初始损伤对焊接节点疲劳性能的影响

为研究焊接节点的初始损伤对疲劳寿命和损伤演化的影响规律,从损伤力学角度引入了基于裂纹尺寸的损伤变量,介绍了两种常用的疲劳损伤演化模型:Chaboche模型和Lemaitre模型,并分别基于两种演化方程探讨了初始损伤对疲劳寿命和损伤变量的影响,提出了基于初始损伤疲劳寿命折减系数的概念. 以非承载角焊缝焊接节点为例得到了焊接节点在不同初始损伤情况下的疲劳寿命折减系数和疲劳损伤曲线.结果表明:当初始损伤分别小于0.055和0.002时,在Chaboche模型和Lemaitre模型中可以忽略其对疲劳寿命的影响,Lemaitre模型比Chaboche模型对初始损伤的影响更为敏感,推荐采用Chaboche模型来描述焊接节点的疲劳损伤演化. 

Effect of Initial Damage on Fatigue Performance of Welded Joints

In order to investigate the effect of initial damage of a welded joint on its fatigue life and damage evolution, adopting the damage variable based on crack size from the damage mechanics, two common fatigue damage evolution models, the Chaboche model and the Lemaitre model, were used to discuss the effect of the initial damage on the fatigue life and damage variable of the welded joint, and a concept of fatigue life reduction factor that is based on the initial damage was proposed. Then, the fatigue life reduction factors and fatigue damage curves under different initial damage were obtained from a non-carrying fillet welded joint in a case study. The results show that when the initial damage is less than 0.055 or 0.002, its effect on the fatigue life can be ignored in both the Chaboche model and the Lemaitre model. The Lemaitre model is more sensitive to the initial damage than the Chaboche model, and the Chaboche model is more appropriate to describe fatigue damage evolution of welded joints.