Removable camera based 2D digital image correlation for planar slender area quasi-static deformation measurement

Abstract

As one of the non-contact full-field measurement techniques, digital image correlation (DIC) has attracted much attention and has gained rapid acceptance in various fields, owing to its well-known advantages of a simple optical setup and low environmental vulnerability. In practical applications, the effective resolution of image is reduced due to the large difference in the size of the specimen in different directions, which makes it impossible to make effective full-field measurement. To significantly improve DIC-based deformation measurement for planar slender specimen without losing resolution, a removable camera based DIC method is proposed in this study for quasi-static high-resolution deformation and strain measurement. An industrial camera was mounted on a stable sliding table structure composed of linear sliding guide rail and ball screw. Under the control of the program, the camera moved with the sliding table to capture parts of the specimen at different positions. A correlation based image stitching method and overlapped region minimization method were proposed and were applied to these images, and their corresponding displacement fields and strain fields was calculated based on DIC. To verify the feasibility and effectiveness of the proposed removable camera based DIC method, static error test and quasi-static three-point bending test were performed. The results indicate that compared with a single fixed camera based DIC, the strain resolution could be increased by approximately 5 times by stitching 5 images while ensuring the same displacement measurement accuracy by using the proposed method. It concluded that the use of the removable camera array has great potential to perform deformation measurements of slender area without losing resolution.