High Load NiTi Shape Memory Alloy Actuators: A Study of Cyclic Behavior

This paper advances the knowledge of the cyclic thermomechanical behavior and fatigue of high load SMA-Actuators. Due to their small volume and weight, these actuators provide an attractive alternative to conventional actuators. Especially in production plants and machines, where the requirements for installation space and weight are becoming increasingly crucial for a successful manufacturing process, they find a wide field of application. Quite in contrast to small force applications, more massive geometries and new integration concepts of the shape-memory-components (SMC) are substantial. However, well developed semi-finished products are not yet available. Furthermore, this changes mechanical and functional cycle fatigue, an issue well known from wire based small force SMA-Actuators. Comprehending how these changes significantly alter the SMA behavior will eventually enable novel designing and optimizing. Therefore, the cyclic behavior of the SMC is investigated, using a high load SMA-Actuator, that has been designed for integration in machines tools. The SMCs, cycled in the SMA-Actuator have been manufactured with different methods. Here, a classical manufacturing process is compared to an additive process (PBF-LB/M). The additive processed SMCs show microcracks and pores. Nevertheless, the cyclic properties exceed those of the classical processed specimen in all measured properties. Especially the tiny hysteresis, low shortening of the SMC can be highlighted.