Thermomechanical cyclic behavior modeling of SMA materials and structures

A 3D thermomechanical macroscopic model describing the cyclic effects in SMA has been developed by Sant-Sulpice et al.. The essential of this model is based on the introduction of a variable describing the development of jammed martensite. As it is known, a residual strain under cyclic thermomechanical loadings is developed in SMA like the ratcheting effect in plasticity. The origin of the evolution of the residual strain in SMA can be the plasticity or the development of jammed martensite. In some SMAs, its origin has been verified and it has been concluded that it is mainly due to the jammed martensite. This permits to justify the models constitutive equations. The developed model has been validated by simple thermomechanical cyclic tests. It has been integrated numerically in Cast3M finite elements code. This study is organised in two parts. The first one concerns the numerical scheme and the validation tests on a volumic element under simple cyclic loadings, cyclic proportional and non proportional loadings. The second part concerns the numerical study of SMA structures. Two coil sprins actuators under cyclic assisted shape memory effect are also studied