We analysis the alignment technique by investigating the problems associated with the alignment between camera and specimen in 2D image-based digital image correlation(DIC) measurements of material properties of the dynamic behavior of parts.Using the alignment method, we applied 4 reference points at the specimen corners, measured the distance between the reference points by photogrammetry and made it the reference length. Then we varied the orientation of the 2D camera by tilting it by diverse angle (upwards, downwards, left and right) and analyzed by DIC software the distance between a point at the top and one at the bottom.Using the regression and optimization, we found the optimum orientation for these 2 distance and thus the optimum alignment of the camera. To determine the error associated with the alignment of the so aligned 2D camera, we used a reference bar of known length, varied its orientation and compared measurement result with the bar’s real length. Comparison of measurements using an aligned and a non-aligned 2D camera reveals that the non-aligned camera gives a higher error.Unaligned cameras have high alignment errors in both the vertical and horizontal directions. In addition, the aberration of the lens is reflected, the error of measurement becomes even larger. On the other hand, if the camera is aligned with the method used in this study, the error of alignment can be minimized in the vertical and horizontal directions, so the effect of the improvement is great even if the lens aberration is considered. Further, results are compared with those obtained with 3D DIC equipment.We showed that application of the presented alignment method leads to an improved alignment between camera and specimen, thereby increasing the accuracy of DIC measurement based on 2D images.
Volume 11 | 08-Special Issue
Pages: 1995-2005