Hardness of common metals - Rigid limit case – plastic

Qualitative analysis has shown that elasticity has little influence on contact pressure in the case of pointed indenters and/or common metallic materials with a yield stress lower than their Young's modulus. Here, we describe the relationship between plastic flow stress and the hardness of low-hardenability materials, then describe the influence of hardening on the usual indentor shapes: sphere, cone of revolution, pyramid. Finally, we analyze the case of hardness tests carried out on heterogeneous materials, such as thin-film-coated materials or those showing a continuous variation in hardness with distance from the surface (parts subjected to diffusion treatment, for example).

This article is part of a series on hardness testing:

• Body hardness and qualitative analysis [M 4 154] ;

• Hardness of common metals. Rigid-plastic limit case [M 4 155] ;

• Hardness of materials. Influence of elasticity [M 4 156] ;

• Hardness of bodies. Analysis of other behaviors [M 4 157] ;

• Find out more [Doc. M 4 158].

Most of the symbols used in this article have already been introduced in [M 4 154]. Readers may find it useful to refer to their table of symbols.