Micromechanical Modelling of the Superelastic Behavior

Abstract
Shape Memory behavior in polycrystalline material is very sensitive to the local stress state. To take this features into account, we have developed a micromechanical approach based on a kinematical description of the physical strain mechanisms and a definition of a local thermodynamical potential. Volume fractions of the different variants of martensite are chosen as internal variables to describe the evolution of the microstructural state of the material. Physical limitations excerted on these variables are accounted using a constrained potential. Dissipative aspects at the origin of the hysteretic behavior of these alloys, need to define a dissipative potential. This analysis determines the local constitutive equations for the behavior. Global relationship are determined using a self consistent approach. Results obtained by this way are in good agreement with experimental observations performed on Cu-based Shape Memory alloys. In addition, this modelling is able to determine the kinetics of the phase transition and to give the evolution of the transformation strain for different thermomechanical loading paths.