Behaviour of Iron and Steel Materials during Tensile Testing Aug28

Behaviour of Iron and Steel Materials during Tensile Testing...

Behaviour of Iron and Steel Materials during Tensile Testing The mechanical properties of iron and steels are often assessed through tensile testing. The testing technique is well standardized and can be conducted economically with a minimum of equipment. Since iron and steel materials are being utilized in structural applications, they are to have tensile properties which meet the requirements of the relevant codes and standards. These requirements in the code and standards are the minimum strength and ductility levels. Due to this, information available from tensile testing is often underutilized. However, direct examination of many of the metallurgical interactions which influence the results of tensile testing can considerably improve the usefulness of the testing data. Examination of these interactions, and correlation with metallurgical / material /application variables such as heat treatment, surface finish, test environment, stress state, and anticipated thermo-mechanical exposures, can lead to significant improvements in both the efficiency and the quality of utilization of iron and steel materials in the engineering applications. Tensile testing of iron and steel materials is done for many reasons. Tensile properties are normally included in material specification to ensure quality and are often used to predict the behaviour of these materials during different forms of loading other than uniaxial tension. The result of tensile testing is normally used in the selection of these materials for engineering uses. It provides a relatively easy and cheap technique for developing mechanical property data for the selection, qualification, and utilization of these materials in engineering applications. This data is generally used to establish the suitability of these materials for a particular application, and/or to provide a basis for comparison with other substitute materials. The elastic moduli of iron and steel materials are dependent on the rate at which the test sample...

Fire Resistant Steels...

Fire Resistant Steels Steel is inherently a noncombustible material. It loses strength when heated sufficiently.  Steel structural properties and its yield strength considerably decrease when it is heated to temperatures seen in a fire scenario. The critical temperature of a steel structural member is the temperature at which it cannot safely support its load. Building codes and structural engineering standard practice defines different critical temperatures depending on the structural element type, configuration, orientation, and loading characteristics. The critical temperature is often considered the temperature at which its yield stress has been reduced to 60 % of the room temperature yield stress. Fire is a chemical phenomenon that occurs as a result of thermal processes. When a steel section is exposed to a fire then the level of temperature increase on the face of steel section depends on thermal inertia, exposure of surface area and the protective coating. As the rate and amount of heat flow from the fire environment to steel section increase, the temperature, and thus the risk of failure for the steel section also increases. Since the steel has a very high thermal conductivity, exposed surface of the steel section easily transmits the conveyed heat from the fire source to the other members of the whole structure in a short period of time. Heat is transmitted in between the steel sections from high temperature sections to low temperature sections by way of conduction, radiation or convection modes. Steel sectional properties and its yield strength considerably reduce as it absorbs heat upon exposure to a high temperature level. A steel structural member may easily collapse during a fire if the temperature is allowed to reach a critical value. The fire resistance of the steel member is related to some important factors including the section size, the perimeter...