Investigation of fatigue strength of root of lap fillet welds of thin sheet and improvement method

This study investigates the dominant factors of fatigue strength at the root of thin-sheet lap fillet arc welds, which are frequently used in automobile chassis components. A method to improve the root fatigue strength was investigated. The direction of fatigue crack propagation at the root coincided with the direction of maximum circumferential stress range. The circumferential stress was reduced by increasing the distance from the toe to the root (penetration width). Fatigue strength originating from the root was improved in welded joints where the penetration width was increased by adjusting the welding aim point and heat input.