Fully coupled thermomechanical model for shape memory alloys accounting for phase transformation, martensitic reorientation, transformation-induced plasticity and fatigue damage

Abstract

The present work proposes a 3D model, based on the thermodynamical coupling of different strain mechanisms such as the forward and reverse phase transformation, the martensitic reorientation, the transformation-introduced plasticity and the fatigue damage. To achieve this goal, all the above mentioned mechanisms are described through the martensitic volume fraction as the coupling parameter. A recently developed, thermomechanically coupled, SMA constitutive law, including both the phase transformation and martensitic reorientation mechanisms, has been validated under non-proportional loading conditions through a series of comparisons between numerical and experimental results. This model is extended further in order to capture the accumulated TRIP residual strain induced by the martensitic transformation, accounting in addition for the accumulated fatigue damage, which evolves during the cyclic loading. The fatigue damage is incorporated into the constitutive law through the concepts of continuum damage theory. Numerical investigation under strongly non-proportional thermomechanical loading conditions demonstrate the capabilities of the new framework.