Extension of the strain energy density method for fatigue assessment of welded joints to sub-zero temperatures

Abstract

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.