直径1422mmX80管道环焊接头应变能力数值模拟方法

鉴于高钢级管材的组织特征及焊缝失效对于管道安全的重要影响,管道环焊缝承载能力成为当前管道行业的研究热点,以中俄东线全自动焊口为研究对象,准确考虑环焊接头根焊、热影响区、母材、填充焊4个区域材料本构关系的差异性,基于有限元方法建立了分析管道环焊接头应变能力的数值仿真模型。定量分析了母材屈强比、运行内压、载荷类型等组合工况下焊缝强度匹配系数等对管道环焊缝裂纹扩展驱动力的影响。采用静裂纹起裂的失效判定方法,以表观断裂韧性值为临界准则,结合中俄东线管材及环焊接头材料特性参数实际变化范围,计算了在设计工况范围内最不利条件下中俄东线环焊接头的应变能力。结果表明:提高焊缝区强度匹配能够有效减小接头的裂纹扩展驱动力,增加管道内压或提高母材屈强比会使相同强度匹配条件下的裂纹扩展驱动力更大,拉伸载荷下的裂纹扩展驱动力要大于弯曲载荷下的裂纹扩展驱动力。该方法既可以用于根据焊接接头性能要求指导焊接参数的确定,也可以用于在役管道含缺陷焊接接头的适用性评价。

Numerical simulation method for strain capacity of girth welding joint on X80 pipeline with 1 422 mm diameter

In consideration of the structural characteristics of high-grade steel pipes and the great influence of weld failure on the safety of pipelines, the bearing capacity of girth welds of pipelines has become a research hotspot in the pipeline industry. The full-automatic joint in the China–Russia Eastern Gas Pipeline was taken as the research object, and the differences of material constitutive relations in the four zones of root welding, heat affected zone, base metal and fill welding in girth welding joint were accurately considered. The numerical simulation model based on finite element method was established for analyzing the strain capacity of pipeline girth welding joints. Quantitative analysis was made on the influence of the matching ratio of toughness and other factors on the driving force of crack growth in pipeline girth welds under combined operating conditions of base metal yield ratio, operating internal pressure and load type. The failure determination method of static crack initiation was adopted. The apparent fracture toughness value was taken as the critical criterion. In combination with the actual variation range of the material characteristic parameters of pipes and girth welding joints of the China–Russia Eastern Gas Pipeline, the strain capacity of the China–Russia Eastern Gas Pipeline girth welding joints under the most unfavorable conditions within the design operating conditions was calculated. The results show that improving the strength matching of weld zone is conducive to reduce the driving force of crack growth in the joint effectively. Increasing the internal pressure of the pipeline or raising the yield ratio of the base metal will cause the driving force of crack growth larger under the same strength matching condition, and the driving force of crack growth under tensile load is greater than that under bending load. This method can be used not only to guide the determination of welding parameters according to the performance requirements of welded joints, but also for the applicability assessment of defective welded joints in service pipelines.