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    Item type:Publication,
    Review of methods for the high-cycle fatigue strength assessment of steel structures subjected to sub-zero temperature
    (2022-03-01) ;
    In recent years, there has been a growing interest in exploring the resources of the Arctic regions and an increase in shipping in regions with seasonal sub-zero temperatures. Such low temperatures impose challenging requirements for the structural integrity of steel structures and their weldments. Hence, specific knowledge of the behavior of materials and weldments and how to account for temperature effects is crucial to ensure safe operations. A number of recent studies have shown that fatigue strength at sub-zero temperatures is a major knowledge gap. This is exacerbated by the fact that this effect is not addressed in international standards. In this context, this study presents a comprehensive review of the current state of the art of high-cycle fatigue strength assessment methods for steel structures subjected to sub-zero temperature. The main objective is to provide an overview of how to account for temperature effects on fatigue strength when designing steel structures.
    Publicationtype: Journal Article
      57
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    Item type:Publication,
    Guidance for Material Selection Based on Static and Dynamic Mechanical Properties at Sub-Zero Temperatures
    It is well known that material properties undergo significant changes with temperature. In order to meet extreme environmental requirements for ships and offshore structures operating in Arctic regions, the effect of temperature on material behavior needs to be considered. In recent studies, significantly higher fatigue strength was observed for base materials and welded joints in comparison to room temperature. Fatigue strength increased even for temperatures far below the allowed service temperature based on fracture toughness results; however, sub-zero temperatures fatigue data are scarce and the effects of steel strength and welding type on fatigue strength changes are unknown. Material selection for ships and offshore structures is typically based on empirical Charpy and fracture toughness relations at the design temperature, minus a safety margin. Thus, this study presents material test results including fatigue tests of butt-welded joints, tensile test, and Charpy impact toughness tests at room and sub-zero temperatures of different structural steel types. Additionally, the effect of welding techniques and steel strength are discussed. The results can be used to extend design approaches for ships and offshore structures subject to sub-zero temperatures and to improve material selection for ships and offshore structures operating in Arctic regions.
    Publicationtype: Journal Article
      123
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    Item type:Publication, Access status: with files ,
    Extension of the strain energy density method for fatigue assessment of welded joints to sub-zero temperatures
    (Wiley-Blackwell, 2020-07-26) ; ;
    Fricke, Wolfgang 
    ;
    Within stress-based fatigue assessment concepts, causes that do not influence the fatigue stress parameters, such as temperature, can only be accounted for by means of modification factors. The strain energy density (SED) method allows to account for changing material support effects and Young's modulus with temperature directly. Thus, in this study, a concept is presented to extend the SED method for fatigue assessment of welded joints at sub-zero temperatures. For this purpose, fatigue test results of welded joints made from normal and high-strength structural steel are assessed in the range of 20°C down to −50°C. The results are evaluated based on the formula that is used to derive the SED control radii of welded joints and compared with results of studies on SED-based assessment of notched components at high temperatures. From the estimates of the control radii, a temperature modification function for SED is derived for design purposes.
    Publicationtype: Journal Article
    Scopus© Citations 16  185  536
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    Item type:Publication,
    Sub-Zero Temperature Fatigue Strength of Butt-Welded Normal and High-Strength Steel Joints for Ships and Offshore Structures in Arctic Regions
    (American Society of Mechanical Engineers (ASME), 2020-06) ; ; ; ;
    Ships and offshore structures operating in Artic regions face specific challenges such as ice loads and seasonal low temperatures. In order to meet these extreme environmental requirements, the effect of temperature on material behaviour needs to be considered. It is well known that static material properties (yield strength, fracture toughness etc.) undergo significant changes with temperature. In recent studies, significantly higher fatigue strength was observed in welded joints in comparison to estimates based on international standards. Fatigue strength increased even for temperatures far below the allowed service temperature based on fracture toughness results; however, studies on fatigue strength of structural steel at sub-zero temperatures are scarce. Moreover, material selection for ships and offshore structures is usually based on empirical Charpy and fracture toughness relations at the design temperature, minus a safety margin. This study aims at introducing an S-N curve database for welded joints that can be used to verify the fatigue design approaches for ships and offshore structures subject to sub-zero temperatures. Therefore, the effect of temperature on the fatigue strength of butt-welded normal and high strength steel structures is analysed experimentally for sub-zero temperatures. For this purpose, fatigue test results of SAW and MAG welded joints for temperatures down to −50 °C are analysed and the potential for changes regarding material selection for ships and offshore structures are discussed.
    Publicationtype: Conference Paper
      196
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    Item type:Publication,
      53
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    Item type:Publication,
      127