基于DIC-FEM的岩石Ⅰ型裂纹损伤扩展研究

Damage propagation research of rock mode I crack based on DIC-FEM

针对岩石Ⅰ型裂纹的损伤演化,提出一种求解裂纹尖端区域损伤变量场的方法。采用含Ⅰ型预制裂纹的巴西半圆盘试件进行三点弯曲加载,通过数字图像相关方法和有限元方法分别得到裂纹尖端区域的应变场,建立含损伤变量的目标函数并采用最小二乘法求解损伤变量。研究结果表明:数字图像相关方法和有限元方法协同分析可得到裂纹尖端的损伤场;裂纹尖端损伤场的局部化带几何特征和演化过程同应变局部化带具有一致性,同裂纹扩展过程相关;损伤场的局部化带长度可表征断裂过程区长度,用于岩石裂纹失稳扩展前兆分析。

In view of the damage evolution of rock mode I crack,a method is proposed to solve the damage variable field in the crack tip region.In the experiment,a Brazilian half disk specimen with mode I prefabricated crack was used to carry out three-point bending loading and the strain field in the crack tip region was obtained by digital image correlation method and finite element method respectively.The objective function containing damage variables was established and the damage variables were solved by using the least square method.The results show that the damage field of crack tip can be obtained by using digital image correlation method and finite element method.The geometric characteristics and evolution of the localization zone of the crack tip damage field are consistent with the strain localization zone and are related to the crack propagation process.The length of localized zone of damage field can represent the length of fracture process zone,which can be used to analyze precursor of rock crack instability propagation.