考虑残余应力影响的桥式起重机多轴疲劳寿命评估

Multi-axial Fatigue Life Assessment of Bridge Crane Considering the Effect of Residual Stress

桥式起重机桥架结构是典型的焊接结构,在日常服役时主梁焊缝区域经常出现疲劳裂纹。为保证起重机的服役安全,基于多尺度有限元分析方法建立危险裂纹区域的多级子模型;在二级子模型上建立热-结构耦合焊接有限元模型并模拟分析了焊接的全过程,通过模拟焊后热处理分析对残余应力的影响;结合多轴临界面法构建了以应变幅值作为多轴损伤参量的疲劳分析方法,评估了危险裂纹区域的疲劳性能。结果表明:所提方法将结构整体疲劳问题转化成局部焊接位置的疲劳问题,不仅增加了计算效率,还能考虑疲劳细节处更多的影响因素,为起重机焊缝部位的疲劳寿命评估和延寿提供了一定的参考。

The bridge structure of bridge crane is a typical welded structure,and fatigue cracks often appear in the weld area of the main beam during daily service.In order to ensure the service safety of the crane,a multi-level sub model of the dangerous crack region was established based on the multi-scale finite element analysis method.The thermal structural coupling welding finite element model was established on the secondary sub model,and the whole welding process was simulated and analyzed.The influence of post weld heat treatment on residual stress was simulated.Combined with the multiaxial critical interface method,a fatigue analysis method using the strain amplitude as the multiaxial damage parameter was constructed,and the fatigue performance of the dangerous crack region was evaluated.The results show that the proposed method transforms the overall fatigue problem of the structure into the fatigue problem of the local welding position,which not only increases the calculation efficiency,but also considers more influencing factors of the fatigue details,and provides a certain reference for the fatigue life assessment and life extension of the crane weld.