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塔式起重机起重臂下弦杆疲劳裂纹影响因素多,裂纹形成过程复杂。从塔式起重机起重臂的工作载荷和焊接残余应力特征出发,应用断裂力学理论分析了起重臂疲劳裂纹萌生点和疲劳裂纹的扩展过程。针对塔式起重机承受随机载荷的特点,应用时间循环法估算塔式起重机起重臂的疲劳裂纹扩展寿命。研究结果表明:疲劳裂纹在下弦杆与腹杆焊接处萌生;疲劳裂纹扩展的主要原因是交变应力与变幅小车循环次数的累积作用,并为现役塔机的安全评定提供了理论分析依据。
The fatigue crack of the lower chord of the tower crane has many influencing factors and the crack formation process is complicated. Based on the working load and welding residual stress characteristics of tower crane boom, the application of fracture mechanics theory is used to analyze the crack initiation and fatigue crack propagation of boom. Aiming at the characteristics of tower crane under random load, the fatigue crack growth life of tower crane boom is estimated by time circulation method. The results show that the fatigue crack initiation occurs at the weld of the lower chord and the web. The main reason of the fatigue crack growth is the cumulative effect of alternating stress and the number of trolley cycles, and provides the theoretical basis for the safety assessment of the existing tower crane.