含环向裂纹管道三通的塑性失效载荷

INVESTIGATION ON PLASTIC FAILURE LOAD OF PIPING BRANCH JUNCTIONS WITH CIRCUMFERENTIAL CRACKS

采用弹塑性有限元方法,系统分析了内压载荷下含环向裂纹管道三通的塑性失效载荷。探讨了管道三通塑性失效有限元分析中的建模技术,包括变形参量选取,网格收敛性研究等。给出了塑性失效载荷随裂纹尺寸变化的规律,以及不同裂纹位置(包括肩部和腹部)对三通塑性失效载荷的影响。最后根据有限元数值解建立了简单的塑性失效载荷估算式,研究结果可为下一步含缺陷管件完整性评定提供参考数据。

By means of the elastic-plastic finite element approach, the plastic failure load of piping branch junctions with circumferential cracks subjected to internal pressure was investigated systematically. The finite element analysis techniques and building model approach, including the mesh convergence study and the selection of deformation parameters etc. , for collapse failure FE analysis of piping branch junction was discussed. The relationship between the plastic failure load and the crack dimension as well as the influence of crack location (e.g. , the corner and the flank) on the plastic failure load was established. Finally, referring to the data of FEM, a simple formula was built up by the regression analysis on the basis of least square method. It is worth noting that the effect of corner crack on failure load is very small, even for the case of larger crack angle, and could be negligible in practice. The concept of area weakening factor is not suitable for plastic failure load calculation of piping branch junction. These research results can be used as the basis for the integrity assessment of cracked piping fittings.