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泡沫子弹冲击固支单梁的耦合分析模型

A COUPLING ANALYSIS MODEL OF CLAMPED MONOLITHIC BEAM IMPACTED BY FOAM PROJECTILES

  • 摘要: 使用泡沫金属子弹进行冲击可以模拟爆炸载荷的作用, 这一加载技术已被应用于防护结构的抗冲击性能测试中, 然而泡沫子弹作用于被测试结构上的真实载荷以及二者间的相互作用过程尚不明晰. 本文以泡沫子弹冲击固支梁的情形为例, 开展了对该冲击过程的理论分析和数值模拟研究. 基于泡沫材料的冲击波模型与固支单梁的结构冲击动力学响应模型, 构建了描述泡沫子弹冲击固支梁过程的耦合分析模型. 给出了不同响应阶段下子弹和单梁的动力学控制方程, 并采用Runge-Kutta方法得到了方程的数值解. 基于三维Voronoi技术, 建立了泡沫子弹冲击固支单梁的有限元模型并进行了数值模拟. 通过与有限元模拟结果的对比发现, 相较于经典的脉冲加载模型, 耦合分析模型能更好地预测泡沫子弹和单梁的速度变化规律, 也能准确地预测子弹对单梁的真实冲击压强. 当泡沫子弹的初始动量相同时, 由于子弹自身的压溃行为, 子弹的初始冲击速度、密度和长度的改变都会对冲击过程产生影响. 最后, 通过耦合分析模型分别分析了泡沫子弹的密度、长度、初速度对冲击压强的峰值、衰减速度和持续时间的影响, 并针对具有不同特征的目标模拟载荷给出了泡沫子弹的筛选策略. 所构建的耦合分析模型为研究泡沫子弹与被测试结构之间的相互作用规律以及泡沫子弹的设计提供了理论基础.

     

    Abstract: The impact of foam metal projectiles may simulate the effect of explosion load. This loading technology has been applied in the impact resistance test of different protective structures. However, the actual impact load on the tested object and the interaction mechanism between the projectile and the tested object are still unclear. In this paper, the theoretical analysis and numerical simulation of the impact process of a foam projectile on a beam fixed at both ends were carried out. Based on the shock wave model of the foam and the structural dynamic response model of the clamped beam, a coupling analysis model describing the impact process was developed. The governing equations of different response stages were presented, and the numerical solution of the governing equations was obtained by using the Runge-Kutta method. The finite element model of a clamped monolithic beam impacted by a foam projectile was constructed by using the Voronoi technique and the impact process was simulated. Compared with the simulation results, it is found that the coupling analysis model can not only predict the velocity variation of projectiles and beams better than the impulsive loading model, but also obtain the actual impact pressure accurately. When the initial momentum of the foam projectile is identical, the change in the initial velocity, density, and length of the projectile can still affect the impact process due to the crushing behavior of the projectile. Finally, the effects of the density, length, and initial velocity of foam projectiles on the peak value, attenuation velocity, and duration of impact pressure were analyzed through the coupling analysis model, and the selection strategy of foam projectiles was proposed for the target simulation loads with different characteristics. The coupling analysis model provides a theoretical basis for studying the interaction mechanism between foam projectiles and the tested structure and the design guide of foam projectiles.

     

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