Improved Calibration Coefficients for the Hole-Drilling Method Considering the Influence of the Poisson Ratio

For residual stress analyses with the incremental hole-drilling method adequate evaluation formalisms in order to transform the measured strains into stresses are required. The Integral Method is the most important theory used for analyses of nonlinear residual stress depth distributions. It is based on a calibration, which is carried out by Finite-Element-Analyses. For the sake of simplicity the used numerical models often represent an ideally cylindrical hole and ideal elastic material behavior with fixed elastic constants. The adaption of the calibration coefficients from the numerical simulations to the real experimental state is often performed by simple correction factors or is ignored completely. The following investigation highlights the influence of the Poisson ratio on the calibration coefficients for the most commonly used strain gage rosettes geometries, which are standardized by ASTME837-08. It comes out that the application of existing simple correction factors is only valid within a small range and better approximations can be obtained by alternative strategies.