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本文从裂纹顶端必然钝化和应力应变有界的客观事实出发,通过对实验数据的分析指出:裂纹扩展的判据是最大切应力判据(延性断裂机制)或最大正应力判据(解理断裂机制)。结合特定的条件,由上述基本判据可导出相应的临界关系。在平面应变、小范围屈服情况下,这临界关系正是众所周知的K_1=材料常数K_(Ic),而在平面应力、小范围屈服情况下,则得出K_c=(π/8kσ_Fε_F~2BE)~(1/2)的结果。对影响K_(Ic)的因素也作了讨论。
Based on the fact that the crack tip must be passivated and the bounded stress and strain bounded, the analysis of the experimental data shows that the criterion of crack propagation is the criterion of maximum shear stress (ductile fracture mechanism) or the criterion of maximum normal stress Fracture mechanism). Combined with the specific conditions, the corresponding critical relations can be derived from the above basic criteria. In the case of plane strain and small-scale yielding, the critical relationship is well-known K_ = material constant K_ (Ic), and in the case of plane stress and small-scale yield, K_c = (π / 8kσ_Fε_F ~ 2BE) ~ (1/2) results. The factors affecting K_ (Ic) are also discussed.