Residual Stress Effect on Limiting Cycle Amplitudes in Welded Joints

The paper proposes a method for determining diagrams of the limiting cycle amplitudes of welded joints with steady-state residual tensile stresses based on the test results of small-sized specimens and presents the corresponding calculation dependencies. This technique is an express method for estimating the fatigue resistance characteristics of welded joints if full-scale tests are not feasible. The analysis of literature data for various types of welded joints shows a good fit of the experimental and calculated values of the endurance limits of welded joints of low-carbon steels with low-alloy, low-strength steels. It is shown that the inclined section of the diagram with steady-state residual stresses is shifted in parallel relative to the diagram of cycle amplitudes of welded specimens without residual stresses. It has been established that the diagrams of the limiting cycle amplitudes of welded joints with different values of the steady-state residual stresses end on a line where each point at different average cycle stresses corresponds to the minimum limiting cycle amplitude of the welded joint with its particular value of the ultimate steady-state residual stress, which ensures the realization of the ultimate stress cycle. With the same value of the steady-state residual stress, the endurance limit of welded joints decreases with an increase in the yield strength. It is shown that low values of steady- state residual stresses result in nearly the same endurance limit reduction of butt welded joints of steels of different strengths. In contrast, their higher values aggravate the endurance limit deterioration of steels with higher mechanical characteristics.