Evaluating non-uniform residual stress by the hole-drilling method with concentric and eccentric holes. Part II: application of the influence functions to the inverse problem

This part deals with the applications of the influence functions developed in part I to solve the inverse problem of determining residual stresses from the measured relaxed strains. The effects of the hole eccentricity and the number of strain gauges on the accuracy of the reconstructed residual stresses are considered for typical experimental conditions. Influence functions for eccentric holes reduce the error in the reconstructed residual stress for typical experimental conditions below 1%, instead of 10% which would be obtained neglecting the eccentricity. The analysis was also applied for comparing the performance of three- and six-element rosettes for compensating eccentricities. When the eccentricity is not included in the elaboration, six-element rosettes with couples of opposite strain gauges halve the error committed by using the equivalent three-element rosette. However, if the eccentricity is included in the influence functions, the three element rosette can predict with a smaller error.