Multiphysics modelling and design of shape memory alloy wave springs as linear actuators

This paper explores the merits of shape memory wave springs as powering elements of solid state actuators. Advantages and disadvantages of the wave construction in comparison to the traditional helical shape are presented and discussed by means of dimensionless functions. The main assets of the wave springs are the higher electrical resistance (leading to simpler electrical drives) and the lower cooling time (leading to enhanced working frequency). The wave geometry is also superior in purely mechanical terms to the helical counterpart when axial space is at a premium. A step-by-step design procedure is proposed, leading to the optimal wave spring meeting the multiphysics design specifications and constraints. A case study is finally reported, showing the application of shape memory wave springs to the design of a telescopic linear actuator.