穿透裂纹和表面半椭圆裂纹模型的失效评定曲线比较

针对弹塑性材料裂纹管道的J积分计算建立了等效穿透裂纹和表面半椭圆裂纹2种有限元模型。在等效穿透裂纹模型中应用了1／4节点单元，在表面裂纹模型中采用了线弹簧单元。用这2种模型计算J积分，分别对3个实际含裂纹管段建立了失效评定曲线。比较了2种模型的失效评定曲线和R6通用曲线的差别，指出穿透裂纹模型偏于保守，建议在油气管道断裂的工程评定中采用半椭圆表面裂纹模型。

Comparison of Failure Assessment Curves Between Through-wall Flaw Model and Surface Flaw Model

Two kinds of finite element models were set up to compute J integral for cracked pipeline made of the elastic-plastic material. They are the through-wall flaw model in which the quarter-point element was used in tip of crack and the semi-elliptical surface flaw model in which the linear spring element is placed along the flaw. With the two models of cracked pipeline, failure assessment curves were given respectively for three pipes in an actual pipeline. These curves were compared to the general curve in R6. It shows that the equivalent through-wall flaw model is over-conservative. The elliptical flaw model is recommended in engineering assessment of oil and gas pipelines.