Mechanical Properties and their Determination - Summary

Mechanical properties from the basis for calculations of dimensions of machine or structure of part. Conveniently, these properties are determined by experiments in laboratory. Tensile tests perform universal testing machine help define such properties as ultimate tensile strength, yield strength % elongation, modulus of resilience & modulus of toughness. These properties have been explained. The idea of static loading, rate of straining, elastic and plastic deformations and concepts of true stress and strains have been introduced.

The tendency of material to become brittle and factors that may cause such tendency are important considerations before engineers. Impact tests on notched specimen for determination of such tendency are performed.

The material in practice is several times needed to resist scratching and wearing. Hardness of materials, which can be measured on several scales through indentation are described. Different types of indenters and the impressions they leave on surface and factors by which they are influenced are discussed. The stresses applied on machine parts and structures very with time. The materials fail at low stress level under varying stresses and behaviour is called fatigue. The highest stress level at which material will not fail for 107 cycles is defined as fatigue strength. A host of factors affect fatigue strength. Determination of fatigue strength from experiments is a boring exercise. It is illustrated through exercise.

The material deforms constantly under constant stress/load over a long period of time. This behaviour, accentuated along high temperature, said creep is discussed. It has been discussed how this behaviour is considered for calculating life time or temperature out of three variables. Brief description of materials to be used for high temperature has also been given.