Basics of Tribology Oct31

Basics of Tribology

Basics of Tribology Expenditure on machine condition monitoring and maintenance constitutes a significant cost in a steel plant. Tribology helps in reducing this expenditure. Tribology is a new word coined by Dr. H. Peter Jost in England in 1966. ‘The Jost Report’, provided to the British Parliament – Ministry for Education and Science, indicated ‘Potential savings of over £ 515 million per year for industry by better application of tribological principles and practices’. But tribology is not a new field. Tribology comes from the Greek word, ‘tribos’, meaning rubbing or to rub. And from the suffix, “ology” means the study of. Therefore, tribology is the study of ‘rubbing’, or ‘the study of things that rub’. Tribology is the science and technology of interacting surfaces in relative motion. It is the study (Fig 1) of (i) friction, (ii) wear, and (iii) lubrication. Fig 1 Study of tribology Tribology is the science and technology of interacting surfaces in relative motion and is commonly known as the study of friction, wear and lubrication. It is the science and technology of friction lubrication and wear and is of considerable importance in material and energy conservation. It is an old knowledge of great importance when it comes to everything in movement but as a scientific discipline tribology is rather new. Tribology, although one of the oldest engineering discipline, it is one of the least developed classical sciences to date. The reason is that tribology is neither truly a single discipline nor well represented by steady state processes. It involves all the complexities of materials. Tribology is multidisciplinary in nature, and includes mechanical engineering (especially machine elements as journal and roller bearings and gears), materials science, with research into wear resistance, surface technology with surface topography analysis and coatings, and...

Lubricants

Lubricants A lubricant (also sometimes called as “lube”) is a substance (usually a liquid) introduced between two moving surfaces to reduce the friction between them which in turn improves the efficiency and reduces the wear. It also has the function of transporting foreign particles. A good lubricant possesses the following characteristics: High boiling point Low freezing point High viscosity index Thermal stability Hydraulic Stability Demulsibility Corrosion prevention High resistance to oxidation Lubrication is the process, or technique employed to reduce wear of one or both surfaces in close proximity, and moving relative to each other, by interposing a substance called lubricant between the surfaces to carry or to help carry the load (pressure generated) between the opposing surfaces. The interposed lubricant film can be a solid, (e.g. graphite and MoS2 etc.) a solid/liquid dispersion, a liquid, a liquid-liquid dispersion (a grease) or, exceptionally, a gas. Types of lubrication are shown in Fig 1. Fig 1 Types of lubrication Besides doing the function of lubricating, lubricants also carries out some or all of the following functions: Act as a coolant to remove the frictional heat which may be sometimes considerable. Keeps moving parts apart. Reduces friction between moving parts It dissolves and transports contamitants and debris arising both from internal and external sources. Acts as a hydraulic medium in some applications It protects against wear of highly loaded machine parts It prevents corrosion and rusting of machine parts It helps in transmitting power It offers protection against the accumulation of deposits (sludges and varnish) in lubrication system. It acts as a seal for gases It resists aeration and foaming, which can cause mal-functioning It resists or aid emulsion formation in wet systems. It stops the risk of smoke and fire of objects It has ability...