Abstract
In this paper, T-joint samples in a 1300 MPa yield strength steel were produced using conventional or low transformation temperature (LTT) type consumables. The welded samples were either subjected to high-frequency mechanical impact (HFMI) treatment or to shot-peening. Fatigue testing was performed under fully reversed, constant amplitude bending load. Shot-peening gave a significant increase in fatigue strength for more than around 50,000 cycles. Shot-peened LTT welds had the highest fatigue strength, with conventional welds being shot-peened having slightly lower fatigue strength. HFMI treatment of conventional and LTT welds improved the fatigue strength also, but to a lesser extent, keeping the slope in the SN diagram close to three, while shot-peened samples had a slope of 5–7. Significant differences in compressive residual stress were seen between the different welds, with the most compressive stress found in the shot-peened samples. This was probably one of the main reasons for the improved fatigue life of shot-peened samples.
Highlights
Due to the increasing environmental requirements, there is a strong demand for lighter structures
Shot-peening Conventional clear that the fatigue strength (FAT) values of high-frequency mechanical impact (HFMI)-treated samples and as-welded samples were all higher than IIW FAT 225
What is undoubtedly clear is that shot-peening of the welds gave a considerable improvement in fatigue strength, compared to both conventional and low transformation temperature (LTT) welds, treated by HFMI
Summary
Due to the increasing environmental requirements, there is a strong demand for lighter structures. Lighter components can be manufactured by using higher-strength steels than is commonly used today [1]. Fatigue loading is mostly the critical loading event during the life time of a component and welded connections are often the prime location of fatigue failure. This is especially problematic for welded highstrength steels as fatigue strength of welds usually is not deemed to increase by increasing static strength [2]. Recommended for publication by Commission XIII - Fatigue of Welded Components and Structures
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