Feasibility of shape memory alloy in a tuneable mass damper to reduce excessive in-service vibration

The applications of shape memory alloy (SMA) in vibration reduction are benefited by its superelasticity and thermomechanical properties. This study is a part of a series of research projects focused on reduction of timber floor vibration. In this study, the feasibility of this tuneable mass damper is tested for in-service vibration reduction. At first, the effect of temperature ranging from 11 °C to 120 °C on the dynamic characteristics of SMA was investigated under different pre-stressed levels. At higher temperatures, the damping ratio reduces while stiffness increases, and vice versa with decreasing temperature. SMA is sensitive to temperature when the pre-stressed level is near the phase transformation stress. Next, the analytical model of timber floor system was built and idealised as a two-degree-of-freedom system. Thirdly, a series of lab tests were carried out, and a damper consisting of an SMA bar was added on a cantilever beam with different natural frequencies, which represents floor system in the model. The results show that the vibration response of the system can be significantly reduced by the damper developed in this project, when the damper has resonance with the system. The mass of the system was then changed so as to make the damper out-of-tuned; the damper was then retuned by cooling/heating on SMA. After retuning of the damper, the response of the system was effectively reduced, which demonstrates the effectiveness and feasibility of employing SMA in the damper system.