残余应力对水下耐压结构典型焊接接头疲劳强度的影响

摘要

The Typical welded joint of the underwater pressure structure is often built with high strength steel that is sensitive to residual stress. Therefore,it is necessary to study the influences of residual stress on the fatigue strength of the typical welded joint. In this paper, numerical simulation on the welding residu⁃al stress of the typical welded joint is conducted based on the ANSYS APDL language. Then,using the lo⁃cal stress-strain method, the numerical analysis for the fatigue strength in both cases of ignoring and con⁃sidering the residual stress is carried out. The results show that the maximum residual stress and the short⁃est life cycle of the joint both occur near the welding line of the concave cone. Specifically,the fatigue life cycles are 104,which belongs to the category of low-cycle fatigue. Meanwhile, the fatigue life decreases as the fatigue load increases, which indicates that the existence of the residual stress reduces the fatigue life of the typical welded joint significantly.%水下耐压结构典型焊接接头模型常采用高强度钢建造，对焊接残余应力较为敏感，因此有必要针对残余应力对其疲劳强度的影响进行相关研究。采用ANSYS的APDL语言编程，通过数值模拟分析得到典型焊接接头的焊接残余应力；并基于局部应力—应变法，对水下耐压结构典型焊接接头考虑与不考虑残余应力这2种情况下结构的疲劳寿命进行数值分析。研究发现：典型焊接接头在凹锥面焊缝附近其残余应力最大，寿命最短；其寿命周期为104，属低周疲劳范围；随着外载荷的增加，疲劳寿命最小值也随之减小；残余应力的存在会明显降低典型焊接接头的疲劳寿命。