Cruciform welded joints: hot-dip galvanization effect on the fatigue life and local energetic analysis

Abstract

Even in a well-controlled technological process, a certain variability in the final product is present and this is very well the case of welded joints, where each single joint is slightly different from the others in terms of fillet dimensions, distortion, notch opening angle and root radius and material properties. When the fatigue life assessment of a welded joint is carried out using the Notch Stress Intensity Factors, their dimensions, so their critical values, vary as a function of the notch opening angle, according to William’s solution. This constitutes an adjunct level of complicacy in the implementation of the method, the most explicative case being the inability to use the same material property value in the same joint, this varying from weld toe to weld root. So considered, the local Strain Energy Density, averaged on a critical volume of carefully chosen radius on the base of the class of material and surrounding the notch’s tip, has the great advantage of being a scalar value of relatively simple numerical computation, almost independent of mesh refinement and independent of the notch-opening angle. The aim of the paper is to adopt the local SED method to analyze the results of a series of tests executed on fillet welded galvanized and non-galvanized cruciform steel joints. The tests are performed in atmosphere at room temperature. The interest is particularly focused on the influence of the zinc layer on the fatigue life of the joint and on the fitness of the method for its prediction, regardless of coating thickness.