Deformation of Fixed Support Steel Plate under Explosion Load in Negative Pressure Environment
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摘要: 为研究负压爆炸载荷作用下结构的动态响应,以固支钢板为防护工程的简化单元,开展了负压爆炸实验,探究固支钢板在负压爆炸载荷作用下的变形规律,分析不同负压环境下固支钢板的极限应变和失效条件。采用AUTODYN对负压爆炸载荷作用下固支钢板的动态响应进行数值模拟,通过对比实验结果,验证了数值模拟结果的准确性。结果表明:随着初始环境压力的下降,相同爆距下钢板中心点的最大挠度和最大速度减小;负压爆炸载荷作用下,钢板整体出现塑性大变形,迎爆面形成凹坑,钢板四周在垂直于固支边界指向钢板中心的方向上出现明显的拉伸变形,钢板边缘区的挠度变化基本相同,中心点的最大挠度随着环境压力的下降而减小。通过双向应变假设,确定了钢板的动态极限应变为0.269。建立了负压环境下炸药爆炸冲击波的反射比冲量公式,并对基于刚塑性假设和能量准则提出的失效判据进行检验。研究结果可为负压环境下爆炸空气冲击波威力等效评估、高原环境下目标毁伤评估提供参考。Abstract: In order to study the dynamic response of the structure under explosion load in negative pressure environment, the negative pressure explosion experiments were carried out for the fixed supported steel plate, which is as a simplified unit of the protection project. The deformation law, and the ultimate strain and failure conditions of the fixed supported steel plate under different negative pressures were analyzed. The numerical simulation of the dynamic response of the fixed supported steel plate under negative pressure explosion load was carried out by AUTODYN, and the accuracy of the numerical simulation results was verified by comparing the experimental results. The results show that when the initial ambient pressure decreases, for the same burst distance, both the maximum deflection and the maximum velocity at the center point of the steel plate decrease. Under the negative pressure explosion load, the steel plate produces large plastic deformation, the oncoming surface forms a pit, and obvious tensile deformation occurs at the edges perpendicular to the boundary direction. The deflection changes in the edge zone are basically the same, and the maximum deflection at the center point decreases with the decrease of environment pressure. Through the bidirectional strain assumption, the dynamic limit strain of the steel plate is determined to be 0.269. The reflectance specific impulse formula of explosive blast wave under negative pressure environment was established, and the failure criterion based on rigid-plastic hypothesis and energy criterion were examined. The research results can provide a reference for the equivalent evaluation of the shock wave power of explosive air in negative pressure environment and the target damage assessment in plateau environment.
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表 1 实验工况
Table 1. Experimental conditions
Case pe/kPa W/g TNT equivalence/g Explosion distance/mm 1 60 150 130 150 2 80 150 130 150 3 101 150 130 150 4 101 200 170 50 表 2 开裂处钢板厚度的测量结果
Table 2. Measurement results of steel thickness at crack
Measuring
pointThickness/
mmDown gauging
rateBidirectional
ultimate strainMeasuring
pointThickness/
mmDown gauging
rateBidirectional
ultimate strain1 0.60 0.40 0.291 5 0.64 0.36 0.250 2 0.62 0.38 0.270 6 0.54 0.46 0.361 3 0.52 0.48 0.387 7 0.66 0.34 0.231 4 0.68 0.32 0.213 8 0.70 0.30 0.195 表 3 失效判别式的相关参数
Table 3. Relevant parameters for failure discriminant
Case ir/(Pa∙s) v0/(m∙s−1) $ \dot{\varepsilon } $/s−1 α σd/MPa εm η 1 742.1 94.5 326.8 2.52 592.2 0.059 0.219 2 816.8 104.1 359.9 2.55 599.3 0.071 0.264 3 882.8 112.5 389.0 2.57 604.0 0.082 0.305 4 3204.1 408.2 1411.4 3.04 714.4 0.915 3.401 ρs/(g·cm−3) A/MPa B/MPa n C m Tm/K 7.85 293.8 230.2 0.578 0.0652 0.706 1795 表 5 不同环境压力对应的空气密度
Table 5. Air densities at different environment pressures
Pressure/kPa Density/(kg·m−3) Pressure/kPa Density/(kg·m−3) 101 1.225 40 0.484 80 0.967 20 0.242 60 0.725 -
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