Effect of low temperatures on constant amplitude fatigue properties of Q345qD steel butt-welded joints

The development of transportation infrastructures stimulates increasingly more welded steel bridges in cold and severe cold regions in China. The low temperature there imposes additional challenges for the welded fatigue details. This study firstly examines experimentally the fatigue properties of the butt-welded joints made of Q345qD bridge steel under high-cycle constant-amplitude tensile action at the room and low temperature of -60 degrees C. The experimental results reveal the occurrence of multiple fatigue crack initiation and illustrate that the low temperature increases slightly the fatigue strength of the butt-welded details. The numerical simulation examines the fatigue crack propagation behavior of butt-welded joints with initial pre-existing single and multiple cracks under the room and low temperature, which achieves a good agreement with the experimental results. Based on the experimental and numerical validation, this study finally discusses the effect of the low temperature on the fatigue life of butt-welded joints and demonstrates that the lower fracture toughness under the low ambient temperatures influences marginally on the fatigue crack propagation life of the butt-welded details. The enhanced resistance to the fatigue crack propagation of structural steels at low temperatures contributes to the improved fatigue strengths of the butt-welded joints.