聚能装药射流形成的自适应物质点法模拟

聚能装药可用来穿透装甲、岩石、混凝土等高强度日标,在国防工业以及石油工业有重要应用.质点类无网格法,如SPH和MPM,可以避免网格畸变,比基于网格的传统方法更适合聚能装药问题的模拟.该文针对物质点法中可能发生的数值断裂问题,提出了自适应分裂质点的方案.当质点在某一方向的累积应变达到一定阈值,即将质点一分为二,从而使物质点法可以更有效的表达射流形成过程中强烈的拉伸变形.采用C++语言编制了可自适应分裂质点的三维物质点法程序MPM3DPP,应用Johnson-Cook材料模型用来考虑应变率效应和热软化效应,Mie-Gruneisen状态方程用于金属在高压下的压力计算,Jones-Wilkins-Lee(JWL)状态方程用于描述爆炸产物等膨胀过程,并在压力项加入人工粘性用来处理冲击波.模拟并分析了爆炸飞片、聚能射流等问题,通过数值模拟,对射流形成过程中的变形情况以及温度、速度的分布进行分析.模拟结果和经验公式吻合.

ADAPTIVE MATERIAL POINT METHOD FOR SHAPED CHARGE JET FORMATION

Shaped charges have many useful applications in defense industry and in oil industry for penetrating hard targets such as armor, tanks, rocks or concrete walls. Meshfree particle methods,such as SPH and MPM,are more suitable than traditional mesh-based methods in simulating shaped charge problems. In this paper, an adaptive splitting scheme was introduced to eliminate the numerical fracture in MPM. A particle will be split into two new particles if the accumulated strain exceeds the critical value in certain direction. Compared with MPM,the extreme large stretch deformation in jet formation can be better simulated by using AMPM. A three dimensional MPM code,MPM3DPP,is developed by using C++ programming language. The Johnson-Cook material model is implemented which takes strain rate and thermal effect into consideration. The Mie-Gruneisen equation of state is used to update metal pressure,and Jones-Wilkins-Lee (JWL) equation of state is used to model the expansion of high explosive products. Artificial bulk viscosity is added to the pressure term to simulate shock wave. Two numerical examples including explosive driven flyer and shaped charge jet formation are illustrated. The results fit well with empirical formula.