Constitutive modelling of concrete material subjected to low-velocity projectile impact: insights into damage mechanism and target resistance

This paper presents a numerical study to improve the understanding of the complex subject of penetration and perforation of concrete targets impacted by low-velocity projectiles. The main focus is on the damage mechanisms and the major factors that account for the target resistance of the concrete. An improved continuous surface cap model recently proposed was employed. The model was first equipped with element erosion criteria and was adequately validated by comparisons with ballistic experiments. Comprehensive numerical simulations were carried out where the individual influence of tensile, shear, and volumetric behaviors (pore collapse) of a concrete target on its ballistic performance was investigated. Results demonstrated that cratering on the front face and scabbing on the rear face of the concrete target were mainly dominated by its tensile behavior. The major target resistance came from the second tunneling stage which was primarily governed by the shear and volumetric behaviors of the concrete. Particularly, this study captured the pore collapse-induced damage phenomenon during the high-pressure tunneling stage, which has been extensively reported in experiments but has usually been neglected in previous numerical investigations. 目 的 弹体冲击作用下, 混凝土靶呈现三个阶段的典型破坏模式, 即正面成坑、 中间掘隧道及背面震塌, 但对三个阶段损伤破坏机理及混凝土靶抗侵彻阻力主要影响因素的认识一直存在很大争议. 拟标定近期提出的较为完善的混凝土帽盖弹塑性损伤本构, 全面探究弹体低速冲击下(弹体速度低于500 m/s)混凝土拉伸、 剪切及体积压缩行为对混凝土靶抗侵彻阻力及损伤破坏的影响机制. 创新点 1. 全面分析混凝土拉伸、 剪切及体积压缩行为对混凝土靶抗侵彻阻力及损伤破坏的影响机制; 2. 成功预测弹体在混凝土靶掘隧道高压力阶段孔隙坍缩引起的损伤行为. 方 法 1. 改进混凝土帽盖弹塑性本构, 引入单元删除准则(公式(19)), 标定模型参数(图2); 2. 与公开弹道试验定性定量结果对比, 验证材料本构、数值模型和参数的合理性(图6~8); 3. 数值模拟究混凝土拉伸、 剪切及体积压缩行为对混凝土靶体抗侵彻能力及损伤破坏模式的影响, 并与公开文献中主要发现进行讨论. 结 论 1. 混凝土正面成坑及背面震塌的形成主要由其拉伸力学行为决定, 而中间高压力掘隧道过程则由混凝土剪切及体积压缩行为决定. 2. 单轴压缩强度不是混凝土靶抗侵彻阻力主要影响因素, 其高压力下的剪切及体积压缩行为起决定作用, 且中间高压力掘隧道阶段是混凝土靶抗弹体侵彻的主要过程. 3. 拉伸力学行为在混凝土靶抗侵彻阻力计算模型中被普遍忽视, 但本文研究发现混凝土拉伸力学行为可显著影响弹体的残余速度, 因此其作用不容忽视.