论文部分内容阅读
利用两个基本假设:(1)裂纹启裂方向沿裂尖距其近旁等应变能密度线最近的方向;(2)当裂纹尖端近旁材料的有效应力达到1型平面应变裂纹开裂的临界应力时即发生启裂,由引给出了复合型裂纹的基于应变能和应力的混合型开裂准则,第一个假设,开裂角方程可以写成[(1—k)sinθ_0+sin2θ_0]K_Ⅰ~2+2[2cos2θ_0+(1—k)cosθ_0]K_ⅠK_Ⅱ-[(1—k)sinθ_0+3sin2θ_0]K_Ⅱ~2=0。该方程与Sih等人的复合型裂纹的S准则的结论相同。而Sih的S准则的开裂角经大量实验证明是有效的、较为准确的。本文的假定(1)有明确的理论基础,完全不同于S准则中的应变能密度因子。由第二个假定,开裂条件可以写成C_(11)K_Ⅱ~2+2C_(12)K_ⅠK_Ⅱ+C_(22)K_Ⅱ~2+C_(33)K_Ⅲ~2+=K_(IC)~2式中C_(ij)=3/4b_(ij)(θ_0);θ_0就是由第一个假设给出的开裂角,b_(ij)是θ的函数(见王锋,断裂力学)。
Two basic assumptions are used: (1) the crack initiation direction is along the nearest direction of the strain energy density line near the crack tip; (2) when the effective stress of the material near the crack tip reaches the critical stress of type 1 plane strain crack initiation That is, crack initiation occurs, which gives mixed cracking criteria based on strain energy and stress for complex cracks. The first hypothesis is that the cracking angle equation can be written as [(1-k)sinθ_0+sin2θ_0]K_I~2+2. [2cos2θ_0+(1−k)cosθ_0]K_IK_II-[(1-k)sinθ_0+3sin2θ_0]K_II~2=0. This equation is the same as the S-criterion of the complex crack of Sih et al. However, Sih’s S-criterion angle has proved to be effective and accurate through a large number of experiments. The hypothesis (1) in this paper has a clear theoretical basis and is completely different from the strain energy density factor in the S criterion. From the second assumption, the cracking condition can be written as C_(11)K_II~2+2C_(12)K_IK_II+C_(22)K_II~2+C_(33)K_III~2+=K_(IC)~2 where C_ (ij) = 3/4b_(ij)(θ_0); θ_0 is the cracking angle given by the first hypothesis, and b_(ij) is a function of θ (see Wang Feng, Fracture Mechanics).