Characterization of double strain-hardening behavior using a new flow of extremum curvature strain of Voce strain-hardening model

The traditional flow models with an emphasis on Voce family flow models are criticized using a typical monotonic strain-hardening material and a double strain-hardening (DSH) material. The DSH behavior is quantitatively expressed in detail using SUS304. They are, however, negatively evaluated especially for the DSH material that simultaneously experiences wide ranges of strain (e.g., during cold forging). After characterizing the Voce strain-hardening model (VSHM) with an emphasis on not only asymptotic stress but also a new concept of extremum curvature strain (ECS), the Voce-Ludwik model coupled with ECS is presented to describe the DSH flow behavior, based on the mathematical characteristics of VSHM. It has been found that the proposed Voce-Ludwik model can reflect DSH behavior using the nature of the strain at the ECS, which has the distinct advantage of modeling thermoviscoplastic flow behaviors of the DSH materials including stainless steels, copper alloys, aluminum alloys, etc.