Mirror-assisted Multi-view Digital Image Correlation with Improved Spatial Resolution

Accurate measurements of panoramic/dual-surface kinematic fields are essential to elastoplastic mechanics for the determination of true stress-strain curves, through-thickness strain and the identification of 3D anisotropic parameters. Recently, a novel mirror-assisted multi-view digital image correlation (DIC) method that uses only a two-camera stereo-DIC system and two auxiliary planar mirrors was proposed. It has been convincingly demonstrated to be a cost-efficient and effective technique for measuring 360-deg panoramic/dual-surface kinematic fields. Nevertheless, in this method, the mirrors need to be partly decorated with speckle patterns and the latter clearly captured by the cameras to estimate the reflection transformation of both mirrors. Capturing the speckle patterns on the two mirrors occupies a part of the precious spatial resolution of the cameras, considerably reducing the effective spatial resolution left for the DIC measurement. In this work, an alternative method for estimating the reflection transformation is proposed to improve the spatial resolution of the mirror-assisted multi-view DIC. This method estimates the reflection transformation of the two mirrors by adjusting the mirrors to three or more diverse poses, thus eliminating the need of speckling the mirrors. A set of real tests were carried out, and the results well demonstrated the accuracy and effectiveness of the proposed method.