基于多因素的焊接结构疲劳裂纹扩展速率分析

Analysis on growth rate of fatigue crack of welded structures based on multi-factor

以Donahue等提出的疲劳裂纹扩展速率计算模型为基础,通过引入形状系数、张开比和残余应力等参数,建立了适用于焊接结构的疲劳裂纹扩展速率计算模型,分析了多种因素对焊接结构疲劳裂纹扩展速率的影响规律。结果表明,焊板厚度和焊缝余高的变化均会对焊接结构疲劳裂纹的扩展速率产生影响,在对焊接结构表面形状进行设计时应保有一定的焊缝余高;有效应力比的增大会降低焊接结构疲劳裂纹的扩展速率,且裂纹深度的变化不会改变有效应力比对焊接结构疲劳裂纹扩展速率的影响;残余应力的增大会提高焊接结构疲劳裂纹的扩展速率,且残余应力对疲劳裂纹扩展速率的促进作用随着裂纹深度的增加而增大,在对焊接结构的疲劳性能进行设计时须考虑残余应力对结构性能的影响。

Based on the calculation model of growth rate of a fatigue crack proposed by Donahue et al,a calculation model of growth rate of a fatigue crack applied to welded structures was established by inducing the parameters of shape factor,crack opening ratio,and residual stress.In addition,influences of various factors on the growth rate of fatigue crack of welded structures were analyzed.The results indicate that both plate thickness and excess weld metal have impacts on the growth rate of a fatigue crack of welded structures,and a certain height of excess weld metal should be retained while designing the surface shape of welded structures.Furthermore,the growth rate of a fatigue crack of welded structures decreases with increasing effective stress ratio,and such a phenomenon is independent of the crack depth.The increase of residual stress accelerates the growth rate of a fatigue crack of welded structures,and this rate will increase while crack depth grows.Thus,the impact of the residual stress must be considered while the fatigue performance of welded structures is designed.