Macroscopic constitutive law for SMA: Application to structure analysis by FEM

An SMA constitutive law has been developed and implemented in a finite element code in order to analyse the response of structures in shape memory alloys. The model is based on a thermodynamical approach of the martensitic phase transformation. The internal state is described by an original choice of internal variables: the martensite volume fraction and the mean transformation strain (MTS) of the martensite which takes a tensorial form. The martensite volume fraction depends on the martensitic phase transformation, while the reorientation process and the influence of the stress level are introduced with the MTS. This model allows to simulate both the superelasticity and the shape memory effect and takes into account the reorientation of the martensite variants.The implementation of this model in the FE code ABAQUS is ensured with the subroutine Umat (User MATerial) where the thermomechanical tangent operators are computed. Application of this finite element analysis is presented.