Determine hardness of material:
Hardness is surface property. It can be defined as resistance of material against permanent deformation of surface in the form of scratch, indentation, cutting, or mechanical wear. The requirement of hardness test arises from the fact that in numerous engineering applications, 2 components in contact are made to slide over each other. Eventually, their surfaces are scratched and they may fail because of mechanical wear. This result in not only quick replacement of both parts but also incurs big loss in the terms of money.
For instance, piston ring of an I.C engine remains in sliding contact with cylinder body when piston reciprocates within the cylinder. If proper care is not taken in the selection of materials for then, the piston rings and cylinder will wear soon.
In this case replacement or repairing of cylinder block will require much time, trouble and money. Thus, the material of piston rings and cylinder block should be taken such that wear is least on cylinder. Thus in case of repairing, cheaper piston rings can be easily replaced. This envisages that the material of cylinder block should be harder than material of piston rings so that cylinder wears the least. This can be ascertained by the conduct of hardness test. This is why it is essential to know how this test can be conducted.