颗粒物质冲击损伤特性研究

Impact damage of granular material

在离散元(DEM)模拟过程中,颗粒物质的接触刚度对模拟结果有重要影响,而构成颗粒物质的材料本身存在大量的微观缺陷,由于在颗粒物质运动过程中反复冲击接触作用,必然导致颗粒物质内部微观缺陷的扩展和融合,使得颗粒物质的物理力学性质不断劣化,具体表现为接触刚度不断降低,直至发生冲击破碎。如何在离散元模拟过程中考虑颗粒物质的冲击损伤特性具有重要意义;以Hertz弹性接触力学为基础,结合连续损伤理论,定义了颗粒物质冲击损伤变量,建立了颗粒物质冲击损伤演化方程,提出了冲击损伤累积确定方法。结果表明:较小的冲击速度可以导致颗粒物质产生损伤,损失累积弱化了颗粒物质的接触刚度,损伤累积可导致颗粒破碎,在离散元模拟过程中应考虑颗粒物质的损伤累积。

The normal contact stiffness of granular material has a significant influence on the simulation results obtained with the discrete element method （DEM）.Under repeated impacts during movement,micro-defects existing in granular material expand and converge.Thus particles＇physical mechanical properties are weakened,i.e.,the particle contact stiffness decreases gradually till a particle finally crashes.Based on Hertz elastic contact theory and the continuum damage mechanics,here an impact damage variable of granular material was defined and an impact damage evolution equation was built to calculate impact damage accumulation.The results indicated that the material damage can be detected even at lower impact velocity,and the accumulation of impact damage weakens the contact stiffness and may result in final breakage of particles;the damage accumulation should be taken into consideration in the discrete element simulation process.