Low-cycle Fatigue behavior of Large-size Dissimilar Steel Welded Tube-plate Structure

摘要

Based on the FEM analysis of the distributions and varieties of the stresses and the strains of the large-size dissimilar steel welded tube-plate structure under cyclic loading, the fatigue crack initiation sites of this structure were predicted. The low-cycle fatigue test was performed to verify the prediction and to study the cracks propagating paths as well. The results indicated that the weld toes linked to the two surfaces of the plate were the positions with the peak values of the maximum stress and the stress amplitude. The plastic deformations in the first loading cycle introduced the tensile-compressive repeated stress cycle at the weld toes during the subsequent loading cycles. It induced the fatigue cracks initiating at the weld toes linked to the two surfaces of the plate respectively. After initiating from the surfaces the cracks propagated along the fusion lines with a short distance then turn into the base metal in the sections vertical to the surfaces. The depth of the crack initiating from the compressed surface was shorter than the one from the tensioned surface.