An elasto-viscoplastic self-consistent model for polycrystalline material with imperfect interface under coupled thermo-mechanical loads

A coupled thermo-mechanical self-consistent constitutive model is proposed for elasto-viscoplastic polycrystalline materials with imperfect interfaces. In the developed model, a new linearization equation is adopted, and the self-consistent model is improved by introducing the thermal strain term and considering the imperfect interfaces between grains. The developed model is compiled and employed in finite element analysis by calculating the algorithmic tangent operator, affine strain increment, and thermal strain increment locally and globally. The effective elastic moduli of isotropic and cubic grains are analyzed to show the influence of the imperfect interface. The developed constitutive model is used to simulate the strain rate jump tests of 96Sn-4Ag alloy at constant temperatures. The parameters adopted in the model are calibrated and determined by fitting the experimental stress–strain curves. Without changing these parameters, the model is then applied to predict the deformation responses of 96Sn-4Ag alloy in total constraint, in-phase, and out-of-phase thermal cycling experiments. In addition, the implementation scheme of local grains is modified to describe the deformation characteristic of the 96Sn-4Ag alloy under coupled thermo-mechanical loads better.