Formulation of a representative plastic strain and representative plastic strain rate by using a conical indentation on a rigid visco-plastic material

The indentation test consists in pressing an indenter on the surface of a tested material and in measuring continually the load F in function of the displacement h of the indenter. In order to analyze the indentation curve F(h) and extract material properties, one method among others uses the notion of the representative strain. The first aim of this paper is to investigate a new concept of a representative plastic strain as well as a new concept of a representative plastic strain rate. The second aim is to couple the effect of work hardening and strain rate to define the corresponding representative plastic strain and the corresponding representative plastic strain rate. It is shown that there are respectively two representative plastic strains and a plastic strain rate: the former obtained using the hardness of indentation and the latter obtained using the loading curve. Then, it is shown that the values of the representative strain and of the strain rate depend on the material behavior and its constitutive parameters. (C) 2014 Elsevier Ltd. All rights reserved.