Damping capacity of shape memory alloys

• Main Author: Ng, Chun Yong
• Other Authors: Liu Yong
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/60091
• Institution: Nanyang Technological University

High damping materials have been attracting much interest and attention in engineering applications. However, little research has been done on the heat-dependent effects on damping capacity of a material if subjected to heating or isothermal environment. Shape Memory Alloys (SMAs) such as NiTi have shown that it can exhibit high damping capacity, excellent shape memory effect and superelasticity. It is known that the damping capacity of a material varies under different external parameters (i.e. frequency and stress). The main purpose of this study is to investigate how the damping capacity would be affected by different external parameter and also the influence of heat effects on damping when material is working under an environment with and without temperature variation. The influencing factors on the damping capacity of NiTi wire were studied; independent variables such as temperature, strain amplitude and frequency were selected to measure the effects that these variables have on damping capacity. Experiments were carried out under the heating and isothermal condition before evaluating the differences between both methods. The experimental results obtained from the Dynamic Mechanical Analyser (DMA) machine have shown how the 3 parameters affect the damping capacity. Upon heating, the damping capacity of the NiTi wire was observed to be high at low temperature, peaked at transformation temperature and then a significant reduction in damping was noticed at high temperature. When subjected to strain, the results show that the damping capacity increases with increasing strain amplitude but reduces when amplitude was further increased. On the other hand, the continual increase in frequency shows a decrease in damping capacity at low frequency range, but rises at high frequency range. Finally, the heat effects on the damping capacity were evaluated by comparing the value of Tan δ when specimen was held under heating and isothermal conditions. It was found out that the damping capacity significantly increased under heating condition at the transformation phase.