R-phase shape memory alloy helical spring based actuators: Modeling and experiments

The main goal of this paper is to propose some analytical or pseudo-analytical tools facilitating the study and modeling of SMA helical spring-based actuators. Particular attention is paid to R-phase SMA helical spring-based actuators (i.e., springs made in NiTi and concerned by R-phase transformation phenomena). First, simplified models (i.e., based on beam theory framework) of R-phase SMA helical springs taking into account detwinning and assisted two-way memory effect are proposed and validated. Then, these models are used to determine the thermo-mechanical behavior of a linear bias-spring actuator. An actuator is built and used to validate the proposed models.