Shakedown theorems for shape memory alloys structures with functional fatigue — Application to nitinol stents

Shape memory alloys (SMAs) offer interesting perspectives in various fields such as aeronautics, robotics, biomedical sciences, or structural engineering. The distinctive properties of those materials stem from a solid/solid phase transformation occurring at microscopic level. Modeling the rather complex behavior SMAs is topic active research. Lately, SMA models coupling phase-transformation with permanent inelasticity have been proposed to capture degradation effects which are frequently observed experimentally for cyclic loadings — phenomenon referred functional fatigue. In this paper, classical static and kinematic shakedown plasticity theory extended material models. Those results give conditions energy dissipation remain bounded, beneficial fatigue life. Analytical limits obtained 3-bar truss example compared numerical step-by-step simulations. We consider problem nitinol stent submitted pressure mixed pressure–bending an application, showing how approach presented can be combined finite-element analysis study 3D structures.