焊接结构件疲劳裂纹扩展的数值研究
Numerical Study on the Fatigue Crack Propagation of Welded Structure Component

针对焊接结构件中出现地裂纹现象，建立塔式起重机起重臂有限元模型。采用有限元数值模拟，同时考虑残余应力的影响，计算QTZ40塔机起重臂下弦杆与水平腹杆焊接处在变幅小车满载和空载状态下，不同长度裂纹对应的应力强度因子，建立裂纹应力强度因子幅与裂纹长度的函数关系，进而估算塔机起重臂的疲劳寿命。结果表明：应力强度因子幅随裂纹长度的增加而增大，当裂纹长度到达某一值后，应力强度因子幅呈指数型加快形式，故采取有效措施防止裂纹的快速扩展，可提高结构的疲劳寿命。
Aiming at welded structure inevitably cracks phenomenon, we build tower crane boom finite element model, taking into account the effect of residual stress, which is used to calculate QTZ40 tower crane jib bottom chord and horizontal web welding rod at full load and no-load state car horn, different crack lengths corresponding to the stress intensity factor, through simulation analysis. Then we establish stress intensity factor range as a function of the crack length, and then estimate the tower crane arm fatigue life. The results show that: with the stress intensity factor range crack length increases, when the crack length reaches a certain value, the stress intensity factor range exponentially accelerated form, so to take effective measures to prevent the rapid expansion of the crack can improve the fatigue life