FD&E Total Life T-Sample Residual Stress Analytical Predictions and Measured Results 2019-01-0528

The SAE Fatigue Design & Evaluation Committee 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 measurement were pursued to provide a sufficiently accurate 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 fabrication to provide accurate inputs for the welding simulations. Both destructive (contour method, x-ray diffraction (XRD) with etching) and non-destructive (surface XRD, energy dispersive diffraction (EDD), neutron diffraction(ND)) residual stress measurements were performed on the same or similarly welded samples. The sample is constructed with multiple-pass fillet welds, which induce large gradients in residual stress 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 various measurement results show agreement in the regions where the simulations are not as well aligned. 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.