Effect of TIG-dressing on fatigue strength and weld toe geometry of butt welded connections in high strength steel

When high strength steels are applicated in dynamically loaded structures, fatigue problems can arise. In most current design codes, the fatigue strength of high strength steels is either not discussed or determined as similar to mild steels. This assumption can be related to the dominance of the crack propagation life during in the total fatigue life when considering welded connections. Weld improvements can increase the length of the crack initiation life and thus increase the total fatigue life and may lead to a difference in fatigue strength between high strength steel and mild steels. This study focuses on the the effects of TIG-dressing on the weld toe geometry and the fatigue strength of TIG-dressed specimens. First a literature study is presented which summarizes earlier researches into the effect of TIG-dressing on fatigue strength and the behaviour of high strength steel in fatigue conditions, both in an as welded situation as after TIG-dressing. The weld toe geometry before and after TIG-dressing is determined. This leads to a extensive data set containing the geometry of the complete weld. The weld toe is then described with the aid of four parameters: weld toe radius, weld toe angle, weld height and undercut. Any influence of the static strength of the material, or any differences between rolled and cast steel are investigated. A comparison is made between the as welded specimens and TIG-dressed specimens. This changed geometry has been coupled to a changed fatigue strength with the aid of the notch stress approach. FEM analyses of the weld toe, based on measured geometries, have been carried out to determine stress concentration factors. Adjustments of the fatigue strength to account for loading mode, thickness, residual stress and mean stress have been derived from literature. A small reduction in residual stress, caused by the TIG-dressing procedure, has also been derived from literature. Fatigue tests have been carried out on 24 specimens ranging fr
Steel Structures
Structural Engineering
Civil Engineering and Geosciences