Experimental and numerical investigation of thermomechanical cycling of notched NiTi shape memory ribbon using SMA model accounting for plastic deformation

Shape memory alloys (SMAs) are being increasingly applied as thermally driven actuators. The commercially available SMA elements, however, frequently contain stress risers, either due to internal or surface defects the required component shape. Stress risers represent a potential danger for preliminary fatigue failure of such actuators but its actual mechanism is not very clear. This paper presents combined experimental (2D DIC analysis strains) and numerical (SMA model with plastic deformation) stress, strain phase fraction fields evolving in thin NiTi shape ribbon an artificial notch subjected cyclic cooling-heating through transformation range under constant external force. It appeared that, even if only low tensile externally upon thermal cycling, local at tip sharply increases during first cooling forward martensitic (MT) proceeding heterogeneously space. heterogeneity gives rise deformation notch-tip, which gradually accumulates cycling shields from overloading. Hence, performance actuator riser depends much on deformability alloy.