裂纹起裂角预测方法研究

Study on Predicting Crack Initiation Angle

为研究裂纹起裂角的预测方法,提出一个适用于岩石类材料小范围的屈服准则,旨在预测弹塑性材料的破坏行为。基于该屈服准则,推导出Ⅰ、Ⅱ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,基于裂纹沿塑性区最短路径扩展这一假设,在所提屈服准则的基础上导出新的断裂准则,该准则可预测裂纹开裂初始角。相较于其他断裂准则,所提准则与文献试验结果吻合更好,能更加精确地预测裂纹起裂角。

In order to predict the initiation angles of cracks,a new yield criterion was established for geotechnical materials with small plastic deformation. According to this yield criterion,the radii 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 showed 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 the plastic core region boundary,a fracture criterion which can predict crack initiation angles was obtained. The pre-existing test results agrees well with this fracture criterion,and its prediction result is more precise than those by other criteria.