Influence of High Frequency Impact Treatment (HiFIT) on fatigue strength of welded joints of high-strength steel S700MC for bridges applications

The paper deal with experimental fatigue test of arc welded joints of thermomechanicaly rolled structural steel S700MC, uses for heavy duty application like steel bridges structures. The aim of the work was to compare the fatigue strength of welded joints in two conditions, i.e. as-welded and after HiFIT process as a post-weld treatment and set the influence of HiFIT process on fatigue strength improvement. For this purpose three different welded joints have been prepared. The experimental test series were consist of butt welded joints, T-joints with longitudinal and transverse stiffeners. In the paper the fatigue characteristics S-N of welded joints have been presented as well as calculated fatigue category FAT. The study shows that the fatigue strength of welded joints of S700MC steel grade after HiFIT treatment is much more higher in each cases than the fatigue strength of non-treated welded joints. The obtained results can be used by engineers at the design stage or estimating the remaining fatigue life of the welded steel structure made of similar high-strength steel used for bridges application.