A series of fatigue tests on welded panels and small specimens representing a typical longitudinal stiffener to transverse web connection in the hull of a vessel was conducted under a range of loading conditions. The conclusions are as follows. (1) The panel tests gave fatigue results in agreement with published data for similar joints expressed in terms of the linearly extrapolated hot spot stress range at the weld toe as defined by the IIW (Hobbacher, 2007). (2) In terms of the nominal applied stress the small specimens gave a fatigue performance confirming IIW class FAT63 (Hobbacher, 2007). (3) Miner's rule was reasonably accurate under the loading spectra examined here. (4) In general, the specimens and panels tested under constant amplitude and specimens tested under variable amplitude loading gave longer life under compressive loading than under tensile loading. Based on the fatigue test results it is recommended to use improvement factor on fatigue strength of 1.2 if applied stress is fully compressive and linear interpolation between 1 and 1.2 if applied stress range is between alternating or fully compressive. This applies to the loading patterns where mean stress level is not changing. (5) Residual stress relaxation due to the applied tensile fatigue or static loading is beneficial if the subsequent fatigue loading produces stress ranges that are partly or fully compressive. This was demonstrated when fully compressive cycles were applied after tensile cycles of fatigue loading. (6) Additional fatigue testing combined with welding residual stress measurements are required to derive fatigue models accounting for mean stress effect in welded structures under application of mean stress changing from positive to negative and back. This type of loading pattern is typical for ship structures and should be properly accounted for in fatigue assessments.


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    Title :

    Fatigue testing to identify effect of mean stress on fatigue strength of welded joints in ship structures


    Additional title:

    Ermüdungsprüfung zur Identifizierung des Effekts der mittleren Spannung auf die Ermüdungsfestigkeit von Schweißverbindungen in Schiffsstrukturen


    Contributors:


    Publication date :

    2013


    Size :

    8 Seiten, 15 Bilder, 6 Tabellen, 3 Quellen


    Type of media :

    Conference paper


    Type of material :

    Storage medium


    Language :

    English




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