A general hereditary multimechanism-based deformation model with application to the viscoelastoplastic response of titanium alloys

The formulation of a general model for the hereditary behavior of materials , in the viscoelastic and viscoplastic regimes, is presented. In this, we u tilize the complete-potential structure as a general framework, together wi th the notion of strain- and stress- partitioning in terms of separate cont ributions of several submechanisms (viscoelastic and viscoplastic) to the t hermodynamic functions (stored energy and dissipation). Detailed numerical treatments are given for both (i) the implicit integration algorithm for th e governing flow and evolutionary rate equations of the model, and (ii) the automated parameter-estimation methodology (using the software code COMPAR E) for characterization. For illustration, a specific form of the model pre sented is characterized for the TIMETAL 21S material using a very comprehen sive test matrix, including creep, relaxation, constant strain-rate tension tests, etc. Discussion of these correlations tests, together with comparis ons to several other experimental results, are given to assess the performa nce and predictive capabilities of the present model as well as the effecti veness and practical utility of the algorithms proposed. (C) 2001 Published by Elsevier Science Ltd.