A constitutive model to predict the pseudo-elastic stress-strain behaviour of SMA

Shape memory alloys (SMAs) are a wide class of materials characterized by the property to recover the initial shape also after high values of deformations. This is due to the ability of SMAs to change, in a reversible manner, their microstructure from an initial structure, often named austenite, to a final structure, named martensite. The transformations of microstructure can take place with or without one or more intermediate phases, but always without re-crystallization, implying a microstructure changing inside the crystals, without any new boundary creation. The stress-strain behaviour depends on the crystal structures. In this work, a simple model to predict the stress-strain behaviour of a PE SMA has been proposed. The results have been compared to an experimental tensile test carried out on a NiTi SMA alloy.