弹道明胶的动态力学测试方法研究

Study on dynamic mechanical testing method of ballistic gelatin

弹道明胶是一种超软材料,其波阻抗很低,采用经典的霍普金森杆测试技术无法获得其在高应变率下的力学特性。该文采用3种基于霍普金森杆的改进方法分别对其动态压缩力学特性进行测试,并对比3种方法的优缺点。实验结果表明:铝杆配合半导体应变片的测试方法对透射信号的提升有限,无法获得弹道明胶的动态力学数据;基于聚偏氟乙稀(polyvinylidene fluoride,PVDF)压电薄膜传感器的方法避免对透射信号的测量,可以获得满意的测试数据;撞击杆直接加载法在小应变阶段的测试结果可信,但在大应变阶段的测试结果无效。综合来看,使用PVDF压电薄膜传感器的测试方法可以较好地获取弹道明胶的动态力学特性。

As a kind of Ultra-soft materials,ballistic gelatin has very low wave impedance,and therefore their mechanical properties at high strain rates cannot be obtained by using classical split Hopkinson pressure bar testing techniques.In this paper,three methods based on the Hopkinson bar were used to test its dynamic compression mechanical properties.The advantages and disadvantages of the three methods were compared.The method of aluminum bar and semiconductor strain gauges has limited enhancement of transmission signals,and dynamic mechanical data of Ultra-soft materials cannot be obtained.The method of PVDF(polyvinylidene fluoride)piezoelectric film sensor avoids measuring the transmission signal and can obtain satisfactory test data.The impact bar direct strike method and the high-speed photography test method can obtain stronger transmission signals,but require higher sampling frequency for high-speed photography.In conclusion,the PVDF method is recommended for the dynamic mechanical testing of ballistic gelatin.