Global-local deformation measurement of stress concentration structures using a multi-digital image correlation system

The digital image correlation (DIC) technique is a method of measuring the displacement and strain of the entire area of a structure by comparing surface images taken by digital cameras before and after deformation of the structure. The DIC technique is currently being spotlighted because it can overcome the weakness of conventional contact measurement methods. So far a single DIC system with one camera or two cameras has been used for most applications. However, many structures need two or more DIC systems in order to measure their deformation efficiently and precisely. For example, the stress concentration problem and the cylindrical shell buckling problem are typical applications for a multi-DIC system. This study focuses on the stress concentration problem. The paper presents a globallocal deformation measurement method with a multi-DIC system. First, a tensile test of an aluminum beam was performed and compared with the strain gage method to validate the accuracy of DIC method. Then the tensile test specimens with a hole or a notch were prepared, and one DIC system measured the local deformation near a hole or a notch and the other DIC system measured the global deformation of the specimen. The results confirmed the proposed multi-DIC technique can be applied to the stress concentration problem.