Moving inelastic discontinuities and applications to martensitic phase transition

In this work, equations of the kinetics and kinematics are developed for heterogeneous materials containing inelastic discontinuities with moving boundaries. From the derived free energy and the power of external forces one obtains the driving force acting on the moving boundary. Introducing the interface operators and some hypothesis on inelastic fields, one gets the driving force for the formation of an ellipsoidal domain. The theoretical model is illustrated by the derivation of nucleation and growth conditions of a martensitic plate inside an inhomogeneous plastic strain field. The obtained results are combined with a study of the kinetics and kinematics to derive the constitutive equation of an austenitic single crystal, from which the overall behavior of polycrystalline TRIP steels is deduced using the self-consistent scale-transition method. Comparison with experimental data shows a good agreement.