Fatigue life characterization and modeling of a Ni–Ti snake-like element for mini actuation

Abstract

The interest in the design of shape memory alloy (SMA) actuators is recently broadened thanks to their high power density and versatility. In particular, snake-like Ni–Ti actuators demonstrated high potential at the mini- and micro-scales as SMA non-conventional active elements, due to their capacity to provide significant displacements in a very limited space and over a high number of thermo-mechanical cycles. In this study, the fatigue behavior of a snake-like Ni–Ti element has been investigated to identify the Wöhler F-N curve. Moreover, a validated digital twin of the device was prepared and used to evaluate the stress distribution throughout the fatigue tests, to convert the experimental data into a Wöhler stress-life curve. The numerical description of shape memory behavior was performed through the Petrini–Bertini constitutive model, which also allowed a better insight for future shape and functional optimization of the device.