Experiments on shape memory alloy actuator and practical applicability considerations

This paper describes the design and the experimental work on a force-generating Shape Memory Alloy (SMA) actuator concept. The objective of the work was to test the applicability of the actuator concept for semi-active vibration control. The actuator was designed for bolt-force adjustment in structural joints. The SMA material applied was standard commercial NiTiNol alloy. Two different actuator designs were constructed and tested: a smaller air-heated design, and a larger water-heated design. The actuator's ability to generate a force as a function of the bolt pre-tension was studied in the experiments. The magnitude of the forces generated was from 1 kN to 70 kN. In terms of design and control, non-linear behaviour of the actuator was considered a challenge. For the industrial application point-of-view, the long-term behaviour and the price of the material were considered the greatest challenges. Ability to generate large forces relatively quickly was seen as a promising opportunity. Furthermore, both actuator constructions were relatively simple and consisted of small number of components.