Hardness

AbstractHardness is a measure of a material's resistance to deformation. Here hardness is taken to be the measure of a material's resistance to indentation by a tool or indenter harder than itself. This seems a relatively simple concept until mathematical analysis is attempted; the elastic, plastic, and elastic recovery properties of a material are involved, making the relationship quite complex. Further complications are introduced by variations in elastic modulus and frictional coefficients.As a consequence, numerous practical applications of indentation hardness are in use and others are being developed. Many types of hardness tests have been devised. The most common in use are the static indentation tests, eg, Brinell, Rockwell, and Vickers. Dynamic hardness tests involve the elastic response or rebound of a dropped indenter, eg, Scleroscope. Although indentation hardness tests are usually classified as non‐destructive, they do in fact leave a permanent indentation on the surface of the workpiece.Hardness ConversionsDespite variations in hardness test procedures and the variations in physical properties of the materials tested, hardness conversions from one test to another are possible.