Presents performances and results of the numerical solution of problems of the forward and reverse transformation in the rod of NiTi when heating and cooling under constant stress. Solving problems in the so-called “double-connected” formulation, ie, taken into account the effect of the stresses and strains on the phase composition and phase changes in the phase composition of the distribution of the material temperature and its change over time. It uses a thermodynamic model of behavior of shape memory alloys (SMA), is not relying, in contrast to the known analogues, on any a priori hypotheses about the rate of dissipation. Model extended to the case of materials with nonlinear dependence of the total deformation under the influence of a direct conversion of the DC voltage on the magnitude of the voltage. A comparison of the results of solving problems within the framework of linear and nonlinear models.