A plastic dissipation-based yield surface and flow rule characterization through mesostructural simulation

Abstract

An evolving yield criterion, along with one or multiple state (internal/history) variables and a flow rule, are essential components of any conventional plasticity model. Ideally, to characterize a yield criterion, yield points should be identified at every level of state variables across different loading paths. However, this process presents two significant challenges: first, experimentally determining many of the required continuum-level variables is nearly impossible, and second, a unifying approach is needed to correlate separate pieces of multiaxial stress-strain data with the evolution of the yield surface. This study addresses these challenges by proposing a methodology for characterizing the initiation and evolution of the yield surface while assessing the normality rule. The approach uses: (1) plastic dissipation as a unifying scalar state variable, (2) the advantages of mesoscale simulations to provide variables at every stage of deformation, (3) an appropriate mathematical form for the yield criterion, and (4) nonlinear implicit data fitting techniques for parameter identification. The practical application of the proposed methodology is demonstrated using simple 2D voided solids.