Abstract
Welded joints are prone to fatigue cracking with the existence of welding defects and bending stress. Fracture mechanics is a useful approach in which the fatigue life of the welded joint can be predicted. The key challenge of such predictions using fracture mechanics is how to accurately calculate the stress intensity factor (SIF). An empirical formula for calculating the SIF of welded joints under bending stress was developed by Baik, Yamada and Ishikawa based on the hybrid method. However, when calculating the SIF of a semi-elliptical crack, this study found that the accuracy of the Baik-Yamada formula was poor when comparing the benchmark results, experimental data and numerical results. The reasons for the reduced accuracy of the Baik-Yamada formula were identified and discussed in this paper. Furthermore, a new correction factor was developed and added to the Baik-Yamada formula by using theoretical analysis and numerical regression. Finally, the predictions using the modified Baik-Yamada formula were compared with the benchmark results, experimental data and numerical results. It was found that the accuracy of the modified Baik-Yamada formula was greatly improved. Therefore, it is proposed that this modified formula is used to conveniently and accurately calculate the SIF of semi-elliptical cracks in welded joints under bending stress.
Highlights
Welded structures are constructed by welding various steel plates together
In British Standards Institution (BSI) [25] and the Institute of Welding (IIW) fatigue document [26], the stress intensity factor (SIF) of a surface crack in welded joints under tension or bending stress is predicted by multiplying the weld toe magnification factor (MK factor) [27] with the SIF of a semi-elliptical surface crack on a rectangular plate [28]
Very few discussions have been carried out regarding regarding whether these correction factors are appropriate
Summary
Welded structures are constructed by welding various steel plates together. Weld defects are occasionally found in the welded joints and can either be introduced during the fabrication process or generated in service. Lindroth et al [13] suggested a weight function for semi-elliptical surface cracks in T-shaped welded joints This weight function can be used to determine the SIF in situations with two-dimensional stress distribution. The accuracy of the computed SIF is dependent on many factors, including the type of elements; mesh quality; mesh refinement; integration schemes; and the shape of the welding around the crack front These factors control the accuracy of the stress and displacement fields obtained from the numerical models of the welded joints. In BSI [25] and the IIW fatigue document [26], the SIF of a surface crack in welded joints under tension or bending stress is predicted by multiplying the weld toe magnification factor (MK factor) [27] with the SIF of a semi-elliptical surface crack on a rectangular plate [28] (referred to as the Raju-Newman solution in the following discussion). Various factors that have different influences onofthe are isolated Formula and multiplied to estimate the SIF of welded joints, expressed
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