Hole Eccentricity Correction for Hole-Drilling Residual Stress Measurements 

Abstract

Background

Hole eccentricity is a major source of stress evaluation error when making hole-drilling residual stress measurements. Consequently, tight limits must be applied to the acceptable size of hole eccentricity.

Objective

This research is aimed at developing a compact procedure that can correct for the effects of hole eccentricity and thus enable a larger eccentricity range to be allowed.

Method

A numerical scheme is developed that computes the strain response that would be measured with a centered hole from the experimental strain measurements made with an eccentric hole.

Results

The proposed numerical procedure enables the allowable maximum size limit of hole eccentricity to be increased by a factor of six compared with measurements made without eccentricity error correction.

Conclusions

The proposed method provides a practical method to correct for the effects of hole eccentricity. Its method of computing the corresponding strains for a centered hole makes it compatible for use with the standardized measurement procedure described in ASTM E837-20.

Appendix

Table 1 lists the polynomial coefficients d₁–d₄ in equation (21) to calculate the α, β and γ values for a Type A rosette with hole diameters D₀ = 0.3D, 0.4D and 0.5D, and for specimen thicknesses W = 0.25D, 0.3D, 0.4D and 0.6D. These hole diameters and specimen thicknesses correspond to those tabulated in ASTM E837-20. The resulting α, β and γ values can then be interpolated using the same procedures described in ASTM E837-20 for interpolating the $\overline{\mathbf{a} }$ and $\overline{\mathbf{b} }$ values. Note that ASTM E837-20 limits the maximum hole depth to the minimum of 0.2D or 0.6 W. The latter limit affects specimens of thickness W less than 0.33D.

Table 1 Polynomial coefficients d₁–d₄ in equation (21) to calculate the α, β and γ values for a Type A rosette with hole diameters D₀ = 0.3D, 0.4D and 0.5D, and for specimen thicknesses W = 0.25D, 0.3D, 0.4D and 0.6D