Shape Memory Alloys for small scale actuation

Abstract

Shape Memory Alloys (SMAs), materials that can undergo a fully recoverable strain change due to a thermal cycle, and which can be produced in a form that is superelastic are only utilized limitedly. In this thesis, I investigated the relationship between the material properties of shape memory alloy micro-wires and their mechanical performance. This study was conducted with two main types of SMAs, the first a commercially available NiTi wire, and the second an emerging Cu-based alternative. This comparison allows an understanding of the current state of the art for small scale actuation with SMA wires, and to evaluate the Cu-based alternative SMA, which has a reduced cost and improved thermal properties. This thesis evaluates Cu-based SMAs as substitutes for NiTi in terms of activation strain of wire during a shape memory cycle, power consumption during actuation, heating and cooling times during actuation, and cost. Furthermore this thesis includes studies on the processing of Cu-based alternatives to enhance shape memory properties of interests, such as transformation temperature and fatigue, and suggests future work to improve Cu-based SMA wires..