多孔材料冲击特性的数值研究

使用物质点方法对多孔材料的冲击响应过程进行模拟研究.重点考察了孔隙度、冲击波强度和空隙平均大小对波后物质状态参量的影响,计算了局域旋度和散度随时间的演化及其涨落. 研究表明,在孔隙度较低时, 波后系统可以达到一个近似动力学平稳态,下游区域的空隙反射回的稀疏波使得物理量随时间轻微振荡.在孔隙度较大时, 波后物质不易被压实, 冲击波的衰减明显.在孔隙度一定的前提下, 更大的平均空隙导致波后系统温度的进一步提高.冲击波的衰减速率依赖于孔隙度、平均空隙大小和冲击波强度.局部湍流和体积耗散是非均匀材料中机械能转化为热能的重要机制;加载的冲击波越强, 材料的多孔特征越显著.压强、密度、温度、粒子速度趋于或远离平衡的节奏并不同步. 

NUMERICAL STUDY ON POROUS MATERIALS UNDER SHOCK

Shock responses of porous materials are studied using the material-point method. The effects of porosity, mean-cavity-size, shock strength, local divergence and vorticity are investigated. In materials with very small porosity, the shocked portion may arrive at a nearly steady state; the mean pressure and density oscillate slightly due to the tension waves reflected back from the cavities in the downstream portion. In materials with larger porosity, the shock compressibility decreases and the attenuation of shock waves becomes more evident. Under fixed porosity, a higher mean-cavity-size results in a higher mean temperature. The attenuation of shock waves depends on the porosity, mean-cavity-size, and shock strength. Local turbulence mixing and volume dissipation are two important mechanisms for transformation of kinetic energy to heat. The stronger the loaded shock, the stronger the porous effects. The pressure, density, temperature and particle speed do not approach their equilibriums at the same rate.