Modified effective notch stress method for fatigue evaluation of rib-deck welds integrating the critical distance approach

Abstract

To evaluate the reliability of the IIW-recommended effective notch stress (ENS) method and propose proper parameters for modification, fatigue testing data of 109 rib-deck welded specimens covering four cracking types were reviewed, and corresponding finite element models were established for parametric analysis. The critical distance approach was also integrated for improving the evaluation reliability. The effects of notch radius (r) and critical distance (a) on fatigue strength, and the effects of different methods for mean stress correction on the scatter ratio (Tσ) were investigated. Results show that the FAT71 S-N curve could be directly applied to the fatigue evaluation of rib-deck welds without mean stress correction; however, referring to the FAT225 S-N curve in notch stress system provides unconservative results. Instead, employing the FAT198 S-N curve combined with the Gerber method for mean stress correction or using the FAT200 S-N curve combined with the Walker method is recommended. Additionally, the FAT22 S-N curve is applicable while the notch radius (r) and critical distance (a) are valued 0.5 and 0.01 mm, respectively. The findings are of importance for improving the reliability of applying the ENS method to the fatigue evaluation of rib-deck welds.