Compact Calibration Data for Hole-Drilling Residual Stress Measurements in Finite-Thickness Specimens

Abstract

The conventional way to present Integral Method calibration data for hole-drilling residual stress measurements is in the form of a large triangular table of numbers. In the common case where 20 drilling steps are used for the hole-drilling measurement, 231 numerical coefficients are needed. While such tables are effective, their bulk inhibits their use for other than the most common experimental arrangements; the convenience and usefulness of the hole-drilling method would be much extended if the bulk of the calibration data could be reduced. Here, a two-variable polynomial formulation is proposed to represent the hole-drilling calibration data. It comprises 15 numerical coefficients and provides calibration data with average accuracy within 1%, with occasional outliers reaching around 2%. The compactness of the calibration stimulated exploration of hole-drilling response beyond the conventional “thick” specimen case, also to include finite thickness specimens down to very thin (through-hole) geometries. Tables of calibration data are provided here for ASTM E837 Type A, B and C strain gauge rosettes, for various hole diameters, for conventional “thick” specimens, and for finite thickness specimens down to the through-hole case.