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焊接残余应力对含裂纹环焊缝管道承载能力的影响

Effect of welding residual stress on load-carrying capacity of girth-welded pipelines with cracks

  • 摘要: 针对焊接残余应力对含裂纹环焊缝管道承载能力影响尚不明确的问题,建立了动态断裂有限元模型,研究了焊接残余应力作用下含裂纹环焊缝管道的承载特性. 动态断裂有限元模型基于全尺寸管道焊接试验验证的残余应力场,采用子模型技术实现了焊接残余应力场的传递. 同时,考虑到环焊缝管道中母材、焊缝和热影响区的材料性能差异,利用小冲杆试验获取了环焊缝各区域的弹塑性力学性能参数,并通过三点弯曲试验的有限元试算标定了相应区域的Gurson-Tvergaard-Needleman (GTN) 损伤参数.基于动态断裂有限元模型,研究焊接残余应力对含裂纹环焊缝管道承载能力的影响. 结果表明,焊接残余应力集中于焊缝,内表面轴压应力随距焊缝中心距离先升后降,环向应力由拉应力快速转为压应力. 焊接残余应力对管道的最大承受拉伸载荷和失效时裂纹嘴张开位移的影响较小. 管道所能承受的临界位移和拉伸应变能力(tensile strain capacity,TSC)受到焊接残余应力的影响而分别下降12.42%和13.04%,表明焊接残余应力的存在会降低管道抵抗拉伸断裂的承载力.

     

    Abstract: To address the unclear effects of welding residual stress on the load-carrying capacity of girth-welded pipelines with cracks, a dynamic fracture finite element model was established to investigate the bearing capacity of girth-welded pipelines with cracks under welding residual stress. The dynamic fracture finite element model was based on a residual stress field validated through full-scale pipeline welding experiments and utilized submodeling techniques to transfer the welding residual stress field. Additionally, by considering the material property differences between the base metal, weld metal, and heat-affected zone in the girth-welded pipeline, small punch tests were conducted to obtain the elastic-plastic mechanical properties of each region. The Gurson-Tvergaard-Needleman (GTN) damage parameters for the corresponding regions were calibrated through finite element simulations of three-point bending tests. Based on the dynamic fracture finite element model, the influence of welding residual stress on the bearing capacity of girth-welded pipelines with cracks was investigated. The results have shown that welding residual stress is concentrated in the weld metal, with the distance between the axial compressive stress on the inner surface and the weld center first increasing and then decreasing. The hoop stress rapidly transitions from tensile to compressive stress. The welding residual stress has a minimal effect on the maximum tensile load that the pipeline could withstand and the crack mouth opening displacement at failure. However, the pipeline’s critical displacement and tensile strain capacity (TSC) decrease by 12.42% and 13.04%, respectively, due to welding residual stress, indicating that its presence reduces the pipeline’s resistance to tensile fracture.

     

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