The thermomechanical modelling of the macroscopic behavior of NiTi shape memory alloys was studied. A phenomenological 3D-model, based upon the thermodynamics of irreversible processes was presented. Three main physical mechanisms were considered: the martensitic transformation, the reorientation of martensite and the inelastic accommodation of twins in self-accommodated martensite. The description of such strain mechanisms allow an accurate analysis of shape memory alloy behavior under complex thermomechanical paths, especially when transformation occurred at low stress level. Moreover, some key characteristics such as tension–compression asymmetry and internal loops inside the major hysteresis loop were taken into account. Numerical simulations for various theromechanical loading paths were presented to illustrate the present model capability to capture the complex behavior of shape memory alloys.

Constitutive Model for Shape Memory Alloys Including Phase Transformation, Martensitic Reorientation and Twins Accommodation. Y.Chemisky, A.Duval, E.Patoor, T.Ben Zineb: Mechanics of Materials, 2011, 43[7], 361-76