Finite element simulation of strain rate effects on localized unstable pseudoelastic response of shape memory alloys

A macromechanical total-deformation constitutive model of pseudoelasticity previously developed by the authors is employed within a two-dimensional finite element framework to numerically investigate the effect of strain rate and boundary conditions on the overall mechanical response and nucleation/evolution of transformation bands in NiTi strips during both forward and reverse transformations.The simulation results are compared with the experimental observations previously reported by other researchers, and it is shown that the present method successfully captures the nucleation and propagation of localized deformation bands during both loading and unloading.It is confirmed that the number of propagating fronts plays a key role in the pseudoelastic response of material in nonisothermal conditions.Special attention is paid to the morphology of the transformation fronts and its evolution.The numerical analysis indicates that the predicted morphology of the fronts is highly sensitive to imperfections and misalignments in the boundary conditions, especially during the reverse transformation.