裂纹起裂角预测方法研究

本文提出一个新的屈服准则，该屈服准则适用于岩石类材料的小范围屈服，旨在预测弹塑性材料的破坏行为，基于该屈服准则，推导出了I型，II型以及I-II混合型裂纹尖端塑性区半径并对在单轴拉伸和纯剪切等荷载作用下的裂纹尖端塑性区进行了分析。结果显示，荷载加载方式、裂纹倾斜角和材料内摩擦角对塑性区的形状与大小有显著影响。根据对裂纹尖端塑性区的分析，基于如下假设：裂纹沿塑性区最短路径扩展，本文在提出的屈服准则的基础上导出了新的断裂准则，该准则可预测裂纹开裂初始角。相较于其他断裂准则，文献实验结果与本文提出的准则吻合地更好，能更加精确的预测裂纹的起裂角。

Study on Predicting Crack Initiation Angle

A new yield criterion was established for geotechnical materials with small plastic deformation before fracturing, and according to this yield criterion, the radiuses of the plastic region around crack tips for mode I crack, mode II crack and I-II mixed mode crack were obtained, and the plastic regions under uniaxial tension and pure shear were analyzed. The results show that loading conditions, crack inclination angles and material internal friction angles affect the plastic core regions significantly. Based on the assumption that cracks propagate along the shortest radius of a core region boundary, a fracture criterion which can predict crack initiation angles was obtained. The pre-existing test results agree well with this fracture criterion, and its prediction result is more precise than those by other criteria.