Re-evaluation of Fatigue Evaluation Procedures for Weld Root Failure and Effects of Residual Stresses 2019-01-0529
The Fatigue Design Master S-N curve for weld root failure was proposed in 2013. The FE modeling guidelines and the design master S-N curve for weld root failure was constructed using the mesh-insensitive structural stress method. Along increasing the demands of validating the design master S-N curve, various weld root fatigue failure cases were reanalyzed based on well-documented recent studies. The fatigue failure cases include various geometric conditions such as weld shape, weld size, and plate thickness, and loading modes. The investigation showed that the proposed root failure modeling guideline and the master S-N curve approach are good to use for practical applications showing weld root failure. Through the study, the failure mode associated with weld size was studied using the test results and FE based structural stress method. As comparing FE results with the test results, the structural stress method demonstrates the predictability of failure mode (i.e., toe failure or root failure) based on the relationship between plate thickness and weld size.
It was observed that the level of residual stresses at the weld root region are drastically affected by the gap size or penetration. Therefore, the combined effects of the level of residual stresses and applied loading affect the fatigue failure mode when the size parameter of weld is located midway between the toe failure and root failure.