FEM SIMULATION OF THE MARTENSITIC-TRANSFORMATION IN NITI ALLOYS

Numerous studies have demonstrated the influence of elastic and plasti c strain energies on the martensitic transformation in shape memory al loys. In recent years the Finite Element Method (FEM) has been applied to a wide range of elastic and plastic problems, however, few FEM ana lyses of shape memory phenomena have been reported. In this paper the FEM method has been used to model the martensitic transformation. The model assumes a two variant shear transformation in a two dimensional grain. Plastic deformation accompanying the transformation is accounte d for using the Estrin-Mecking constitutive model. The spatial distrib ution of elastic and plastic strain energies developed during the tran sformation is shown to determine variant structure. Calculations of th e effect of applied stress on variant structure and the effect of stre ss and repeated thermal cycling on the transformation temperatures are presented.