Experimental and numerical investigation on the shock characteristics of U-notched ZL205A specimens under dynamic mixed-mode loading

Abstract Shock environment assessment and improvement during stage separation is an important issue of concern in aerospace engineering. This paper focuses on shock response caused by dynamic fracture of aluminum alloy separation plate, which usually undergoes mixed mode loading during separation. Based on Split Hopkinson Tensile Bar (SHTB) apparatus, five groups of U-notched ZL205A specimens with different loading angles (0°, 30°, 45°, 60°, and 90°) are designed to simulate mixed mode loading for shock characteristics testing. There piezoelectric accelerometers are used to measure the acceleration time histories, and the maximum shock response spectrum (SRS) are applied for shock data analysis. Meanwhile, the ANSYS/LS-DYNA finite element software is implemented for numerical analysis. The actual fracture angles measured from the recovered specimens are used to describe the actual fracture modes. The numerical and experimental results are in good agreement, showing that the shock response along the specimen’s length and thickness directions increases with the fracture angle, while there is a slight distinction in the specimen’s width direction with different fracture angles. On average, the shock response is more remarkable in pure tensile fracture mode, which is 2.6 times the pure shear fracture mode. As a result, increasing the study of shear fracture component is meaningful for the shock reduction through the structural design of separation plate.

摘要：级间分离过程中的冲击环境评估与优化是航空航天工程领域备受关注的重要课题。本文聚焦于铝合金分离板动态断裂引发的冲击响应——该类分离板在分离过程中通常承受复合型载荷作用。本研究基于分离式霍普金森拉杆（Split Hopkinson Tensile Bar, SHTB）装置，设计了五组带有U型缺口的ZL205A铝合金试样，通过设置不同加载角度（0°、30°、45°、60°与90°）来模拟复合型载荷以开展冲击特性测试。采用三台压电式加速度传感器采集加速度时程曲线，并以最大冲击响应谱（Shock Response Spectrum, SRS）作为冲击数据分析的依据。同时，借助ANSYS/LS-DYNA有限元软件开展数值仿真分析。通过回收试样实测的实际断裂角度表征试样的实际断裂模式。数值仿真与实验结果吻合良好，结果表明：沿试样长度与厚度方向的冲击响应随断裂角度增大而提升，而不同断裂角度下试样宽度方向的冲击响应差异相对较小。总体而言，纯拉伸断裂模式下的冲击响应更为显著，其峰值约为纯剪切断裂模式的2.6倍。综上，通过优化分离板结构设计以降低冲击响应，加强对剪切断裂组分的研究具有重要意义。