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The equilibrium-equivalent structural stress method has been recently developed through several joint industry projects as a robust method to analyze welded components using finite element methods. This method has been proven effective in correlating a large amount of published fatigue test results in the literature. The authors employed this equilibrium-equivalent structural stress method for a competition organized by the SAE Fatigue Design & Evaluation (FD&E) Committee to predict the fatigue life of a rectangular hollow section joint. Among all the methods used by many participants, the authors’ life prediction was selected as the best, based on the actual test results. This paper provides the details of the SAE FD&E fatigue challenge problem definition, test results, and our structural stress approach. The predicted mean life by the equilibrium-equivalent structural stress method utilizing the proposed ASME Div. II Structural Stress curve was in excellent agreement with the actual mean life of the experimental results. Other stress indexes (such as the maximum principal stress and the von Mises stress) had maximum stress at a location different from the actual crack location. Furthermore, the equilibrium-equivalent structural stress showed significant mesh tolerance with only a few percent difference in stresses when halving the mesh size. [Copyright &y& Elsevier]

In this paper, the influence of the residual stresses induced by the fillet rolling process on the fatigue process of a ductile cast iron crankshaft section under bending is investigated. The stress concentration near the fillet of the crankshaft section under bending without consideration of residual stresses is first investigated by a two-dimensional elastic finite element analysis. The plastic zone development and the residual stress distribution near the crankshaft fillet induced by the fillet rolling process are then investigated by a two-dimensional elastic–plastic finite element analysis. In order to use the two-dimensional finite element analysis to shed light on the residual stress distribution due to the three-dimensional rolling process, the rolling depth after the unloading of the roller in the two-dimensional finite element analysis is determined by the fillet surface profiles measured by the shadowgraphs taken before and after the fillet rolling process. After the rolling process, a bending moment is then applied to the crankshaft section. With consideration of the stresses due to the rolling process and the bending moment, the fatigue failure near the fillet is investigated based on a linear elastic fracture mechanics approach. An effective stress intensity factor, which combines the stress intensity factors due to the bending moment and due to the residual stresses, is defined. An effective stress intensity factor range is then approximated and compared to an assumed threshold stress intensity factor range to determine if the crack can continue to propagate for a given crack length. The results indicate that the four-bubble failure criterion only determines the crack initiation life for small cracks initiated on the surfaces of fillets. The four-bubble failure criterion does not indicate whether a fatigue crack initiated on the fillet surface can propagate through or arrest in the compressive residual stress zone induced by the rolling process. [Copyright &y& Elsevier]