I-II复合型裂缝断裂角的分层剪滞模型与分析

采用修正的剪滞理论建立了岩石、混凝土等准脆性材料的I-II复合型裂缝在单向拉伸荷载作用下的计算模型,得到了与实验相吻合且优于传统S判据的断裂角。通过对远场应力、斜裂缝区应力以及子层位移的合理简化,得到了求解剪滞分析模型的边界条件,进而得到了含斜裂缝的各子层位移分布函数。引入最大应力集中因子,对I-II复合型裂缝前缘应力场进行简化;基于斜裂缝沿最大应力集中因子方向扩展,得到裂缝的断裂角。根据斜裂缝的应力分布,设置不同的子层分区,得到了更为细化的位移分布模式。通过对计算数据的分析,针对单向拉伸荷载作用下的I-II复合型裂缝,建立了按应力场分区设置子层的分层剪滞模型,得到更为精确的斜裂缝断裂角。

Layered shear-lag model and analysis on fracture initiation angle of I-II mixed mode crack

Based on the modified shear-lag model,a new calculation model of I-II mixed mode crack of quasi-brittle materials such as rock,concrete and so on under simple tension load is established,and the fracture angle is obtained to be coincided with the experimental data and to be superior to the conventional S criterion.Through the reasonable simplification,the conditions of far-field stress,stress in the area of oblique crack and displacement of sub-layer,the boundary conditions to solve the shear-lag analysis model are obtained,and then the distribution function of displacement of each sublayer including the oblique crack is gotten.Introducing the maximum stress concentration factor,the frontal stress field of I-II mixed mode crack is simplified.Based on extension of the oblique crack along the direction of the maximum stress concentration factor,the fracture angle of the crack is obtained.According to the stress distribution of the oblique crack,the different sub-layer zones are set to obtain more precise model of displacement distribution.Through the analysis on the calculated data,a shear-lag calculation model with zoning sub-layers according to stress field is built for the I-II mixed mode crack under simple tension load to obtain more precise fracture angle of the oblique crack.