Axial distribution of fragment initial velocities from cylindrical casing with different length-to-diameter ratios
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摘要: 针对精确预测不同长径比(L/D)的圆柱套筒在一段起爆下的破片初速分布问题,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。Abstract: To accurately predict the initial velocity distribution of cylindrical casing under central point detonation at one end 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.
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表 1 不同L/D的数值模拟试样
Table 1. Simulation samples with different L/D
模型 D/mm L/mm L/D δ/mm 模型 D/mm L/mm L/D δ/mm 1 23.6 23.6 1.0 3.04 5 23.6 59.0 2.5 3.04 2 23.6 29.5 1.25 3.04 6 23.6 70.8 3.0 3.04 3 23.6 35.4 1.5 3.04 7 23.6 94.4 4.0 3.04 4 23.6 47.2 2.0 3.04 8 23.6 118 5.0 3.04 密度/(g·cm−3) AJC/MPa BJC/MPa n CJC m D1 D2 D3 D4 D5 7.83 507 320 0.28 0.064 1.06 0.15 0.72 1.66 0.005 -0.84 爆速/(m·s−1) 爆轰压力/GPa E/(kJ·m−3) AJWL/GPa BJWL/GPa R1 R2 ω 7980 29 8.5×106 542 7.68 4.2 1.1 0.24 工况 套筒材料 装药材料 D/mm L/mm δ/mm 1 ASI1045 B炸药 23.60 77.30 3.04 2 ASI1045 B炸药 23.56 77.15 6.69 表 5 7个数值模型得到的A1、B1、C1、D1系数
Table 5. Coefficients A1, B1, C1 and D1 obtained from seven numerical models
L/D A1 B1 C1 D1 L/D A1 B1 C1 D1 1.0 0.465 2.282 0.425 0.823 2.5 0.465 1.293 0.296 1.970 1.25 0.465 1.983 0.326 1.121 3.0 0.465 1.267 0.303 2.030 1.5 0.465 1.607 0.299 1.399 4.0 0.466 1.175 0.301 2.072 2.0 0.466 1.314 0.291 1.83 5.0 0.466 1.137 0.297 2.086 表 6 9个用于验证公式的试样参数
Table 6. Nine sample parameters used to validate the formula
工况 装药 D/mm L/mm D/L δ/mm 工况 装药 D/mm L/mm D/L δ/mm 工况 装药 D/mm L/mm D/L δ/mm V1-1 B炸药 20 20 1.0 3.0 V2-1 B炸药 30 30 1.0 4.0 V3-1 HMX 20 20 1.0 3.0 V1-2 B炸药 20 40 1.2 3.0 V2-2 B炸药 30 60 1.2 4.0 V3-2 HMX 20 40 1.2 3.0 V1-3 B炸药 20 60 3.0 3.0 V2-3 B炸药 30 90 3.0 4.0 V3-3 HMX 20 60 3.0 3.0 注:所有工况中套筒均材料均为ASI1045. -
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