A constitutive model for shape memory alloys considering tensile-compressive asymmetry and plasticity

Shape memory alloys (SMAs) are materials that present, among other characteristics, the capacity to undergo large permanent strains, and then, after a proper increase on the temperature, recover its original shape. Constitutive models consider phenomenological aspects of thermomechanical behavior of these alloys. The present contribution proposes a constitutive model to consider both the tensile-compressive asymmetry and plastic strains that occur in the thermomechanical behavior of SMAs. A numerical procedure is proposed in order to deal with nonlinearities of the formulation. Comparisons between experimental and numerical results predicted by the proposed model show that they are in close agreement. Moreover, numerical simulations show that the model is capable to capture the general behavior of SMAs, allowing the description of important characteristics of these alloys as pseudo-elasticity, one-way and two-way shape memory effect, phase transformation due to temperature variations, internal sub-loops due to incomplete phase transformations and tensile-compressive asymmetry.