Assessment of fatigue strength of steel butt-welded joints in as-welded condition – Alternative approaches for curve fitting and mean stress effect analysis |
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Institution: | 1. Department of Engineering and Management, University of Padova, Stradella San Nicola 3, 36100 Vicenza, Italy;2. School of Marine Science and Engineering, University of Plymouth, Drake Circus, Plymouth, England, United Kingdom;3. Department of Mechanical Engineering, Nelson Mandela Metropolitan University, Port Elizabeth, South Africa;1. Key Laboratory of High Performance Ship Technology (Wuhan University of Technology), Ministry of Education, Wuhan 430063, China;2. School of Transportation, Wuhan University of Technology, Wuhan 430063, China;1. Department of Mechanical Engineering, Aalto University School of Engineering, P.O. Box 12200, FIN-00076 Aalto, Finland;2. Centre for Advanced Steels Research, University of Oulu, P.O. Box 4200, FIN-90014 University of Oulu, Finland;1. Montanuniversität Leoben, Department Product Engineering, Chair of Mechanical Engineering, Austria;2. KTH-Royal Institute of Technology, Department of Aeronautical and Vehicle Engineering, Division of Lightweight Structures, Sweden |
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Abstract: | Experimental fatigue data for butt-welded joints in as-welded condition and under constant amplitude tensile loading (secondary bending included) were analyzed using the nominal stress system and the notch stress system. Two approaches were used; a standard fitting procedure and minimization of the sum of squared perpendicular distances from a line with a fixed and free slope. In all cases, the latter method gave better agreement between the experimental and predicted fatigue life and fatigue strength. The analyses showed both with all broken specimen data included and with reduced data that the FAT225 curve, as recommended by IIW, might be too optimistic for the notch stress approach in the case of butt-welded joints in as-welded condition. It was also found that use of the local stress ratio instead of the applied stress ratio might explain many issues concerning current observations and apparent inconsistencies in reported literature. |
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Keywords: | Butt joints Fatigue strength Effective notch stress Local stress ratio Master SN-curve Residual stresses |
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