On the study of mystical materials identified by indentation on power law and Voce hardening solids

We conduct an incisive investigation of the existence of a one-to-one correspondence between a material's elastoplastic properties and its indentation responses, with particular emphasis on the residual imprint. We first unravel a so-called "mystical material" pair reported by Chen et al. (2007) by examining the specimens' post-indentation morphologies, despite using a single self-similar indenter. Next, using Metric Multidimensional Scaling (MDS), we mitigate the mystical material issue for materials hardening according to the popular Hollomon's power law equation. In contrast, the same exact protocol reveals the absence of a one-to-one correspondence between the single indentation response and Voce hardening parameters. To alleviate this, we propose a multi-depth indentation strategy.