| Split Hopkinson bar(SHB) technique is one of the most effective methods for testing the dynamic behavior of materials at high strain rates. In order to meet the dynamic testing needs of aviation, aerospace, military and other fields, the application of SHB has been gradually extended to test the dynamic mechanical performance of low dimension materials, such as thin film and fiber, and micro scale devices. In this paper, both the mini SHT(P)B and the reluctance electromagnetic launcher have been improved. And eventually the mini SHTB and SHPB are applied to analysis the dynamic property of fiber materials and MEMS microstructure, respectively.To improve the reluctance electromagnetic launcher, the accelerating mechanism of the single-stage launching model was analyzed. The eddy current loss of the bullet, the electromagnetic leakage of the launcher and the dead resistance of the consumption circuit, which affected the launching speed of the bullet were optimized using the finite element method. Then, the single-stage launcher was improved, and the launching speed of the bullet was increased to 20m/s, fulfilling the requirement of the impact velocity for most dynamic tests.To improve the mini SHTB, the propagation process and characteristics of the stress wave was deeply analyzed and studied. The bars, including the incident bar, the bullet and the flange, were optimized using the finite element method and the optimizing design parameters of the bars were obtained simultaneously. According to the results of the analysis, an electromagnetic launching mini SHTB, which is appropriate for testing the dynamic property of single fiber materials, was built. In this system, a sensitive piezoelectric force transducer replaced the conventional transmission bar. Finally, the dynamic tensile test of single Kevlar®129 fiber was conducted using the apparatus and the stress-strain curve at high strain rates was obtained at the same time. Compared with the existing results, the feasibility and stability of the new apparatus for the dynamic tensile performance test of a single fiber are proved.A high acceleration loading system with high and low temperature loading function, including the mini impact loading system, the temperature box system and high-speed microscopy imaging system, was built. Basing on the dynamic testing system, the experiment studying the dynamic characteristics of the MEMS fuze mechanism was carried out at the temperature of-40℃,-20℃,0℃,25℃ and 50℃, respectively. And the movement and failure behavior under different temperature and high acceleration with a peak value of 40360 g and pulse width of 62μs were investigated. |
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