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Open AccessFEA Stress Determination for Weld Fatigue Using Hot-Spot Stress Method: Benchmarking and Rail Application
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Welded joints in rail steel structures are typically assessed for fatigue using two different stress range approaches: nominal stress range and hot-spot stress range when using SN methods. The nominal stress range is a traditionally simplified method that provides a conservative estimation but lacks accuracy in considering stress concentrations. On the other hand, the hot-spot stress range method is a more advanced and refined approach that offers a more precise evaluation of stress concentration, making it suitable for complex geometries. The BS7608-2015 British standard, Guide to Fatigue Design and Assessment of Steel Products, incorporated the hot-spot method for evaluating weld joints, especially when using numerical methods such as Finite Element Analysis (FEA). The weld classes are now categorically defined for both nominal and hot-spot approaches in new introductions, whereas earlier, it was based on the nominal stress approach only. Choosing the appropriate stress method depends on various factors, including the weld joint geometry, stress orientations, loading conditions, the desired level of accuracy, and primarily the available SN curve data for predicting fatigue damage. The work presented in this paper explores the hot-spot stress approach for determining stress in weld fatigue assessment for Rail Track Maintenance Equipment. The identified welds were assessed for variation in hot-spot stress on different mesh types, weld modeling techniques, and their effect on the fatigue damage factor using IIW and BS7608 guidelines. The joints under study were F2 and D class with nominal and hot-spot stress assessment, respectively, as per BS7608. These are more common weld joints in structural evaluations of rail equipment. The hot-spot approach for stress variation was studied on smaller models first. Subsequently, the approach was applied to assess the weld fatigue in rail equipment, and the results were compared with those obtained using the nominal stress approach.
