三维裂隙组扩展及贯通过程的试验研究

EXPERIMENTAL RESEARCH ON PROPAGATION AND COALESCENCE PROCESS OF THREE-DIMENSIONAL FLAW-SETS

采用一种透明性良好、在低温下呈脆性破裂特征的非饱和树脂材料,制作一些含三维裂隙组的试样(原生裂隙采用薄铝片进行模拟),研究单轴压缩条件下平行三维裂隙组的扩展与贯通过程。试验结果表明:试验早期阶段,各裂隙在端部均以包裹式翼裂纹起裂,并独立地扩展。随着各裂纹间相互作用的加强,会引起次生裂纹在预置裂隙端部附近反向扩展的现象,并形成一种新的断裂模式——包裹式反翼裂纹。最终,试样被包裹式翼裂纹与反翼裂纹主导的宏观破裂面所劈裂,并且裂纹在整个断裂过程中能够始终保持一种稳定的扩展。此外,裂隙组的分布方式将影响着三维裂纹的扩展参数,尤其是对裂纹初始扩展角的影响较大,使得包裹式翼裂纹的扩展角约偏转了10°。最后,讨论了三维裂隙组断裂的基本模式与断裂机制。

A team of transparent specimens using a type of casting resin are employed,which has brittle fracture properties of rock-like material under frozen environment. The primary flaws in samples are made of three thin aluminum films. The propagation and coalescence process of three-dimensional(3D) flaw sets were observed. The experimental results show that wrapping wing cracks individually initiate and grow from every pre-existing flaw end at the beginning of fractures. Then the interaction roles between the flaws gradually become stronger and stronger,and principally,the secondary cracks are induced to extend towards the direction opposite to wing crack. This type of crack is so called wrapping anti-wing crack(against wrapping wing crack). The whole specimens will be broken off by the coalescence fracture of wrapping wing and anti-wing cracks. Furthermore,the distribution type of 3D flaws will greatly affect some parameters of growth and coalescence of 3D cracks. Especially,the initial growth angle of crack will change by about 10°. Finally,the primary fractured pattern and mechanism of 3D flaw sets are discussed in this paper.