Preliminary theoretical study on the rebound effect of projectiles penetrating ultra-high performance concrete targets
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摘要: 为了探究弹体在侵彻超高性能混凝土过程中弹体出现的反弹现象,基于空腔膨胀理论,分析了弹体从侵彻到反弹全过程的受力情况;分别以一维弹性杆弹性势能模型和一维应力波模型为理论基础,推导得到两种反弹速度的解析解,分析了影响反弹速度的物理量;通过数值模拟复现了弹体反弹现象,验证了理论模型的合理性,数值计算结果和两种解析解吻合良好。研究表明:侵彻阻力使弹体积累变形势能,侵彻结束后变形势能释放造成弹体反弹;反弹初速与着靶速度无关,与靶体材料的屈服强度和弹头形状系数等成正比,与弹体弹性模量和密度成反比。Abstract: It is a developing trend of protection engineering to use high resistance materials such as ultra-high performance concrete to construct bullet-shielding structures. The phenomenon of projectile body rebound was found in the tests of projectile body penetrating ultra-high performance concrete. The projectile rebound effect is very important in the study of engineering protection, weapon damage and warhead design. In order to study the rebound velocity of projectile body after penetration and its influencing factors, the stress of projectile body from penetration to rebound was analyzed. Based on the expression of penetration resistance given by the cavity expansion theory, a one-dimensional elastic bar potential energy model was established from the perspective of the accumulation of deformation energy by penetration resistance, and a one-dimensional stress wave model was established from the perspective of stress wave generated by penetration resistance. The analytical solutions of the rebound velocity were derived from the two models respectively, and the physical quantities affecting the rebound velocity were analyzed. Through numerical simulation, the rebound phenomenon of the projectile body after penetrating the ultra-high performance concrete is reproduced, and the numerical results of the rebound velocity agree well with the two analytical solutions. Through numerical calculation of the same penetration model with different material parameters, the relationship between the rebound velocity and the material parameters in the analytical solution is verified, and the reliability of the theoretical model is proved. The results show that the projectile body accumulates deformation potential energy due to penetration resistance, and the projectile body bounces back due to the release of deformation potential energy after penetration. The initial rebound velocity is independent of the target velocity, proportional to the target material, yield strength and warhead shape coefficient, and inversely proportional to the elastic modulus and density of the projectile body. The results can preliminarily predict the rebound velocity and provide a reference for the design of ultra-high performance concrete protective structure and warhead.
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a0/MPa a1 a2/MPa−1 a1f a2f/MPa−1 a0y/MPa a1y a2y/MPa−1 60.48 0.446 3 0.001 052 0.4417 0.000 989 38.32 0.625 0.003 090 ρc/(kg·m−3) ν ft/MPa b1 b2 b3 Ω W/mm 2 567 0.2 12 0.15 −4.39 1.15 0.75 2 注:a0、a1、a2、a1f、a2f、a0y、a1y为失效面参数,ν为泊松比,ft为抗拉强度,b1、b2、b3为损伤参数,Ω为剪胀参数,W为试件宽度。 表 2 侵彻深度的试验与数值计算结果
Table 2. Experimental and numerical results of penetration depth
侵彻初速/(m·s−1) 试验侵彻深度/mm 数值模拟侵彻深度/mm 误差/% 405 70 69 1.43 616 120 109 9.17 表 3 反弹速度的数值计算结果和理论预测值
Table 3. The results of numerical calculation and theoretical prediction of the rebound velocity
弹体 vi/(m·s−1) vr/(m·s−1) 与数值模拟的误差/% 数值模拟 弹性势能模型 一维弹性波模型 弹性势能模型 一维弹性波模型 7850-210 300 8.2 14.12 19.2 44.0 57.3 400 10.6 14.12 19.2 24.4 44.8 500 17.0 14.12 19.2 −20.0 11.5 600 13.3 14.12 19.2 5.7 30.7 700 16.7 14.12 19.2 −17.9 13.0 800 15.9 14.12 19.2 −12.4 17.2 3925-105 300 16.3 28.25 38.4 42.8 57.5 400 24.5 28.25 38.4 14.0 36.2 500 25.8 28.25 38.4 9.4 32.8 600 34.2 28.25 38.4 −20.0 10.9 700 37.1 28.25 38.4 −30.2 3.40 800 33.7 28.25 38.4 −18.3 12.2 -
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