Application of Modified Chebyshev Points to Decrease Residual Stress Noises in Hole-Drilling Method

The uncertainty on the values of the measured residual stresses in hole-drilling integral method, the most widely used technique for measuring residual stress, will be called hereinafter as residual stress noises, which initiate high sensitivity of stress to strain measurement errors due to ill-conditioning of inverse integral equations. This study aimed to investigate the use of Chebyshev points to decrease residual stress noises in the hole drilling method. The Chebyshev points were extended to hole-drilling increments from surface to specified interior depth. The bending of an aluminum beam was used to validate the extended method, and the results were compared with the standard reduction noises technique, Tikhonov-Morozov, and optimum steps technique. The result obtained from the extended method was shown to lead not only an accurate determination of de-noised residual stress, but also a simple calculation procedure in comparison with the Tikhonov-Morozov and optimal steps method. The results indicate that the use of modified Chebyshev points decreased the mean absolute error of residual stress to 8.17 MPa from 14 MPa in Tikhonov-Morozov and 10.52 MPa in optimum steps methods.