User Influence on Two Complementary Residual Stress Determination Methods: Contour Method and Incremental X-Ray Diffraction

The combination of various residual stress measurement methods is a common practice to complete knowledge that a single measurement method cannot provide. In this study, incremental X-Ray diffraction is combined with the contour method to measure a bent notched specimen to study the methods robustness. A finite element analysis model is built and validated with strain measurement of the bending process thus providing prior knowledge of the residual stress field. Three-dimensional neutron diffraction residual stress measurements are also performed to obtain a reference measurement with a non-destructive method and to validate the simulated stress field. In-depth stress gradient measured by X-ray diffraction is corrected with four different methods that all show good correlation with neutron diffraction measurements. Correction methods, assumptions and uncertainties are discussed and differences are observed on the robustness of the methods. Contour method measurements are performed and results are also in agreement with neutron measurements. The results provided by the contour method are complementary to those of the X-Ray diffraction since, despite a lower accuracy on the edges where X-ray diffraction is performed, the contour method offers the complete cartography of longitudinal stress in a symmetry plane of the bent specimen. Uncertainty of the contour method due to the post-processing procedure is discussed.