Ultra-Long Life Fatigue Behavior of Welded Joints with Shot Blast Treatment

Abstract:

In order to investigate the ultra-long life fatigue properties of welded joints, ultrasonic fatigue tests of base material and welded joints were carried out using Q345q steel in ambient air at room temperature with a stress ratio R=-1. The results showed that the fatigue strength of specimens with welded joints dropped about 60% compared with that of base steel. To improve the fatigue properties of welded joints, two groups of specimens were treated by shot peening with different degrees which produced different compressive residual stresses on samples. It was found that the shot peening treatment could improve the fatigue strength of welded joints obviously. The fatigue fracture surface was analyzed by scanning electron microscopy. The fractography showed that there were two kinds of crack initiation mechanism in the Q345q base steel, crack inition from defects on the surface for high cycle fatigue failure and in the interior of the sample in very high cycle fatigue range. However, almost all cracks of welded joints initiated from defects caused by welding process. The failure of welded joints usually happened at the section of welded toes in the area of fusion or geometric discontinuity.

• Periodical: Applied Mechanics and Materials (Volumes 275-277)
• Pages: 179-183
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.275-277.179
• Online since: January 2013
• Authors: Chao He, Yong Jie Liu, Qingyuan Wang
• Keywords: Fractography Analysis, Shot Blast Treatment, S-N Curves, Ultrasonic Fatigue, Welded Joint

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