Evaluating Non‐Uniform Residual Stress by the Hole‐Drilling Method with Concentric and Eccentric Holes. Part I. Definition and Validation of the Influence Functions

Abstract: Residual stresses play a fundamental role in predicting the resistance of several structural components, in particular when operating under alternating loads or in aggressive environments. Among the measurement techniques, the hole‐drilling method is unrivalled in terms of cost and flexibility. The currently available data reduction techniques do not account for some important parameters, in particular the hole eccentricity, and can be directly used only with certain rosettes or require the partial holes to be drilled at fixed depths. This paper presents a general approach for interpreting hole‐drilling measurements that includes the hole eccentricity and several other geometric and material parameters. The method is based on analytical influence functions relating the measured relieved strains to the residual stress by means of integral equations. By elaborating the results of accurate finite‐element simulations, continuous analytical influence functions are produced, which can be used to reduce the error in the reconstructed residual stress. We focus on the definition of the influence functions, their evaluation and assessment.