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为提高管道凹坑缺陷应变评估方法的准确性,基于韧性断裂模型和损伤力学,建立管道凹坑损伤评估模型。结合有限元方法,研究2种典型凹坑缺陷(平滑型凹坑和曲折型凹坑)不同区域的损伤程度,计算在不同管规格和内压下的凹坑缺陷临界失效应变。数值模拟结果表明:不同类型凹坑的各部位损伤程度不同,且可能产生裂纹的部位也不同;不同管规格之间的临界失效应变差别较小;由于内压的回弹作用,不同内压下的非约束型凹坑的临界失效应变不同,可进而得到内压和临界失效应变的拟合关系;凹坑缺陷的应变评估需要将凹坑分为约束型和非约束型,选用不同的应变标准分别予以评估。
In order to improve the accuracy of the method for evaluating the strain of the dent in the pipeline, a model for assessing the pit damage is established based on the ductile fracture model and the damage mechanics. Combined with the finite element method, the damage degree of two typical pit defects (smooth pits and zigzag pits) was studied and the critical failure strains of pits with different tube sizes and internal pressures were calculated. The numerical simulation results show that the damage degree of different parts of pits is different, and the parts that may crack may also be different. The difference of critical failure strains between different pipe sizes is small. Due to the rebound effect of internal pressure, Of the non-constrained dimples have different critical failure strains, and then the fitting relationship between the internal pressure and the critical failure strain can be obtained. For the evaluation of the dimple defects, the dimples need to be classified into constrained and non-constrained types. Different strain standards Be assessed separately.