The welding process of steel structures such as ships, bridges, vehicles etc. induces residual stresses and distortions, which can affect the fatigue behaviour and structural durability significantly. The high tensile residual stresses at welded joints in complex structures particularly reduce the fatigue strength and eliminate almost completely the effect of mean stresses. Usually, high tensile residual stresses up to the yield strength are conservatively assumed at the weld toes. This conservative assumption can result in misleading fatigue assessments, and the general assumption of residual stresses up to the yield strength and its harmful affect on the fatigue strength is under debate. Areas with compressive residual stresses may be present in complex structures, where the details are less critical than predicted. This is shown here for a practical case in shipbuilding. The side structure of tankers is known for high fatigue loading due to passing waves and roll motions of the ship. Beneficial compressive residual stresses cause the initiation of fatigue cracks at other locations in less-strained areas in fillet-welded stiffener ends. A finite element analysis of the structural hot-spot stresses shows that the highest hot-spot stress of 89 MPa occurres at the vertical flat bar connected to the T-bar carrying part of the load, while full-scale fatigue tests show a different picture with better fatigue behaviour of the T-bar and shortest fatigue for the L-bar. Another example for the effects of residual stresses concerns the stress initiation and propagation at a structural detail (i.e. crack initiation and propagation) under fully compressive load cycles. Fatigue cracks are possible here due to high tensile residual stress fields. The conclusion is that the welding-induced residual stresses should be known in advance for a reliable fatigue assessment, which becomes possible to an increasing extent by numerical welding simulation.


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    Titel :

    Effects of residual stresses on the fatigue behaviour of welded steel structures


    Beteiligte:
    Fricke, W. (Autor:in)


    Erscheinungsdatum :

    2005


    Format / Umfang :

    14 Seiten, 17 Bilder, 12 Quellen



    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Print


    Sprache :

    Englisch




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