Abstract
This study is devoted to thermomechanical analysis of the martensitic transformation of Shape Memory Alloys (SMA) with various scales and through tensile test, three-dimensional finite element simulations and molecular dynamics simulations. The study is restricted to the pseudoelastic behaviour of a CuAlBe single crystal. The observations by kinematic and energetical coupled imaging techniques allow us to characterize the front of phase change, which appears during a mechanical loading on a SMA sample. The energetic analysis of this experimentation enables us to interpret the phase transformation as a strong thermomechanical coupling, and to neglect the intrinsic dissipation. These hypotheses found the monovariant thermomechanical model and allow hysteretic phenomena and time effects without the intervention of irreversibility. Thus, the front of phase change is numerically generated and compared to experience and literature. In a second time, an ideal model of SMA is suggested at the crystalline scale. The use of molecular dynamics on this sample allows to apply a thermomechanical solicitation, and to build the associated energetic potential. The evolution of the sample behaviour according to its size is numerically studied then debated. A tendency to convexification of the energetic potential is noticed, as well as a complex microstructure development.