Diffraction Assisted Image Correlation: A Novel Method for Measuring Three-Dimensional Deformation using Two-Dimensional Digital Image Correlation
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Digital Image Correlation (DIC) provides a full-field non-contact optical method for accurate deformation measurement of materials, devices and structures. The measurement of three-dimensional (3D) deformation using DIC in general requires imaging with two cameras and a 3D-DIC code. In the present work, a new experimental technique, namely, Diffraction Assisted Image Correlation (DAIC) for 3D displacement measurement using a single camera and 2D-DIC algorithm is presented. A transmission diffraction grating is placed between the specimen and the camera, resulting in multiple images which are then used to obtain apparent in-plane displacements using 2D-DIC. The true in-plane and out-of-plane displacements of the specimen are obtained from the apparent in-plane displacements and the diffraction angle of the grating. The validity and accuracy of the DAIC method are demonstrated through 3D displacement measurement of a small thin membrane. This technique provides new avenues for performing 3D deformation measurements at small length scales and/or dynamic loading conditions.
Keywords3D digital image correlation Diffraction Small scale Membrane Displacement
The research reported in this paper was conducted while SX was a postdoctoral scholar and AG was a summer undergraduate research fellow (SURF) in the Graduate Aerospace Laboratories at the California Institute of Technology (GALCIT). It was supported by the Caltech Center for the Predictive Modeling and Simulation of High-Energy Density Dynamic Response of Materials through the U.S. Department of Energy’s National Nuclear Security Administration Award# DE-FC52-08NA28613, which is gratefully acknowledged. The authors thank M. Mello and J. Notbohm for stimulating discussions.
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