A Robust Structural Stress Parameter for Evaluation of Multiaxial Fatigue of Weldments

Abstract

In this paper, the applicability of a new mesh-insensitive structural stress method is examined for the evaluation of multiaxial fatigue behaviors in welded joints. The mesh-insensitive structural stress method proves to be effective in characterizing stress concentration effects in multi-axial fatigue of welded components. In seeking an effective structural stress based fatigue parameter, some well-known published test data were analyzed. These include those published by researchers, e.g., from the Electric Power Research Intitute (EPRI), the Fraunhofer-Institute for Structural Durability (LBF), the University of Illinois at Urbana-Champaign (UIUC), and the Welding Institute (TWI) under bending, torsion, and in-phase and out-of-phase loading combinations. An effective structural stress parameter has then been formulated in a form of a proposed modified Gough's ellipse for considering both in-phase and out-of-phase multiaxial loading conditions. The aforementioned multiaxial fatigue data from a total of five independent sources can be effectively correlated with a structural stress based parameter presented in this paper, without introducing any other material-related empirical parameters. The present method is rather simple to use for day-to-day finite element based fatigue evaluation of welded joints in actual structures subjected to multiaxial loading conditions.