大包内联箱三通与支管焊接结构应力-应变分析

Analysis of stress and strain for welding structure at header link and pipe

针对某厂大包内联箱三通与支管开裂失效现象,采用有限元法对焊接及运行过程中残余应力和变形进行模拟分析。结果表明:焊后高应力区主要集中在焊缝区,峰值达1 172 MPa,沿轴向随着距焊缝距离的增加逐渐减小;管内外壁焊缝上残余应力较高,且内壁高于外壁。管件在运行过程中沿轴向等效应力分布为较高应力→低应力→高应力→低应力→较高应力,焊缝外表面等效应力最高,峰值为1 100 MPa,沿管径向内逐渐降低;焊缝截面上可观察到高应力组成的Y型区域,这极易导致管件在运行过程中沿管外壁开裂失效。运行过程中焊缝中心应力相对于焊后应力提升了12.9%,管壁表面焊缝中心处于高度危险状态。最后,提出预防措施,将为实际工程提供重要的理论依据,减少同类焊接结构开裂失效的发生。

According to the phenomenon of crack failure at header link and pipe of a plant,the residual stress and deformation during the process of welding were simulated using finite element method. The results show that high stress areas are mainly concentrated in the weld with the peak value of 1 172 MPa,and along the axial direction,the stress decreases with the increase of distance;the residual stress of weld on inner and outer tube wall is higher,and the inner residual stress is higher than the outer one. The equivalent stress along the axial direction is distributed as：higher stress→low stress→high stress→low stress→higher stress,the highest equivalent stress is at the outer surface with the peak value of 1 100 MPa,and gradually reduces along the pipe diameter inwards;Y type of high stress can be observed on the cross section of weld,which easily leads to crack failure of the pipe along the outer wall. The center stress of weld is increased by 12.9% during the process of running compared to that after welding,the weld center of wall surface is at high risk. Finally,measures to prevent such cracks were proposed,which will provide important theoretical basis for the actual engineering and reduce the occurrence of cracking failure for the same kind of welding structure.