桥梁焊接构件疲劳损伤测试与分析

Measurement and analysis on fatigue damage of bridge welded components

对桥梁结构中典型的焊接构件的缩尺试样进行实验研究,探讨了焊接构件在高频动载下的高周疲劳损伤破坏过程及其特征.通过动态捕捉焊接试样在焊趾附近的应变变化情况,直观描述了疲劳损伤演化过程中的3个典型阶段;通过研究疲劳实验过程中试件固有频率的变化情况,定量给出了试样的疲劳损伤演化曲线,为研究结构的疲劳损伤情况提供了一种新的方法.结果表明:在焊接试样的总疲劳寿命中,对应于疲劳裂纹萌生期和扩展期的寿命占主要部分,达到总疲劳寿命的90%左右,而产生宏观可见的疲劳裂纹到试件断裂的寿命周期很短,只占到总疲劳寿命的10%左右.疲劳裂纹源和裂纹扩展区部分的图像呈放射状的人字形条纹,人字纹指向裂源,其反向为裂纹的扩展方向.

Experiments were taken to study the hot-spot stress distribution and the behavior of high cycle fatigue damage in the vicinity of welded toe of typical components available in steel bridges. By recording the dynamic local strain and stress distribution nearby the welded toe under cyclic load, the process of fatigue crack generation and propagation were monitored. The fatigue damage evolution curves of the welded specimens were obtained by investigating the system frequency changes. The results show that the total fatigue life of the welded specimens are composed of two parts, the life corresponding to fatigue crack initiation and growth, being about 90% of the total life, and the period of fatigue crack propagation, being only 10% of the total life. Fatigue cracks develop in the shape of semi-ellipse, and the pattern of fatigue crack growth looks like headstand Y with the head pointing at the origin of the cracks.