缺陷对脆性材料碎裂过程的影响

Effects of defects on fragmentation processes of brittle materials

采用特征线方法模拟脆性材料中应力波的传播过程,采用内聚力模型模拟断裂点的断裂过程,运用C++语言开发了一个模拟脆性圆环发生一维膨胀碎裂过程的实用工具ExpRing,简要给出了该程序的理论基础和使用说明。采用此程序模拟了具有初始缺陷的脆性圆环在均匀膨胀作用下的碎裂过程,探讨了不同应变率下,缺陷分布特征对碎裂过程和平均碎片尺寸的影响。计算结果表明:(1)在一定的应变率范围内,等间距分布的点缺陷会控制断裂点的位置及碎片个数,在碎片尺寸-应变率曲线上形成一个缺陷控制碎裂平台;(2)点缺陷的间距和弱化程度将影响缺陷控制碎裂平台的宽度和位置;(3)具有缺陷的脆性材料的表观强度呈现应变率硬化特征;(4)在一定的应变率范围内,正弦分布型缺陷同样导致缺陷控制碎裂的现象。

The method of characteristics was used to analyze the stress wave propagations in the brittle materials.The random nucleation and the growth of the cracks in the brittle materials were described by using the cohesive fracture model.A practical simulation tool,ExpRing was developed for simulating the fracture and fragmentation in an expanding brittle ring.The ExpRing code was briefly explained.By using this code,the fragmentations of the rings with different intrinsic defects were simulated.The calculation results show：（1） within a certain strain-rate range,the equally-spaced point defects will control the final fracture sites and the fragment sizes and it can induce a defect-controlled-fragmentation（DCF） platform in the relation curve between the fragment size and the strain rate;（2） the spacing and the magnitude of the defects will alter the width and the location of the DCF platform;（3） the strength of the brittle materials with initial defects exhibit an apparent strain-rate effect.And further study displays that the materials with sinuously-distributed defects exhibit similar fragmentation behaviors to the materials with equally-spaced point defects.