脆性材料裂纹与损伤相互作用的试验研究

为研究岩石等脆性材料的损伤对裂纹动态扩展的影响,采用动态透射焦散线方法,模拟脆性材料裂纹与损伤相互作用的动态过程,进行多种损伤情况下有机玻璃试样裂纹动态扩展过程试验研究,讨论不同类型损伤对脆性材料裂纹动态扩展规律的影响和裂纹与损伤相互作用的机制。试验结果表明:不同类型的损伤对裂纹扩展影响不同,除裂纹型损伤外,其他几种类型损伤的存在均会引起裂纹扩展出现短暂停滞,停滞时间与损伤的尺寸及距离扩展裂纹路径的距离有关系;裂纹扩展路径上存在单个圆孔时会影响裂纹扩展速度,裂纹消耗能量增大;而多个圆孔情况下,材料局部弱化,裂纹扩展速度增大,而裂纹扩展消耗能量降低;表面损伤和局部贯通裂纹的尺寸、相对裂纹扩展路径距离等影响裂纹扩展速度,但能量消耗并未增大;对称裂纹相互竞争,同步扩展,裂纹尖端位置或裂纹长度的微小差别(例如裂纹长度相差3.68%)就会对裂纹起裂产生明显影响,导致2个裂纹起裂时间不同,裂纹扩展以后,先起裂的裂纹尖端应力强度因子大说明能量集中到相应裂纹尖端,从而越有利于该裂纹的扩展,扩展速度也就越大(相差约38.9%),相同条件下裂纹扩展所消耗的能量也越大。

Experimental study on the interaction of crack and defects of brittle materials under dynamic loading

The study on the interaction of the damage and crack of brittle material under dynamic loading has great importance on the explanation of rock rupture mechanism. The dynamic method of caustics was carried out using polymethyl methacrylate(PMMA) specimens to simulate the interaction process between the crack and defects of brittle materials under dynamic loading. The dynamic crack propagation mechanism，the effects of different types of defects on the crack propagation and the interaction mechanism of crack and defects were discussed. The experimental results show that the crack arrest occurs followed by the increasing or decreasing of crack propagation velocity when there are defects near the crack path. The size of the defects and their distance from the crack path influences the arrest time. The fracture energy consumption increases when there is a circle hole near the crack path，while the multiple holes near the crack tip reduce the crack resistance of crack and the energy consumption. Other type of defects such as the surface crack and the combination of through and surface cracks influence the crack propagation velocity except the energy consumption. The symmetric cracks interact with each other during crack propagation. The minor difference between two symmetric cracks influence the crack initiation and propagation process，and lead to the asymmetric propagation of the two cracks. The crack position，crack propagation velocity，stress intensity factor and energy release rate etc.，can be obtained using the method of caustics which is a promising method for investigating the dynamic interaction between crack and defects.