Lagging for control of shape memory alloy actuator response time

Shape memory alloys (SMA) are a particular class of materials that undergo a crystallographic transformation in the solid state. This effect can be utilised in the design of ultra-light mechanical actuators with significant environmental and economic benefits. Despite the advantages of SMA actuators, they are subject to a series of technical limitations, in particular, a relatively slow expansion rate, which typically occurs by free convective heat transfer to the ambient environment. Alternate heat transfer modes, including conduction and forced convection are more effective, but are not practical for typical applications. This article presents a novel method that enables significantly enhanced heat transfer in a practical and cost-effective manner. The novel method proposed in this work consists of lagging the SMA with a conductive material in order to manipulate the heat transfer rate. An experimental apparatus was developed to validate the proposed method.