Print Email Facebook Twitter Effect of TIG-dressing on fatigue strength and weld toe geometry of butt welded connections in high strength steel Title Effect of TIG-dressing on fatigue strength and weld toe geometry of butt welded connections in high strength steel Author Van Es, S.H.J. Contributor Bijlaard, F.S.K. (mentor) Kolstein, M.H. (mentor) Pijpers, R.J.M. (mentor) Hendriks, M.A.N. (mentor) Houben, L.J.M. (mentor) Faculty Civil Engineering and Geosciences Department Structural Engineering Programme Steel Structures Date 2012-03-16 Abstract 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 from S460 to S1100, made from both cast and rolled steels. The specimens are also adjusted for loading mode, thickness, residual stress and mean stress and compared with the developed model and a larger dataset of comparable as welded specimens. Due to the relatively small number of specimens per steel grade, a reliable quantitative fatigue strength improvement cannot be specified. A extensive qualitative analysis gives insight in the overall trends. From all used plates, hardness measurements are available, which have not been thoroughly analyzed. During the fatigue tests, crack dimensions have been determined during the crack propagation life. These measurements also have not been analyzed. Both data sets are added in annexes and are digitally available at the author or one of the members of the graduation committee. Subject TIG-dressinggeometrytestsfatigueradiusangleimprovementbuttweldhighstrengthsteel To reference this document use: http://resolver.tudelft.nl/uuid:ca59ce6d-ab40-485d-a1a4-b659cd537554 Part of collection Student theses Document type master thesis Rights (c) 2012 Van Es, S.H.J. Files PDF Master_Thesis_-_SHJ_van_Es.pdf 23.76 MB Close viewer /islandora/object/uuid:ca59ce6d-ab40-485d-a1a4-b659cd537554/datastream/OBJ/view