Axial Distribution of Fragment Initial Velocities from Cylindrical Casing with Different Length-to-diameter Ratios
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摘要: 一端中心起爆装药的圆柱套筒是破片型武器最常用的结构,其破碎产生的破片初速是评估杀伤威力和防护结构性能的重要参数。针对精确预测不同长径比(L/D)下圆柱套筒的初速分布问题,首先基于试验验证的数值模型研究了L/D对破片初速的影响,在此基本上,提出了适用于L/D≥1圆柱套筒的初速分布计算模型,该模型中添加了与L/D相关的受轴向稀疏波影响的修正项,最后,通过试验和数值模拟对所提出的初速计算模型进行了验证。研究结果表明:不同L/D下的破片初速分布均呈现两端初速低,中间高的变化趋势,且L/D越大,破片初速越大,当L/D达到5时,最大破片初速与Gurney公式计算结果之间的相对误差仅为1.99%;公式计算结果与试验结果和数值计算结果的平均误差不超过6%,表明了该模型在预测不同L/D下的破片初速分布是可靠的。研究工作可为破片毁伤威力评估及反恐工程中防护装置的结构设计提供参考。
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Abstract: Cylindrical casing filled with charge under central point detonation at one end is the frequently-used structure for fragment weapons, whose fragment initial velocity produced by its fracture serves as an important parameter for evaluating the lethal power and the protective structures. To accurately predict the initial velocity distribution of cylindrical casing with different length-diameter ratios (L/D), it studied the impact of L/D ratios on the initial velocity of fragments and the applicability of existing empirical models for the initial velocity of fragments founded on the numerical model of experimental verification. On this basis, a correction term related to L/D ratio, which was often influenced by the axial rarefaction waves, was added to the fragment initial velocity index model. By fitting the data obtained from numerical simulations, the function expression of the correction term was derived and the calculation model for the initial velocity distribution of cylindrical casing with L/D ratio≥1 was obtained. Finally, the applicability of the established fragment initial velocity calculation model was validated through experimental data and numerical simulations. The research results indicate that the initial velocity distribution of fragments under different L/D ratios exhibits a trend where the initial velocities are lower at both ends and higher in the middle. Additionally, as the L/D ratio raises, the initial velocity of the fragment also increases. When the L/D ratio reaches 5, the relative error between the maximum initial velocity of the fragments and the calculated result using the Gurney formula is only 1.99%. However, the existing models for calculating initial velocities of fragment display significant errors when predicting smaller L/D ratios in cylindrical casing. The average error between the formula calculation results and the experimental and numerical simulation results does not exceed 6%, indicating that the proposed model is reliable for predicting the initial velocity distribution of fragments under different L/D ratios. The research work provides valuable insights for assessing the lethal power of fragment weapons and the structural design of protective devices in anti-terrorism projects.
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