含局部减薄弯头塑性极限载荷的数值分析

局部减薄是一种压力管道表面常见的体积型缺陷，它不仅会降低管道的承载能力，而且还可能引起管道破坏，导致严重的事故．采用数值分析方法，对内压和面内弯矩作用下含局部减薄弯头的极限载荷进行了研究，分析了载荷组合、缺陷形状、位置、尺寸对弯头极限承载能力的影响，讨论了导致弯头破坏的典型失效模式．提出了含局部减薄缺陷弯头的塑性极限载荷工程估算式．计算结果为含缺陷弯头的安全评定提供了理论依据．

NUMERICAL ANALYSIS OF PLASTIC LIMIT LOADS OF LOCALLY THINNED ELBOWS

Local wall-thinning, as a common defect on thesurfaces of pipelines, not only reduces the load-carryingcapacities, but also causes serious failure accidents ofpipelines. In this paper, a computational method for plas-tic limit loads is adopted. The plastic collapse analysis ofdefective pipe elbows under internal pressure and bend-ing moment is performed by the proposed algorithm. Thedefects considered here include part-through spherical, el-lipsoidal and rectangular slots. Based on a number of nu-merical examples, the limit loads of pipe elbows are com-puted for a range of geometric parameters. The effectsof axial, circumferential, small and large area local wall-thinnings with different sizes on load-carrying capacities ofpipe elbows under internal pressure and in-plane bendingmoment are analyzed. Some typical failure modes corre-sponding to different configurations of slots and loadingforms are studied. The computational results can providetheoretical foundations for the safety assessment of defec-tive pipe elbows.