基于统一强度理论的复合型裂纹断裂准则

提出一个复合型裂纹等效应力断裂准则，用以解决工程上普遍存在的复合型裂纹的断裂问题。该准则通过借鉴强度理论对复杂应力状态的处理方法，将等效应力作为度量复合型裂纹开裂的基本物理量。该准则在预测发生临界扩展时提出两个基本假设，(1)裂纹沿着等效应力最小的方向开始扩展。(2)等效应力达到临界值时裂纹开始扩展。根据选取的等效应力计算公式的不同，等效应力准则有不同的形式，当等效应力的计算采用总应变能理论时，等效应力准则等价于应变能密度准则；当等效应力采用σr时，等效应力准则可近似逼近最大周向应力理论。采用统一强度理论计算等效应力。最后通过与实验结果及其他理论的计算结果对比，验证基于统一强度理论的复合型裂纹断裂准则满足工程精度要求，且适用性好。

MIXED MODE FRACTURE CRITERIA BASED ON UNIFIED STRENGTH THEORY

A mixed mode fracture criteria based on Yu's Unified strength theory was presented to solve the mixed mode cracks fracture problem, which is in existence universally. This criteria use equivalent stress as the basic measure of fracture, which refer to strength theory. Two assumption was presented when predict critical fracture of crack: (1) the crack grow up along the direction of the minimal equivalent stress; (2) the crack begin to grow when the equivalent stress arrived critical value. In accordance with the selected formula to compute the equivalent stress, the criteria has different form: it equal to strain energy density criteria when use strain energy theory to compute equivalent stress; and it similar to Maximum Principal Stress Criterion. At last, we verified the mixed mode fracture criteria based on Yu's Unified strength theory through comparing with the result of experiment and the calculation result using the other theory. The results show that this criteria can meet the need of engineering and have a good adaptability.