Design, Characterization, and Finite-Element Optimization of a Two-Way Assisted Through SuperElasticity Torsion Actuator

Abstract

The present study aims at developing a new Shape Memory Alloy (SMA) autonomous torsion actuator that exhibits Two-Way reversible memory effect Assisted by SuperElasticity. The developed actuator noted hereafter TWASE is composed by a single NiTi compact component having two distinct SMAs parts on one single axis: a SuperElastic part (length L SE ) and a Shape Memory Effect part (length L SME ). The proposed design ensures twisting the actuator when heated, this activates then the superelastic part putting back the actuator into its original shape as a result of a decrease in temperature. Hence, the actuator moves and goes back to the initial position autonomously (self-reversible). It has been established that the actuation efficiency is strongly dependent on the length ratio (k SME ) of the SME part with respect to the total length of the torsion actuator. Experimentally, an actuator with a length ratio of 3/5 has been developed and tested. The actuator’s axis is subjected to a specific heat treatment for obtaining a SMA wire with two distinct zones. A FE analysis using a proper UMAT subroutine into Abaqus software has been performed to predict the kinematics and the thermomechanical response of the actuator and finally to optimize it accordingly. The developed computational model captures the actuator responses and the subsequent optimizations are carried out leading to the improved specifications, which are confirmed experimentally. The experimental validation has been carried out using a prototype set-up of a torsion bench built by 3D printing. The actuation response of TWASE is numerically analyzed for several length ratio configurations. Based on the numerical simulations, the performance of the actuator has been optimized in terms of rotation angle and length ratio. The best ratio of shape memory to superelastic parts in the actuator has been predicted to 1/4 for obtaining the expected two-way reversible memory effect (TWASE).