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

Abstract

A1-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 plating 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 pressurised or refrigerated storage tanks. Much research on the fatigue strength of A1-alloy welded joints has been carried out. However, because of difference in previous and advanced welding techniques, there are difficulties in applying past research results to new designs. The research discussed in this paper was carried out with the following purposes. (1) To collect data on the fatigue strength of welded joints 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 joints. (3) To propose a fatigue strength assessment correlated to the stress concentration of the bead tow. (4) To assess the control method used in the yard to keep a certain value of fatigue strength.