Validation of a strain gauge rosette setup on a cantilever specimen: Application to a calibration bench for residual stresses

It is commonly known that the most difficult part of measuring residual stresses through diffraction or relaxation methods is the high sensitivity of the results to input errors, such as noise in the strain data. Then, quantifying and minimizing stress uncertainties is at least as important as the residual stress results themselves. Results are often validated by leveraging different measurement techniques, although each method is somehow specialized at detecting residual stresses at different locations and length scales. This leads to a fundamental lack of ground truth data and an inherent difficulty in detecting biases. The authors have introduced a calibration bench that facilitates the application of a well-known bending stress distribution on a specimen while conducting residual stress measurements using either the Hole-Drilling Method (HDM) or X-ray Diffraction (XRD). By leveraging Bueckner's superposition principle, the bench allows for determination of both the residual stress distribution and the reference stress distribution through a single experimental setup. This approach not only enables direct evaluation of accuracy but also identification of any procedural systematic errors, as the reference stress distribution is known with a high degree of certainty. In this work, a detailed characterization of the stress and strain fields generated by the externally applied load was pursued. Then, the calibration bench was used to perform a validated characterization of residual stresses produced by two shot peening treatments, through both XRD and HDM. Additionally, both techniques were employed to verify the recognized bending stresses, thereby validating the findings of the residual stress measurements.