The weldability of high-strength steels (HSSs) is limited by their loss of strength, toughness and fatigue properties. In demanding applications, the fatigue properties of welds are among the strictest requirements. This paper presents a weldability analysis focusing on the microstructure and fatigue properties of 6 mm thick S690 and S355 HSS plates joined by friction stir welding. Their fatigue properties are compared to design recommendations and to fatigue properties obtained with other welding techniques. Results show that the high-quality friction stir welded steel joints outperform high-quality arc welds and FAT80 design recommendations. The fatigue strength of the friction stir welded joints is increased with material yield strength. The mechanisms governing crack initiation at different maximum stress levels are discussed.
ARTICLE HISTORY
High-strength steel hybrid joints that combine adhesive and bolts have been studied both experimentally and numerically. The fatigue strength of the double lap joint has been experimentally measured under completely reversed cyclic loading. Finite element analysis was used to estimate the stress state at the contact interface of the lap joint. The fatigue strength of bonded and clamped interfaces which have previously been characterized using napkin ring specimens has been combined with the finite element results. The region of the double lap joint which showed fretting damage corresponded well with the region estimated to have significant damage based on the assessment. The resulting fatigue strength assessment was conservative with respect to the experimental results.
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