Full 3D Strain Measurement by Digital Volume Correlation From X-Ray Computed and Optical Scanning Tomographic Images.

Currently, the determination of mechanical data fields during a loading is generally performed by non-contact optical techniques like mark tracking or Digital Image Correlation techniques. However, these methods are only surface measurement techniques and even if we add the measurement of out-plan displacements, we can't calculate all the three-dimensional strain components. To obtain the full 3D strain tensor, DIC techniques [1] have been extended to Digital Volume Correlation (DVC) [2,3,4,5]. So we are able to investigate 3D mechanical phenomena in the core of materials or structures without hypothesis nor using numerical simulation. DVC allows the measurement of 3D displacement by considering a 3D material transformation which can be assimilated at a pure translation or at a translation combined with a local gradient. This technique needs volume images which contain a 3D random distribution of grey levels. In order to obtain a subvoxel accuracy, a trilinear interpolation of the grey levels is used and the final positions are calculated with an optimization of a correlation coefficient, In this study, we present 3D measurements made by images from X-ray computed tomography and optical scanning tomography. In order to define the fields of application of both techniques, we show their performances and we evaluate their measurement uncertainty. [ABSTRACT FROM AUTHOR]

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