Fundamental Resarch on Impact Energy absorbing Actuators of Shape Memory Alloys

点击翻译按钮获取中文摘要

In this research, impact energy absorbing actuators of shape memory alloys (SMA) was studied by using both the shape memory effect and superelasticity of SMA.Three types of SMAs, temperature-sensitive SMA, magnetic SMA (Ni2MnGa) and stress-sensitive SMA (FeNiSi), were used. When collision of cars is predicted by sensors, magnetic field is applied to the SMA actuators so that the collision energy can be absorbed by the shape memory effect and superelasticity of SMA actuators.First, the relationship between impact force and absorbed energy, impact response of SMA material, the method of magnetic field generation and influence of temperature are clarified theoretically and experimentally in this research. Next the concept of impact energy absorbing actuator was proposed. In order to increase the response speed, magnetic field and stress were also used to induce phase transition in SMAs in addition to temperature. Hence, the possibility of impact energy absorbing SMA actuators, which were impossible for traditional SMAs, has been shown.In the last of this research project, the static characteristics of magnetic SMA and stress-sensitive SMA were investigated. The static characteristics include the relationship between the critical magnetic field strength and temperature for phase transition of magnetic SMA, and the relationship between critical stress and temperature of stress-sensitive SMA.Based on the static characteristics, impact response test was performed. By applying large electric current with capacitors, the response time of SMA actuators was decreased to about 10ms in the experiment.