焊接构造对T型接头超低周疲劳性能的影响

为了研究焊接细节对钢结构超低周疲劳性能的影响，以T型接头为对象，在通用有限元程序Abaqus平台上，开发基于Arlequin算法的结构多尺度计算程序. 利用多尺度算法，开展焊接接头的局部弹塑性有限元分析. 比较焊趾半径、厚钢板未熔透长度及焊趾表面凹凸对局部塑性应变履历的影响，利用Coffin-Manson模型对T型接头的超低周疲劳特性进行定性讨论. 数值计算结果表明，焊趾位置是焊接接头的超低周疲劳易损位置，厚钢板的未熔透长度对焊接部位局部塑性应变的影响不大；焊趾半径对焊趾局部塑性应变有较大的影响，增大焊趾半径可以有效提升钢结构在循环荷载下的超低周疲劳性能；焊趾表面的平整性是影响焊趾局部塑性应变履历的重要因素，尖锐的凹坑会明显降低焊接接头的超低周疲劳性能，磨平的焊趾表面可以减少局部塑性应变，提高接头的超低周疲劳强度.

Effects of welding details on ultra-low cycle fatigue performance of T-welded joint

T-welded joint was adopted as a research object and a structural multi-scale calculation program was proposed based on Arlequin algorithm on the general finite element program Abaqus platform in order to analyze the effects of welding details on ultra-low cycle fatigue performance of steel structures. Local elastic-plastic finite element analysis of T-welded joints were conducted, and the local plastic strain characteristics were analyzed. The effects of welding details, such as weld toe radius, unfused length of thick steel plate and unevenness of weld toe surface on local plastic strain history were compared. The ultra-low cycle fatigue characteristics of T-welded joints were discussed by qualitatively using Coffin-Manson model. The numerical calculation results show that weld toe position is the vulnerable position of T-welded joints, and the influence of the unfused length of the steel plates on the local plastic strain history of the welded part is negligible. The local plastic strain history is more sensitive to the change of the weld toe radius, and the increase of the weld toe radius can significantly improve the ultra-low cycle fatigue performance of the structure under cyclic loading. The flatness of weld surfaces is an important factor on the plastic strain history of welding areas. Sharp dents can significantly reduce the ultra-low cycle fatigue performance of welded joints whereas a smoother welding surface is beneficial to reduce the local plastic strain and improve the ultra-low cycle fatigue strength of joints.