Improvement Of The Fatigue Life For Offshore Welded Connections

Author:  Bignonnet, Lieurade, Picouet
Source:  Conf: Weld.of Tub.Struc., July '84 (Book)
Doc ID:  1984081
Year of Publication:  1984
Abstract:  
The advantages provided by using high-strength structural (HSS) steels for offshore construction might be limited by the fatigue resistance properties of the welded connections. Since fatigue crack propagation characteristics are not significantly different between low- and high-strength structural steels, the best way to improve the fatigue resistance of welded joints in HSS steels is to introduce a longer initiation period. For this purpose, an improved weld procedure and a post-weld improvement technique have been developed. The over-all geometry of the fillet weld is controlled to obtain the best stress flow and the lowest stress concentration in the weld toe region. The weld toe run is done at the beginning of the welding. This improved weld procedure gives smaller stress concentrations. The second step to improve the fatigue resistance of such welded joints is post-weld shot peening. Fatigue tests were carried out on 30 mm thick T shape welded joints of AFNOR E460 steel. Comparative results between as-welded and shot-peened specimens show the efficiency of the improved weld procedure and of shot peening in improving the fatigue resistance of welded structures. Descriptors: Offshore drilling rigs-- Welding; High strength low alloy steels-- Welding; Tube joints-- Welding; Shot peening; Crack propagation; Fatigue strength; Gas metal arc welding; Impact strength