Comparison between stress-strain plots obtained from indentation plastometry, based on residual indent profiles, and from uniaxial testing

Abstract

This paper is focused on comparisons between stress-strain plots from conventional uniaxial (tensile or compressive) testing and those obtained from indentation experiments, via iterative FEM modeling of the process in which the plasticity is represented using a constitutive law. Both Ludwik-Hollomon and Voce equations are used in the current work. Advantages of a spherical indenter shape, and of using the residual indent profile as the main experimental outcome, are highlighted. It is shown via detailed study of two different materials, with low and high work hardening rates, that the methodology (here termed indentation plastometry) can be used to obtain (nominal) tensile stress-strain curves, which incorporate the onset of necking and the ultimate tensile strength. High levels of fidelity are observed between these and corresponding plots obtained by conventional tensile testing. It is noted that, while there is also excellent consistency with the outcomes of uniaxial compression tests, the latter inevitably involve some experimental complications that are best avoided. It is concluded that indentation plastometry has the potential to become a mainstream testing methodology in the near future.