Fluid-Activated High-Load SMA Actuators With Enhanced Dynamics

This paper explores fluid-based activation of high-load shape memory alloy (SMA) actuators, which significantly enhances dynamic performance compared to conventional activation methods. High-load SMA-actuators are compact and capable of generating forces in the kilo-Newton range, making them ideal for applications in production plants where space and weight are critical. However, conventional activation methods of SMA-wire based actuators, such as Joule heating, are impractical due to the low electrical resistance of these actuators, leading to high current requirements. Instead, external resistance wire heating combined with air cooling is commonly used, but this limits dynamic performance.
In contrast, fluid-based activation offers improved dynamics, albeit with increased complexity. This study investigates various innovative designs for integrating fluid activation in high-load SMAs, including single and double-walled components. Experimental results demonstrate that fluid-cooled actuators achieve over 23 times higher cooling rates and up to 10 times faster heating rates than air-cooled counterparts, with the single-walled design performing best. Key design parameters, such as minimizing thermal capacity and effective sealing, are crucial for optimizing performance. The findings highlight the potential of fluid activation in enhancing the thermal dynamics of high-load SMA actuators, despite challenges in maintaining optimal fluid temperatures.