Effects of Bead shapes on Fatigue strength of Al Alloy Butt Welded Joints

Abstract

Recently, Al-alloys are widely used in large scale welded structures with various degrees of plate thickness. For example, 1 m/m thick plates are used on honey-comb structures and on shell plate of hulls. Medium thick plates (4-9 m/m) are used in structural members of ships and 10-60 m/m thick plates are used for large structures such as pressurized or refrigerated storage tanks.
Many researches have been carried out on the fatigue strength of Al-alloy welded joints. However, because of difference in previous and advanced welding techniques, there are difficulties to apply past research results to the subject newly designed. The present research was carried out with the following purposes.
(1) To Collect data on the fatigue strength of welded joint with various bead shapes within plate thicknesses of 1 m/m to 60 m/m and to analyse the data by bead shape factors.
(2) To Propose a new calculation formula of stress concentration factors around weld beads on thick plate joint.
(3) To Propose a fatigue strength assessment correlated to the stress concentration of the bead toe.
(4) To Assess the control method used in the yard to keep a certain value of fatigue strength.