Acoustic emission during fatigue crack propagation in a micro-alloyed steel and welds

Abstract

► Different AE source mechanisms during fatigue in Q345 steel were proposed. ► AE behaviors of the weld were studied and compared with those of the base metal. ► The AE transition was compared with the linear elastic fracture mechanics. ► Effects of the micro-structure and load range on AE behaviors were discussed. The acoustic emission (AE) behaviors and source mechanisms during fatigue crack propagation in the base metal and weld of Q345 steel were investigated in this study. The fatigue properties and acoustic emission characteristics were analyzed based on the micro-structural and fractographic observations. The source mechanisms of acoustic emission for the three stages during fatigue were proposed, which were crack initiation, plastic activities ahead of the crack tip, and shearing of ligaments between micro-voids and micro-cracks respectively. The effects of the micro-structure and peak load on acoustic emission during fatigue crack propagation were also discussed in this study. The results showed that the acoustic emission was more sensitive to the changes in the fracture mode and could be used to monitor the fatigue damage developed in structures.