Overview of Profilometry-based Indentation Plastometry and its Industrial Usage

This paper includes a review of the current state-of-the-art in a technique for extracting the (quasi-static) stress-strain relationship of a metallic sample from an indentation experiment, as well as an industrial case study using the technique to map the stress-strain
properties of a forged part. The technique, called profilometry-based indentation plastometry (PIP), uses a large (either 1 mm or 0.5 mm radius) spherical indenter to create a residual indent under relatively high applied loads (kN range). The indent profile is measured, and iterative finite element method (FEM) simulation of the indentation is carried out to converge on the true stress-strain curve of the indented material (with the indent profile as the target outcome). Commercial products are now available that automatically complete indentation, profilometry and convergence upon Voce plasticity parameter values, which describe the full stress-strain curve within a few minutes.The review covers the technique’s advantages as an indentation-based technique, firstly in the mapping of samples and secondly in giving insight into the direction and sense of anisotropy from the breakdown in radial symmetry. The case study demonstrates the application of the technique in both of these areas for characterising a forged part, comparing the results from PIP to conventional uniaxial testing. It is shown that the scale of PIP unveils local inhomogeneity unable to be detected by tensile testing, where these differences can be linked to the prior plastic strains introduced during forging. Additionally, anisotropy is detected by PIP relating to aligned FeNiAl precipitates that give a sense of the strength and direction of the
anisotropy.