基于Voronoi随机模型研究多孔材料的动态特性

利用随机Voronoi技术生成2维随机模型,结合有限元分析方法系统研究多孔材料在x1-x2平面内冲击载荷作用下的动态特性.模型包含胞孔形状的不规则性和孔壁厚度的不均匀性,以及孔壁的随机不完整性.模拟结果发现,在中低速冲击时Voronoi模型并不出现如规则蜂窝模型一样的"X"和"V"形的变形,而出现几条局部随机变形带;在冲击速度比较高时,局部变形带并不明显,在冲击面端附近区域出现"I"形的变形.发现平台冲击压力和胞孔形状不规则度之间具有比较复杂的关系;很小的孔边不完整性将会造成材料强度很大的"丢失";尽管组成多孔材料的母材是理想弹-塑性材料,但应用Voronoi随机模型描述的多孔材料是一应变率敏感材料.

STUDY OF THE DYNAMIC CRUSHING BEHAVIOR OF CELLULAR MATERIALS BY USING THE VORONOI RANDOM MODELS

The in-plane dynamic crushing behavior of cellular materials is investigated by using the Voronoi models with the imperfections of configuration and finite element method. The simulation results reveal that when the impact velocities is low and moderate, the Voronoi model does not appear the "X" and "V" shaped deformation as in a perfectly order honeycomb and the random local deformation band is found. However, the "I" shaped deformation is seen near the loading face at high impact velocities and the local deformation band is not clearly seen. It is also found that the relation between plateau crush pressure and cell shape irregularity is complicated;the cellular material that is described by the Voronoi model is the material witch is sensitive to the strain rate, despite the matrix material is elastic-perfectly plastic. It is the behavior of the cellular materials that a few cell walls deleted lead to both plateau crush pressure and densification strain energy to decrease sharply.