基于3D-VCCT的多裂纹输气管道断裂分析方法

A 3D-VCCT based method for the fracture analysis of gas line pipes with multiple cracks

现行的国家标准因不能准确反映含缺陷输气管道多裂纹干涉效应,从而使得评定结果偏于保守。为了提高含缺陷输气管道安全评估的准确性,在对比奇异单元法和三维虚拟裂纹闭合技术(Three-Dimensional Virtual Crack Closure Technology,3D-VCCT)的基础上,优选3D-VCCT建立输气管道多裂纹干涉模型,并通过分析裂纹相互干涉作用因子的变化,研究了附属裂纹对主裂纹前缘各点的干涉影响。研究结果表明:①随附属裂纹尺寸的变化,平行共线裂纹的最强干涉效应发生在裂纹近表面点并表现为增强效应;②一定条件下,平行共轴裂纹的干涉效应在裂纹最深点和表面点较为显著,并且最深点表现为增强效应,而表面点则表现为减弱效应;③当裂纹间的水平间距大于主裂纹长半轴的6倍时,平行共线裂纹与平行偏置裂纹的干涉效应微乎其微,可将多裂纹简化为单裂纹进行分析。结论认为,该研究成果不仅可以为多裂纹输气管道的断裂分析提供技术参考,而且还可以为输气管道多裂纹的安全评定提供理论依据。

The current national criteria with more conservative evaluation results can not accurately reflect the interference effect of multiple cracks on the safety assessment of gas line pipes. In view of this, we compared the singular element method with the three-dimensional virtual crack closure technology (3D-VCCT). Based on this, the 3D-VCCT was selected to establish a multi-crack interference model of gas line pipes. Finally, the interference effect of subsidiary cracks on the front points of the main crack was studied by analyzing the variation of the interference factors between cracks. And the following research results were obtained. First, as the subsidiary crack size changes, the strongest interference effect of a parallel collinear crack occurs near the surface and manifests as enhancement effect. Second, under certain conditions, the interference effect of a parallel collinear crack is more significant at the deepest point and the sur- face point of the crack, and it presents as an enhancement effect at the deepest point and as a weakening effect at the surface point. Third, when the horizontal spacing between cracks is greater than 6 times of the long half axis of the main crack, the interference effect between the parallel collinear crack and the parallel offset crack is negligible, and multiple cracks can be simplified as a single crack in the process of analysis. This research can provide a technical reference for fracture analysis on multi-crack gas line pipes and the theoretical basis for their safety assessment.