冲击载荷作用下颗粒材料动态力学响应的近场动力学模拟
PERIDYNAMICS SIMULATION FOR DYNAMIC RESPONSE OF GRANULAR MATERIALS UNDER IMPACT LOADING
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摘要: 颗粒材料在冲击载荷作用下的动态力学行为是学术界关注的热点问题. 新近问世的近场动力学(peridynamics)理论将材料视为由大量有限体积和有限质量的物质点组成,基于非连续性和非局部作用假定建模,建立空间积分形式的运动方程,自然适应于颗粒材料动态力学行为的描述与分析. 发展了描述颗粒间接触作用的物质点尺度的排斥力模型,考虑近场动力学方法中非局部长程力特征,改进了近场动力学中的初始微观弹脆性(prototype microelastic brittle, PMB) 模型的本构力函数,并消除了原PMB 模型中存在的“边界效应” 问题. 计算分析了冲击载荷作用下碳化钨陶瓷颗粒体系的动态力学响应,得到了不同冲击速度下颗粒体系的冲击波速,PD计算结果与试验结果高度一致;通过颗粒物质点尺度作用描述单颗粒尺度的接触作用,很好地再现了颗粒的转动与平动、颗粒挤压变形以及颗粒破碎等现象;刚性冲击板附近同时存在严重的颗粒破碎与轻微的颗粒损伤,远离冲击板的部分颗粒出现破损,且颗粒破碎主要是由颗粒间挤压、碰撞以及相对滑动剪切作用造成的. 研究结果表明,所发展的计算模型和分析方法能很好地反映颗粒材料动态力学行为,具有广泛的应用价值.Abstract: The dynamic mechanical behavior of granular materials under impact load is a complex issue. Peridynamics as a new theory based on discontinuous and nonlocal hypothesis regards materials as compositions of massive material points with finite volume and finite mass, and builds an integral governing equation to reflect the motion law of material points. For all the features mentioned above, peridynamics is certainly suitable for describing and analyzing the dynamic behavior of particles. An improved PMB model considering the feature of nonlocal long range force and eliminating the “boundary e ect” and a repulsive force model at material point level to describe the inter-particle contact interaction are proposed. Then the method is applied to analyze the dynamics responses of tungsten carbide (WC) ceramic granular system su ering from impact loading. Wave velocities of the system were calculated accurately under di erent impact velocities compared with the experiment results. Phenomena of the motion, including translation and rotation, deformation and crushing of particles are reappeared. There are both total damaged particle and slight damaged particle near the impactor, and there are also particles far out from the impactor which are damaged. The extrusion, collision and shear slide between particles result in the particle crushing. The results indicate that the calculation model and analysis method developed here can well reflect the dynamic behavior of granular materials and have large application value.