含凹坑缺陷管道的塑性拉伸失稳载荷分析

现有缺陷管道剩余强度评估方法,大多将塑性极限分析理论中的塑性极限载荷作为管道塑性失效的控制载荷,而塑性极限载荷是基于弹性-理想塑性材料而言的,用来表达管道的极限承载载荷时容易引起不必要的概念混乱。引入了弹塑性稳定理论中的塑性拉伸失稳载荷以表述韧性管道材料的极限承载载荷,并将对应的管道失效压力称为塑性拉伸失稳压力。基于塑性拉伸失稳理论,运用大应变弹塑性有限元分析方法求解带凹坑缺陷管段的拉伸失稳载荷。结果表明,计算所得塑性拉伸失稳压力与实验所测管道失效压力十分接近,可以用来描述管道的塑性失效压力。

Analysis on Plastic Tensile Instability Load for Pressure Pipelines with External Pits

Almost all of the existing criteria for evaluating the residual strength of pipelines with defects take the plastic limit load(PLL) as the threshold load of pipelines’ plastic collapse,while PLL is only qualified for elasto-perfectly plastic material models.Conception confusions may be caused with the PLL’s using to express the ultimate bearing load(UBL) of pipes.To express the UBL of pipes made with ductile materials by using plastic tensile instability load(PTIL) was tried,and a relative plastic tensile instability pressure(PTIP) was used to express plastic collapse pressure(PCP) of pipes.PTIP of pipes with external pits was then obtained via 3-D large strain and elasto-plastic finite element analysis(FEA).The conclusion was that PTIP showed a good correlation with the PCP of tested pipes and was suitable to express the PCP.