The reasons of unique thermomechanical properties of shape memory alloys (SMA) are thermoelastic phase and structure transformations. These processes are diffusion-less. This is a way the properties of SMA are considered usually as scleronomous. Following the result of recently experimental investigation the properties of SMA are not complete scleronomic. In this article the simplest model of rheonomous properties of SMA is proposed. The time-dependent behavior of SMA in strain-controlled and stress-controlled loading, in the case of step-wise loading in the regime of martensite inelasticity and super-elasticity so as the phenomena of stress relaxation are simulated. Theoretical results do not contradict the experimental data.