Presentation of Calibration Coefficient to Measure Non- Uniform Residual Stresses by the Integral Ring-core Method

The aim of this paper is to compare incremental and integral techniques in non-uniform residual stress measurement by the ring-core method and to present a procedure to determine the calibration coefficients of the integral technique. The mathematical basis of the integral technique for use in the ring-core method is explained. To determine the calibration coefficients of the integral technique a 3D FE model was introduced and the calibration coefficients are also presented in separate tables. The FE analysis of the pure bending and ring-core method were used to show the effectiveness of the presented coefficients and compare the integral and incremental techniques. The results indicated that the calculated non-uniform residual stresses by the integral technique were closer to the real values in comparison with the incremental method. Moreover, it was observed that the accuracy of the results decreased by increasing the depth of the groove.