考虑刚性弹弹头形状的混凝土(岩石)靶体侵彻深度半理论分析

基于动力球型空腔膨胀理论和冲击成坑+钻孔区两阶段侵彻模型,以截卵形弹头弹体为例,运 用曲面积分,引入表征弹头形状和弹靶摩擦效应的量纲一系数、质量比和冲击因子,提出了综合考虑弹头形状 变化、成坑区深度、弹靶摩擦阻力的混凝土和岩石靶体的刚性弹垂直侵彻深度的计算公式。该公式在相关参 数取特殊值时,可退化为经典的侵彻深度计算公式。通过与8组不同弹头形状弹体冲击混凝土和岩石靶体的 侵彻实验数据、已有10个(半)经验公式计算结果对比,验证了本文公式的适用性。并结合实验和参数影响分 析,给出了混凝土和岩石靶体的弹靶摩擦系数和与冲击因子相关的不同弹头形状弹体成坑系数的建议值。     

动能杆斜撞击靶板后效破片描述研究

针对动能杆式弹大倾角斜撞击靶板产生的靶后破片,建立了其初始破片云数学描述模型,并在此基础上对斜撞击靶后破片特征分布进行了建模。仿真结果与工程试验结果的比较表明,该模型具有较高的可信度。     

刚性平头弹正侵彻钢筋混凝土靶的阻力模型

本文基于素混凝土侵彻理论,将钢筋混凝土中钢筋的失效模式简化为弯曲剪切失效后,建立了刚性平头弹侵彻钢筋混凝土靶的阻力模型,侵彻深度的计算结果与Young公式吻合良好,表明本文提出的理论模型可较为合理地预测侵彻深度。进一步分析了不同着靶点的位置对弹体侵彻的影响,结果表明：当弹体直径与钢筋网眼尺寸的比值小于1时,弹体撞击到网眼中心处侵彻深度最大;当弹体直径与网眼尺寸的比值大于1时,最不利着靶点位置视其比值而定。最后,基于防护角度的最不利工况,建立了侵彻深度的工程计算公式。

     

Flat ended projectile penetrating ultra-high strength concrete plate target

Reactive powder concrete (RPC), a composite that has been developed in recent years, is a special mixture that is cured to have a higher compressive strength than that of concrete (about 200 MPa). Adding a few steel fibers can markedly increase its mechanical properties, such as tensile and bending strength, impact resistance and toughness. Hence, RPC is highly promising for use in the containment structures of nuclear power plants and in the protection of military facilities. This study evaluates the resistance of ultra-high strength concrete targets by high-velocity impact experiments. Test variables include the impact velocity and the amount of steel fibers added. The experimental results reveal that RPC plates, because of their higher compressive strength, are more fragile than normal concrete (NC) plates. However, adding a small amount of steel fibers significantly improved the impact resistance of the target plates. Moreover, a numerical simulation based on the nonlinear finite element code LS-DYNA was performed. The results of the numerical simulation have a good agreement with the experimental data and can be used for further research.     

基于细观混凝土模型的刚性弹体正侵彻弹道偏转分析

为研究混凝土细观因素对刚性弹正侵彻弹道偏转的影响,基于骨料随机投放的思路建立混凝土三维细观几何模型,分析刚性弹正侵彻过程中发生弹道偏转的原因及可能影响因素,定量讨论混凝土细观因素对弹道偏转的影响。结果表明:混凝土细观数值模型可以较好地反映弹体正侵彻过程中弹道偏转等典型物理现象,且细观参数对于弹体弹道偏转有显著影响。刚性弹正侵彻细观混凝土时,存在一个弹体直径/骨料最大粒径比的特征比值。     

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。     

尖头弹穿甲韧性金属靶模型分析

基于延性扩孔模式,分析了尖头弹穿甲韧性金属靶的Chen-and-Li模型和Forrestal-and-Warren模型。结果表明,2种模型形式相同但适用范围不同,差异源于分别应用球形和柱形动态空腔膨胀理论。将2种模型与相关尖头弹穿甲金属靶的实验数据做了比较,对应于尖头刚性弹对韧性金属靶的延性扩孔穿甲,理论分析与实验结果吻合。     

斜侵彻混凝土靶的刻槽弹体的结构响应

基于刚塑性理论和侵彻载荷理论分析,将刻槽弹体简化为空间自由变截面梁,给出了弹体在侵彻混凝土早期的刚体响应行为,得到了弹体任一截面弯矩、剪力以及屈服函数的分布规律。基于此理论分析,得到了刻槽弹体壁厚、材料屈服强度、初速及倾角对弹体弯曲的影响规律。     

Normal perforation of a thin infinite plate by a flat-headed cylindrical projectile

Analytical formulae for calculating the stress acting on the contact surface between projectile and target and for calculating the moving velocity of this contact surface under impact are both suggested in this paper. These formulae can be thought of as a generalization of the well-known Hopkins and Kolsky’s theory in plastic domain. And then, an analytical formula for calculating ballistic limit is also suggested. It is also proved in this paper that the shear stress acting on the cylindrical surface of the plug is distributed uniformly.     

长杆弹对混凝土的侵爆效应

对适用于长杆弹在混凝土介质中侵彻和爆炸全过程的三维数值模拟方法和技术进行了研究。描述了进行相应数值模拟的有关方法和关键技术。确定了靶体C30混凝土材料所使用的本构模型及其相应的参数。对卵形头长杆弹在C30混凝土中侵彻到一定深度再爆炸的全物理过程进行了三维数值模拟,分别给出了C30混凝土靶体在侵彻和爆炸作用下的破坏效应图像。将侵彻计算图像与实验结果进行了比较,两者定性符合。     

平头弹穿透间隙式双层靶的穿甲模式

平头弹贯穿单层金属靶,随着靶厚的增加和弹速的增高,穿甲模式均可能由剪切冲塞向绝热剪切冲塞转换。因此,对于双层或多层靶的穿甲,其不同层的靶板失效模式可能是不同的。本文中对相关的平头弹穿甲Weldox 700E单层及双层间隙式钢靶的实验数据进行分析,讨论其穿甲模式。弹速较高时,贯穿第1层靶发生绝热剪切失效,弹速降低,贯穿第2层靶板发生绝热剪切失效或剪切冲塞失效, 最终失效模式为绝热剪切和剪切冲塞混杂。     

Generation of cracks in a perforated reinforced plate

A problem of fracture mechanics on crack nucleation in a reinforced plate attenuated by a periodic system of circular holes is considered. Crack nucleation is modeled by a pre-fracture band in the plastic flow state with a constant stress, which is considered as a region of attenuated bonds between material particles. Determining unknown parameters characterizing the emerging crack reduces to solving a singular integral equation. The condition of crack emergence is formulated with allowance for the criterion of the limiting opening of the faces of the material pre-fracture band. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 6, pp. 170–180, November–December, 2008.     

弹体侵彻厚混凝土靶迎弹面成坑效应

为研究弹体侵彻厚混凝土靶的迎弹面成坑效应,总结了侵彻实验中的成坑现象,分析了经验公式对成坑深度、成坑直径和成坑角等成坑效应的预测效果;考虑了撞击速度、靶板强度、配筋以及弹体直径和质量等因素的影响,采用量纲分析方法建立了新型成坑效应计算公式及成坑阶段耗能计算公式;基于新型成坑效应计算公式,对成坑效应的影响因素和成坑耗能进行了参数化分析。结果表明:无量纲成坑深度受靶板强度、配筋率和弹体质量的影响较大;对于钢筋混凝土,成坑深度随撞击速度提升呈先增大后减小再增大的变化规律;在常见的侵彻速度和质量范围内,成坑角为15°～24°,质量对成坑角影响较小;迎弹面成坑耗能占弹体总动能的10%～25%,且配筋率和靶板强度对成坑耗能比例的影响较小;弹体质量越小,成坑阶段耗能占比越大。新型成坑效应计算公式对成坑深度、直径和角度的计算结果与实验数据吻合较好,可为侵彻弹体设计和工程防护提供参考。     

截锥形弹穿甲单加筋板的破坏特性

为准确掌握截锥形弹体垂直穿透单加筋板后的打击深度,需要清楚知道弹体穿甲加筋板后的剩余速度.截锥形弹正穿甲板架,形成与截锥面相同的凿块,面板产生花瓣形破坏,腹板受到锥面的挤压发生塑性变形,翼板发生翻转,在此破坏模型基础上,确定板架的能量消耗方式.穿甲过程中,板架耗能主要通过凿块的剪切变形、凿块的动能、板架的挤压塑性变形、...     

Bending of a radially prestressed annular plate by tilting a central rigid inclusion

A thin annular plate contains a rigid, circular, central inclusion. The plate is subjected to a large axisymmetric radial load at its outer edge, where it is also restrained against transverse displacement and rotation. A couple applied to the rigid inclusion causes it to rotate about its diameter out of the plane of the plate. We use the method of matched asymptotic expansions to find an approximate expression for the applied couple as a function of the angle of rotation of the rigid inclusion. If the outer radius of the annulus is very large compared to the inner radius, then the couple required to rotate a truly rigid inclusion is 25% higher than the couple required to rotate an inclusion whose membrane strain stiffness is the same as that of the plate (cf. ref. [3]) through the same small angle.