FD&E Total life T-sample residual stress analytical predictions and measured results

The Society of Automotive Engineers Fatigue Design & Evaluation Committee [SAE FD&E] is actively working on a total life project for weldments, in which the welding residual stress is a key contributor to an accurate assessment of fatigue life. Physics-based welding process simulation and various types of residual stress measurements were pursued to provide a representation of the residual stress field at the failure location in the fatigue samples. A well-controlled and documented robotic welding process was used for all sample fabrications to provide accurate inputs for the welding simulations. One destructive (contour method) residual stress measurement and several non-destructive residual stress measurements-surface X-ray diffraction (XRD), energy dispersive X-ray diffraction (EDXRD), and neutron diffraction (ND)-were performed on the same or similarly welded samples. The sample is constructed with multiple-pass fillet welds, which induce large residual stress gradients through the one-inch thickness. The simulation and measurement comparisons focus on a through-thickness line in the middle of the T-Joint sample, where the maximum loading and residual stresses occur. The residual stress profile changes from tensile to compressive and back to tensile through the mid-section thickness. The simulations capture the trend in the residual stress field and a similar magnitude as the measurement through most of the sample thickness. The measurement results show agreement in regions where the simulations are not as well aligned to the measurements. Further discussion on the sensitivity of the fatigue analysis to the residual stress field selected and the accuracy of the fatigue analysis results is included in an adjoining paper and presentation.