Q345qD 桥梁钢对接焊缝疲劳裂纹扩展性能试验研究

摘要

The experimental study on fatigue crack growth rate and threshold of butt welds for Q345qD plates of 6.1,10.0 and 23.5 mm thickness was performed,aiming to implement fatigue assessment of welded structural details of existing steel bridges based on fracture mechanics.Two data processing methods were employed to de-rive fatigue crack growth parameters with 95% guarantee.It turns out that the fatigue crack growth rate based on data of each specimen is larger than that based on group method of data handling in terms of normal stress inten-sity range (10 ~70 MPa·m0.5 ).The fatigue crack growth rate will increase as the stress ratio increases.For Q345qD butt welds of this batch,the fatigue crack growth rate is slower than the universal steel performance pro-vided by BS7910.The fatigue crack growth threshold will decrease with the increase of the stress ratio,and the quantitative relationship is also developed in this paper.%为采用断裂力学方法对既有钢桥焊接细节进行疲劳评估，对6．1，10．0和23．5 mm 的 Q345qD 桥梁钢对接焊缝进行疲劳裂纹扩展速率试验和疲劳裂纹扩展门槛值测定试验，基于两种数据处理方法得到了不同厚度、不同应力比下的疲劳裂纹扩展速率参数。试验结果表明：在通常的应力强度因子幅值范围（10～70 MPa·m0．5）内，基于单试件数据点的处理结果对应的裂纹扩展速率明显高于基于成组数据点的处理结果；Q345qD 对接焊缝的疲劳裂纹扩展速率随应力比增加而增加；本批次的 Q345qD 对接焊缝的疲劳裂纹扩展性能优于 BS7910中给出的通用钢材疲劳裂纹扩展性能；Q345qD 对接焊缝疲劳扩展门槛值随应力比增加而降低，并给出了门槛值随应力比变化的公式。