细长尖头刚性弹对金属靶板的斜侵彻/穿甲分析

给出细长尖头刚性弹（如尖卵、尖锥形）斜侵彻/穿甲金属靶的一个分析模型。在细长尖头弹对中厚度金属靶的斜穿甲中,韧性孔洞扩张为主要的穿甲机理;着靶初期,发生方向角的改变。研究表明,金属靶的斜穿甲仅由4个量纲一参数控制,即冲击函数I、弹体几何函数N、量纲一靶厚和撞击斜角。分析得到显式的侵彻深度、终点弹道极限、剩余速度和撞击方向改变角表达式。该模型可预期跳飞发生的临界条件。理论预期与实验结果吻合较好。     

动能侵彻弹体的质量侵蚀模型分析

通过对高速侵彻弹体的质量侵蚀实验现象进行分析,建立了质量侵蚀的工程理论模型,可对动能侵彻弹体头部侵蚀后的头形和质量侵蚀进行预期. 讨论弹体质量侵蚀的主要影响因素,认为弹体动能(或质量和速度)以及混凝土骨料硬度对弹体的质量侵蚀有显著影响,给出了更一般化的弹体质量侵蚀与撞击函数$I$的关系. 通过图形分析明确弹体的质量侵蚀主要发生于头部,并且侵蚀后的弹头仍接近尖卵形,可以通过头形变化预期弹体的质量损失.      

A3钢钝头弹撞击45钢板破坏模式的数值分析

不同速度范围内的A3钢钝头弹撞击45钢靶板分别表现为泰勒撞击、向日葵型花瓣帽形失效和靶板冲塞穿甲等3种不同的破坏模式,利用LS-DYNA对这种复杂的破坏机理和相应的影响因素进行了数值模拟研究。采用Johnson-Cook强度模型和累积损伤失效模型描述弹靶材料的力学性能,并考虑了塑性变形的绝热温升效应。数值模拟再现了不同破坏模式的失效过程,得到了与实验一致的结果。研究还指出,弹靶的冲塞穿甲实际是在高速撞击下,弹体发生花瓣帽形变形失效后继续穿甲靶板的后续结果。     

Modeling on mass abrasion of kinetic energy penetrator

An engineering model on mass abrasion of kinetic energy penetrator is presented to predict the nose shape and mass loss of the residual projectile after high-speed penetration into concrete. The experimental analysis indicates that the kinetic energy of penetrator (i.e., mass and velocity of projectile) and the hardness of aggregate of concrete significantly affect the mass abrasion of projectile. A theoretical upper limit exists for the mass loss. More general relationship between mass loss and impact function I of projectile is constructed. Graphical discussion declares that the most mass loss occurs on the nose of the projectile and the eroding nose approaches to an ogival shape with a smaller value of caliber-radius-head (CRH). A relative rate of mass abrasion on ogive-nose is further defined and analyzed. The mass loss from abrasion on kinetic energy (KE) penetrator may be evaluated through the variation of nose shape.     

Analysis of the mechanics of perforation of projectiles in metallic plates

A mathematical model has been developed to describe the mechanism of normal perforation of projectiles in metallic targets. The perforation process is considered to be divided into three interconnected stages. The analysis accounts for an effective mass of the bullet due to part of the target material moving with the bullet, the deformation of the bullet during penetration, and the increased strength of the target material at high rates of loading. The analysis enables the residual velocity to be calculated as a function of the target thickness and its mechanical and physical properties, and of the mass, geometry and impact velocity of the projectile. The geometry of the cavity, i.e. entrance and exit diameters and plug thicknesses, are factors in the analysis and are empirical quantities. The present theory can also predict the force-time curve and the contact time for the perforation process.     

带前舱物的钝头弹对金属靶的正穿甲分析

进一步发展了考虑结构响应的剪切冲塞模型,计及前舱物的作用,对带前舱物的钝头弹穿甲金属靶的工程问题进行了刚塑性分析,用于分析终点弹道极限和剩余速度。除剪切破坏之外,模型还考虑了靶板弯曲、膜力拉伸和前舱物撞击引起的靶板预结构响应等。给出了简洁的终点弹道性能公式,与相关实验结果较吻合。     

Semi-theoretical analyses of the concrete plate perforated by a rigid projectile

Based on the three-stage perforation model, a semi-theoretical analysis is conducted for the ballistic performances of a rigid kinetic projectile impacting on concrete plates. By introducing the projectile resistance coefficients, dimensionless formulae are proposed for depth of penetration (DOP), perforation limit thickness, ballistic limit velocity, residual velocity and perforation ratio, with the projectile nosed geometries and projectile-target interfacial friction taken into account. Based on the proposed formula for DOP and lots of penetration tests data of normal and high strength concrete targets, a new expression is obtained for target strength parameter. By comparisons between the results of the proposed formulae and existing empirical formulae and large amount of projectile penetration or perforation tests data for monolithic and segmented concrete targets, the validations of the proposed formulae are verified. It is found that the projectile-target interfacial friction can be neglected in the predictions of characteristic ballistic parameters. The dimensionless DOP for low-to-mid speed impacts of non-flat nosed projectiles increases almost linearly with the impact factor by a coefficient of 2/(πS). The anti-perforation ability of the multilayered concrete plates is dependent on both the target plate thickness and the projectile impact velocity. The variation range of the perforation ratio is 1–3.5 for concrete targets.     

An investigation of oblique perforation of metallic plates by projectiles

An experimental and analytical study was performed on the mechanics of oblique perforation of metallic plates by projectiles. The purpose was to determine the dependence of the velocity drop on the angle of impact for prescribed mechanical and physical properties of the projectile and the target plate. The ballistic experiments were carried out with 0.22-in.-caliber lead bullets on target plates of commercially pure aluminum and an aluminum alloy which ranged from 2.0 to 6.0 mm in thickness. Transient measurements were taken which included high-speed photographs of the perforation process. The theoretical model that had been developed previously by the authors for the case of normal perforation was modified to include the effects of the angle of impact. The experimental observations for the present test conditions indicate that the main modification to the analysis is the use of the total projectile path as the effective target-plate thickness. Reasonably good agreement between the experimental and theoretical results was obtained.     

细长薄壁弹体的屈曲和靶体等效分析

利用金属靶开展动能深侵彻弹的穿甲屈曲实验研究。实验观察到长/短型弹体动塑性屈曲破坏分别表现为轴向皱褶型和轴向外翻撕裂型2种基本模式。不同的屈曲破坏模式与弹体几何、撞击初条件以及靶材等密切相关。区别于刚性尖头弹穿甲金属靶的韧性隧道开孔,尖头弹因屈曲破坏易变形为钝头形,导致弹体穿透靶板表现为挤凿穿甲。利用薄壁中空柱壳的弹性欧拉屈曲分析和弹体塑性屈服的极限分析给出弹体动塑性屈曲的临界条件。同时给出屈曲实验中混凝土靶和金属靶的等效条件。     

刚性弹体斜侵彻贯穿混凝土靶的姿态偏转理论模型

为描述刚性弹体斜侵彻贯穿混凝土靶的弹体姿态变化,针对已有贯穿模型存在的问题,在斜侵彻贯穿过程中考虑了弹体转动惯量对姿态偏转的影响,根据弹体贯穿靶板后的成孔特性重新假设了背靶面崩落块形状,并在弹体贯穿出靶的剪切冲塞阶段引入了弹体姿态二次偏转机制,从而建立了刚性弹体斜侵彻贯穿混凝土靶的姿态偏转理论模型,同时给出了混凝土薄靶、中厚靶和厚靶的分类方法。多种侵彻状态的理论模型计算结果均与实验测量结果吻合较好,表明本文理论模型可有效预估弹体斜侵彻贯穿混凝土靶的弹体出靶姿态。     

卵形头部刚性弹侵彻厚靶的半解析模型

基于确定靶体中速度势和速度场的方法分析刚性卵形头部弹体对有限厚靶的侵彻问题。推导了靶体中速度场与应力场的计算方法,利用据此编制的计算程序,计算了卵形头部钢弹体对铝靶的侵彻与穿透问题,给出了侵彻深度与剩余速度同初始碰撞速度的关系。结果表明,在对实验参数不经过任何调整的情况下,得到了同试验曲线相吻合的结果。可以看出该方法的有效性。     

穿甲/侵彻问题的若干工程研究进展

作为爆炸力学的一个分支,穿甲/侵彻力学是研究高速/超高速弹体撞击靶体后,钻入或穿透靶体的力学, 又称终点弹道学.综述作者及其合作者最近几年在穿甲及侵彻力学领域的若干工程研究工作,包括混凝土靶的侵彻和穿甲、控制刚性弹侵彻动力学的无量纲数、金属靶穿甲的理论模型、钻地弹的相关力学问题、穿甲弹体的破坏与失效等.同时也给出该领域的国外最新研究工作进展.      

On the ballistic resistance of double-layered steel plates: An experimental and numerical investigation

Civil and military ballistic protection systems often consist of thin, high-strength steel plates. Such plates may either be monolithic or layered with or without spacing. The idea of using layered plates instead of a monolithic one in order to increase the ballistic perforation resistance is not new, and the effect of using targets made up of several thinner plates has been investigated in the literature for a long time. However, results by various authors are contradicting and detailed experimental and numerical work is still required.In the present study, the ballistic perforation resistance of double-layered steel plates impacted by blunt and ogival projectiles was investigated both experimentally and numerically. In the tests, 12 mm thick (monolithic or layered) targets of Weldox 700 E were impacted using a gas-gun at sub-ordnance velocity, and the ballistic limit velocity of the different target combinations was obtained. In general, good agreement was obtained between the numerical simulations and the experimental results. It was found that in the case of blunt projectiles a large gain in the ballistic limit is offered by double-layered systems. These advantages seem to disappear when ogival projectiles are used. However, the main conclusion from both the experimental and numerical studies is that the overall protection level, i.e. the minimum ballistic limit velocity obtained independently of projectile nose shape, seems to increase significantly by double-layering the target.     

Experimental Study on the Perforation Process of 5754-H111 and 6082-T6 Aluminium Plates Subjected to Normal Impact by Conical,Hemispherical and Blunt Projectiles

This paper presents an experimental investigation on the perforation behaviour of 5754-H111 and 6082-T6 aluminium alloys. The mechanical response of these materials has been characterized in compression with strain rates in the range of $10^{-3}~s^{-1} < \dot {\varepsilon } < 5 \cdot 10^{3}~s^{-1}$ . Moreover, penetration tests have been conducted on 5754-H111 and 6082-T6 plates of $4~mm$ thickness using conical, hemispherical and blunt projectiles. The perforation experiments covered impact velocities in the range of $50~m/s < V_{0} < 200~m/s$ . The initial and residual velocities of the projectile were measured and the ballistic limit velocity obtained for the two aluminium alloys for the different nose shapes. Failure mode and post-mortem deflection of the plates have been examined and the perforation mechanisms associated to each projectile/target configuration investigated. It has been shown that the energy absorption capacity of the impacted plates is the result of the collective role played by target material behaviour, projectile nose shape and impact velocity in the penetration mechanisms.     

On the deep penetration and plate perforation by rigid projectiles

We present results of a large number of 2D numerical simulations in which we investigated various aspects in the deep penetration of rigid short projectiles into semi-infinite targets, as well as their perforation through thin metallic plates. In particular, we analyze the effect of the entrance phase on the penetration characteristics of short ogive and spherical nosed projectiles. The second issue which we investigate here concerns the perforation of metallic plates by sharp nosed projectiles. Our simulation results show that a simple model, which is based on energy conservation, accounts for the residual velocities when the target is penetrated by the ductile hole enlargement process. In addition, we define a new concept, the effective resisting stress which the plate exerts on the projectile during perforation. We show that it has some valuable insights for the process of perforation and we perform a parametric study to understand its dependence on various parameters. This effective stress, which determines the ballistic limit velocity of the projectile, depends on the strength of the plate, as well as on its thickness, as we show here.     

Rigorous model-based uncertainty quantification with application to terminal ballistics—Part II. Systems with uncontrollable inputs and large scatter

This Part II of this series is concerned with establishing the feasibility of an extended data-on-demand (XDoD) uncertainty quantification (UQ) protocol based on concentration-of-measure inequalities and martingale theory. Specific aims are to establish the feasibility of the protocol and its basic properties, including the tightness of the predictions afforded by the protocol. The assessment is based on an application to terminal ballistics and a specific system configuration consisting of 6061-T6 aluminum plates struck by spherical 440c stainless steel projectiles at ballistic impact speeds in the range of 2.4–2.8 km/s. The system's inputs are the plate thickness, plate obliquity and impact velocity. The perforation area is chosen as the sole performance measure of the system. The objective of the UQ analysis is to certify the lethality of the projectile, i.e., that the projectile perforates the plate with high probability over a prespecified range of impact velocities, plate thicknesses and plate obliquities. All tests were conducted at Caltech's Small Particle Hypervelocity Range (SPHIR), which houses a two-stage gas gun. A feature of this facility is that the impact velocity, while amenable to precise measurement, cannot be controlled precisely but varies randomly according to a known probability density function. In addition, due to a competition between petalling and plugging mechanisms for the material system under consideration, the measured perforation area exhibits considerable scatter. The analysis establishes the feasibility of the XDoD UQ protocol as a rigorous yet practical approach for model-based certification of complex systems characterized by uncontrollable inputs and noisy experimental data.     

Analyses of the penetration process considering mass loss

Based on the dynamic cavity-expansion theory and momentum theorem, the key parameters of projectile penetrating into concrete target, i.e., the penetration time and time histories of DOP, deceleration, mass loss, instant mass loss rate and nose shape, are obtained by incremental calculation considering mass loss of projectile. The calculation results are consistent with the experimental results. Due to the mass loss and thus nose blunting effects, the pulse shape of deceleration may be quite different from that obtained in the analysis of a rigid projectile, and then the dissimilarity is analyzed. It is found that the pulse shape of deceleration is determined by the drag force and essentially determined by the performances of target and projectile, i.e., the shear strength of target, the Moh’s hardness of aggregate in concrete and the CRH value of projectile nose. Further analysis indicates that the pulse shape of deceleration is more sensitive to the performance of target than that of projectile.     

动能深侵彻弹的力学设计(I):侵彻/穿甲理论和弹体壁厚分析

在作者先前工作的基础上,进一步明确了适合于动能深侵彻弹的撞击函数和弹体几何函数的有效范围,可用于相关弹体结构的力学设计。同时从理论上研究了弹体的抗压/拉和抗弯能力,分别从抗压/拉和抗弯两方面来确定动能深侵彻弹弹体的极限壁厚。针对不同撞击速度的细长中空弹体斜侵彻混凝土靶,分析得到不出现弯曲破坏的弹体最大临界斜角和壳体壁厚下限,并给出弹体抗弯能力的最薄弱位置。对弹体的壳体厚度、局部加固和焊接位置提出建议。     

Characterization of hole-diameter in thin metallic plates perforated by spherical projectiles using genetic algorithms

The empirical and semi-empirical models available in literature for the estimation of hole-diameter in thin metallic plates by the strike of spherical projectile are mostly valid for the data for which these have been developed. This may be partly attributed to the form of the model employed for their development. The behavioural constraints and the limiting conditions are not satisfied by these models. In the present paper, some of the non-dimensional models have been developed that satisfy the behavioural constraints and limiting conditions. The data used in the development of earlier statistical models has been reanalyzed for the development of new models for the characterization of hole-diameter with a view towards seeing whether better characterization is possible. The genetic algorithm coupled with the penalty function method has been used for the constrained optimization of model parameters that result in low errors and high correlation coefficients.