Supplementary information files for Mechanics of ballistic impact with non-axisymmetric projectiles on thin aluminium targets. Part I: Failure mechanisms

Supplementary files for article Mechanics of ballistic impact with non-axisymmetric projectiles on thin aluminium targets. Part I: Failure mechanisms The ballistic performance of thin aluminium targets under normal and oblique impacts with platelike projectiles is investigated with emphasis on the local projectile-induced target response. Three projectiles of 5 mm thickness with decreasing bluntness were considered, with the ratio of the projectile’s equivalent diameter to the target’s thickness (deq/hT ) within the range of 0 to 4.89. The obtained results suggest that defeat mechanisms, and target resistance measures were different from those observed in impact with equivalent axisymmetric projectiles, as a result of a high projectile’s cross-sectional aspect ratio. Projectiles with inclined nose sections inflicted a shear-dominant failure that was locally energetically expensive and depended on the product of length (LN) and half-angle (α) of the projectile’s nose. On the other hand, projectiles with blunt sections were associated with retardation of their penetration capacity due to dynamic effects, followed by a low-energy mechanism associated with membrane stretching and tensile failure of targets. A total of 48 experiments were performed at normal-impact conditions, to estimate the critical velocity of perforation/penetration and examine the real-time deformation patterns at sub-critical velocities, by employing the digital image correlation technique. Overall, the critical velocity showed a quadratic dependence on deq/hT , where the benefit of ballistic performance decreased with an increase in this ratio. The observed non-monotonic behaviour of the critical velocity with increasing impact obliquity in some cases and the distinction in failure mechanisms highlight the importance of the projectile’s geometrical parameters for the energy transfer mechanisms. Also, the lack of correlation between the critical velocity and the local work in the target defeat term suggests that the resultant energy transfer mechanisms considerably contributed to the dissipation of the projectile’s kinetic energy. Experimental data were utilised for calibrating the material model and separate experimental results for validating the numerical (finite-element) model. A total of 119 simulations were carried out for normal and oblique impact incidences to examine the role of the projectile’s (i) rotation, (ii) geometrical features, and (iii) obliquity on the target’s dynamic performance and induced defeat mechanisms. The conclusions of this study form the basis for considering the role of the projectile’s geometrical parameters on the energy transfer mechanisms in the target through statistical and semi-analytical approaches presented in the second part of this work.

《非轴对称弹体撞击薄铝靶的弹道力学特性 第一部分：失效机制》论文补充文件。本研究针对板状弹体正撞击与斜撞击下薄铝靶的弹道性能展开探究，重点关注弹体诱导的靶体局部响应。本研究选用3枚厚度为5mm、钝度依次降低的弹体，弹体等效直径与靶体厚度的比值（deq/hT）取值范围为0至4.89。研究结果表明，由于弹体横截面高纵横比的影响，靶体失效机制与抗弹性能指标均与等效轴对称弹体撞击时的观测结果存在显著差异。弹头部倾斜的弹体将引发以剪切为主的失效模式，该局部失效过程的能量消耗较高，且与弹头部长度（LN）及半角（α）的乘积相关。而弹头部钝形的弹体则因动态效应出现侵彻能力衰减，随后伴随以靶体膜拉伸与拉伸失效为特征的低能耗失效机制。本研究通过数字图像相关（digital image correlation）技术，在正撞击工况下完成了总计48组试验，用于估算穿孔/侵彻临界速度，并观测亚临界速度下靶体的实时变形模式。整体而言，临界速度与deq/hT呈二次函数关系，且弹道性能的增益随该比值的升高而降低。部分工况下观测到临界速度随撞击斜角增大呈现非单调变化，加之失效机制存在显著差异，均凸显出弹体几何参数对能量传递机制的重要影响。此外，临界速度与靶体失效过程中的局部功之间不存在相关性，这表明最终的能量传递机制在弹体动能耗散过程中发挥了重要作用。本研究利用试验数据对材料本构模型进行校准，并通过独立的试验结果验证数值（有限元）模型的可靠性。针对正撞击与斜撞击工况，本研究共计开展了119组仿真试验，以探究弹体的（i）旋转运动、（ii）几何特征以及（iii）撞击斜角对靶体动态响应与诱导失效机制的影响。本研究的结论为后续通过本研究第二部分提出的统计与半解析方法，探究弹体几何参数对靶体能量传递机制的影响奠定了基础。