On the improvement of calibration coefficients for hole-drilling integral method: Part I - Analysis of calibration coefficients obtained by a 3-D FEM model

One of the important factors affecting the accuracy of stress values obtained from hole-drilling method is the calibration coefficient. A three-dimensional model was established to determine the calibration coefficients for integral method. The constraint conditions and loading conditions during hole-drilling can be simulated more realistically with this method. With this new model, coefficients (a) over bar (i,j), and (b) over bar (i,j) could be determined within one computation procedure. The relationship between calibration coefficients and plate thickness was investigated over a wide range of plate thickness. It has been found that the calibration coefficients determined in this work may vary with thickness of plates and the thickness range for thin plates was thus well defined. The calibration coefficients can thus be extended to measure the residual stresses of either thin or thick plates. Comparison of calibration coefficients with those determined by other studies was also conducted.