Universal Procedure for Correction of Plasticity Effect in Hole-Drilling Uniform Residual Stress Measurement

Abstract

Background The hole-drilling method is a well-known and widely used technique for the determination of residual stresses, but is limited to materials with linear elastic behaviour. This can be a problem when high residual stresses are measured, since a local yielding can occur due to stress concentration around the drilled hole. Objective If the residual stress exceeds about 80% of the material yield stress, the error caused by the plasticity effect becomes significant. In order to correctly evaluate high uniform residual stresses, a universal procedure for a correction of the plasticity effect is introduced. Methods The procedure uses a neural network and is capable of correcting any combination of uniform residual stresses with magnitudes up to the material yield stress. It also covers a wide range of material parameters, hole diameters, and strain gauge rosettes and it is independent of the orientation of the strain gauge rosette. Results The correction procedure was tested by more than a million randomly generated stress states that covered the entire range of input parameters and performs remarkably well, since the error of the corrected residual stresses is negligible even for the states with residual stress magnitudes equal to the material yield stress. Conclusions The proposed correction extends the application range of the hole-drilling method to high uniform residual stresses and therefore can be very useful for practical measurements.

Residual Stress Determination with the Hole-Drilling Method on FDM 3D-Printed Precurved Specimen through Digital Image Correlation

“…These methodologies (through-hole and incremental blind hole) are covered by the ASTM E837 standard [4,5], which provides a reference for the implementation of the method, including best practices and calculation instructions to obtain the calibration coefficients. The implementation of this measurement technique can, however, require attention to certain details that are disregarded by the standard, such as the plasticity effect [6][7][8], possible small thickness of the plate in which the residual stress needs to be measured [9], the possibility of a chamfer at the bottom of the hole [10], and imperfect local planarity of the specimen, such as when the residual stress measurement is performed at the external surface of a cylindrical shaft [11]. Another source of uncertainty is the hole's eccentricity; however, this can be corrected provided that the eccentricity itself is accurately known [12][13][14][15].…”