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通过综合考虑Williams展开式中奇异应力项和非奇异应力项(T应力),运用断裂力学方法深入探讨远场拉–压、压–压应力组合下裂纹尖端起裂特性。在最大周向应力准则中考虑T应力的影响作用,并将其作为拉伸破裂判据;在剪切破裂方面,提出考虑法向应力影响的最大剪应力准则。通过对拉伸和剪切破裂发生条件的探讨,进一步阐明剪切破坏与裂纹倾角、内摩擦角、抗拉强度、黏聚力等参数之间的关系。研究结果表明,Williams展开式中非奇异应力项对于裂纹起裂角有重要的影响,所提出理论比传统理论计算的起裂角与实验结果更加吻合。随着内摩擦角的增大,剪切破裂减弱而拉伸破裂增强。随着黏聚力增大或者抗拉强度降低,拉伸破裂增强而剪切破裂减弱。
By considering the singular stress term and the non-singular stress term (T stress) in the Williams expansions, the fracture initiation behavior of the crack tip under the combination of far-field pull-pressure and compression-compression stress is investigated by means of fracture mechanics. The effect of T stress is taken into account in the maximum circumferential stress criterion and used as the criterion for tensile failure. In the case of shear failure, the maximum shear stress criterion considering normal stress is proposed. The relationship between shear failure and crack dip angle, internal friction angle, tensile strength, cohesion and other parameters is further clarified through the discussion of the conditions of tensile and shear fracture. The results show that the Williams non-singular stress term has an important influence on the crack initiation angle. The proposed theory is more consistent with the experimental results than the traditional theory. As the internal friction angle increases, the shear failure decreases and the tensile fracture increases. As the cohesion increases or the tensile strength decreases, the tensile fracture increases and the shear fracture decreases.