43.5 Conclusions The analysis we performed shows that the proposed iDIC approach to residual-stress estimation is robust and reliable not only in isotropic materials, but also in orthotropic ones. Although the algorithm requires estimation of calibration coefficients based on the material and geometric parameters, the final estimate is usually within 10 % of the expected results. The most influential parameter is the radius of the hole. However, an error is significant only in the case of underestimation of the true value, whilst an overestimation appears to have little or no effect on the accuracy. Material parameters obviously directly affect the final results. However, the estimates in the two principal directions appear to be weakly correlated. Finally, a poorly estimated center location appears to have little influence on the accuracy of the results, with errors being below 5 % in all cases. References 1. ASTM E837-08e1, Standard test method for determining residual stresses by the hole-drilling strain-gage method (American Society for Testing and Materials, West Conshohocken, 2008). doi:10.1520/E0837-08E01 2. A.J. Albertazzi, C. Kanda, M.R. Borges, F. Hrebabetzky, A radial in-plane interferometer for ESPI measurement, in Laser Interferometry X. Techniques and Analysis, ed. by M. Kujawinska, R.J. Pryputniewicz, M. Takeda. Proceedings of SPIE, vol. 4101 (Bellingham, Washington, 2000), pp. 77–88 3. A. Baldi, A new analytical approach for hole drilling residual stress analysis by full field method. J. Eng. Mater. Technol. 127(2), 165–169 (2005) 4. G.S. Schajer, M. Steinzig, Full-field calculation of hole drilling residual stress from electronic speckle pattern interferometry data. Exp. Mech. 45(6), 526–532 (2005). doi:10.1177/0014485105059553 5. G.S. Schajer, Advances in hole-drilling residual stress measurements. Exp. Mech. 50, 159–168 (2010). doi:10.1007/s11340-009-9228-7 6. A. Baldi, Residual stress measurement using hole drilling and integrated digital image correlation techniques. Exp. Mech. 54, 379–391 (2014). doi:10.1007/s11340-013-9814-6 7. A. Baldi, Residual stress analysis of orthotropic materials using integrated digital image correlation. Exp. Mech. 54, 1279–1292 (2014). doi:10.1007/s11340-014-9859-1 0.98 1 1.02 1.04 1.06 1.08 1.1 1.12 1.14 1.16 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2 stress value / expected value estimated radius / true radius σx = 100, σy = τxy = 0 σx = σy = 70.71, τxy = 0 σx = σy = 0, τxy = 100 Fig. 43.5 Influence of the radius of the hole. The three curves correspond respectively to different residual stress fields. Note that the τestimation is not affected by this parameter 43 Sensitivity Analysis of i-DIC Approach for Residual Stress Measurement in Orthotropic Materials 361
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