Comparison of Total Fatigue Life Predictions of Welded and Machined A36 Steel T-Joints

A new total fatigue life methodology was utilized to make fatigue life predictions, where total fatigue life is defined as crack initiation and subsequent crack propagation to a crack of known size or the component’s inability to carry load. Fatigue life predictions of an A36 steel T-joint geometry were calculated using the same total fatigue life methodology for both welded and machined test specimens that have the same geometry. The only significant difference between the two analyses was the inclusion of the measured weld residual stresses in the welded specimen life predictions. Constant amplitude tests at several load levels and R ratios were analyzed along with block cycle and variable amplitude loading tests. The accuracy of the life predictions relative to experimental test lives was excellent, with most within a factor of +/- two. Also, welded joint fatigue life predictions demonstrate approximately the same accuracy as the machined joint fatigue life predictions when compared to their experimental test fatigue results. When the welded and machined analysis results were overlaid, the two sets of analysis results appear to be consistent with each other.