Micromechanical modeling of the stress-induced superelastic strain in magnetic shape memory alloy

A constitutive model for magnetic shape memory alloys (MSMAs) is developed through a combined consideration of micromechanical and thermodynamic theories. The kinetic equation is established in terms of the thermodynamic driving force derived from the reduction of Gibbs free energy of MSMA. An equation that balances the thermodynamic driving force with the corresponding resistive force is obtained to calculate the volume fraction of the martensite variant under different given stress, temperature and magnetic field. The nonlinear and hysteretic strain response of MSMAs is investigated for stress-induced reorientation under constant magnetic field. The theoretical results are found to be in good agreement with experimental data.