Ⅰ-Ⅱ复合型裂纹等σ_θε_θ线面积断裂准则

The area fracture criterion of isoline σ_θε_θ for Ⅰ-Ⅱ mixed mode crack

为了研究构件中的复合型裂纹开裂角和裂纹扩展临界值,根据Ⅰ-Ⅱ复合型裂纹尖端附近等σθεθ线所围成的面积大小的变化,提出了Ⅰ-Ⅱ复合型裂纹断裂等σθεθ线面积断裂准则,推导了Ⅰ-Ⅱ复合型裂纹扩展的开裂角公式和断裂扩展准则表达式,结果表明纯Ⅱ型裂纹的θ0及断裂韧度比c cKⅡ/KⅠ随泊松比的增大而降低。同时给出了Ⅰ-Ⅱ复合型等σθεθ线面积断裂准则的理论预测曲线,并与部分实测值进行了对比分析,与其他准则以及试验数据对比分析表明:本准则的Ⅰ-Ⅱ复合型裂纹断裂准则公式推导简单,工程应用方便;其理论预测值与现有部分材料的实验值相比误差在12%以内,表明本文提出的Ⅰ-Ⅱ复合型裂纹等σθεθ线面积断裂准则可以应用于部分材料的复合型断裂问题分析。

The composite crack initiation angle and the expanding critical value of the cracks in bearing members are studied in this paper.A criterion of isoline σ_θε_θ for I-II mixed mode crack based on the changes in the size of the area formed by isoline σ_θε_θ is proposed,crack expanding initiation angle formula and the fracture expanding criterion are established,the 0 θ for Ⅱ mode crack and fracture toughness cc KK ⅡⅠ / varying with Poisson ratio have been analyzed,it is found that 0 θ for Ⅱ mode crack and fracture toughness cc KK ⅡⅠ / decreases with the increasing of the poisson's ratio.A theoretic prediction curve is given based upon the fracture criterion of isoline σ_θε_θ for I-II mixed mode,and a comparason with the tested data is made.These results are of important theoretical significance and practical value in determining the complex stress states of bearing members in different projects.By comparason with other criteria and test data,it is shown that the deduction of the formula for fracture criterion of isoline σ_θε_θ for I-Ⅱ mixed mode cracks is simple,thus,it is convenient to apply it to the practice,and the error of its theoretically predicted values to the measured values for some materials is less than 12%,which proves that the fracture criterion of isoline σ_θε_θ for I-II mixed mode crack proposed in this paper is applicable to the analysis of mixed-mode fracture problems.