
Data – It consists of a collection of facts, observations, or measurements used for analysis and decision-making. Data can be numerical, such as counts or measurements, or categorical, such as labels or classifications. Data serves as the starting point for analysis. It is what people examine, manipulate, and interpret to draw conclusions or make predictions about a particular phenomenon or population. Data forms the bedrock of analysis and decision-making. In statistics analysis, data consist of numbers, letters, or special characters representing measurements of the properties of one’s analytic units, or cases, in a study. Data are the raw material of statistics.
Data acquisition system – It is a system which includes measurement devices, sensors, a computer, and data acquisition software. A data acquisition system is used for acquiring, storing, visualizing, and processing data. This involves collecting the information needed to understand electrical or physical phenomena.
Data analysis – It can be defined as a data science used to break data into individual components for inspection and integrating these components to create knowledge. It is described as a set of concepts and methods intended for presentation of the data in a form which improves the quality of the decision making. It is the process of collecting, modelling, and analyzing data using different logical methods and techniques. Informally, there is a five-step ‘value-chain’ approach for extracting useful value from the data using data analysis. These steps are (i) organizational needs identification of data, (ii) collection of the data, (iii) data exploring and cleaning, (iv) data analyzing, (v) interpreting the data and drawing inferences. The data interpretation helps in making a decision and measuring of the outcome for the purpose of updating the process or system with the results of the decision.
Data associativity – It is the ability of a computer-aided engineering system to share design information among a variety of computer-based applications (such as design, drafting, and numerical-controlled machining) without each application having to translate or transfer the data. Associativity also needs that applications can recognize when geometry or other information has been changed so that the application can adjust its own data to these changes.
Database – A database is an electronically stored, systematic collection of data. It can contain any type of data, including words, numbers, images, videos, and files. It is a collection of specific information, such as alloy compositions or mechanical properties. Several databases are accessible through on-line connections or with a CD-ROM (compact disc read-only memory).
Data compression – It is a technique which allows information to be transmitted more compactly than originally expressed, for example, codes.
Data highway – It is a single-cable link which provides communication between control stations which are physically separated.
Data integration – It is the process of combining data from multiple source systems to provide a complete, accurate, and up-to-date dataset and unified sets of information for both operational and analytical uses.
Database management system (DBMS) – It is a software to store, manage, retrieve, and edit data.
Data networks – It is a network for interconnection of computers and peripherals.
Data sheet – In statistical process controls, it is a tool for the systematic collection of data.
Daubing – It is filling of cracks in moulds or cores by specially prepared pastes or coatings for preventing penetration of metal into these cracks during pouring.
Day bin – It is a bin normally having a capacity of one day consumption. It receives bulk material from the bulk material storage and convey it for use in a process for the production of the product.
Day-light – It is the distance, in the open position, between the moving and the fixed tables or the platens of a hydraulic press. In the case of a multi-platen press, daylight is the distance between adjacent platens. Daylight provides space for removal of the moulded / formed part from the mould / die.
DC casting – It is direct chill casting and is a continuous method of making ingots for rolling or extrusion by pouring the metal into a short mould. The base of the mould is a platform which is gradually lowered while the metal solidifies, the frozen shell of metal acting as a retainer for the liquid metal below the wall of the mould. The ingot is normally cooled by the impingement of water directly on the mould or on the walls of the solid metal as it is lowered. The length of the ingot is limited by the depth to which the platform can be lowered, hence, it is frequently called semi-continuous casting.
DC intermittent non-capacitive arc – It is a low-voltage electrical discharge used in spectrochemical analysis to vapourize the sample material. Each current pulse has the same polarity as the previous one and lasts for less than 0.1 second.
DC plasma excitation – The use of a high-temperature plasma jet to excite an element in a sample, for example, for atomic emission spectroscopy.
Deactivation – It is the process of prior removal of the active corrosive constituents, normally oxygen, from a corrosive liquid by controlled corrosion of expendable metal or by other chemical means, thereby making the liquid less corrosive.
Deadband – It means that the quantity of power supply of an actuator can be varied without initiating valve obturator motion. The area of a signal range or band where no action occurs. The technical term for deadband is hysteresis.
Dead-burned – It is term applied to materials which have been fired to a temperature sufficiently high to render them relatively resistant to moisture and contraction. It is the state of a basic refractory material resulting from a heat treatment which yields a product resistant to the atmospheric hydration or recombination with carbon di-oxide.
Dead-burned magnesite – It is the granular product obtained by burning (firing) magnesite or other substances convertible to magnesia, upon heating above 1,450 deg C long enough to form dense, weather-stable granules suitable for use as a refractory or in refractory products.
Dead-burned refractory dolomite – It is the refractory grade doloma which is obtained by burning dolomite above 1,450 deg C long enough to form a dense hydration-resistant material composed mainly of lime and magnesia.
Dead loads – These are structural loads are because of the of the structures. These consist of a constant magnitude over time. They include the self-weight of structural members, such as walls, plasters, ceilings, floors, beams, columns, and roofs. Dead loads also include the loads of fixtures that are permanently attached to the structure.
Dead-man zone – It is the stagnant flow region (dead-man) which is a discontinuous mass of partially reacted coke particles in the centre part of the hearth.
Dead soft – It is a temper of non-ferrous alloys and some ferrous alloys corresponding to the condition of minimum hardness and tensile strength produced by full annealing.
Dead time – It is the total time during which the spectrometer is processing information and is unavailable to accept input data.
Dead weight tester – It uses the most fundamental pressure measurement technique. It is favoured for the primary calibration of pressure sensors, or piston gauge. This device uses calibrated weights (masses) which exert pressure on a fluid (usually a liquid) through a piston. Dead weight testers can be used as primary standards because the factors influencing accuracy are traceable to standards of mass, length, and time. The piston gauge is simple to operate. The pressure is generated by turning a jack-screw which reduces the fluid volume inside the tester, resulting in increased pressure.
Dead zone / band / space – It is defined as the range of different input values over which there is no change in output value. It is that range of possible values for which the instrument does not give a reading even there is changes in the parameter being measured. Any instrument which shows hysteresis also displays dead space. However, some instruments which do not suffer from any substantial hysteresis can still show a dead space in their output characteristics. Backlash in gears is a typical cause of dead space. Backlash is normally experienced in gear-sets used to convert the translational motion to rotational motion.
Dealloying – It is the selective corrosion of one or more components of a solid solution alloy. It is also called parting or selective leaching.
Debinding – It is one of the main production steps in the ceramic and powder-metallurgical industries. It refers to the thermal or catalytic removal of additives used in steps prior to production such as casting.
Debond – It is a deliberate separation of a bonded joint or interface, normally for repair or rework purposes. It is also an unbonded or non-adhered region, a separation at the fibre-matrix interface because of the strain incompatibility.
Debossing – It is the process of creating recessed relief images and designs in materials. A debossed pattern is sunken into the surface of the material but might protrude somewhat on the reverse side. The process consists of depressing (in a blanking die) a portion or portions of the material below the ordinary surface level, normally to form lettering or decoration. Sometimes the background, rather than the lettering itself, is debossed, leaving the letters at the original level of the material, hence giving the appearance of embossing, otherwise the lettering itself is pressed down, giving the appearance of engraving.
Debris, wear – It is the particles which become detached in a wear process.
Debulking – It is compacting of a thick laminate under moderate heat and pressure and / or vacuum to remove most of the air, to ensure seating on the tool, and to prevent wrinkles.
Deburring – It is the removing of burrs, sharp edges, or fins from metal parts by filing, grinding, or rolling the work in a barrel containing abrasives suspended in a suitable liquid medium. It is sometimes called burring.
Debye-Scherrer method – It is a method of x-ray diffraction using monochromatic radiation and a polycrystalline sample mounted on the axis of a cylindrical strip of film.
Debye ring – It is a continuous circle, concentric about the undeviated beam, produced by mono-chromatic x-ray diffraction from a randomly oriented crystalline powder. An analogous effect is obtained using electron diffraction.
Decalescence – It is a phenomenon, associated with the transformation of iron to iron on the heating (super-heating) of iron or steel, revealed by the darkening of the metal surface owing to the sudden decrease in temperature caused by the fast absorption of the latent heat of transformation.
Decarburization – It is the loss of carbon from the surface layer of a carbon-containing alloy because of the reaction with one or more chemical substances in a medium which contacts the surface.
Decay constant (lambda) – It is the constant in the radioactive decay law dN = -lambda Ndt, where ‘N’ is the number of radioactive nuclei present at time ‘t’. The decay constant is related to half-life t(1/2) by the expression t(1/2) = ln 2/lambda.
Decay, radioactive – It is the decrease in the radioactive nature of any material with the passage of time. This is because of the spontaneous emission from the atomic nuclei of either alpha or beta particles and is frequently accompanied by gamma radiation.
Deceleration period – In cavitation or impingement erosion, it is the stage following the acceleration period or the maximum rate period (if any), during which the erosion rate has an overall decreasing trend although fluctuations can be superimposed on it.
Decentralized peripherals – It is used to operate sensors and actuators through a centralized controller in production (factory) automation applications. It is used to describe distributed input / output devices connected through a fast serial data link with a central.
Decibel (dB) – It is a unit which is used to measure sound intensity and other physical quantities. A decibel is one tenth of a bel (B), a unit named after Graham Bell, the inventor of the telephone. Its logarithmic scale is convenient to represent the entire range of human hearing.
Decile – Deciles are used to divide a numeric variable into 10ths, whereas the quartiles divide it into quarters, and percentiles into 100ths. An approximate value for the ‘r’th decile can be read from a 6 cumulative frequency graph as the value corresponding to a cumulative relative frequency of 10r %. So, the 5th decile is the median and the second decile is the 20th percentile.
Decision matrix – It is a formalized process by which design concepts or materials are ranked prior to a selection decision.
Decision tree analysis – It is a diagrammatic technique used to illustrate a chain of decisions and to examine the implications of multiple decision-making or situational outcomes.
Deck – In mining, it is the area around the shaft collar where men and materials enter the cage to be lowered underground.
Decline – In mining, it is a sloping underground opening for machine access from level to level or from surface, It is also called a ramp controller.
Decobaltification – It is the corrosion in which cobalt is selectively leached from cobalt-base alloys or from cemented carbides with cobalt binders.
Decohesion – It is the process of creating a pair of free surfaces where a grain boundary or second-phase boundary existed previously.
Decohesive rupture – It is a brittle fracture which shows little or no bulk plastic deformation and does not occur by dimple rupture, cleavage, or fatigue. This type of fracture is normally the result of a reactive environment or a unique micro-structure and is associated almost exclusively with rupture along grain boundaries.
Decommissioning – It is the final phase in the life cycle of a nuclear installation covering all activities from shutdown and removal of fissile material to environmental restoration of the site through to its agreed end state, and / or it is the process of closing down a facility followed by reducing residual radioactivity to a level which permits the release of the property for unrestricted use.
Decommissioning plan – It is a plan for the decommissioning of a nuclear facility.
Decommissioning waste management plan – It is a part of the decommissioning plan which sets out the steps and costs involved in disposal of the waste at the time of decommissioning a nuclear power station.
Decomposition – It is the separation of a compound into its chemical elements or components.
Decomposition potential (or voltage) – It is the potential of a metal surface necessary to decompose the electrolyte of a cell or a component thereof.
DECON – It is a method of decommissioning in which the equipment, structures, and portions of a nuclear facility and site containing radioactive contaminants are removed. The contaminants are safely buried in a low-level radioactive waste landfill or decontaminated to a level which permits the property to be released for unrestricted use shortly after cessation of operations.
Decontamination – It is the reduction or removal of (radioactive) material from any structure, area, object, or person. Decontamination can be accomplished by treating the surface to remove or decrease the contamination.
Decoration (of dislocations) – It is the segregation of solute atoms to the line of a dislocation in a crystal. In ferrite, the dislocations can be decorated with carbon or nitrogen atoms.
Decorative chromium plating – It is different from hard chromium plating in terms of thickness and the type of undercoating used. The average thickness of decorative plating is actually very thin, normally not more than 1.25 micrometers. A decorative chromium deposit is used mainly for its pleasing blue-white colour. Its highly reflective appearance is maintained in service since chromium can resist tarnish, chemicals, scratches, and wear. Decorative chromium plating baths normally produce deposits in the range of 0.13 micrometers to 1.25 micrometers in thickness. These deposits normally reproduce the finish of the substrate, or, in a multilayer system, the undercoating which is applied prior to the chromium layer. Optimum lustre of the final chromium deposit is got by plating the substrate coating to a uniformly bright condition.
Deep drawing – Deep drawing is a sheet forming process in which in its simplest form, a cylindrical shape or alike is produced from a thin disc of sheet metal by subjecting it to a compressive force (while it is held between a die and blank holder) through a circular punch which mainly work on the blank thickness. Deep drawing process is used to produce containers from flat circular blanks. The central portion of sheet of blank is subjected to pressure applied by punch into a die opening to get a sheet metal of needed shape without folding the corners. This normally needs the use of presses normally having a double action for blank holding force and punch force.
Deep drawing cup test – The deep-drawing cup test is as per standard ISO 11531. The deep-drawing cup test is a sheet metal testing method in which a circular plate (round blank) is punched out of a sheet metal strip and then formed into a cup by a drawing die. The largest possible ratio between the diameter of the round blank and the diameter of the drawing die, which just allows the perfect production of a cup, is called the limiting drawing ratio ‘B-maximum’ and is a quality characteristic for the forming capacity of the sheet metal material. The ears, which form as a result of the flow properties of the material, are undesirable since they necessitate rework on the drawn products when they occur in practice.
Deep drawing sheet – It is the sheet which is produced with specific characteristics that permit deformation by deep drawing. Examples of these characteristics are softness, high ductility and low tensile strength.
Deep drawing steel – It is a high-quality low carbon steel possessing high ductility and desirable grain size which permits deep drawing.
Deep-draw mould – It is a mould having a core which is long in relation to the wall thickness.
Deep etching – In metallography, it is macro-etching, especially for steels, for determining the overall character of the material, i.e., the presence of imperfections, such as seams, forging bursts, shrinkage-void remnants, cracks, and coring.
Deep foundation – It is a type of foundation which transfers equipment loads to the earth farther down from the surface than a shallow foundation does to a subsurface layer or a range of depths. A pile or piling is a vertical structural element of a deep foundation, driven or drilled deep into the ground at the erection site of the equipment.
Deep geological repository – It is a nuclear waste repository excavated below 300 metres within a salt dome or bed-rock. It entails a combination of waste form, waste package and engineered seals which is designed to provide a high level of long-term storage without future maintenance.
Deep ground bed – It is one or more anodes installed vertically at a nominal depth of 15 metres or more below the earth’s surface in a drilled hole for the purpose of supplying cathodic protection for an underground or submerged metallic structure.
Deep-well Injection – It consists of deposition of raw or treated, filtered hazardous waste by pumping it into deep wells, where it is contained in the pores of permeable subsurface rock.
Defect – It is an imperfection (deviation from perfection) which can be shown to cause failure by a quantitative analysis and which would not have occurred in the absence of the imperfection. In manufacturing, a defect is (ai a failure to conform to stated specifications, (ii) non-satisfaction of customer requirements, (iii) deviation from the norm, and (iv) when a product leaves the assembly line in sub-standard condition, differs from the manufacturer’s intended result, or differs from other ostensibly identical units of the same product line. It is also a discontinuity whose size, shape, orientation, or location makes it detrimental to the useful service of the part in which it occurs. It is also a discontinuity or discontinuities which by nature or accumulated effect (e.g., total crack length) render a part or product unable to meet minimum applicable acceptance standards or specifications. This term designates rejectability.
Defective – It is a quality control term, describing a unit of product or service containing at least one defect, or having several lesser imperfections that, in combination, cause the unit not to fulfill its anticipated function.
Defect repair – It is an action taken to remedy a product that is nonfunctional or does not match expectations or requirements.
Define – It is the phase in the portfolio life cycle in which projects, programmes, and any organizational changes needed to realize strategic objectives are identified and examined.
Define (x-rays) – It is to limit a beam of x-rays by passage through apertures to obtain a parallel, divergent, or convergent beam.
Definition – it is the clarity or sharpness of a microscopic image.
Definitive estimate – A definitive estimate reaches a total project cost estimate by computing cost estimates for all a project’s work packages. Definitive estimating is considered a highly accurate estimation technique, with estimates falling within a ten-percent range of the actual budget.
Deflash – It is the process of removing excess material (flash) from the parting line of a moulded rubber product.
Deflashing – It is a finishing technique used to remove the flash (excess, unwanted material) on a plastic moulding.
Deflection – In metal-forming and forging, it is the quantity of deviation from a straight line or plane when a force is applied to a press member. Normally it is used to specify the allowable bending of the bed, slide, or frame at rated capacity with a load of pre-determined distribution.
Deflection temperature under load (DTUL) – It is the temperature at which a simple cantilever beam deflects a given amount under load. It was earlier called heat distortion temperature.
Deflector – It is a flat or angle like section placed longitudinally over the conveyor making an angle (can be adjustable or fixed) with the conveyor axis. This acts as an obstruction to the movement of the load and deflects them to one side of the conveyor axis.
Deflocculating – It is thinning the consistency of a slip by adding a suitable electrolyte.
Deflocculation – It is a state of colloidal suspension in which the individual particles are separate from one another, this condition being maintained by the attraction of the particles for the dispersing medium (for example, hydration) or by the assumption of like electrical charges by the particles, hence resulting in their mutual repulsion, or both.
Deformability – In tribology, it is that quality of a plain bearing material which allows it to adjust itself to shaft deflections and minor misalignments by deformation or by wearing away of bearing material without producing operating difficulties.
Deformation – It is a change in the form of a body because of the stress, thermal change, change in moisture, or other causes. It is measured in units of length.
Deformation bands – These are the parts of a crystal which have rotated differently during deformation to produce bands of varied orientation without individual grains.
Deformation curve – It is a graph in which corresponding values of stress and strain are plotted against each other. Values of stress are normally plotted vertically (ordinates or y-axis) and values of strain horizontally (abscissas or x-axis).
Deformation energy – It is a measure of the energy absorption characteristics of a material determined by measuring the area under the stress-strain diagram.
Deformation limit – In drawing, It is the limit of deformation which is reached when the load needed to deform the flange becomes higher than the load-carrying capacity of the cup wall. The deformation limit (limiting drawing ratio, LDR) is defined as the ratio of the maximum blank diameter which can be drawn into a cup without failure, to the diameter of the punch.
Deformation lines – These are thin bands or lines produced by cold working in grains of some metals, particularly those of face centered cubic structure. They are not removed by repolishing and re-etching.
Deformation processes – These processes transform solid materials from one shape into another. The initial shape is normally simple (e.g., a billet or sheet blank) and is plastically deformed between tools, or dies, to get the desired final geometry and tolerances with needed properties.
Deformation processing – It is a class of manufacturing operation which involves changing the shape of a work-piece by plastic deformation through the application of a compressive force. It is frequently carried out at high temperature.
Deformation twin – It is a twin formed in a crystal by simple shear and / or simple shear plus shuffle movements under external loading.
Deformation under load – It is the dimensional change of a material under load for a specified time following the instantaneous elastic deformation caused by the initial application of the load.
Deformation wear – It is the sliding wear involving plastic deformation of the wearing surface. These are several forms of wear which involve plastic deformation, hence this term is imprecise and is not to be used.
Degasification – It is the process of removing contaminants like hydrocarbons from a sample to prevent interference with adsorption systems and analyses in chemistry. It involves cleaning the sample and ensuring a clean surface to avoid issues like blockages and desorption during analysis.
Degasifier – It is a substance which can be added to molten metal to remove soluble gases which can be otherwise occluded or entrapped in the metal during solidification.
Degassing – It is a chemical reaction resulting from a compound added to molten metal for removing gases from the metal. Inert gases are frequently used in this operation. It is also a fluxing procedure used for aluminum alloys in which nitrogen, chlorine, chlorine and nitrogen, and chlorine and argon are bubbled up through the metal to remove dissolved hydrogen gases and oxides from the alloy.
Degaussing – It is the process of decreasing or eliminating a remnant magnetic field. Because of the magnetic hysteresis, it is normally not possible to reduce a magnetic field completely to zero, so degaussing typically induces a very small known field referred to as bias. Degaussing is also used to reduce magnetic fields in cathode ray tube monitors and to destroy data held on magnetic storage.
Degradation – It is a deleterious change in the chemical structure, physical properties, or appearance of a material.
Degreasing – It is the removal of grease and oils from a surface. It can be accomplished by immersion in liquid organic solvent, by solvent vapours condensing on the parts being cleaned (vapour degreasing), or by spraying the parts with solvent.
Degree of polymerization – It is the number of structural units, or mers, in the average polymer molecule in a sample measure of molecular weight.
Degrees of freedom – It is a technical term reflecting the number of independent elements comprising a statistical measure. Certain distributions need a degrees of freedom value to fully characterize them. It is the number of ways a value can differ from others – one less than the total number of in a sample (n-1). Degrees of freedom is also the number of independent variables (such as temperature, pressure, or concentration within the phases present) which can be altered at will without causing a phase change in an alloy system at equilibrium, or it is the number of such variables which are to be fixed arbitrarily to define the system completely.
Deionization – It is the removal of ions from a solution by any method. In the case of water, this typically refers to mineral ions such as sodium, iron, and calcium.
Delamination – It is the separation of layers in a laminate or composite material because of failure of the matrix, either in the matrix itself or at the interface between the matrix and the fibre. It is either local or covering a wide area. It can occur in the cure or subsequent life.
Delamination wear – It is a wear process in which thin layers of material are formed and removed from the wear surface. A ‘delamination theory of wear’ proposed by N.P. Suh in the early 1970s involves the nucleation and propagation of cracks so as to form lamellar wear particles. However, there are other ways to form lamellar wear particles (for example, by the loss of transfer layer fragments), and the term delamination wear is not to be used unless further clarification of the context of usage is provided.
Delayed ageing, delayed age hardening – It consists of retarding natural ageing by holding the alloy below room temperature. If the alloy is raised to room temperature, then natural ageing proceeds at the expected rate.
Delayed fishscaling – Fishscaling is the appearance in a porcelain enamel coating in which the evolution of hydrogen from the base metal (iron or steel) causes loss of adhesion between the enamel and the base metal. Delayed fishscaling occurs after the final porcelain enamel processing.
Delayed yield – It is a phenomenon involving a delay in time between the application of a stress and the occurrence of the corresponding yield-point strain.
Deleterious substance – It is a substance which, if added to any water, degrades or alters or forms part of a process of degradation or alteration of the quality of that water so that it is rendered or is likely to be rendered deleterious to the aquatic life. It is also a water which contains a substance in such quantity or concentration, or that has been so treated, processed or changed, by heat or other means, from a natural state that it, if added to any other water, degrades or alters or forms part of a process of degradation or alteration of the quality of that water so that it is rendered or is likely to be rendered deleterious to the aquatic life.
Deliverable – It is a final product or product component which is to be provided to a customer as per the contractual stipulations.
Delivered At Place (DAP) – ‘Delivered at Place’ means that the seller delivers when the goods are placed at the disposal of the buyer on the arriving means of transport ready for unloading at the named place of destination. The seller bears all risks involved in bringing the goods to the named place.
Delivered At Terminal (DAT) – ‘Delivered at Terminal’ means that the seller delivers when the goods, once unloaded from the arriving means of transport, are placed at the disposal of the buyer at a named terminal at the named port or place of destination. “Terminal” includes a place, whether covered or not, such as a quay, warehouse, container yard or road, rail or air cargo terminal. The seller bears all risks involved in bringing the goods to and unloading them at the terminal at the named port or place of destination.
Delivered Duty Paid (DDP) – ‘Delivered Duty Paid’ means that the seller delivers the goods when the goods are placed at the disposal of the buyer, cleared for import on the arriving means of transport ready for unloading at the named place of destination. The seller bears all the costs and risks involved in bringing the goods to the place of destination and has an obligation to clear the goods not only for export but also for import, to pay any duty for both export and import and to carry out all customs formalities.
Delivered Duty Unpaid (DDU) – It means that the seller delivers the goods to the buyer, not cleared for import and not unloaded from any arriving means of transport at the named place of destination. The seller has to bear all the costs and risks involved in bringing the goods thereto, other than, where applicable, any duty for import in the country of destination. Such duty has to be borne by the buyer as well as any costs and risks caused by his failure to clear the goods for import in time.
Delphi technique – It is an estimation method based on expert consensus. Experts make estimates individually and simultaneously and then review their estimates as a group before making another set of estimates. The process is repeated, with the pool of estimates typically becoming narrower after each round of review until a consensus is reached.
Delta ferrite – Delta ferrite is the high temperature form of iron, formed on cooling low carbon concentrations in iron-carbon alloys from the liquid state before transforming to austenite. In highly alloyed steels, delta ferrite can be retained to room temperature. It is a solid solution of one or more elements in body-centered cubic iron. Unless otherwise designated (for example, as chromium ferrite), the solute is normally assumed to be carbon.
Delta iron – It is the solid phase of pure iron that is stable from 1,400 deg C to 1,539 deg C and possesses the body-centered cubic lattice.
Delta layer – It is the second layer of zinc iron alloy growth from the base steel formed during the galvanizing process. The chemical composition of the delta layer is around 90 % zinc and 10 % iron. The delta layer is 60 % harder than the base steel it protects from abrasion and corrosion. It is the thickest alloy layer in the galvanized coating. Reactive steels increase the delta layer thickness.
Delta-wye transformer – It is a type of connection of a three-phase transformer.
Demand factor – It is the fraction of actual use of some quantity, related to the maximum which can be used in a specified time.
Demand management -It is a planning methodology which is used to forecast, plan for and manage the demand for products and services. This can be at macro-levels as in economics and at micro-levels within individual organizations. Demand management has a defined set of processes, capabilities and recommended behaviours for the organizations which produce goods and services.
Demarest process – It is a fluid forming process in which cylindrical and conical sheet metal parts are formed by a modified rubber bulging punch. The punch, equipped with a hydraulic cell, is placed inside the work-piece, which in turn is placed inside the die. Hydraulic pressure expands the punch.
Demineralized (DM) water – It is that water where are the minerals of the water has been removed. DM water is also used as boiler feed water. The demineralization process is usually done when the water is to be used for chemical processes and the minerals present may interfere with the other chemicals. With the demineralization process, the water is softened by the removal of the undesired minerals. Demineralized water has a higher conductivity than deionized water.
Dendrite – It is a crystal which has a tree-like branching pattern, being most evident in cast metals slowly cooled through the solidification range.
Dendritic powder – It consists of particles normally of electrolytic origin typically having the appearance of a pine tree.
Dendritic segregation – It consists of inhomogeneous distribution of alloying elements through the arms of dendrites.
Denickelification – It is the corrosion in which nickel is selectively leached from nickel-containing alloys. Most commonly, it is observed in copper-nickel alloys after extended service in fresh water.
Denier– It is a yarn and filament numbering system in which the yarn number is numerically equal to the weight in grams of 9,000 meters. It is used for continuous filaments. The lower the denier, the finer is the yarn.
Dense conventional castables – These are created with high alumina cement and can withstand temperatures from 1,300 deg C to 1,800 deg C. These refractory castables are very good for common furnace applications, burner blocks, specialty muffle furnaces and boiler work. These castables are much stronger than insulating castables with strengths normally equaling those of normal firebrick of the same class. In dense conventional castables, hot strength behaviour with increasing temperature is principally dependent on the cement type (low, medium-purity, or high purity calcium aluminate cement), and the quantity used in the formulation.
Dense refractories – These are shaped refractories with their true porosity less than 45 %. These refractories have high-density and offer very good resistance in challenging operating environments, such as slags with different chemical compositions, fumes, dust, and gases.
Densification – It refers to the compacting process of material under specific conditions, such as palletization, briquetting, and extrusion. It is widely used in different industries to increase bulk density, improve transportation, reduce dust generation, and enhance handling and logistics efficiency.
Density, absolute – It is the mass per unit volume of a solid material, expressed in grams per cubic centimeter or kilograms per cubic metre.
Density, apparent – It is the weight in air of a unit volume of a material.
Density, bulk – It describes the measure of mass and volume including the pore space. Bulk density is normally considered in conjunction with apparent porosity. It is a measure of the weight of a given volume of the material.
Density (of gases) – It is the mass of a unit volume of gas at a stated temperature and pressure.
Density (of solids and liquids) – It is the mass of a unit volume of a material at a specified temperature.
Density ratio – It is the ratio of the determined density of a powder compact to the absolute density of metal of the same composition, normally expressed as a percentage. It is also referred to as percent theoretical density.
Density, relative – It is also called specific gravity. It is a dimensionless quantity and defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Relative density for solids and liquids is nearly always measured with respect to water at its densest (at 4 deg C) and for gases, the reference is air at room temperature (20 deg C). The term ‘relative density’ is preferred, whereas the term ‘specific gravity’ is gradually being abandoned.
Dent – For rolled products, it is a sharply defined surface impression on the metal which can be caused by a blow from another object. For extrusions, it is a synonym for handling mark.
Dent, expansion – It is a localized surface deviation from flat generated by expansion of vapour during thermal treatment of cold-rolled coiled sheet.
Dent, repeating – It consists of repeating depression caused by a particle adhering to a rotating roll over which the metal has passed.
Deoxidation – It is the removal of excess oxygen from the molten metal. It is normally carried out by adding materials with a high affinity for oxygen.
Deoxidation products – These are those non-metallic inclusions which form as a result of adding deoxidizing agents to molten metal.
Deoxidized copper – It is the copper from which cuprous oxide has been removed by adding a deoxidizer, such as phosphorus, to the molten bath.
Deoxidizer – It is a substance which can be added to molten metal for removing either free or combined oxygen.
Deoxidizing – It is the removal of oxygen from molten metals through the use of a suitable deoxidizer. Sometimes it refers to the removal of undesirable elements other than oxygen through the introduction of elements or compounds which readily react with them. In case of metal finishing, it is the removal of oxide films from metal surfaces by chemical or electro-chemical reaction.
Dependency – It is a logical relationship between project activities in a network diagram which determines when a dependent activity can begin.
Dependent failures – These are failures of two or more elements of a system where these failures cannot be considered independent (q.v.). Common cause and common mode failures are dependent failures.
Dependent t-test – It is a data analysis procedure which assesses whether the means of two related groups are statistically different from each other, for example, one group’s mean score (time one) compared with the same group’s mean score (time two). It is also called the paired samples t-test.
Dependant variable – A variable is considered dependent if it depends on an independent variable. Dependent variables are studied under the supposition or demand that they depend, by some law or rule, on the values of other variables.
Depletion – It is selective removal of one component of an alloy, normally from the surface or preferentially from grain-boundary regions.
Desulphurization – It is a chemical process for the removal of sulphur from liquid iron or molten steel.
Dephosphorization – It is the elimination of phosphorus from molten steel.
Depleted uranium – Depleted uranium is uranium mainly composed of the isotope uranium-238. Typically, it has a percentage of uranium-235 smaller than the 0.7 % found in natural uranium. It is obtained from used fuel elements or as by-product tails, or residues, from uranium isotope separation.
Depolarization – It is a decrease in the polarization of an electrode.
Depolarizer – It is a substance which produces depolarization.
Deposit – It is the coating or layer of surfacing material applied by a thermal spraying process. In geology, it is an anomalous occurrence of a specific mineral or minerals within the Earth’s crust.
Deposit attack or corrosion – It is the corrosion which is occurring under or around a discontinuous deposit on a metallic surface. It is also called poultice corrosion.
Deposited metal – It is the filler metal which has been added during welding.
Deposition – It is the process of applying a material to a base by means of vacuum, electrical, chemical, screening, or vapour methods. It is frequently with the assistance of a temperature and pressure container.
Deposition efficiency – In arc welding, it is the ratio of the weight of deposited metal to the net weight of filler metal consumed, exclusive of stubs. In thermal spraying, the ratio, usually expressed in percent, of the weight of spray deposit to the weight of the material sprayed.
Deposition rate – In thermal spraying, it is the weight of material deposited in a unit of time. It is normally expressed as kilograms per hour.
Deposition sequence – It is the order in which the increments of weld metal are deposited.
Depreciation – It is the periodic, systematic charging to expense of plant assets reflecting the decline in economic potential of the assets.
Depressions – In continuous casting process, these are local deformations in the cast surface. Depressions can be longitudinal or transverse. Longitudinal depressions appear like the shallow ditches oriented along the length of the cast product. They occur due to the uneven heat transfer in the mould. These depressions can be controlled by uniform cooling in the mould, by centering of the liquid steel jet in the mould, by controlling the fluctuations of the mould steel level, use of a casting powder with suitable viscosity and melting characteristics, and by regularly monitoring the degree and uniformity of the mould wear. Transverse depressions can occur cyclically along the strand length. The peritectic steels with low carbon and high manganese contents and the stainless steels are sensitive to this defect. The transverse depressions can be caused by the fluctuations in the mould level, large quantity of casting powder, and by the turbulence of steel the sub-meniscus level. These depressions are controlled by controlling the mould steel level, having proper mould taper, use of a casting powder with suitable viscosity and melting characteristics, and proper positioning of the input nozzle and its support.
Depth of cut – It is the thickness of material removed from a work-piece in a single machining of the part.
Depth of field – It is the depth in the subject over which features can be seen to be acceptably in focus in the final image produced by a microscope.
Depth of fusion – It is the distance which the fusion extends into the base metal or previous pass from the surface melted during welding.
Depth of penetration – In various analytical techniques, it is the distance the probing radiation penetrates beneath the surface of a sample.
Derivative – It is an image created from the master image, through some kind of image editing process to create a user or working copy. The process normally involves a loss of information to reduce the size by sampling it to a lower resolution, using lossy compression techniques, or altering an image using image processing techniques. Typically, derivatives are made for purposes such as web access, including ‘thumbnail’ images, or as ‘reference’ or ‘service’ images which can fit completely within an average monitor.
Derived standards – In the SI (The International System of Units) system, there are seven basic measurement units as given in Tab 1.
| Tab 1 SI Base Units | |||
| Sl. No. | Base quantity | Name of Base Unit | Symbol |
| 1 | Length | meter | m |
| 2 | Mass | kilogram | kg |
| 3 | Time | second | s |
| 4 | Electric current | ampere | A |
| 5 | Thermodynamic temperature | kelvin | K |
| 6 | Amount of substance | mole | mol |
| 7 | Luminous intensity | candela | cd |
All of the other units are derived from the seven basic units. Tab 2 lists the most common derived SI units, together with the base units which are used to define the derived unit. As an example, the unit of frequency is the hertz which is defined as the reciprocal of time, i.e., 1 hertz (1 Hz) is one cycle per second.
Descaling – It is removing the thick layer of oxides formed on some metals at high temperatures. It is also a chemical or mechanical process for removing scale or investment material from castings.
Descaling equipment – It is placed before the mill after the reheating furnace. High pressure water is sprayed onto the surface of the hot rolling stock steel to remove the scale. The equipment required for this process basically consists of a high-pressure pump, powered by an alternating current motor, which can be controlled by a variable speed drive. High pressure pump supplies water through specifically designed header and nozzles, which are directed at the hot steel. The removal of scale takes place due to the combined action of the water pressure and the rapid cooling of the steel.
Describing function – It is a method for analyzing non-linear control systems.
Descriptive – In data analysis, it is an analysis method which summarizes the data to reach a simple presentation as a result. This method can be categorized into (i) univariate analysis, and (ii) bivariate analysis.
Descriptive statistics – It is the body of statistical techniques concerned with describing the salient features of the variables used in one’s study. If one has a large set of data, then descriptive statistics provides graphical (e.g., boxplots) and numerical (e.g., summary tables, means, quartiles) ways to make sense of the data. The branch of statistics devoted to the exploration, summary, and presentation of data is called descriptive statistics. If people need to do more than descriptive summaries and presentations, they are to use the data to make inferences about some larger population. Inferential statistics is the branch of statistics devoted to making generalizations.
Desiccant – It is a hygroscopic substance which is used to induce or sustain a state of dryness (desiccation) in its vicinity. Normal encountered pre-packaged desiccants are solids (e.g., silica gel, and calcium oxide) which absorb water. Desiccants for specialized purposes can be in forms other than solid, and can work through other principles, such as chemical bonding of water molecules. Industrially, desiccants are widely used to control the level of water in gas streams.
Design – It is the concept of or proposal for an object, a process, or a system. The word design refers to something which is or has been intentionally created by a thinking agent, and is sometimes used to refer to the inherent nature of something, i.e., its design. The verb to design expresses the process of developing a design.
Design allowables – These are statistically determined materials property values which are derived from test data. They are limits of stress, strain, or stiffness which are allowed for a specific material, configuration, application, and environmental condition. The selection of appropriate design allowables for structures composed of composite materials is necessary for the safe and efficient use of these materials.
Design and engineering – It consists of the task of translating a set of functional requirements of the project into a full set of specifications and drawings providing the details needed. It involves a variety of special fields which include (i) process engineering, (ii) civil engineering, (iii) structural engineering, (iv) mechanical engineering, (v) electrical engineering, (vi) fluid engineering, (vii) instrumentation and control engineering, (viii) automation and control activities, (ix) geo-technical engineering, and (x) environmental and safety engineering etc.
Design appraisal – It is a procedure by which a certifying authority appointed by the purchaser, appraises the design parameters of the equipment and / or materials he is buying. The supplier is required to submit drawings, calculations and documents as required to the certifying authority in conjunction with those normally needed for review and acceptance by the purchaser.
Design approach for equipment foundation – The task for designing of foundations for equipments with dynamic loads in addition to the normal data on the equipment is to contain (i) the technical characteristics of the equipments (name, type, number of rotations per minute, power, and total weight, etc.), (ii) information about the magnitudes, places of application, and directions of action of static loads, as well as about amplitudes and frequencies, places of application, and direction of dynamic loads, (iii) data on the maximum permissible deformations of the foundations and their basement, (iv) requirements for placement of equipment on the foundations, (v) drawings of the dimensions of the foundation within the location of the equipment, fasteners, as well as auxiliary equipment, communications, and hole sizes, (vi) drawings of all communications adjacent to the foundation, (vii) data on the geological conditions of the construction site and soil properties, (viii) information about the location of the designed foundation relative to the nearest structures, and (ix) requirements for the protection of the foundation from ground-water, as well as other external factors characteristic of the design environment.
Design assembly drawing – It is an assembly drawing or a design layout which is first drawn when an equipment is designed to clearly visualise the performance, shape, and clearances of different parts comprising the equipment.
Design basis –The set of requirements which bound the design of systems, structures, and components within the facility. These design requirements include consideration of safety, plant availability, efficiency, reliability, and maintainability. Some aspects of the design basis are important for safety, although others are not.
Design basis accident – It is a postulated accident leading to accident conditions for which a facility is designed in accordance with established design criteria and conservative methodology. It is also a postulated accident which a nuclear facility is to be designed and built to withstand without loss to the systems, structures, and components necessary to ensure public health and safety.
Design code – It is a set of rules or regulations which tell the designer what to do and when and under what circumstances. While codes are frequently developed by technical or professional groups, they frequently are adopted by governmental jurisdictions and become legal requirements. Examples are the building code for the structural safety of buildings and the fire code.
Design constraint – It is a design parameter (variable) which is required to fall within a fixed range of values.
Design control drawing – It discloses the basic technical information and performance requirements necessary for a contractor to complete the detailed design required to develop and produce an item. The drawing in itself does not provide complete design for which a detailed design drawing is needed. It includes those details which are necessary to develop the detail design of the item such as (i) configuration, mounting, mating, and other necessary dimensions, (ii) performance, installation, reliability, and interchangeability requirements, (iii) test requirements, (iv) schematic, connection, or other appropriate diagram (if electrical, electronic or other circuitry is involved), (v) the mating connections, their location, and a connection diagram, and (vi) reference to other documentation.
Design defect – It is an aspect of a design or product which causes it to fail to perform as safely or reliably as an ordinary consumer expects.
Design drawing – Design drawing is made during the initial stages of the project and used for all initial activities including contract bidding. Design drawings are subject to revision with the progress of the project. Design drawing is used to develop and communicate ideas about a developing design.
Design factor – It is the quantity of lifting value a magnet is labelled against the lifting value under ideal conditions. Ideal conditions are when a magnet is new and pulled off a newly machined, thick, low carbon steel plate. The kilograms of pull it takes to break the magnet away from the steel surface is the ‘maximum’ lifting value. Design factor (de-rating) values are then determined by taking this maximum lifting value and dividing it by the manufacturers design factor. Design factors are minimum 2:1 and in the majority of cases 3:1.
Design features – These are the elements which comprise a part, such as walls, holes, and grooves, and the solid elements, such as rods, cubes, and tubes.
Design for assembly (DFA) – It is a methodology for examining the assembled parts of a product in terms of the time and cost for assembly of each part. The overriding strategy is to produce an acceptable design with the minimum number of parts.
Design for disassembly (DFD) – It is a methodology for designing a product so that it can be economically disassembled and the material from which the individual parts are made can be recovered and reused.
Design for the environment (DFE) – It is a design methodology in which environmental factors are considered of equal importance to performance factors. It is sometimes called green design.
Design for function and fit – It is an expression which exemplifies the two central rules of design namely (i) first and foremost, the design is to perform the function for which it is intended, and (ii) the design is to be designed to tolerances appropriate to the application.
Design for manufacture, design for manufacturability (DFM) – It is an approach toward integrating the product and process concepts so that the best match is made between product and process requirements. Design for manufacture includes detailed examination of the design so that it is most easily and inexpensively manufactured by the intended process.
Design for ‘X’ (DFX) – It is a catch phrase which describes the understanding that engineering designs increasingly are to be consciously designed for factors other than function and tolerances. These issues include design for assembly, design for manufacture, and design for installation, maintenance, safety, and disposal etc.
Design intent – It is a general term used with respect to describing and documenting the aspects of some part of the design which are crucial to the success of the design.
Design layout – It is an engineering drawing, either two-dimensional or three-dimensional, which shows the individual parts of a system in relationship to one another. An assembly drawing frequently serves the same purpose.
Design of experiments (DOE) – It is a methodology involving statistically designed experiments in which the character and sequence of individual experiments are planned in advance so that data are taken in a way which provides the most unbiased and precise results commensurate with the available time and money. The chief classes of statistically designed experiments are (i) blocking designs to remove the effect of background variables from the experimental error, (ii) factorial designs, in which all levels of each factor in an experiment are combined with all levels of every other factor, and (iii) response surface designs, which determine the empirical relation between the factors (independent variables) and the response (performance variable).
Design optimization – It consists of the process of searching for the best combination of design parameters. Design optimization suggests that for a given set of possible designs and design criteria there exists a single design which is the best or optimal.
Design parameters – It is a term used to describe the main variables of a design issue. It is sometimes called the design attributes or design characteristics. Design parameters define the object or process which is being designed and hence provide a means for changing the design for improving the performance.
Design performance measures – It consists of the performance measures which are functions of the design parameters and are used to quantify the effectiveness of a given design. Performance measures frequently are grouped into an objective function and the problem constraints.
Design review – A design review is a milestone within a product development process whereby q design is evaluated against its requirements in order to verify the outcomes of previous activities and identify issues before committing to, and if need be, to re-prioritize further work. The ultimate design review, if successful, hence triggers the product launch or product release. The conduct of design reviews is compulsory as part of design controls, when developing products in certain regulated contexts.
Design rules – These are a set of guidelines which are developed from experience and which tell the designer how to make decisions in typical situations. Frequently these rules suggest how to design to minimize cost of manufacture, e.g., to try to design the part so it can be machined on one machine tool only.
Design sensitivity – It is an analytical method for determining the importance of each design parameter to the performance of the design (output measure) and the critical ranges of those parameters.
Design standards – These are agreed-upon descriptions of best solutions to repetitive design issues, arrived at by general consent of an appropriate broad-based technical group. While standards do not have the force of law, they frequently are incorporated into a design code.
Design team – It is a multi-functional group which contains not only the technical expertise to design the product but also expertise in manufacturing and marketing.
Design temperature – It is the design temperature of the piping system in which the valve is operating in. The valve is to be designed to this temperature.
Desiliconization of hot metal – It is the removal of silicon from the hot metal prior to the oxygen converter process. Silicon removal is beneficial to the converter to reduce the chemical attack on the basic refractory lining and to allow the use of only minimal amounts of slag-making fluxes, thereby maximizing process yield. These are several methods which are being used for desiliconization of hot metal including adding iron ores or sinter to hot metal during its flow in blast furnace runner.
Desizing – It is the process of eliminating sizing, which is normally starch, from gray (also greige) goods before applying special finishes or bleaches (for yarn such as glass or cotton). It is also removing lubricant size following weaving of a cloth.
Desorption – It is a process in which an absorbed material is released from another material. Desorption is the reverse of absorption, adsorption, or both.
Destructive distillation – It is a chemical process in which decomposition of unprocessed material is achieved by heating it to a high temperature. The term normally applies to the processing of organic material in the absence of air or in the presence of limited amounts of oxygen or other reagents, catalysts, or solvents, such as steam or phenols. It is an application of pyrolysis. The process breaks up or ‘cracks’ large molecules. Coke, coal gas, gaseous carbon, coal tar, ammonia liquor, and coal oil are examples of commercial products historically produced by the destructive distillation of coal. Destructive distillation of any particular inorganic feedstock produces only a small range of products as a rule, but destructive distillation of many organic materials commonly produces very many compounds, often hundreds, although not all products of any particular process are of commercial importance.
Desulphurizing – It is the removal of sulphur from molten metal by reaction with a suitable slag or by the addition of suitable compounds.
Detail design – It is the final phase of design in which all information on materials, manufacturing processes, dimensions, and tolerances are supplied. The output of this design phase is a complete set of drawings and product specifications. It is also known as parametric design.
Detail drawing – Detail drawing is the engineering drawing of any kind of geometric structure which is to be constructed. The drawing is more detailed and pay attention to the intricate designs and details of any construction project. Detail drawing is an engineering drawing presenting single item (object / equipment component / work-piece etc.). The drawing is meant for enabling a person in a workshop to produce (by machining / casting / forging / fabricating etc.) the desired item. Such details as dimensional tolerances, surface finish, special treatments, material to be used for the component etc. are specified. The number of views to be presented depends on the complexity of the item. In several situations, sectional views are included to show hidden details which cannot conveniently and explicitly appear in any external view.
Detailed assembly drawing – It is normally made for simple equipments, comprising of a relatively smaller number of simple parts. All the dimensions and information necessary for the construction of such parts and for the assembly of the parts are given directly on the assembly drawing. Separate views of specific parts in enlargements, showing the fitting of parts together, can also be drawn in addition to the regular assembly drawing.
Detailed emergency planning zone – It is the area around a facility for which the regulations need the local authority to prepare a detailed off-site emergency plan with the purpose of restricting, as far as reasonably practicable, exposure to the public in the event of a radiation emergency.
Detailed engineering – It takes place during the actual project execution phase. It consists of producing drawings and documents which are necessary for (i) manufacturing of the plant and equipment, (ii) carrying out civil foundations, (iii) fabrication of building and technological structures, (iv) erection of structures as well as plant and equipment, (v) laying of cables and making of electrical and instrument connections, and (vi) laying of pipes and piping connections etc. During the detailed engineering, the information from the suppliers is integrated with other information of the project. Also, the responsibility of carrying out the detailed engineering is split between the suppliers and the project engineering personnel including the project consultants.
Detailed feasibility report – It aims to provide an independent assessment which examines all aspects of a proposed project, including technical, economic, financial, legal, and environmental considerations. This information then helps decision-makers determine whether or not to proceed with the project. Detailed feasibility report evaluates a set of proposed project paths or solutions to determine if they are viable.
Detailed project report – It is a blueprint of a project with an extensive and elaborative outline of a project, which includes essential information such as the resources and tasks to be carried out in order to make the project turn a success. Detailed project report is the document which gives a 360-degree view of any project. It is a vital document
Detection limit – It is the level at which radioactivity can be detected above background levels.
Detent – It is a spring-return device which maintains the position of the spool of a directional control valve in position.
Detergency and dispersant property – With the exception of detergency and dispersant property in the combustion chamber, deposits in the lubricating oil are controlled by its detergent power. The role of the detergent additives is to reduce the quantity of deposits formed and their removal easy. The detergent property imparted to the lubricating oils by additives seems to perform differently depending upon whether deposits result from high or low temperatures. Low temperature deposits are mainly come from the fuel combustion and the detergency function of the lubricating oil is to keep them in suspension or in solution in the lubricating oil. However, high temperature deposits are mainly related to the oxidized fraction of the oil. The role of detergency here is not only to maintain these products in suspension, but also to stop the development of those chain reactions which promote the formation of varnishes and lacquers. The physical and functional properties of the lubricating oils depend on the properties of the carbon atoms in the various ring structures and aliphatic side chain.
Detergent – It is a surface-active agent which possesses the ability to clean soiled surfaces. Types of Detergents are anionic, cationic, and nonionic.
Detergent additive – In lubrication technology, it is a surface-active additive which helps to keep solid particles suspended in an oil.
Detergent oil – It is a heavy-duty oil containing a detergent additive. Detergent oils are used mainly in combustion engines.
Determination – It is the ascertainment of the quantity or concentration of a specific substance in a sample.
Detinning – It is the slow corrosion of the tin coating of a can.
Detonation flame spraying – It is a thermal spraying process variation in which the controlled explosion of a mixture of fuel gas, oxygen, and powdered coating material is utilized to melt and propel the material to the work-piece.
Detritus – These are the particles which become detached in a wear process.
Deuteron – It is the nucleus of the atom of heavy hydrogen, deuterium. The deuteron is composed of a proton and a neutron. It is the simplest multi-nucleon nucleus. Deuterons are used as projectiles in several nuclear bombardment experiments.
Developed blank – It is a sheet metal blank which yields a finished part without trimming or with the least quantity of trimming.
Development – In mining, it is the underground work carried out for the purpose of opening up a mineral deposit. It includes shaft sinking, cross=cutting, drifting and raising.
Development drilling – It consists of drilling to establish accurate estimates of mineral reserves.
Deviation – A deviation is a departure from the specified standards or from an established process. Deviations can be intentional or unintentional, and they can occur at any stage of the production process. In statistical process control, it is difference between desired and actual values. It is used for difference between individual values and their mean.
Deviation score – It is the difference between a variable’s value and the mean of the variable.
Deviation (x-ray) – It is the angle between the diffracted beam and the transmitted incident beam. It is equal to twice the Bragg angle theta.
Deviatoric stress – It is the non-hydrostatic component of the state of stress on a body. It is the deviatoric component which causes shape change (plastic deformation).
Devitrification – It is the crystallization of an amorphous substance. In porcelain enamel, it is a surface defect caused by crystallization of the enamel because of the overfiring or contamination, resulting in the loss of the glassy, vitreous appearance of the surface.
Dewar flask – It is a vessel having double walls, the space between being evacuated to prevent the transfer of heat and the surfaces facing the vacuum being heat reflective. It is used to hold liquid gases and to study low-temperature phenomena.
Dewaxing – In casting, it is the process of removing the expendable wax pattern from an investment mould or shell mould. It is normally carried out by melting out because of the application of heat or by dissolving the wax with an appropriate solvent.
Dew point – It is the temperature and pressure at which a gas begins to condense to a liquid.
Dew point analyzer – It is an atmosphere monitoring device which measures the partial pressure of water vapour in an atmosphere.
Dezincification – It is a type of corrosion in which zinc is selectively leached from zinc-containing alloys leaving a relatively weak layer of copper and copper oxide. It is normally found in copper-zinc alloys containing less than 85 % copper after extended service in water containing dissolved oxygen.
Dezincification resistant brass – It is a duplex brass which has an arsenic addition and a special heat treatment to prevent dezincification by soft, acidic, water supplies. Sometimes the term is applied to arsenical, aluminum or admiralty brasses which also have arsenic additions. These alloys need no special heat treatment since no beta phase is present.
D-glass – It is a high boron content glass made especially for laminates needing a precisely controlled dielectric constant.
Diabase – It is a common basic igneous rock usually occurring in dykes or sills.
Diagnosis – It is used in several different disciplines, with variations in the use of logic, analytics, and experience, for the determination of cause and effect. In systems engineering and computer science, it is typically used to determine the causes of symptoms, mitigations, and solutions.
Diagonal rolling – It is a special case of cross rolling. The mechanism of plastic deformation is here a similar one. However, work rolls axes are not parallel, but skew. Hence, the rolling stock not only rotates, but also feeds forward in the direction of its longitudinal axis, because of the skew axes of the rolls. This mode of rolling is used for the rolling of seamless tubes. It is the popular method for the production of hollow semi-finished products.
Diagram – It is a drawing, sketch, plan, or chart which makes something clearer or easier to understand.
Dial gauge – It is also known as a dial gauge indicator. It is a precision instrument employing numerical indicators and an internal mechanism to measure various components or objects accurately. A dial gauge is used to measure small linear displacements or dimensional variations with high precision and accuracy.
Diamagnetic material – It is a material whose specific permeability is less than unity and is hence repelled weakly by a magnet.
Diameter – In geometry, a diameter of a circle is any straight-line segment which passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid for the diameter of a sphere.
Diametric projection – In diametric projection, all dimensions along two axes are drawn to ‘true size’ The dimensions along the third axis are halved. This projection is preferred when one view of the object is to be emphasized than the other two views (i.e., when one view is of more interest than the other views).
Diamond – It is the hardest known mineral. It is composed of pure carbon. Low-quality diamonds are used to make bits for diamond drilling in rock.
Diamond drill – It is a rotary type of rock drill which cuts a core of rock that is recovered in long cylindrical sections, two centimeters or more in diameter.
Diamond driller – It means a person who operates a diamond drill.
Diamond drilling – It is drilling method which gets a cylindrical core of rock by drilling with an annular bit set with diamonds.
Diamond film – It is a carbon-composed film, normally deposited by chemical vapour deposition or related process, which has three characteristics namely (i) a crystalline morphology which can be visually discerned by optical microscopy, (ii) a single-phase crystalline structure identifiable by x-ray and / or electron diffraction, and (iii) a Raman spectrum typical for crystalline diamond. The sharpness of the sp3 carbon-carbon bonding peak (wave-number 1,332 cm-1) is frequently used to determine the perfection of the film.
Diamond-like film – It is a hard, non-crystalline carbon film, which is normally grown by chemical vapour deposition or related techniques, and which contains predominantly sp2 carbon-carbon bonds.
Diamond pyramid hardness test – It is also known as Vickers hardness test which is a micro-indentation hardness test employing a 136-degree diamond pyramid indenter (Vickers) and variable loads, enabling the use of one hardness scale for all ranges of hardness–from very soft lead to tungsten carbide.
Diamond pyramid number – It is system of assigning values to metals quantifying their hardness.
Diamond tool – It is a diamond, shaped or formed to the contour of a single-point cutting tool, for use in precision machining of non-ferrous or non-metallic materials. It is also an insert made from poly-crystalline diamond compacts.
Diamond wheel – It is a grinding wheel in which crushed and sized industrial diamonds are held in a resinoid, metal, or vitrified bond.
Diaphragm – It is a porous or permeable membrane separating anode and cathode compartments of an electrolytic cell from each other or from an intermediate compartment. It is also universal die member made of rubber or similar material used to contain hydraulic fluid within the forming cavity and to transmit pressure to the part being formed.
Diaphragm forming – It is a method of simultaneously consolidating and forming thermoplastic composites in which the lay-up is sandwiched between two heat-formable sheets (frequently superplastic aluminum sheets) and placed under gas pressure in a press to form and consolidate the desired shape.
Diaphragm valve – A diaphragm valve is a linear motion valve which is used to start, regulate, and stop fluid flow. The name is derived from its flexible disk, which mates with a seat located in the open area at the top of the valve body to form a seal. Diaphragm valves are, in effect, simple ‘pinch clamp’ valves. A resilient, flexible diaphragm is connected to a compressor by a stud moulded into the diaphragm. The compressor is moved up and down by the valve stem. Hence, the diaphragm lifts when the compressor is raised. As the compressor is lowered, the diaphragm is pressed against the contoured bottom in the straight through valve or the body weir in the weir-type valve.
Diaspore clay – It is a rock consisting essentially of diaspore bonded by fireclay.
Diatomic – It means composed of two atoms, of the same or different elements.
Diatomic molecule – It is a molecule composed of only two atoms, of the same or different elements.
Dichromate treatment – It is a chromate conversion coating produced on magnesium alloys in a boiling solution of sodium dichromate.
Didymium – It is a natural mixture of the rare-earth elements praseodymium and neodymium, frequently given the quasi-chemical symbol Di.
Die – It is a tool, normally containing a cavity, which imparts shape to solid, molten, or powdered metal mainly because of the shape of the tool itself. It is used in several press operations (including blanking, drawing, forging, and forming), in die casting, and in forming green powder metallurgy compacts. Die-casting and powder metallurgy dies are sometimes referred to as moulds.
Die (in casting) – It is metal form(s) used to produce a die casting, a lost foam pattern, or a wax pattern. It is a metal block used in the die casting process, incorporating the cavity or cavities that form the cast component, the molten metal distribution system, and means for cooling and ejecting the casting.
Die (in forging or extrusion) – It is metal forms between which metal is forged or through which metal is extruded. The shapes of the dies control the form and shape of the finished parts.
Die assembly – It consists of the parts of a die stamp or press which hold the die and locate it for the punches.
Die block – It is a block, frequently made of heat-treated steel, into which desired impressions are machined or sunk and from which closed-die forgings or sheet metal stampings are produced using hammers or presses. In forging, die blocks are normally used in pairs, with part of the impression in one of the blocks and the rest of the impression in the other. In sheet metal forming, the female die is used in conjunction with a male punch.
Die body – It is the stationary or fixed part of a powder pressing die.
Die casting – It is a casting made in a die.
Die casting process – It is a metal casting process which is characterized by forcing of liquid metal under high pressure into a mould cavity. The mould cavity is created using two hardened dies made of tool steel. These dies are machined into shape and work similarly to an injection mould during the process. Majority of die castings are made from specifically zinc, copper, aluminum, magnesium, lead, pewter (alloy of tin, copper and antimony) and tin-based alloys. Die castings of ferrous metal are also possible.
Die casting, cold chamber – It is the die casting process in which the metal injection mechanism is not submerged in molten metal.
Die casting, gravity – It is the term used in for producing a casting by pouring molten metal (gravity pouring) into a metal mould, with no application of pressure. It is also called as the permanent mould casting process.
Die casting, hot chamber It is the die casting process in which the metal injection mechanism is submerged in the molten metal.
Die casting, pressure – It is a casting made in a metal mould (set of metal dies) in which the metal is injected under high pressure, by either cold-chamber or hot-chamber die casting machines. It is also used for simply die casting. High-pressure die casting and low-pressure die casting are terms normally used to differentiate between the two processes which are also called die casting and low-pressure permanent moulding respectively.
Die cavity – It is the machined recess which gives a forging or stamping its shape.
Die check – It is a crack in a die impression because of the forging and thermal strains at relatively sharp corners. Upon forging, these cracks become filled with metal, producing sharp ragged edges on the part. Normal die wear is the gradual enlarging of the die impression because of the erosion of the die material, normally occurring in areas subject to repeated high pressures during forging.
Die clearance – It is the clearance between a mated punch and die. It is normally expressed as clearance per side. It is also called clearance or punch-to-die clearance.
Die closure – It is a term frequently used to mean variations in the thickness of a forging.
Die cushion – It is a press accessory placed beneath or within a bolster plate or die block for providing an additional motion or pressure for stamping or forging operations. It is actuated by air, oil, rubber, springs, or a combination of these.
Die drawing – It is a computer aided design (CAD) drawing of the extrusion die showing exact detail of the shape of the profile.
Die, extrusion die – It is the hardened steel aperture through which a heated extrusion billet is pushed to form an extruded profile shape. There are 3 types of die namely (i) flat die for extruding solid shapes, (ii) porthole die for extruding hollow shapes, which leaves one or two ‘weld’ seams along the length of the extrusion so tube produced in this way is called welded tube, and (iii) flat die with mandrel for extruding seamless hollow shapes and seamless tube.
Die forger hammers – These hammers are similar in operation to power-drop hammers but have shorter strokes and more rapid striking rates. The ram is held at the top of the stroke by a constant source of pressurized air, which is admitted to and exhausted from the cylinder to energize the blow.
Die forging – It is a forging which is formed to the required shape and size through working in machined impressions in specially prepared dies. Based on the arrangements of dies, the process of forging can be (i) open die forging, and (ii) closed die forging.
Die forming – It is the shaping of solid or powdered metal by forcing it into or through the die cavity.
Die height – It is the distance between the fixed and the moving platen when the dies are closed.
Die holder – it is a plate or block, on which the die block is mounted, having holes or slots for fastening to the bolster plate or the bed of the press.
Die impression – It is the portion of the die surface which shapes a forging or sheet metal part.
Die insert – It is a relatively small die which contains part or all of the impression of a forging or sheet metal part and is fastened to the master die block.
Dielectric – It is a non-conductor of electricity. It is also the ability of a material to resist the flow of an electrical current.
Dielectric constant – It is the ratio of the capacitance of an assembly of two electrodes separated solely by a plastic insulating material to its capacitance when the electrodes are separated by air.
Dielectric curing – It is the curing of a synthetic thermosetting resin by the passage of an electric charge (produced from a high-frequency generator) through the resin.
Dielectric fluid – It is a dielectric material in liquid state. Its main purpose is to prevent or rapidly quench electric discharges. Dielectric fluids are used as electrical insulators in high voltage applications, e.g. transformers, capacitors, high voltage cables, and high voltage switchgear. Its function is to provide electrical insulation, suppress corona and arcing, and to serve as a coolant.
Dielectric heating – It is the heating of materials by dielectric loss in a high-frequency electrostatic field.
Dielectric loss – It is a loss of energy evidenced by the rise in heat of a dielectric placed in an alternating electric field.
Dielectric material – It is a material which does not allow free flow of electric current.
Dielectric monitoring – It is a means of tracking the cure of thermosets by changes in their electrical properties during material processing.
Dielectric shield – In a cathodic protection system, it is an electrically non-conductive material, such as a coating, plastic sheet, or pipe, that is placed between an anode and an adjacent cathode for avoiding current wastage and for improving current distribution, normally on the cathode.
Dielectric strength – It is the property of an insulating material which enables it to withstand electric stress. It is also the average potential per unit thickness at which failure of the dielectric material occurs.
Dielectrometry – It is the use of electrical techniques to measure the changes in loss factor (dissipation) and in capacitance during cure of the resin in a laminate.
Die life – It is the productive life of a die impression, normally expressed as the number of units produced before the impression has worn beyond permitted tolerances.
Die lines – These are lines or markings on formed, drawn, or extruded metal parts caused by imperfections in the surface of the die.
Die lubricant – It is a lubricant applied to the working surfaces of dies and punches for facilitating drawing, pressing, stamping, and / or ejection. In powder metallurgy, the die lubricant is sometimes mixed into the powder before pressing into a compact. It is also a compound which is sprayed, swabbed, or otherwise applied on die surfaces or the work-piece during the forging or forming process for reducing friction. Lubricant also facilitates release of the part from the dies and provide thermal insulation.
Die match – It is the condition where dies, after having been set up in a press or other equipment, are in proper alignment relative to each other.
Die number – It is the number assigned to a die for identification and cataloging purposes, and which normally is assigned for the same purpose to the product produced from that die.
Die opening – In flash or upset welding, it is the distance between the electrodes, normally measured with the parts in contact before welding has commenced or immediately upon completion of the cycle but before upsetting. In powder metallurgy, it is the entrance to the die cavity.
Die pad – It is a movable plate or pad in a female die. It is normally used for part ejection by mechanical means, springs, or fluid cushions.
Die proof – It is a casting of a die impression made to confirm the accuracy of the impression.
Die pull – It is the direction in which the solidified casting is required to move when it is removed from the die. The die pull direction is to be selected such that all points on the surface of the casting move away from the die cavity surfaces.
Die radius – It is the radius on the exposed edge of a deep-drawing die, over which the sheet flows in forming drawn shells.
Diesel engine – It uses diesel as the fuel. It is an internal combustion engine in which ignition of the fuel is caused by the high temperature of the air in the cylinder because of the mechanical compression (adiabatic compression).
Diesel oil, light – Light diesel oil (LDO) is having flash point above 66 deg C. It is a blend of distillate components and a small quantity of residual components. It is used as a fuel in certain boilers and furnaces.
Diesel oil, high speed – High speed diesel (HSD) oil is a complex mixture of hydro carbons. It is a brown-coloured oily liquid with pungent smell. It has a pungent smell. It is used in diesel engines of mobile equipment, diesel-generator sets, and locomotives. It is the prime mover in a wide range of power generation and pumping applications.
Die separation – It is the space between the two halves of a die casting die at the parting surface when the dies are closed. The separation can be the result of the internal cavity pressure exceeding the locking force of the machine or warpage of the die because of the thermal gradients in the die steel.
Die set – It is a tool or tool holder consisting of a die base and punch plate for the attachment of a die and punch, respectively.
Die shift – It is the condition which occurs after the dies have been set up in a forging unit in which a portion of the impression of one die is not in perfect alignment with the corresponding portion of the other die. This results in a mismatch in the forging, a condition which is to be held within the specified tolerance.
Die sinking – It is the machining of the die impressions for producing forgings of the needed shapes and dimensions.
Die shoes – These are the upper and lower plates or castings which constitute a die set (punch and die holder). It is also a plate or block upon which a die holder is mounted, functioning mainly as a base for the complete die assembly. This plate or block is bolted or clamped to the bolster plate or the face of the press slide.
Die space – It is the maximum space (volume), or any part of the maximum space, within a press for mounting a die.
Die stamping – It is the general term for a sheet metal part which is formed, shaped, or cut by a die in a press in one or more operations.
Die steels – These are steels which are used in die forging for making dies which work under heavy pressure and which produce a flow of metal compressing it into the desired form or shape. These steels are used for making crimping dies, embossing dies, heading dies, extrusion dies, and staking dies etc. These steels are properly heat treated to get the desired properties.
Die swell – It is the expansion of the polymer melt which occurs as the extruded melt exits the die. This is because of the aligned polymer chain
Die welding – It is also known as forge welding and cold welding. It is a solid-state welding in which metals are heated in a forge (in air) and then welded together by applying pressure or blows sufficient to cause permanent deformation at the interface.
Differential –A differential is a gear train with three shafts which has the property that the rotational speed of one shaft is the average of the speeds of the others, or a fixed multiple of that average.
Differential aeration cell – It is an electrolytic cell, the electro-magnetic force of which is because of a difference in air (oxygen) concentration at one electrode as compared with that at another electrode of the same material.
Differential annealing – It is the localized heating of part of a blank so that only specific areas are annealed.
Differential coating – It is a coated product having a specified coating on one surface and a significantly lighter coating on the other surface such as a hot dip galvanized product or electrolytic tin plate.
Differential floatation – It means separating a complex ore into two or more valuable minerals and gangue by flotation. It is also called selective flotation.
Differential heating – It is the heating which intentionally produces a temperature gradient within an object such that, after cooling, a desired stress distribution or variation in properties is present within the object.
Differential interference contrast illumination – It is a microscopic technique using a beam-splitting double-quartz prism, i.e., a modified Wollaston prism placed ahead of the objective together with a polarizer and analyzer in the 90-degree crossed positions. The two light beams are made to coincide at the focal plane of the objective, revealing height differences as variations in colour. The prism can be moved, shifting the interference image through the range of Newtonian colours.
Differential pressure – It is the pressure measured with respect to another pressure and is expressed as the difference between the two values. This represents two points in a pressure or flow system and is referred to as the ‘dp’.
Differential pulley – It is also called chain hoist. It is used to manually lift very heavy objects. It is operated by pulling upon the slack section of a continuous chain which wraps around two pulleys on a common shaft. The two pulleys are joined together such that they rotate as a unit on the single shaft that they share. The relative sizing of the two connected pulleys determines the maximum weight which can be lifted by hand. If the pulley radii are close enough, then the load remains in place (and not lower under the force of gravity) until the chain is pulled.
Differential quenching – It is the selective quenching of the different parts of the same steel object.
Differential scanning calorimetry – It is a thermo-analytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference is measured as a function of temperature. Both the sample and reference are maintained at nearly the same temperature throughout the experiment.
Differential thermal analysis (DTA) – It is a technique in which the difference in temperature between the sample and a reference material is monitored against time or temperature while the temperature of the sample, in a specified atmosphere, is programmed. It is a thermo-analytic technique which is similar to differential scanning calorimetry. In this analysis technique, the material under study and an inert reference are made to undergo identical thermal cycles, while recording any temperature difference between sample and reference.
Diffraction – It is a modification which the radiation undergoes, e.g., in passing by the edge of opaque bodies or through narrow slits, in which the rays appear to be deflected. It is also the coherent scattering of x-rays by the atoms of a crystal which necessarily results in beams in characteristic directions, which is sometimes termed reflection. Diffraction is also the scattering of electrons by any crystalline material through discrete angles depending only on the lattice spacings of the material and the velocity of the electrons.
Diffraction contrast – In electron microscopy, it is the contrast produced by intensity differences in Bragg-diffracted beams from a crystalline material. These differences are caused by regions of varying crystal orientation.
Diffraction grating – It is an artificially produced periodic array of scattering centres capable of producing a pattern of diffracted energy, such as accurately ruled lines on a plane surface.
Diffraction pattern (x-rays) – It is the spatial arrangement and relative intensities of diffracted beams.
Diffraction ring – It is the diffraction pattern produced by a given set of planes from randomly oriented crystalline material.
Diffuse necking – It is the non-uniform strain distribution along the length of a member loaded in tension which develops at the maximum load. The term ‘diffuse’ is used since the neck develops slowly, with little change in load, but an increase in axial strain near the load maximum.
Diffuse transmittance – It is the transmittance value obtained when the measured radiant energy has experienced appreciable scattering in passing from the source to the receiver.
Diffusion – It means spreading of a constituent in a gas, liquid, or solid, tending for making the composition of all parts uniform. It is also the spontaneous movement of atoms or molecules to new sites within a material.
Diffusion aid – It is a solid filler metal sometimes used in diffusion welding.
Diffusion bonding – It is also known as diffusion welding and diffusion brazing. Diffusion welding is a solid-state welding process which produces coalescence of the faying surfaces by the application of pressure at high temperature. The process does not involve macroscopic deformation, melting, or relative motion of parts. A solid filler metal (diffusion aid) can or cannot be inserted between the faying surfaces.
Diffusion brazing – It is a brazing process which produces coalescence of metals by heating them to suitable temperatures and by using a filler metal or an in-situ liquid phase. The filler metal can be distributed by capillary action or can be placed or formed at the faying surfaces. The filler metal is diffused with the base metal to the extent that the joint properties have been changed to approach those of the base metal. Pressure may or may not be applied.
Diffusion, clad material – It is the migration of alloying elements from the core into the cladding layer during thermal treatment. This can be detrimental to the properties and behaviour of both the core and cladding.
Diffusion coating It is a process whereby a base metal or alloy is either (i) coated with another metal or alloy and heated to a sufficient temperature in a suitable environment or (ii) exposed to a gaseous or liquid medium containing the other metal or alloy, hence causing diffusion of the coating or of the other metal or alloy into the base metal with resultant changes in the composition and properties of its surface.
Diffusion coefficient – It is a factor of proportionality representing the amount of substance diffusing across a unit area through a unit concentration gradient in unit time.
Diffusion creep – It refers to the deformation of crystalline solids by the diffusion of vacancies through their crystal lattice. Diffusion creep results in plastic deformation rather than brittle failure of the material. Diffusion creep is more sensitive to temperature than other deformation mechanisms.
Diffusion-limited current density – It is the current density, frequently referred to as limiting current density, which corresponds to the maximum transfer rate that a particular species can sustain because of the limitation of diffusion.
Diffusion staining – It is the patchy surface discolouration which can occur as a result of diffusion in clad material.
Diffusion streak – It is the surface discolouration which can vary from gray to brown and found only on alclad products.
Diffusion welding – It is a solid-state welding process which produces coalescence of the faying surfaces by the application of pressure at high temperature. The process does not involve macroscopic deformation, melting, or relative motion of parts. A solid filler metal (diffusion aid) may or may not be inserted between the faying surfaces.
Diffusion zone – It is the zone of variable composition at the junction between two different materials, such as in welds or between the surface layer and the core of clad materials or sleeve bearings, in which interdiffusion between the different components has taken place.
Digital – It means that the data is represented by a series of digits. Several functions / values can be transmitted over a single pair of cables.
Digital control – It is a control system which processes signals in digital form.
Digital image processing – It is the use of a digital computer for processing the digital images through an algorithm. As a subcategory or field of digital signal processing, digital image processing has several advantages over analog image processing.
Digital images – These images are the electronic snapshots taken of a scene or scanned from documents, such as photographs, manuscripts, printed texts, and artwork. The digital image is sampled and mapped as a grid of dots or picture elements (pixels). Each pixel is assigned a total value (black, white, shades of gray or colour), which is represented in binary code (zeros and ones).
Digital instrument – It is an instrument which represents the measured value in the form of the digital number. It works on the principle of quantization. The quantization is the process of converting the continuous input signal into a countable output signal.
Digital manufacturing – Digitalization of controls during the manufacturing process helps identifying and automatically correcting the flaws in the products during each step of the production process. This in turn improves the product acceptance rates.
Digital measuring device – A digital measuring device is that in which the value of the measured physical quantity is automatically represented by a number on a digital display or by a code, that is, a set of discrete signals. Digital measuring devices can be divided into digital measuring instruments and digital measuring transducers. Digital measuring instruments are self-contained devices which automatically present the value of the measured quantity on a digital display.
Digital preservation – It is a process by which digital data is preserved in digital form in order to ensure the usability, durability and intellectual integrity of the information contained therein. A more precise definition is ‘the storage, maintenance, and accessibility of a digital object over the long term, usually as a consequence of applying one or more digital preservation strategies’.
Digital repository or archive – The digital repository is where digital content, assets are stored and can be searched and retrieved for later use. The repository supports mechanisms to import, export, identify, store and retrieve digital assets. Putting of digital content into a repository enables the people to manage and preserve it, and hence derive maximum value from it.
Digital signal – A digital signal is a signal which represents data as a sequence of discrete values. At any given time, it can only take on, at most, one of a finite number of values. In contrast the analog signal which varies in a continuous fashion and takes on infinity of values in any given range, the digital signal varies in discrete steps and hence takes up only finite different values in a given range.
Digital to analog converter – It is a device in which inputs are a binary number and outputs are an analog voltage or current signal.
Digitization – It is the process of converting information into a digital format. In this format, information is organized into discrete units of data (called bits) which can be separately addressed (normally in multiple-bit groups called bytes). This is the binary data which computers and several devices with computing capacity can process. Text and images can also be digitized. Similarly, digitization of audio and video presentations is also possible.
Dilatant – It is a reversible increase in viscosity with increasing shear stress.
Dilatometer – It is an instrument for measuring the linear expansion or contraction in a metal resulting from changes in such factors as temperature and allotropy.
Diluent – It is normally a liquid inert substance added to some other substance or solution so that the volume of the latter substance is increased and its concentration per unit volume is decreased.
Dilution – It is the process of lowering the concentration of a solute in a solution by simply adding more solvent to the solution, such as water. Diluting of a solution entails adding more solvent without adding more solute.
Dilution (mining) – It means that the rock that is, by necessity, removed along with the ore in the mining process, subsequently lowering the grade of the ore.
Dilution factor – When diluting a sample, it is the ratio of the final volume or mass after dilution to the volume or mass of the sample before dilution.
Dimensional defects – These are mainly related to the shape and dimensions. During the rolling of a material, there can be different defects which can cause the shape not to be as desired or the measurements not to fall within the required tolerances. The majority of the frequent causes of dimensional defects are because of the poor adjustments to the mill control and tension while rolling.
Dimensional management – It is an engineering design methodology which aims to absorb as much variation as possible without affecting the function of the product. It does this through the optimal selection of datums, feature controls, assembly methods, and assembly sequence. It differs from the conventional practice of assigning tolerances to drawings prior to release in that it is more systematic and more global in outlook and uses three-dimensional tolerance analysis computer aided engineering tools.
Dimensional stability – It is the ability of a plastic part to retain the precise shape in which it was moulded, fabricated, or cast.
Dimer – It is a condensation compound formed from two monomers or molecules.
Dimerization – It is the formation of a dimer.
Dimple – In porcelain enamel, it is a cone-like depression defect in the fired enamel surface, somewhat larger than a pinhole.
Dimple rupture – It is a fractographic term describing ductile fracture which occurs through the formation and coalescence of micro-voids along the fracture path. The fracture surface of such a ductile fracture appears dimpled when observed at high magnification and normally is very clearly resolved when viewed in a scanning electron microscope (SEM).
Dimpled rupture fracture – It is a ductile fracture which occurs through the formation and coalescence of micro-voids (dimples) along the fracture path. The fracture surface of such a ductile fracture appears dimpled when observed at high magnification and normally is most clearly resolved when viewed in a scanning electron microscope.
Dimpling – It is the stretching of a relatively small, shallow indentation into sheet metal. In aircraft, it is the stretching of metal into a conical flange for a counter-sunk head rivet.
Diode – It is a two-terminal electronic component which conducts current mainly in one direction (asymmetric conductance). It has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other. A diode vacuum tube or thermionic diode is a vacuum tube with two electrodes, a heated cathode and a plate, in which electrons can flow in only one direction, from cathode to plate. A semi-conductor diode, the most commonly used type today, is a crystalline piece of semi-conductor material with a p–n junction connected to two electrical terminals.
Diorite – It is an intrusive igneous rock composed mainly of sodic plagioclase, hornblende, biotite or pyroxene.
Dip – It is the angle at which a vein, structure or rock bed is inclined from the horizontal as measured at right angles to the strike.
Dip brazing – It is a brazing process in which the heat needed is furnished by a molten chemical or metal bath. When a molten chemical bath is used, the bath can act as a flux. When a molten metal bath is used, the bath provides the filler metal.
Dip coat – In the solid mould technique of investment casting, it is an extremely fine ceramic precoat applied as a slurry directly to the surface of the pattern to reproduce maximum surface smoothness. This coating is surrounded by coarser, less expensive, and more permeable investment to form the mould. In the shell mould technique of investment casting, it is an extremely fine ceramic coating called the first coat, applied as a slurry directly to the surface of the pattern for reproducing maximum surface smoothness. The first coat is followed by other dip coats of different viscosity and normally containing different grading of ceramic particles. After each dip, coarser stucco material (Portland cement, sand and water + lime) is applied to the still-wet coating. A build-up of several coats forms an investment shell mould.
Dip coating – It consists of applying a plastic coating by dipping the article to be coated into a tank of melted resin or plastisol, then chilling the adhering metal.
Diphase cleaning – It is removing soil by an emulsion which produces two phases in the cleaning tank namely a solvent phase and an aqueous phase. Cleaning is done by both solvent action and emulsification.
Dip lance – It is a lance which is dipped in hot metal for the injection of the desulphurization reagents. Dip-lance method can reliably reduce the sulphur content of the hot metal to figures as low as 0.001 %. It allows the use of several desulphurization reagents, such as lime, calcium carbide and magnesium, which remove the sulphur from the hot metal by chemical reaction and convert it to the slag.
Dip needle – It is a compass with the needle mounted so as to swing in a vertical plane, used for prospecting to determine the magnetic attraction of rocks.
Dipolar bond – It is a type of covalent bond formed by the coordination of two or more electrically neutral moieties, the combination of which results in a charge-separated molecule or coordination complex, in which two electrons deriving from the same atom are shared between the donor atom and an acceptor atom, creating an internal two-center molecular dipole moment.
Dipole – It is the electric or magnetic separation of electric charge into a pair of charges of equal magnitude but opposite sign, one positively charged and one negatively charged, separated by some typically small distance.
Dipping – In porcelain enameling, it is the process of coating a metal shape by immersion in slip, removal, and draining. In dry process enameling, it is the method of coating by immersing the heated metal shape for a short time in powdered frit.
Dip plating – It is depositing a metallic coating on a metal immersed in a liquid solution, without the aid of an external electric current.
Dip soldering – It is a soldering process in which the heat needed is furnished by a molten metal bath which provides the solder filler metal.
Dip tube – Extending the blow-down valve on large gate valves needs a tube which is located inside of the valve. This tube is called the dip tube and extends through the bonnet to the bottom of the body cavity.
Direct-bonded basic brick – It is a fired refractory in which the grains are joined predominantly by a solid state diffusion mechanism.
Direct chill casting – It is a continuous method of making ingots for rolling or extrusion by pouring the metal into a short mould. The base of the mould is a platform which is gradually lowered while the metal solidifies, the frozen shell of metal acting as a retainer for the liquid metal below the wall of the mould. The ingot is normally cooled by the impingement of water directly on the mould or on the walls of the solid metal as it is lowered. The length of the ingot is limited by the depth to which the platform can be lowered. Hence, it is frequently being called semi-continuous casting.
Direct current (DC) – It is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current can flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams.
Direct current cleaning – It is electrolytic cleaning in which the work is the cathode.
Direct current electric arc furnace – It is an electric arc furnace in which a single electrode positioned at the centre of the furnace roof is the cathode of the system. Current passes from the electrode through the charge or bath to a cathode located at the bottom of the furnace. Current from the bottom of the furnace then passes through the furnace refractories to a copper base plate to outside cables. It is used in the production of ferroalloys, carbon and alloy steels, and stainless steels.
Direct current electrode negative (DCEN) – It is the arrangement of direct current arc welding leads in which the work is the positive pole and the electrode is the negative pole of the welding arc. It is also referred to as straight polarity.
Direct current electrode positive (DCEP) – It is the arrangement of direct current arc welding leads in which the work is the negative pole and the electrode is the positive pole of the welding arc. It is also referred to as reverse polarity.
Direct current (DC) resistance – It is the ohmic resistance of a conductor which is directly dependent on the conductor material, the conductor gauge and the length of the conductor. A precise measurement of the direct current resistance is possible with a micro-ohmmeter.
Direct current reverse polarity (DCRP) – In arc welding, it occurs when electrode is connected with positive terminal of the welding power source (direct current type) and base metals are connected with the negative terminal.
Direct current straight polarity (DCSP) – In arc welding, it occurs when the plates are positive and the electrode is negative, causing the electrons to go from the electrode tip to the base plates.
Direct extrusion – It is the extrusion process in which a preheated billet is placed in the container and is pushed by the ram through the stationary die to form the extruded section.
Direct fire – It is a method of maturing porcelain enamel so that the products of combustion come in contact with the ware.
Direct-fired tunnel-type furnace – It is a continuous-type furnace where the work is conveyed through a tunnel-type heating zone, and the parts are hung on hooks or fixtures to minimize distortion.
Direct (forward) extrusion – The conversion of an ingot or billet into lengths of uniform cross section by forcing metal to flow plastically through a die orifice. In forward (direct) extrusion, the die and ram are at opposite ends of the extrusion stock, and the product and ram travel in the same direction. Also, there is relative motion between the extrusion stock and the die.
Direct injection burner – It is a burner used in flame emission and atomic absorption spectroscopy in which the fuel and oxidizing gases emerge from separate ports and are mixed in the flame itself. One of the gases, normally the oxidant, is used for nebulizing the sample at the tip of the burner.
Direct iron ore smelting (DIOS) process – It is a smelting reduction process for the production of hot metal. It is a two-stage process. It uses non-coking coal in a powder or granular form to smelt iron ore fines into liquid iron and hence, there is no necessity of a coke ovens plant and a sintering plant. The ore fines are pre-reduced in a fluidized bed furnace and are charged in the smelting reduction furnace along with non-coking coal and fluxes. Oxygen is blown into the smelting reduction furnace. The two stages of the DIOS process consist of (i) pre reduction of iron ore in preliminary reduction furnace (PRF), and (ii) the final reduction and melting in the smelting reduction furnace (SRF). The pre reduction of the ore is carried out in two steps utilizing the exhaust gas from the SRF. Each of the steps uses a fluidized bed reactor which is designed as a vertical furnace.
Directional conclusion – It is a conclusion in a two-tailed test which uses the nature of the sample results to suggest where the true parameter lies in relation to the null hypothesized value.
Directional control valves – These valves determine the path through which a fluid traverses a given circuit. For example, they establish the direction of motion of a hydraulic cylinder or motor. This control of the fluid path is accomplished primarily by check valves, shuttle valves, and two-way, three-way, and four-way directional control valves. Directional control valves can be classified in four ways namely (i) type of construction (poppet valves, and spool), (ii) number of ports (two-way valves, three-way valves, and four-way valves), (iii) number of switching position (two position, and three position), and (iv) actuating mechanism (manual actuation. mechanical actuation, solenoid actuation, hydraulic actuation, pneumatic actuation, and indirect actuation).
Directional drilling – It is a method of drilling involving the use of stabilizers and wedges to direct the orientation of the hole.
Directionally solidified (DS) eutectic composite – It is a metal-matrix composite material produced by directional solidification of the eutectic composition of an alloy.
Directional property – It is the property whose magnitude varies depending on the relation of the test axis to a specific direction within the metal. The variation results from preferred orientation or from fibering of constituents or inclusions.
Directional solidification – It is the controlled solidification of molten metal in a casting so as to provide feed metal to the solidifying front of the casting. Normally this results in the metal solidifying in a preferred direction. In the limit, the solidification can be controlled to grow as a single grain (single crystal casting).
Directly affected people or areas – These are the people or areas whose interests are affected or potentially affected by certain organizational activities.
Direct measuring instrument – It converts the energy of the measurement directly into energy which actuates the instruments and the value of the unknown quantity is measured or displayed or recorded directly. Examples of this category of instruments are ammeters, voltmeters, watt-meters and energy meters.
Direct numerical control computers – These computers distribute instructional data to, and collect data from, a number of machines or machining cells. These control computers occupy a location which is typically remote from the machines under their control. Direct numerical control computer software is developed not only to control individual pieces of production equipment but also to serve as part of a management information system in the manufacturing sector of an organization.
Direct on line starter – It is a kind of motor starter which does not reduce the voltage at the motor terminals.
Direct quenching – It means quenching carburized parts directly from the carburizing operation. It is also used for quenching pearlitic malleable parts directly from the malleabilizing operation.
Direct radiation – It is the radiation received directly from a source such as a nuclear power plant, rather than indirectly as a result of radioactive discharges.
Direct reduced iron – Direct reduced iron (DRI) is produced by the reduction of iron ore (in the form of lumps or pellets) by either non-coking coal or a reducing gas produced by reforming of natural gas. The reducing gas can also be produced by the gasification of coal. The reduction process is conducted at high temperature but substantially below the melting point of iron. Since the reduction reaction takes place in solid state, the lump or pellet retain their original shape, but are considerably lighter due to the removal of the oxygen from the ore. Hence the produced direct reduced iron has a highly porous structure. This porous structure gives direct reduced iron an appearance of a sponge and because of it, direct reduced iron is also known as sponge iron.
Direct shipping ore (DSO) – It is the high-grade iron ore after dry or wet sizing at the ore mine. This ore contains higher than 62 % of Fe. This ore is normally known as natural ore or direct shipping ore. This ore can be directly used in the production of iron and steel.
Direct torque control – It is method of estimating motor torque as part of a variable speed motor drive.
Dirt – It is the foreign debris from rolling or post-rolling operations imbedded in or under the coating.
Dirt content – It is a measure of the size and concentration of foreign particles present in a lubricant. Dirt content is normally reported as the number of particles per cubic centimeter, for specified particle Sizes.
Disaster – It is defined as an event or series of events, which gives rise to causalities and damage or loss of properties, infrastructures, environment, essential services or means of livelihood on such a scale which is beyond the normal capacity of the affected community to cope with. Disaster is also described as a ‘catastrophic situation in which the normal pattern of life or eco system has been disrupted and extra ordinary emergency interventions are required to save and preserve lives and / or environment’.
Disbond – It is an area within a bonded interface between two adherends in which an adhesion failure or separation has occurred. It is also an area of separation between two laminae in the finished laminate (in this case, the term delamination is normally preferred).
Disbondment – It is the destruction of adhesion between a coating and the surface coated.
Disc – It is also spelled as disk. The disc is that part of the valve which allows, throttles, or stops the fluid flow, depending on its position. For a valve having a bonnet, the disc is the third primary principal pressure boundary. The disc provides the capability for permitting and prohibiting fluid flow. With the disc closed, full system pressure is applied across the disc if the outlet side is depressurized. For this reason, the disc is a pressure-retaining part. In the case of a plug or a ball valve, the disc is called plug or a ball. The disc is the third most important primary pressure boundary. With the valve closed, full system pressure is applied across the disc, and for this reason, the disc is a pressure related component. Discs are normally forged, and in some designs, hard surfaced to provide good wear properties.
Disc grinding – It consists of grinding with the flat side of an abrasive disk or segmented wheel. It is also called vertical-spindle surface grinding.
Discharge – It is the release of gaseous or liquid materials to the environment.
Discharge pressure – It is the total pressure on the outlet side of a pump measured near the outlet port. It is sometimes called the back pressure or backing pressure. It is also known as outlet pressure, exhaust pressure, or fore-pressure.
Disc machine – In tribology, it a testing machine for rolling or rolling / sliding contact in which two disc-shaped rollers, with parallel axes of rotation, make tangential contact on their circumferences as they move relative to one another. One or both discs can be crowned on the rolling-contact surface.
Discontinuity – It is an interruption in the normal physical structure or configuration of a part, such as cracks, laps, seams, inclusions, or porosity. A discontinuity may or may not affect the utility of the part. It is also an interruption of the typical structure of a weldment, such as a lack of homogeneity in the mechanical, metallurgical, or physical characteristics of the material or weldment. A discontinuity is not necessarily a defect.
Discontinuous fibre-reinforced composite – It is a ceramic-matrix composite material reinforced by chopped fibres.
Discontinuous precipitation – It is the precipitation from a supersaturated solid solution in which the precipitate particles grow by short-range diffusion, accompanied by recrystallization of the matrix in the region of precipitation. Discontinuous precipitates grow into the matrix from nuclei near grain boundaries, forming cells of alternate lamellae of precipitate and depleted (and recrystallized) matrix. It is frequently being referred to as cellular or nodular precipitation.
Discontinuous yielding – It is the non-uniform plastic flow of a metal showing a yield point in which the plastic deformation is inhomogeneously distributed along the gage length. Under some circumstances, it can occur in metals not showing a distinct yield point, either at the onset of or during plastic flow.
Discounted cash flow – Discounted cash flow analysis is a method of valuing a project, organization, or asset using the concepts of the time value of money. All future cash flows are estimated and discounted by using cost of capital to give their present values. The sum of all future cash flows, both incoming and outgoing, is the net present value (NPV), which is taken as the value or price of the cash flows in question. Using discounted cash flow analysis to compute the net present value takes as input cash flows and a discount rate and gives as output a present value. The opposite process takes cash flows and a price (present value) as inputs, and provides as output the discount rate. The most widely used method of discounting is exponential discounting, which values future cash flows as ‘how much money would have to be invested currently, at a given rate of return, to yield the cash flow in future’.
Discrete cosine transform – It is a mathematical technique for representing a sampled signal as a sum of cosine waves of different frequencies.
Discrete effort – It is the work directly associated with components of a work breakdown structure. It is directly measurable. Discrete effort is one of three types of activities used to measure work performance as part of earned value management.
Discrete Fourier transform – It is a mathematical technique for representing a sampled signal as a sum of sine and cosine waves of different frequencies.
Discrete-time signal – It is a signal represented as a time series of samples taken at regular intervals.
Discrete variable – A set of data is discrete if the values belonging to it are distinct, i.e., they can be counted. Examples are the number of children in a family, the number of rainy days in the month, or the length (in days) of the longest dry spell in the growing season. A discrete variable is measured on the nominal or ordinal scale, and can assume a finite number of values within an interval or range. Discrete variables are less informative than are continuous variables.
Discretionary dependency – It is the preferred way to sequence activities when there is no logical limitation on how they are to be ordered.
Disc spring – It is a spring washer with a conical shape. This shape gives the spring washer its flexible effect. Disc springs are also called Belleville-spring washers and conical spring washers. The properties of the disc spring make it unique in applications where space is limited – but where high force is wanted.
Dishing – It is forming of a shallow concave surface, the area which being large compared to the depth. These are (i) an edge dislocation which corresponds to the row of mismatched atoms along the edge formed by an extra, partial plane of atoms within the body of a crystal, and (ii) a screw dislocation which corresponds to the axis of a spiral structure in a crystal, characterized by a distortion that joins normally parallel planes together to form a continuous helical ramp (with a pitch of one interplanar distance) winding about the dislocation. Most prevalent is the so-called mixed dislocation, which is an combination of an edge dislocation and a screw dislocation.
Disinfection – It is a process which has as its objective destroying or inactivating pathogenic micro-organisms in water.
Dislocation – It is a linear imperfection in a crystalline array of atoms. The two basic types recognized are (i) an edge dislocation which corresponds to the row of mismatched atoms along the edge formed by an extra, partial plane of atoms within the body of a crystal, and (ii) a screw dislocation which corresponds to the axis of a spiral structure in a crystal and is characterized by a distortion joining normally parallel lines together to form a continuous helical ramp (with a pitch of one inter-planar distance) winding about the dislocation. A mixed dislocation, which is any combination of a screw dislocation and an edge dislocation, is prevalent.
Dislocation density – It is the total length of dislocation lines per unit volume, or the number of dislocation lines that cut through a unit cross-sectional area.
Dislocation etching – It is the etching of exit points of dislocations on a surface. It depends on the strain field ranging over a distance of several atoms. Crystal figures (etch pits) are formed at exit points. For example, etch pits for cubic materials are cube faces.
Disordered structure – It is the crystal structure of a solid solution in which the atoms of different elements are randomly distributed relative to the available lattice sites.
Disordering – It means forming a lattice arrangement in which the solute and solvent atoms of a solid solution occupy lattice sites at random.
Dispersal – It is the spread of a radioactive discharge in the environment.
Dispersant additive – · In lubrication technology, it is an additive capable of dispersing cold oil sludge.
Dispersant oil – It is a heavy-duty oil containing a dispersant additive.
Dispersing agent – It is a substance which increases the stability of a suspension of particles in a liquid medium by deflocculation of the primary particles.
Dispersion – It means breaking big particles into small particles and suspend them in water so that they can be removed by rinsing. Alkaline silicates and phosphates are beneficial for dispersion. In data analysis, dispersion is the way of spreading the variables around the central tendency. Common tools are range, variance, and the square root of the variance which is known as standard deviation. In statistical analysis, dispersion is the degree of scatter or concentration of observations around its centre or middle. It is normally measured as a deviation around some central value such as the mean, standard, or absolute deviation, or by an order statistic such as deciles, quintiles, and quartiles.
Dispersion hardening – It is strengthening of a metal or alloy by incorporating chemically stable sub-micron size particles of a non-metallic phase which impede dislocation movement at high temperature.
Dispersion of a distribution – It is the degree of spread shown by a variable’s values, typically assessed with the standard deviation.
Dispersion-strengthened material – It is a metallic material which contains a fine dispersion of non-metallic phase(s), such as alumina, magnesia, silica, cadmium oxide, thorium di-oxide, yttrium oxide, zirconium oxide singly or in combination, to increase the hot strength of the metallic matrix. Examples include dispersion-strengthened copper (alumina) used for welding electrodes, silver (cadmium oxide) used for electrical contacts, and nickel-chromium (yttrium oxide) superalloys used for gas turbine components.
Dispersion strengthening – It is the strengthening of a metal or alloy by incorporating chemically stable sub-micron size particles of a non-metallic phase which slow down dislocation movement at high temperature.
Dispersoid – It is finely divided particles of relatively insoluble constituents visible in the micro-structure of certain metallic alloys.
Displacement – It is the distance that a chosen measurement point on a cracked sample displaces normal to the crack plane as the crack grows. In case of fluid mechanics, displacement occurs when an object is largely immersed in a fluid, pushing it out of the way and taking its place. The volume of the fluid displaced can then be measured, and from this, the volume of the immersed object can be deduced, The volume of the immersed object s exactly equal to the volume of the displaced fluid. A displacement is also a vector whose length is the shortest distance from the initial to the final position of a point undergoing motion. It quantifies both the distance and direction of the net or total motion along a straight line from the initial position to the final position of the point trajectory.
Displacement angle – In filament winding, it is the advancement distance of the winding ribbon on the equator after one complete circuit.
Displacement compression – It consists of reduction of the air volume. Positive displacement machines use reciprocating piston, rotary screw, or vane types to produce air compression. Screw, reciprocating, and vane compressors are positive displacement machines.
Displacement current – It is the effect of a time-varying electric field, which induces a magnetic field just as the motion of electrical charges does.
Display data channel – It is a collection of protocols for digital communication between a computer display and a graphics adapter that enable the display to communicate its supported display modes to the adapter and that enable the computer host to adjust monitor parameters, such as brightness and contrast.
Display device – It is a device which displays data from an information system.
Disposability assessment – It is an advisory process) to provide advice on whether a proposed waste package is suitable for geological disposal.
Disposal – In the context of solid waste, disposal is the emplacement of waste in a suitable facility without intent to retrieve it at a later date. Retrieval can be possible but, if intended, the appropriate term is storage. Disposal can also refer to the release of airborne or liquid waste to the environment (i.e., emissions and discharges).
Disposal facility – it is also known as repository. It is a long-term radioactive waste storage facility.
Disposal well – It is a deep well which is used for the disposal of liquid wastes.
Dissection – In case of a product, it is the systematic process for taking apart and analyzing the product and all its parts. It is an important tool in engineering design. Product dissection helps in understanding how products work, and can also be a source of inspiration when designing a new product. Mechanical dissection is the process of disassembling, inspecting, and reassembling a mechanical device to discover how it works.
Disseminated – It is fine grained material which is scattered quite evenly throughout the rock.
Disseminated ore – It is the ore carrying small particles of valuable minerals spread more or less uniformly through the host rock.
Dissimilar metals – These are two or more different metals in contact. Due to varying surface conductivity, one or more metals can experience accelerated corrosion. Since zinc is high in the galvanic series, it preferentially corrodes to protect most dissimilar metals.
Dissipation – It is the loss of energy in a system.
Dissipation factor, electrical – It is the ratio of the power loss in a dielectric material to the total power transmitted through it. Hence, it is the imperfection of the dielectric. It is equal to the tangent of the loss angle.
Dissociation – It is as applied to heterogeneous equilibria, the transformation of one phase into two or more new phases of different composition.
Dissociation pressure – At a designated temperature, it is the pressure at which a phase transforms into two or more new phases of different composition.
Dissolution – It is the process of dissolving, splitting, or separating into component parts.
Dissolution etching – it is the development of micro-structure by surface removal.
Dissolved oxygen – It is a measurement of the quantity of oxygen available to aquatic organisms. Temperature, salinity, organic matter, bio-chemical oxygen demand, and chemical oxygen demand affect dissolved oxygen solubility in water.
Distillation – It is the process of separating the component substances of a liquid mixture by exploiting differences in the relative volatility of the mixture’s components through selective boiling and subsequent condensation. The apparatus used to distill a substance is called a still, and the re-condensed substance yielded by the process is called the distillate.
Distillation column – It is a critical piece of equipment which is used mainly in the chemical processing to separate mixtures into their parts or fractions. It is used in the distillation of liquid mixtures to separate the mixture into its component parts, or fractions, based on their differences in volatility.
Distilled water – It is that water which is produced by distillation process that is first evaporating the treated water and then condensing the water vapours. Distilled water is the purest form of water and normally used in laboratories for the wet chemical analysis of the materials.
Distortion – It is a deviation from an original size, shape, or contour which occurs because of the application of stress or the release of residual stress. Some steel sections distort during galvanizing due to differential heating and cooling or inbuilt welding stresses. Distortion occurs when the application of heat during the galvanizing process releases stress from the steel induced in the fabrication process or during the steel making process. Distortion is of concern when galvanizing asymmetric structural shapes and / or fabrications.
Distributed control system – It is a computerized control system for a process or plant normally with several control loops, in which autonomous controllers are distributed throughout the system, but there is no central operator supervisory control. Distributed Control System automates industrial equipment used in continuous and batch processes, while reducing the risk to people and the environment.
Distributed impact test – In impingement erosion testing, it is an apparatus or method which produces a spatial distribution of impacts by liquid or solid bodies over an exposed surface of a sample. Examples of such tests are those employing liquid sprays or simulated rain-fields. If the impacts are distributed uniformly over the surface, the term uniformly distributed impact test can be used.
Distributed numerical control – It combines the centralized data base feature of direct numerical control with the distributed computer power available in computer numerical control machine tools. This creates a communications network for the shop floor which eliminates paper tape and provides an automated part program library, status reporting on machine tool operation, and the capability to run part programs of practically infinite length.
Distribution – The set of frequencies or probabilities assigned to different outcomes of a particular event or trial.
Distribution board – It is a piece of electrical switchgear which distributes electric power to multiple branch circuits.
Distribution function – It is the function, denoted F (x), which gives the cumulative frequency or probability that random variable ‘X’ takes on a value less than or equal to ‘x’.
Distribution (or probability distribution) of a variable – It is the collection of all values of a variable along with their associated probabilities of being observed.
Distribution of data – It is a measure to determine the quality characteristics. When the distribution of data is symmetric then there are same numbers of observations below and above the mean. This is what is normally found when only normal variation is present in the data. When a disproportionate number of observations are either above or below the mean, then the data has a skewed distribution.
Distribution transformer – It is a power transformer, normally used to change the utility distribution voltage to a lower voltage for use on the user premises.
Disturbed metal – It is the cold-worked metal layer formed at a polished surface during the process of mechanical grinding and polishing.
Divariant equilibrium – When both the pressure and temperature in a unary system are freely and arbitrarily selected, the situation corresponds to having two degrees of freedom, and the phase rule says that only one phase can exist in stable equilibrium. This situation is known as divariant equilibrium.
Divergent thinking – It is a thought process in which the mind moves in several different directions, combining different bits of information into new patterns until several different solution concepts evolve.
Diversity – It consists of two separate and independent systems that perform the same task so as to reduce the chances of both failing at the same time.
Divided cell – It is a cell containing a diaphragm or other means for physically separating the anolyte from the catholyte.
Divorced eutectic – It is a metallographic appearance in which the two constituents of a eutectic structure appear as massive phases rather than the finely divided mixture characteristic of normal eutectics. Frequently, one of the constituents of the eutectics is continuous and indistinguishable from an accompanying pro-eutectic constituent.
DN value – It is the product of bearing bore diameter in millimeters and speed in revolutions per minute.
Doctor blade or bar – It is a straight piece of material used to spread resin, as in application of a thin film of resin for use in hot melt prepregging or for use as an adhesive film. It is also called paste metering blade.
Document – It is a written, drawn, presented, or memorialized representation of thought. It is an official piece of writing which gives information, proof or evidence. It is also a computer file which contains text that has a name which identifies it.
Documentation – It enables communication of intent and consistency of action. Its use contributes to (i) achievement of conformity to the process or system requirements and improvement, (ii) provision of appropriate training, (iii) repeatability and traceability, (iv) provision of objective evidence, and (v) evaluation of the effectiveness and continuing suitability of a process or a system.
Document control procedure – It establishes methodology for the issuance, maintenance, revision, and distribution of the documents. It also ensures that a person does not refer to any unauthorized document which is not approved.
Dolly – In filament winding, it is the planar reinforcement applied to a local area between windings to provide extra strength in an area where a cut-out is to be made, e.g., port openings. It is normally placed at the knuckle joints of cylinder to dome.
Doloma (MgO.CaO) – It is being widely used in the manufacture of refractory products because of its favourable properties, such as the ability to refine steel melt, high refractoriness, high corrosion resistance in alkaline environments, as well as its favourable hot strength.
Doloma-carbon refractory – It is a refractory brick manufactured predominantly from a mixture of refractory-grade doloma and 2 % to 20 % carbonaceous materials, with resin, tar, pitch, or a combination of these materials as the bonding agent. The refractory-grade doloma can be either dead-burned dolomite, synthetic doloma, fused doloma, or combinations of these materials, and the carbonaceous material can be either graphite, carbon black, or a combination of these materials.
Doloma, fused— It is refractory-grade material consisting predominantly of lime and magnesia which has solidified from a fused or molten state.
Doloma-magnesia refractory – It is a refractory, which can be burned or unburned, manufactured predominantly of a mixture of refractory-grade doloma and refractory-grade magnesia in which the refractory-grade doloma predominates.
Doloma refractory – It is a refractory manufactured predominantly of dead-burned dolomite, synthetic doloma, fused doloma, or combinations of these materials.
Doloma, refractory-grade – It is a dead-burned or fused refractory material consisting predominately of lime and magnesia. The three principal types are dolomite, dead-burned, doloma synthetic, and doloma fused.
Doloma, synthetic – It is a refractory-grade doloma which has been derived from blending magnesia and lime or dolomite and dead-burning to form a dense, hydration-resistant material, and having a MgO content of 30 % to 80 % and maximum CaO content of 70 %.
Dolomite – Dolomite is a common rock-forming mineral. It is a calcium magnesium carbonate. It is the primary component of the sedimentary rock known as dolostone and the metamorphic rock known as dolomitic marble. Dolomite is a complex mineral with a composition of CaCO3.MgCO3. It is used as fluxing material as well as adjusting the MgO content of the slag.
Dolomite brick – A refractory brick which is manufactured substantially or entirely of dead-burned dolomite.
Dolomite, burnt – When dolomite is heated at a high temperature then it loses its reactivity and the product is known as burnt dolomite. Burnt dolomite is a refractory material and is used in the manufacture of basic refractories.
Dolomite, calcined -It is the calcined dolomite (CaO.MgO) which is produced on heating of dolomite (CaCO3.MgCO3). Calcined dolomite is also known as dolime or doloma.
Dolomite, dead-burned – It is a refractory-grade doloma which is obtained by burning dolomite above 1,450 deg C long enough to form a dense hydration-resistant material composed mainly of lime and magnesia.
Dolomite refractories – These refractories are composed of 50 % MgO to 80 % MgO and are produced with sintered dolomite. Because of these refractories showing a good chemical resistance against basic environments (as slag and fluxes) at high-temperature, good thermal shock resistance, low vapour pressure, thermodynamic stability in the presence of carbon, and a suitable abrasion resistance, magnesia-doloma refractories are widely used in ferrous, non-ferrous and cement industries. However, in spite of these advantageous properties, the application of these refractory bricks has not been popular because of their tendency to hydration when exposed to the atmosphere.
Dolomitic lime – It is the lime having some percentage of MgO (normally 2 % to 4 %).
Dolomitic limestone – It is that limestone which contains some dolomite.
Domain, magnetic – It is a substructure in a ferromagnetic material within which all the elementary magnets (electron spins) are held aligned in one direction by inter-atomic forces. If isolated, a domain is a saturated permanent magnet.
Dome – In filament winding, it is the portion of a cylindrical container which forms the spherical or elliptical shell ends of the container. Dome is also the roof of a furnace which is roughly hemispherical in shape. It is also the steam chamber of a boiler.
Dome, hot blast stove – The dome area of the hot blast stove is divided into a working layer, a filling layer and a heat insulating layer. Maintenance of the structural stability of the dome at the high temperatures is important. The dome evenly distributes high-temperature flue gas into the regenerator during combustion. The temperature of the dome area is very high. It is around 1,400 deg C in conventional stoves and around 1,550 deg C in high temperature modern stoves. The refractories used in the working layer are mostly silica brick, mullite brick, andalusite brick, low creep high alumina brick. In the outside of the working layer insulation refractory bricks are used.
Domestic water – It is the water which is used for washing and in wash rooms. In industrial plants normally drinking water is used as domestic water.
Dominic method – It is a qualitative method for evaluating and choosing between alternative design concepts or materials. The method uses an evaluation table in which the evaluation criteria are grouped according to priority (high, moderate, low), and the alternative solutions are ranked as excellent, good, fair, poor, or unacceptable.
Donnan exclusion – It is the mechanism by which an ion exchange resin can be made to act like a semi-permeable membrane between an interstitial liquid and a liquid occluded inside the resin particles. Highly ionized molecules are excluded from the resin particles by electrostatic forces. Weakly ionized or non-ionized molecules can pass through the membrane.
Doppler effect – It is the change in the observed frequency of an acoustic or electro-magnetic wave because of the relative motion of source and observer.
Doppler shift – It is the quantity of change in the observed frequency of a wave because of the Doppler effect. It is normally expressed in hertz.
Dor bar – It is the final saleable product of a gold mine. It is normally consisting of gold and silver.
Dore – It is unrefined gold, normally in bar form and consisting mainly of gold with smaller quantities of other base metals, which is to be further refined to high purity gold bullion.
Dose – It is the measurement characterizing the exposure of individuals subjected to radiation. The term dose is frequently mistakenly used instead of dose equivalent. The absorbed dose is the quantity of energy absorbed by matter (living or inert) exposed to radiation. It is expressed in Grays (Gy). Dose equivalent in living organisms is an absorbed dose which has different effect depending on the type of radiation (alpha, beta and gamma). For taking these differences into account, a dose-multiplying factor is used to produce a ‘dose equivalent’. Effective dose is the sum of weighted dose equivalents deposited on various tissues and organs by internal and external irradiation. The unit of measurement for effective dose is the Sievert (Sv). Lethal dose is the fatal dose of nuclear or chemical origin. Maximum permissible dose is the dose which is not to be exceeded for a given period of time.
Dose limitation – It is the process of limiting radiation doses to individuals. It is also known as the third radiation protection principle.
Dose rate – The dose rate is the quotient of dose and time. For example, rem (roentgen equivalent man) per hour or Sieverts per hour.
Dosimeter – It is the instrument for measuring absorbed dose.
Dosimetry – It is the theory and application of the principles and techniques involved in the measurement and recording of ionizing radiation doses. What is calculated is the absorbed dose in matter and tissue resulting from the exposure to ionizing radiation.
Dot map – It is an intensity map (normally corresponding to an image) in which the intensity in any area is proportional to the concentration of a specific element in that area.
Dot plot – A dot-plot is an alternative to a boxplot where each value is recorded as a dot. It is used when there are only few data values. The dots can be jittered, so each value is made visible. They can alternatively be stacked, to produce a simple histogram.
Double acting actuator – It is an actuator which requires power in both operating directions i.e., no spring.
Double-acting hammer – It is a forging hammer in which the ram is raised by admitting steam or air into a cylinder below the piston, and the blow intensified by admitting steam or air above the piston on the downward stroke. Double acting hammers are similar to gravity hammers in that a lifting cylinder raises the moving tup, but power is also applied to the downward-moving tup to increase the energy capacity. Energy ratings for similar tup weights are considerably more than for gravity hammers, and the die closing speeds are higher also. Power comes from double-acting steam, compressed air, or hydraulic cylinders.
Double-action die – It is a die designed to perform more than one operation in a single stroke of the press.
Double-action forming – It consists of forming or drawing in which more than one action is achieved in a single stroke of the press.
Double-action mechanical press – It is a press having two independent parallel movements by means of two slides, one moving within the other. The inner slide or plunger is normally operated by a crankshaft; the outer or blank-holder slide, which dwells during the drawing operation, is normally operated by a toggle mechanism or by cams.
Double aging – It consists of employment of two different aging treatments for controlling the type of precipitate formed from a super-saturated matrix in order to get the desired properties. The first aging treatment, sometimes referred to as intermediate or stabilizing, is normally carried out at higher temperature than the second.
Double basket hitch – It consists of two single basket hitches placed under the load. On smooth surfaces, the legs tend to draw together as the load is lifted. For countering this, the hitch is braced against a change in contour, or other reliable means, to prevent the slings from slipping. It is also necessary to keep the legs far enough apart to provide balance, but not so far apart that they create angles of less than 60-degree with the horizontal.
Double-beat valve – It is also called drop valve or equilibrium valve. It is a type of poppet valve arranged to allow it to be opened against a high pressure with a minimum of force.
Double bevel groove weld – It is a type of groove weld.
Double block and bleed valve – It is a valve with two seating surfaces that in the closed position provides a seal against pressure from both ends of the valve with a mean of venting / bleeding the cavity between the seating surfaces.
Double bond – It is a bond involving the covalent sharing of two pairs of electrons.
Double dipping – It is the process of dipping steel, which is too large in one dimension to completely fit into the galvanizing pot, more than once in cleaning solutions and molten zinc metal in order to produce a coating which covers the entire surface of the steel. Fabricated items longer or wider than the galvanizing bath in one dimension can be galvanized by double dipping, where one side or end of the fabrication is galvanized first. The fabrication is then rotated or turned over allowing the second section to be galvanized.
Double etching – In metallography, is consists of the use of two etching solutions in sequence. The second etchant emphasizes a particular micro-structural feature.
Double flare bevel groove weld – It is a weld in grooves formed by a member with a curved surface in contact with a planar member.
Double flare V-groove weld – It is a weld in grooves formed by two members with curved surfaces.
Double helical gears – In these gears, thrust loading is eliminated by using two pairs of gears with tooth angles opposed to each other. In this way, the side thrust from one gear cancels the thrust from the other gear. These opposed gears are normally manufactured with a space between the opposing sets of teeth.
Double inclined shaft kilns – This type of kiln (Fig 6) can produce a reactive low carbonate product. It is essentially rectangular in cross-section but incorporates two inclined sections in the calcining zone. Opposite each inclined section, offset arches create spaces into which fuel and preheated combustion air are fired through the combustion chambers. Cooling air is drawn into the base of the kiln where it is preheated, withdrawn and re-injected through the combustion chambers. The circuitous paths for both the gases and the burden, coupled with firing from both sides, ensure an efficient distribution of heat. A range of solid, liquid and gaseous fuels can be used, although they are to be selected with care to avoid excessive build-ups caused by fuel ash and calcium sulphate deposits.
Double-isolation and bleed valve (DIB) – It is a single valve with two seating surfaces, each of which in the closed position provides a seal against pressure from a single source, with a means of venting / bleeding the cavity between the seating surfaces. This feature can be provided in one direction or in both directions.
Double J-groove weld – It is a type of groove weld.
Double layer – It is the interface between an electrode or a suspended particle and an electrolyte created by charge-charge interaction leading to an alignment of oppositely charged ions at the surface of the electrode or particle. The simplest model is represented by a parallel plate condenser.
Double piston effect (DPE) – It is the sealing principle of ball valves whereby line pressure is used on both the upstream and downstream floating seats to cause a dead-tight seal simultaneously on both sides of the ball. With the double piston effect seat configuration when the upstream seat leaks, the pressure entering into the body cavity acts on the downstream seat, which being of the PPE design is then pushed against the ball and the valve seals in both directions.
Double pour roll – These are also called composite or duplex rolls. In order to get both high resistances to wear and high strength, roll makers have developed a roll making technology wherein the outer shell is made hard and the inner core tough by double pouring of metal of different compositions. The shell composition is maintained to give very high wear resistance properties and the core composition to give more strength. These are very costly type of rolls.
Doubler – It is the localized areas of extra layers of reinforcement, normally to provide stiffness or strength for fastening or other abrupt load transfer.
Double-row roller conveyor – This design is used to convey wide and heavy loads. In place of one long and proportionately large diameter roller, two smaller diameter rollers with lengths less than half of the larger roller are used. For the support the inner ends of the pair of rollers, additional support frame is used. This design has lower cost than the same width conventional single row conveyor with longer and larger rollers.
Double salt – It is a salt which is composed of more than one different cation or anion, or which upon hydrolysis forms two different cations and anions. It is also a salt which is a molecular combination of two other salts.
Double shear notch – It is an abrupt deviation from straight on a sheared edge. This offset can occur if the flat sheet or plate product is longer than the blade for the final shearing operation.
Double-shear test – It is a shear test having two stationary, shear blades and one moving one and which uses solid round bars as test samples.
Double square groove weld – It is a type of groove weld.
Double tempering – It is a treatment in which a quench-hardened ferrous metal is subjected to two complete tempering cycles, normally at substantially the same temperature, for the purpose of ensuring completion of the tempering reaction and promoting stability of the resulting micro-structure.
Double U-groove weld – It is a type of groove weld.
Double V-groove weld – It is a type of groove weld.
Double-welded joint – In arc and oxy-fuel gas welding, it is a fusion welded joint which is welded from both sides.
Double wrap basket hitch – It is a basket hitch wrapped completely around the load and compressing it rather than merely supporting it, as it is done in the ordinary basket hitch. The double wrap basket hitch can be used in pairs like the double basket hitch. This method is excellent for handling loose material, pipe, rod or smooth cylindrical loads because the sling is in full 360-degree contact with the load and tends to draw it together. On smooth surfaces, this type of hitch is a better choice.
Double wrap choker hitch – It is formed by wrapping the sling completely around the load and hooking it into the vertical part of the sling. This hitch is in full 360 degrees contact with the load and tends to draw it tightly together. It can be used either singly on short, easily balanced loads or in pairs on longer loads. The loosely-bundled loads are usually lifted with this hitch.
Dowel – It is a wooden or metal pin of different types used in the parting surface of parted patterns and core boxes. In die casting dies, it is the metal pins for ensuring correct registry of cover and ejector halves.
Dowel pin – It is a pin fitted onto the body of quarter turn valves. This pin aligns the adapter plate and restrains the plate and gear operator from moving while the valve is being operated.
Down comer – It is the pipe which carries BF gas from uptake to the dust catcher.
Down-gate – It is the mould channel which connects the pouring basin with the runner or, in the absence of a pouring basin, directly into which molten metal is poured. Sometimes it is referred to as sprue or down-sprue. It is also sometimes used to mean all gates, risers, runners, and similar scrap which are removed from castings after shakeout.
Down-hand welding – It is welding from the upper side of the joint, the face of the weld being horizontal. It is also known as flat-position welding.
Down milling – It is the milling in which the cutter moves in the direction of feed at the point of contact.
Down sprue – It is the mould channel which connects the pouring basin with the runner or, in the absence of a pouring basin, directly into which molten metal is poured. Sometimes it is referred to as sprue or down-gate. It is also sometimes used to mean all gates, risers, runners, and similar scrap which are removed from castings after shakeout.
Dow process – It is a process for the production of magnesium by electrolysis of molten magnesium chloride.
Draft – It is an angle or taper on the surface of a pattern, core box, punch, or die (or of the parts made with them) which facilitates removal of the parts from a mould or die cavity, or a core from a casting. It is also the change in cross section which occurs during rolling or cold drawing.
Draft angle – It is the angle of taper, normally 5-degree to 7-degree given to the sides of a forging and the sidewalls of the die impression.
Drafting – It is the act and discipline of composing drawings which visually communicate how something functions or is constructed.
Drag – It is the bottom section of a flask, mould, or pattern. In thermal cutting, it is the offset distance between the actual and the theoretical exit points of the cutting oxygen stream measured on the exit surface of the material.
Drag chain conveyor – It is a conveyor having one or more endless chains, which slides in a track or tracks, resting at the bottom of a trough, and materials resting directly on the chain are carried by the chain links. The layers of materials above the chain level are moved by the cohesiveness with the material below. The troughs or sliding base surface can be made of steel, concrete or even wood. The chain tracks are frequently made from steel channels. These conveyors normally work in the same horizontal plane with little inclines, for movement of bulk materials, hot materials, abrasive materials, logs / timber, and packages etc. Even cars can be moved in a car assembly line by putting two wheels on one chain.
Drag chain / drag flight feeders – Drag chain/drag flight feeders extract the material from the storage unit. They are suitable for materials of moderate size lumps and of average abrasiveness. The storage unit outlet can have some length along feeder. It can provide enclosed construction. The feeder needs minimum installation heights. It also imparts agitation to the bulk material at the outlet i.e.it improves flow at the hopper outlet. Typical capacity range of drag chain / drag flight feeders is up to 100 cubic meter per hour.
Drag force – It is the resistance force caused by the motion of a body through a fluid, such as water or air. A drag force acts opposite to the direction of the oncoming flow velocity. The first point of view for the cause of drag is the skin friction.
Drag fold – The result of the plastic deformation of a rock unit where it has been folded or bent back on itself.
Drag-in – It is the water or solution which adheres to the objects introduced into a bath.
Drag mark – It is a surface area showing a scratch or abrasion resulting from contact of the hot extrusion with the press equipment or tooling or, in the case of multi-hole dies, with other sections as they exit the press.
Drag-out – It is the solution which adheres to the objects removed from a bath.
Drain – It is a conduit, channel, or other structure constructed or used to carry waste liquid discharges by gravity or pumping.
Drainage – It is the act, process, or mode of becoming emptied or freed of cleaning solutions and / or zinc. Fabricated items immersed in molten zinc are to be designed and to allow the zinc to freely drain from internal and external surfaces are to be suspended correctly during the galvanizing process.
Draining – It is part of the dipping or flow coating process during which the excess slip flows from suitably positioned ware.
Drain plug – It is a fitting at the bottom of a valve, the removal of which permits draining and flushing the body cavity. The vent plug assembly on some ball and gate valves also serves as a drain valve.
Drain time – It is the time needed for porcelain enamel slip applied by dipping, slushing, or flow coating to complete movement across the surfaces of a coated part.
Drape – It is the ability of a polymer sheet or composite sheet to conform to the shape of the mould.
Draw – It is a term used to denote the shrinkage which appears on the surface of a casting. This term has been used formerly for used to describe tempering.
Drawability – It is a measure of the formability of a sheet metal subject to a drawing process. The term is normally used for indicating the ability of a metal to be deep drawn. The drawability of a metal depends on two factors namely (i) the ability of the material in the flange region to flow easily in the plane of the sheet under shear, (ii) the ability of the side-wall material to resist deformation in the thickness direction.
Draw and iron-can bodies – It is the term which refers to a method of fabricating a can body in which a cup is drawn from flat sheet, redrawn to the final diameter, and then wall ironed to reduce the wall thickness and to achieve the needed height.
Draw bead – It is an insert or rib-like projection on the draw ring or hold-down surfaces which aids in controlling the rate of metal flow during deep draw operations. Draw beads are especially useful in controlling the rate of metal flow in irregularly shaped stampings.
Draw-bench – It is the stand which holds the die and draw head used in drawing of wire, rod, and tubing.
Draw depth – It is the depth of the drawn product.
Draw forging – It is a process using two or more moving dies for producing shafts with constant or varying diameters along their length or tubes with internal or external variations. It is frequently incorrectly referred to as rotary forging.
Draw forming – It is a method of curving bars, tubes, or rolled or extruded sections in which the stock is bent around a rotating form block. Stock is bent by clamping it to the form block, then rotating the form block while the stock is pressed between the form block and a pressure die held against the periphery of the form block.
Draw head – It is a set of rolls or dies mounted on a draw-bench for forming a section from strip, tubing, or solid stock.
Drawing – It is a term used for a variety of forming operations, such as deep drawing a sheet metal blank, redrawing a tubular part, and drawing rod, wire, and tube. Drawing is the process of pulling material through a die to reduce the size, change the cross section or shape, or harden the material. In forging, it is an operation of working metal between flat dies to reduce the cross section and increase length. The normal drawing process with regard to sheet metal working in a press is a method for producing a cuplike form from a sheet metal disk by holding it firmly between blank-holding surfaces for preventing the formation of wrinkles while the punch travel produces the needed shape.
Drawing, cold drawing – It consists of pulling of a work-piece through a fixed die at room temperature. It can reduce the size, change the cross section or shape, improve surface finish, improve tolerances or work-harden the material.
Drawing compound – It is a substance applied to prevent pickup and scoring during drawing or pressing operations by preventing metal-to-metal contact of the work and die. It is also known as die lubricant. In metalworking, it is a lubricant which has extreme-pressure properties.
Drawing, engineering – In engineering, drawing can be defined as ‘a graphic representation of an idea, a concept, or an entity which actually or potentially exists in life’. It is a two-dimensional representation of three-dimensional objects. It is a graphic representation of an object, or a part of it, and is the result of creative thought. The drawing itself is a way of communication all necessary information about an abstract, such as an idea or concept or a graphic representation of some real entity, such as a spare part, an equipment, an assembly, a system, a facility, a tool, or a structure. The drawings prepared is to be clear, unmistakable in meaning, and there is not to be any scope for more than one interpretation.
Drawing out – It is a stretching operation resulting from forging a series of upsets along the length of the work-piece.
Drawing (pattern) – It is removing a pattern from a mould or a mould from a pattern in production work.
Drawing quality steels – These are flat rolled steel products which are produced either as rimmed steel or as aluminium killed steel. Special rolling and processing operations help in producing a product, which can stand extreme pressing, drawing or forming operations without creating defects.
Drawing ratios – Drawability can also be expressed in terms of LDR or percentage of reduction based on results of deep-drawing cup testing. The LDR is the ratio of the diameter ‘D’ of the largest blank which can be successfully drawn to the diameter of the punch ‘d’. It is given by the equation ‘LDR = D/d’. Percentage of reduction is then be defined by the equation ‘Percentage of reduction = [100(D – d)]/D’.
Drawing sheet – It is the medium on which drawings are prepared by means of pencils. Drawing sheets are normally of standard sizes. It has drawing space, title block and revision block table, grid reference system, sufficient margins, and the part list (bill of materials).
Drawing stock – It is a hot-worked intermediate solid product of uniform cross section along its whole length, supplied in coils and of a quality suitable for drawing into wire.
Draw marks – These are marring or scratching of a formed metal part by metal pickup on the punch or die.
Drawn fibre – It is the fibre with a certain quantity of orientation imparted by the drawing process by which it was formed.
Drawn-in scratch – It is a scratch occurring during the fabricating process and subsequently drawn over, making it relatively smooth to the touch.
Drawn-over-mandrel – It is a procedure for producing specialty tubing using a drawbench to pull tubing through a die and over a mandrel, giving excellent control over the inside diameter and wall thickness. Advantages of this technique are its inside and outside surface quality and gauge tolerance. Major uses include automotive applications and hydraulic cylinders.
Drawn product – It is a product formed by pulling material through a die.
Drawn shell – It is an article formed by drawing sheet metal into a hollow structure having a pre-determined geometrical configuration.
Drawn tube – It is a hollow product of uniform wall thickness, produced by cold drawing.
Draw plate – In metal forming, it is a circular plate with a hole in the centre contoured to fit a forming punch. It is used to support the blank during the forming cycle. In casting, it is a plate attached to a pattern for facilitating drawing of a pattern from the mould.
Draw point – It is an underground opening at the bottom of a stope through which broken ore from the stope is extracted.
Draw radius – It is the radius at the edge of a die or punch over which sheet metal is drawn.
Draw ring – It is a ring-shaped die part (either the die ring itself or a separate ring) over which the inner edge of sheet metal is drawn by the punch.
Draw stock – It is the forging operation in which the length of a metal mass (stock) is increased at the expense of its cross section. In this, no upset is involved. The operation includes converting ingot to pressed bar using ‘V’, round, or flat dies.
Dredge – It is the sieve used to apply powdered porcelain enamel frit to the ware during dredging.
Dredging – In dry process enameling, it is the application of dry, powdered frit to hot ware by sifting. It is also the removing of sediments and debris from the bottom of lakes, rivers, harbours, and other water bodies.
Dressing – It is the process of eroding the bond matrix in a grinding wheel surface after truing or grinding in order to expose the abrasive grains and hence improve grinding efficiency. It also consists of cutting, breaking down, or crushing the surface of a grinding wheel for improving its cutting ability and accuracy. It is also removing of dulled grains from the cutting face of a grinding wheel to restore cutting quality. In case of galvanizing, the coating is inspected after galvanizing, and irregularities are removed by dressing the surface by buffing or filing.
Drier – It is a catalyst added to speed the cure of oil-based paints. Driers are frequently metal salts of carboxylic acids. It is also an apparatus for removing moisture by forced draught, heating, or centrifuging.
Drift – It is a flat piece of steel of tapering width used to remove taper shank drills and other tools from their holders. It is also a tapered rod used to force mis-mated holes into line for riveting or bolting. Sometimes it is called a drift pin. In mining, drift is a horizontal underground opening which follows along the length of a vein or rock formation as opposed to a crosscut which crosses the rock formation.
Drifter – It is a hydraulic rock drill which is used to drill small-diameter holes for blasting or for installing rock bolts.
Drift expanding test – A test for the weld integrity of a welded tube, normally carried out to ISO 8493. The test is considered passed if no cracks are detected in the tube or at the welded seam after the test. The drift-expanding test is normally performed on tubes having an outside diameter of 150 millimeters and a wall thickness no greater than 10 millimeters.
Drill core logging – It is the process of recording geological observations of drill core either on paper or on computer disk.
Drillhole collar – It is the identification post indicating past drill holes. Information about the hole is to be indicated by a tag and normally include drillhole identification number (drilling log), location, depth, azimuth, and dip).
Drill-indicated reserves – It is the size and quality of a potential ore-body as suggested by widely spaced drillholes. Normally, more work is needed before reserves can be classified as probable or proven.
Drilling – It consists of hole making with a rotary end-cutting tool having one or more cutting lips and one or more helical or straight flutes or tubes for the ejection of chips and the passage of a cutting fluid.
Drilling machine – It is one of the cast house equipment used for drilling the tap hole during its opening.
Drill pipe – It is the pipe used in the drilling of an oil or gas well. Drill pipe is the conduit between the wellhead motor and the drill bit. Drilling mud is pumped down the centre of the pipe during drilling, to lubricate the drill bit and transmit the drilled core to the surface. Because of the high stress, torque and temperature associated with well drilling, drill pipe is a seamless product.
Drinking water – It is that water which is used in various production shops and canteens of the steel plant for drinking purpose. The quality of drinking water is to be maintained at the level which is fit for human consumption.
Drip feed (drop feed) lubrication – It is a system of lubrication in which the lubricant is supplied to the bearing surfaces in the form of drops at regular intervals.
Dripping zone– Dripping zone plays a crucial role in modern high productivity blast furnaces. It affects production rate, hot metal quality, and process efficiency. Dripping zone is a four-phase region, where gas, solid, liquid, and powder coexist with each other. In this zone, solid and liquid flow downward driven by gravity, while gas and powder suspended in the gas flow upward due to the pressure force. The flow of four phases in this zone is considerably different from that in the upper shaft region because of the geometry and the presence of deadman zone at the centre and discrete raceways at the periphery.
Drive, electrical – It is a system in which the motor is located and makes it spin. The electrical drive controls the electrical motor.
Drive gear – It is also called driving gear. It is that gear among a pair of gears which that mesh, which transmits the rotational motion of a motor or other device through the drive shaft.
Drive, mechanical – It consists of a series of components which manages the transmission. This power can be channeled to power other equipment like pumps, blowers, air compressors, and other common industrial machinery.
Drive pins – These are the pins which fit into the bottom of a ball valve stem and engage corresponding holes in the ball. As the operator turns the stem, the drive pins turn the ball. The drive pins transmit the drive torque by shear. The drive pins can be replaced by a tang-drive connection integrally machined in the valve stem.
Drive-shaft – It is a component for transmitting mechanical power and torque and rotation. It is normally used to connect other components of a drive train which cannot be connected directly because of distance or the need to allow for relative movement between them.
Drive system – The drive system frequently offers substantial opportunities to improve energy efficiency and to lower overall system operating costs. There are two principal types of drive systems (i) direct drive, and (ii) belt drive. Gear drives are also used but are less common.
Drive train – It consists of all parts of a valve drive between the operator and the obturator, including the obturator, but excluding the operator. It also includes the anchor pin.
Drop – It is a casting imperfection because of a portion of the sand dropping from the cope or other overhanging section of the mould. In case of valves, there is a drop in set (outlet) pressure of a regulator or control valve because of the travel of its valve or poppet, as the required flow increases from low to maximum. A slight change in the control spring length due to the valve travel will result in spring force variations, translating into a change of set (outlet) pressure.
Drop controllers – Electromagnets hold a load by means of magnetic lines of force which are generated by the magneto-motive force of the energized magnet. When the magnet is de-energized, residual lines of force can remain if there is close contact between the magnet and load. Reverse current drop controllers are used to apply reverse current to the magnet for cancellation of these residual lines. This cancellation results in faster release of the load.
Dropped edge – It is a continuous, downward edge deflection.
Drop etching – In metallography, it is placing of a drop of etchant on the polished surface.
Drop forging – It is the forging got by hammering metal in a pair of closed dies for producing the form in the finishing impression under a drop hammer. It is also the forging method needing special dies for each shape.
Drop hammer – It is a term which is normally applied to forging hammers in which energy for forging is provided by gravity, steam, or compressed air.
Drop hammer forming – It is a process for producing shapes by the progressive deformation of sheet metal in matched dies under the repetitive blows of a gravity-drop or power-drop hammer. The process is restricted to relatively shallow parts and thin sheet from around 0.6 millimeters to 1.6 millimeters).
Drop hammer, gravity – It consists of an anvil or base, supporting columns which contain the ram guides, and a device that returns the ram to its starting position. The energy which deforms the work-piece is derived from the downward drop of the ram. The height of the fall and the weight of the ram determine the force of the blow. In a simple gravity-drop hammer, the upper ram is positively connected to a board (board drop hammer), a belt (belt drop hammer), a chain (chain drop hammer) or a piston (oil-drop, air-drop, or steam-lift drop hammer).
Drop hammer, power – In a power-drop hammer, the ram is accelerated during the down-stroke by air, steam, or hydraulic pressure. This equipment is used almost exclusively for closed-die (impression-die) forging.
Droplet erosion – It is the erosive wear caused by the impingement of liquid droplets on a solid surface.
Drop point – Drop point is the temperature at which grease passes from the semi-solid to the liquid state. Hence, it determines the upper temperature limit for the applicability of grease.
Drop-through – It is an undesirable sagging or surface irregularity, normally encountered when brazing or welding near the solidus of the base metal, caused by over-heating with rapid diffusion or alloying between the filler metal and the base metal.
Drop-weight test – It is conducted by subjecting a series (usually four to eight) of samples to a single impact load at a sequence of selected temperatures to determine the maximum temperature at which a sample breaks. The impact load is provided by a guided, free-falling weight with energy of 340 joules to 1,630 joules depending on the yield strength of the steel to be tested. The samples are prevented by a stop from deflecting less than a centimeter. This is a ‘go – no-go’ test method in which the sample either breaks or fails to break. It is surprisingly reproducible.
Drop-weight tear test (DWTT) – It uses a test sample which resembles a large Charpy test sample. The test sample is 76 mm wide by 305 mm long, supported on a 254 mm span. The thickness of the sample is the full thickness of the material being tested. The samples are broken by either a falling weight or a pendulum machine. The notch in the sample is pressed to a depth of 5 mm with a sharp tool-steel chisel having an angle of 45-degree. The resulting notch root radius is around 0.025 mm. One result of the test is the determination of the fracture appearance transition curve. The average percent shear area of the broken samples is determined for the fracture area neglecting a region of ‘one thickness’ in length from the root of the notch and ‘one-thickness’ from the opposite side of the sample. These regions are ignored since it is thought that the pressing of the notch introduces a region of plastically deformed material which is not representative of the base material. Similarly, the opposite side of the sample is plastically deformed by the hammer tup during impact. The fracture appearance plotted against temperature defines an abrupt transition in fracture appearance. This transition has been shown to correlate with the transition in fracture propagation behaviour in cylindrical pressure vessels and piping.
Dross – It is the scum which forms on the surface of molten metal largely because of oxidation but sometimes because of the rising of impurities to the surface. It is also oxide and other contaminants which form on the surface of molten solder. In case of galvanizing, steel is reacting with molten zinc forms small zinc-iron crystals in the galvanizing bath. These are heavier than zinc and settle to the bottom of the galvanizing pot where they are periodically removed. Dross is the by-product of the galvanizing process which forms by reactions between zinc and loose particles of iron. Dross can exist at all depths of the pot, but normally sinks to the bottom.
Dross inclusions – It is the dross which is carried out on to the work piece upon removal from the galvanizing pot.
Drossing – It is the process of removing dross build-up from the bottom of the pot.
Drum shear – A drum type shear is normally used for product with a simple shape such as flats or rounds. The blades are mounted on a rotating cylinder (or drum) and are set at a ‘lead’ speed to minimize the ‘kinking’ of the bar.
Drum test – The test is based on Japanese standard JIS K2151. A 10 kg representative sample of +50 mm ‘square hole screen’ coke is placed in the specified tumbler drum and rotated for 30 revolutions, removed, screened and replaced in the drum and subjected to a further revolution of 150 revolutions. The drum contains lifters that raise the coke and allow it to fall so that it undergoes a large number of impacts with the drum walls. The indices reported are percentages of material remaining on +15 mm ‘square hole screen’ after 30 revolutions and the same after 150 revolutions. The larger is the value the higher is the coke strength.
Dry and baked compression test – It is a test for determining the maximum compressive stress which a baked sand mixture is capable of developing.
Dry bearing – It is a sliding bearing consisting of a PTFE (poly-tetra-fluoro-ethylene, Teflon) and lead powder lining bonded to a metal backing.
Dry classifiers – Dry classifiers are based on the principle that separation by air fluidization. Air classification is a process of separating categories of materials by way of differences in their respective aerodynamic characteristics. The aerodynamic characteristic of a particular material is primarily a function of the size, geometry, and density of the particles. The process consists of the interaction of a moving stream of air, material particles, and the gravitational force within a confined volume. In the interaction, the drag force and the gravitational force are exerted in different directions upon the material particles. The result is that material particles that have a large drag-to weight ratio are suspended in the air stream, whereas components that have a small ratio tend to settle out of the air stream. The suspended fraction conventionally is referred to as the ‘air classified light fraction’ and the settled fraction is termed ‘air-classified heavy fraction’. The confined volume in which the separation takes place is called an ‘air classifier’.
Dry corrosion – It is the corrosion with gas as the only corrosive agent and without any aqueous phase on the surface of the metal.
Dry-cum-wet processing – In dry-cum-wet process, fines fraction (-10 mm) generated after dry processing of iron ore is further processed in mechanical classifiers, and hydro-cyclones etc. to get -10 mm to + 0.15 mm size product which constitutes the feed material for the sintering process. The classifier / hydro-cyclone overflow i.e., -0.15 mm (100 mesh) size product constitutes the slime and dumped into the tailing pond.
Dry cyaniding – It is an obsolete term. The present term is carbo-nitriding. It is a case-hardening process in which a suitable ferrous material is heated above the lower transformation temperature in a gaseous atmosphere of such composition as to cause simultaneous absorption of carbon and nitrogen by the surface and, by diffusion, create a concentration gradient. The heat-treating process is completed by cooling at a rate which produces the desired properties in the work-piece.
Dry etching – In metallography, it is the development of micro-structure under the influence of gases.
Dry-film lubrication – It is the lubrication which involves the application of a thin film of solid lubricant to the surface or surfaces to be lubricated.
Dry friction – It is the friction which occurs between two bodies in the absence of lubrication. However, this term is inaccurate since it historically implies that there is no intentionally applied lubrication, when in fact, solid lubrication conditions can be considered ‘dry’. Hence, this term is not to be used.
Dry fuel store – It is a building specifically designed for the storage in dry conditions of used nuclear fuel from the operation of a nuclear power plant.
Dry galvanizing – It is the dipping of steel in an aqueous zinc ammonium chloride solution and then thoroughly drying before immersing in the molten zinc bath.
Drying cracks – These are irregular cracks in dry, unfired porcelain enamel caused by uneven or too rapid drying of the ware. The cracks may or may not heal over during the firing operation.
Drying oil – It is a water-insoluble liquid, normally obtained from a plant source, which reacts with oxygen (from the air) to form a cross-linked polymeric film.
Dry laminate – It is a laminate containing insufficient resin for complete bonding of the reinforcement.
Dry lay-up – It is the construction of a laminate by the layering of pre-impregnated reinforcement (partly cured resin) in a female mould or on a male mould, normally followed by bag moulding or autoclave moulding.
Dry lube – It is dry-film moly-di-sulphide applied as a coating to sliding or rotating parts to reduce frictional drag. After application, the film is baked in an oven at high temperature.
Dry lubricant – It is a solid which is used as a powder or thin film on a surface to provide protection from damage during relative movement, and to reduce friction and wear. However, it has been suggested that this term is not to be used as a synonym for solid lubricant since some solid lubricants perform better in the presence of moisture (e.g., graphite). Instead, it has to refer to lubricants which function in low-moisture environments.
Dry objective – It is a microscope objective which is designed for use without liquid between the cover glass and the objective or, in the case of metallurgical objectives, in the space between objective and sample.
Dry permeability – It is the property of a moulded mass of sand, bonded or unbonded, dried at around 100 deg C to 110 deg C, and cooled to room temperature, which allows the transfer of gases resulting during the pouring of molten metal into a mould.
Dry pressing process – It is a simple and cost-effective method, and has been widely used to make parts thicker than 0.5 mm. Pressing methods might include cold, warm, hot, cold-isostatic or hot-isostatic pressing. In refractory brick production, plasticity of refractory powder mix is used in the dry-press process. A minimum of water is added, the material is placed in steel moulds, and pressures up to a0 MPa are applied. The dry-press process, using steel moulds, gives a smooth texture.
Dry process enameling – It is a porcelain enameling process in which the metal article is heated to a temperature above the maturing temperature of the coating, normally 870 deg C to 955 deg C. The coating materials are applied to the hot metal as a dry powder and fired.
Dry processing – In case of iron ore, dry processing is done for meeting the size requirements and involve multi-stage crushing and screening to meet the size requirements needed by different iron smelting processes.
Dry quenching – In the dry quenching process, the red-hot coke is cooled by mixed gas (mainly consisting of nitrogen) circulating in an enclosed system, thereby preventing the release of airborne coke dust. The thermal energy of the red-hot coke, which is lost in the conventional wet quenching, is collected and reused as steam.
Dry ramming mixes – These are based on high purity magnesite and a sintering aid are useful in steel making. magnesite ramming mixes of exceptional purity and stability are used primarily as lining materials for coreless type induction furnaces. Magnesite chrome fused grain ramming mixes provide exceptional density and strength.
Dry-running – In seals, it means running without liquid present at the seal surface.
Dry sand casting – It is the process in which the sand moulds are dried at above 100 deg C before use.
Dry sand mould – It is a casting mould made of sand and then dried at 100 deg C or above before being used.
Dry sand moulding – Dry sand moulds are made by several different processes. Sand mixed with binders which cure by baking is one form of dry sand mould. Other more common dry sand moulding techniques use sand with binders which can be cured by chemical, or catalytic, reaction induced by mixing
Dry-sand rubber wheel test – In wear testing, it is a term used to describe a standard abrasive wear testing method in which a stream of dry quartz sand is passed between a rotating rubber wheel and a stationary test coupon which is held against it under specified normal force.
Dry screening – It refers to the process of removing impurities and unwanted materials from the ore through the use of different screening techniques. This method does not need the use of water, unlike wet screening processes which rely on water to separate particles.
Dry sheet – It is because of failure of the lubricant to meet the agreed-upon minimum limit measured in weight per unit area.
Dry slag granulation process – In this process, it is essentially to atomize the liquid slag and then to cool the particles rapidly so as to produce a glassy slag. The atomization is done using a rotary cup air blast atomizer. The particles cool as they travel through the air and are then cooled further in a fluidized bed. Both of these processes provide the rapid cooling necessary for the formation of glassy slag product. The fluidized bed is a convenient method of containing the slag particles as it prevents the agglomeration of hot particles in addition to providing rapid cooling.
Dry slag pit – It is a pit where liquid slag is diverted for solidifying in case of some problem in the slag granulation plant.
Dry sliding wear – It is the sliding wear in which there is no intentional lubricant or moisture introduced into the contact area.
Dry steam – It is the steam that contains 100 % of water vapour in the gas phase. Steam which contains no water molecules, is referred to as dry steam, or dry saturated steam. Steam tables normally list data based on dry saturated steam values. Dry saturated steam is difficult to produce in a boiler since some water droplets are almost always present. Boiler systems are optimized for generating saturated steam. The actual level achieved is measured as the ‘dryness fraction’. If the water content of the steam is 4 % by mass, then the steam is said to be 96 % dry and has a dryness fraction of 0.96.
Dry strength (casting) – It is the maximum strength of a moulded sand sample which has been dried thoroughly at 100 deg C to 110 deg C and cooled to room temperature. It is also known as dry bond strength.
Dry storage – It is the storage of spent fuel in air or an inert gas rather than water.
Dry surface – It is a foil surface which is substantially free from oily film and suitable for lacquering, printing, or coating with water-dispersed adhesives.
Dry winding – It is a term used to describe filament winding using pre-impregnated roving, as differentiated from wet winding, where unimpregnated roving is pulled through a resin bath just before being wound onto a mandrel.
Dual-metal centrifugal casting – It is the centrifugal castings produced by pouring a different metal into the rotating mould after the first metal poured has solidified.
Dual-phase (DP) steels – The term dual phase steels, or DP steels, refers to a class of high strength steels which is composed of two phases namely a purely ferrite matrix and a dispersed second phase of martensite (5 % to 30 %). In addition to martensite, small quantities of bainite and residual austenite can exist. The steel behaves like composite materials where the ferrite matrix assures high cold formability, and the martensite is the strengthening element. The correct proportion between the two phases allows a continuous yield point, low yielding stress, and a high elongation value, a smooth flow stress curve with a high strain hardening coefficient, and better plasticity and formability. The micro-structure of steel gives a good combination of high tensile strength, low yield-to-tensile strength ratio and very high initial work hardening rate with good elongation values. Dual phase is very formable, providing more flexibility in part design. The strength of the formed part is much higher than high strength low alloy steel, especially at very low strain. The high initial work hardening rate and high tensile strength give dual phase steel a very high capacity to absorb energy, making these steels suitable for use in structural and reinforcement applications.
Dual seat – It is a combination of one uni-directional seat and one bi-directional seat installed in the same valve body. The directions of both seats shall be specified on a separate identification plate. This design provides two sealing barriers in one direction and one sealing barrier in the opposite direction.
Dual seat (both seats bi-directional valve) – It is a valve with two seats, each sealing in both directions.
Dual seat (one seat uni-directional and one seat bi-directional valve) – It is a valve with two seats, one sealing in one direction and the other in either direction.
Dual system shears – These shears are normally used as cooling bed shears. They are equipped with two cutting systems namely (i) crank rotary system, and (ii) crank lever system. The crank lever system is mainly used for cutting sections. The shear is moveable perpendicular to the rolling direction in order to bring the system being used in line of rolling.
Duct – Duct is a tube, canal, pipe, or conduit by which a fluid, air, gas, or other substance is conducted or conveyed.
Ductile – A material is ductile when it is capable of being plastically deformed before fracturing.
Ductile cast iron – It is a cast iron which has been treated while molten with an element such as magnesium or cerium to induce the formation of free graphite as nodules or spherulites, which imparts a measurable degree of ductility to the cast metal. It is also known as nodular cast iron, spherulitic graphite cast iron, and spheroidal graphite (SG) iron.
Ductile crack propagation – It is the slow crack propagation which is accompanied by noticeable plastic deformation and needs energy to be supplied from outside the body.
Ductile erosion behaviour It is the erosion behaviour having characteristic properties (i.e., considerable plastic deformation) which can be associated with ductile fracture of the exposed solid surface. A characteristic ripple pattern forms on the exposed surface at low values of angle of attack.
Ductile fracture – It is the fracture characterized by tearing of metal accompanied by appreciable gross plastic deformation and expenditure of considerable energy.
Ductile iron – Ductile cast iron also known as nodular cast iron, spheroidal graphite iron or SG iron, and spherulitic cast iron. As the name ductile iron suggests this grade of cast iron has a degree of ductility. The main characteristic of this material is the structure of the graphite. Ductile iron is a family of cast graphitic irons which possess high strength, ductility and resistance to shock. Annealed cast ductile iron can be bent, twisted or deformed without fracturing. Its strength, toughness and ductility duplicate many grades of steel and far exceed those of standard gray irons. Yet it possesses the advantages of design flexibility and low-cost casting procedures similar to gray iron. The difference between ductile iron and gray iron is in the graphite formation. Ordinary gray iron is characterized by a random flake graphite pattern in the metal. In ductile iron the addition of a few hundredths of 1 % of magnesium or cerium causes the graphite to form in small spheroids rather than flakes. These create fewer discontinuities in the structure of the metal and produce a stronger, more ductile iron. This nodular graphite structure inhibits the creation of linear cracks hence the ability to withstand distortion.
Ductile to brittle transition – At low temperatures some metals that would be ductile at room temperature become brittle. This is known as a ductile to brittle transition.
Ductile-to-brittle transition temperature – It is the temperature at which the material starts becoming brittle from ductile. Ductile to brittle transition takes place over a range of temperature.
Ductility – It is the ability of a material to deform plastically without fracturing, measured by elongation or of area in a tensile test, by height of cupping in an Erichsen test, or by other means. Galvanized steel is ductile within certain recommended bending radii.
Duct sheet – It is coiled or flat sheet in specific tempers, widths, and thicknesses, suitable for duct applications.
Due diligence – It is the degree of care and caution which is needed before making a decision.
Dummy – It is an imaginary activity inserted into the network to show a precedence relationship, but it does not represent any actual passage of time. It is an imaginary activity which needs no time and is used to maintain the appropriate precedence relationships in a programme evolution review technique (PERT) network.
Dummy activity – In activity-on-arrow diagrams, where arrows represent activities, dummy activities show logical relationships between activities. They are not actual activities themselves – dummy activity arrows are drawn with broken lines to differentiate them from regular activity arrows.
Dummy block – In extrusion, it is a thick unattached disk placed between the ram and the billet to prevent over-heating of the ram.
Dummy cathode – It is a cathode, normally corrugated to give variable current densities, that is plated at low current densities to preferentially remove impurities from a plating solution. It is also a substitute cathode which is used during adjustment of operating conditions.
Dummying – It is plating with dummy cathodes.
Dummy variable – It is a variable in a regression model coded 1 if the case falls into a certain category of an explanatory variable and 0 otherwise. Used to represent qualitative predictors in a regression model.
Dump – It is a pile of broken rock or ore on surface.
Dumping – Dumping occurs when imported merchandise is sold in, or for export to the domestic market at less than the normal value of the merchandise, i.e., at a price that is less than the price at which identical or similar merchandise is sold in the comparison market, the home market (the market of the exporting country), or third-country market (in this case, ‘market’ is used as proxy for ‘home market’ in cases where home market cannot be used). The normal value of the merchandise cannot be below the cost of production.
Dumpy level – It is a commonly used leveling instrument to locate the points in same horizontal plane. It is also called as automatic level or builder’s level. Elevations of different points and distance between the points of same elevation can be determined by dumpy level.
Duoplasmatron – It is a type of ion source in which a plasma created by an arc discharge is confined and compressed by a nonuniform magnetic field.
Duplex ageing – It is a two-age-hardening heat treatment conducted at different temperatures.
Duplex alloys – These are bearing alloys consisting of two phases, in which one is much softer than the other.
Duplex brass – It consists brasses with composition ranging from 58 % to 62 % copper with 38 % to 42 % zinc which have both alpha and beta phases present in their microstructure. Duplex brasses are superior to alpha brasses for hot working, but inferior for cold working.
Duplex coating system – It is the galvanized steel which has been coated with an additional corrosion inhibiting product, typically liquid, powder, or paint. The two separate coating systems work synergistically to provide enhanced corrosion protection. Duplex coating systems enhance the appearance or durability of the steel being protected.
Duplex grain size – It is the simultaneous presence of two grain sizes in substantial quantities, with one grain size appreciably larger than the others. It is also termed mixed grain size.
Duplexing – It consists of any two-furnace melting or refining process. It is also called duplex melting or duplex processing.
Duplex micro-structure – It is a two-phase structure.
Duplex stainless steels – These steels have a mixed structure of bcc ferrite and fcc austenite. The amount of each phase is a function of composition and heat treatment. Most stainless steels are designed to contain about equal amounts of each phase in the annealed condition. The principal alloying elements are chromium and nickel, but nitrogen, molybdenum, copper, silicon, and tungsten can be added to control structural balance and to impart certain corrosion-resistance characteristics. The corrosion resistance of duplex stainless steels is like that of austenitic stainless steels with similar alloying contents. However, duplex stainless steels possess higher tensile and yield strengths and improved resistance to stress-corrosion cracking than their austenitic counterparts. The toughness of duplex stainless steels is between that of austenitic and ferritic stainless steels.
Duplicate measurement – It is a second measurement made on the same (or identical) sample of material for assisting in the evaluation of measurement variance.
Duplicate sample – It is a second sample randomly selected from a population for assisting in the evaluation of sample variance.
Duralumin – It is an obsolete term. This term is frequently applied to the class of age-hardenable aluminum-copper alloys containing manganese, magnesium, or silicon.
Durometer – It is the Durometer (also called shore Durometer) measures hardness in terms of material elasticity. A diamond-tipped hammer is used to strike the testing surface from a known height. The rebound of the hammer is measured. The harder is the material, the higher is the rebound.
Durometer hardness – It is a measure of the indentation hardness of plastics. It is the extent to which a spring-loaded steel indenter protrudes beyond the pressure foot into the material.
Durometer hardness test – It involves forcing a 30-degree tapered indenter into the surface of the sample using calibrated loading springs. A dial gauge indicates the depth of penetration in durometer numbers, which are directly proportional to the load on the spring.
Durometer reading – It is an index which is used for ranking the relative hardness of elastomers.
Dust catcher – It is an equipment for the removal of coarse particles from the exhaust gas of a furnace. The internal construction of the dust catcher is such that there is a sudden change in the direction of the flow of exhaust gas. This causes the large dust-particles to separate because of its higher momentum. The separated particles then settle down because of gravitational force. In blast furnace ironmaking, it is situated by the side of cast house and used for preliminary cleaning of blast furnace gas. It works on the principle of reversing the direction of flow of blast furnace gas for separating coarse dust particles from blast furnace gas.
Dusting – It is a phenomenon, normally affecting carbon-base electrical motor brushes or other current carrying contacts, wherein at low relative humidity or high applied current density, a powdery ‘dust’ is produced during operation. It is also applying a powder, such as sulphur to molten magnesium or graphite to a mould surface.
Duty – It is the specification which gives the load, ambient temperature, and speed under which surfaces are required to move.
Duty cycle – The duty cycle refers to the ratio of a crane’s working time to its total cycle time. In simpler terms, it indicates how frequently a crane is expected to perform its lifting operation in each time frame. It is the proportion of time during which a crane is operated. The duty cycle is expressed as a ratio or as a percentage.
Duty parameter – It is the product of the Sommerfeld number and the square of the length-to-diameter ratio of a journal bearing.
Dwell – It is the portion of a press cycle during which the movement of a member is zero or at least insignificant. It normally refers to (i) the interval when the blank-holder in a drawing operation is holding the blank while the punch is making the draw, or (ii) the interval between the completion of the
forging stroke and the retraction of the ram.
Dye-penetrant test – This is used to detect cracks and involves spraying a dye on the area to be tested. After allowing time for penetration, the surplus dye is removed and the area is then sprayed with a white developer. Any faults are revealed as coloured lines or spots caused by the developer absorbing the dye seeping from the cracks. If more sensitive results are needed, a fluorescent dye is used and the same process is followed. When viewed under ultra-violet light any defects show as a highly fluorescent line or spot.
Dyke – It is a long and relatively thin body of igneous rock which, while in the molten state, intruded a fissure in older rocks.
Dynamic – It means moving, or having high velocity. It is frequently used with high strain rate (less than 0.1 second) testing of metal samples.
Dynamic characteristics – These characteristics of the instrument are concerned with the measurement of quantities which vary with time. These characteristics are those which change within a period of time which is normally very short in nature. The different dynamic characteristics are speed of response, fidelity, lag, and dynamic creep.
Dynamic compression – It is the conversion of the air velocity into pressure. Dynamic machines use axial and centrifugal impellers to impart velocity to the air, which is then converted to pressure. Centrifugal and axial compressors are dynamic machines often operating at high speeds.
Dynamic crystalline materials – These materials are defined by their ability to change parameters such as structure, mass, momentum, and energy fluxes in response to environmental changes. This makes them thermodynamically open systems, constantly exchanging these quantities with their surroundings.
Dynamic deformations – These deformations occur when a structure is subject to the actions of flutter, impact, and so on.
Dynamic electrode force – It is the electrode potential measured when current is passing between the electrode and the electrolyte.
Dynamic friction – it is the friction under conditions of macroscopic relative motion between two bodies. This term is sometimes used as a synonym for kinetic coefficient of friction. However, it can also be used merely to indicate that the type of friction being indicated is associated with macroscopic motion rather than static conditions.
Dynamic load – It is an imposed force which is in motion, i.e., one that can vary in magnitude, sense, and direction.
Dynamic loads because of unbalanced masses – Unbalanced forces in rotating machines are created when the mass centroid of the rotating part does not coincide with the axis of rotation. In theory, it is possible to precisely balance the rotating elements of rotating equipments. In practice, this is never achieved and slight mass eccentricities always remain. During operation, the eccentric rotating mass produces centrifugal forces which are proportional to the square of equipment speed. Centrifugal forces normally increase during the service life of the equipment because of the conditions such as equipment wear, rotor play, and dirt accumulation. A rotating equipment transmits dynamic force to the foundation predominantly through its bearings (with small, normally unimportant exceptions such as seals and the air gap in a motor). The forces acting at the bearings are a function of the level and axial distribution of unbalance, the geometry of the rotor and its bearings, the speed of rotation, and the detailed dynamic characteristics of the rotor-bearing system. At or near a critical speed, the force from rotating unbalance can be substantially amplified, sometimes by a factor of five or more.
Dynamic load testing, dynamic loading – It is a method to assess a pile’s bearing capacity by applying a dynamic load to the pile head (a falling mass) while recording acceleration and strain on the pile head. Dynamic load testing is a high strain dynamic test which can be applied after pile installation for concrete piles. For steel or timber piles, dynamic load testing can be done during installation or after installation.
Dynamic mechanical measurement – It is a technique in which either the modulus and / or damping of a substance under oscillatory load or displacement is measured as a function of temperature, frequency, or time, or a combination thereof.
Dynamic modulus – It is the ratio of stress to strain under cyclic conditions (calculated from data got from either free or forced vibration tests, in shear, compression, or tension).
Dynamic programming – It is a technique for optimization of the solution of a problem by combining solutions to smaller sub-problems.
Dynamic recovery – it is a process occurring in hot working of metals in which a fine sub-grain structure forms within the elongated grains because of the annihilation of dislocations due to easy cross slip and climb. It results in a lowering of the flow stress. Dynamic recovery, as opposed to dynamic recrystallization which occurs in hot working, occurs in metals of high stacking fault energy such as aluminum, alpha-iron, and majority of the body centred cubic metals.
Dynamic recrystallization – It is is a type of recrystallization process, found within the fields of metallurgy and geology. In dynamic recrystallization, as opposed to static recrystallization, the nucleation and growth of new grains occurs during deformation rather than afterwards as part of a separate heat treatment. The reduction of grain size increases the risk of grain boundary sliding at elevated temperatures, while also decreasing dislocation mobility within the material. The new grains are less strained, causing a decrease in the hardening of a material. Dynamic recrystallization allows for new grain sizes and orientation, which can prevent crack propagation. Rather than strain causing the material to fracture, strain can initiate the growth of a new grain, consuming atoms from neighboring pre-existing grains. After dynamic recrystallization, the ductility of the material increases.
Dynamic seal – It is a seal which has rotating, oscillating, or reciprocating motion between its components, as opposed to stationary-type seal such as a gasket.
Dynamic soil properties – Soil dynamics deals with engineering properties and behaviour of soil under dynamic stress. For the dynamic analysis of equipment foundations, soil properties, such as Poisson’s ratio, dynamic shear modulus, soil density, and damping of soil, are normally needed. Satisfactory design of an equipment foundation needs information on soil profile, depth of different layers, physical properties of soil, and ground water level. This information can be obtained by normal sub-surface exploration techniques. In addition, it is necessary to determine dynamic shear modulus, material damping, poisons ratio and mass density of soil for dynamic analysis of the equipment foundation. Dynamic shear modulus of a soil is normally determined from laboratory or field tests. Material damping can be determined from vibration tests on soil columns in the laboratory. The values of dynamic shear modulus and damping can be estimated from empirical estimations for preliminary design purposes. The soil characteristics needed in analysis of foundation are (i) shear modulus, (ii) Poisson’s ratio, (iii) damping of soil, (iv) soil density, and (v) allowable soil pressure.
Dynamic strain aging – It is a behaviour in metals in which solute atoms are sufficiently mobile to move toward and interact with dislocations. This results in strengthening over a specific range of high temperature and strain rate.
Dynamic systems development method – The dynamic systems development method is one of the agile product development methodologies. Like other members of the agile family, it conducts development in a series of iterations, with user-story-based improvements made in increments. The dynamic systems development method operates with fixed cost and time constraints and uses the MoSCoW (a prioritization technique) prioritization method to identify the desired product requirements with these constraints in mind.
Dynamic viscosity – It is the bulk property of a fluid, semi-fluid, or semi-solid substance which causes it to resist flow.
Dynamometer – It is a device for simultaneously measuring the torque and rotational speed (revolution per minute) of an engine, motor or other rotating prime mover so that its instantaneous power can be calculated.
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