Large-Angle Full-Field Strain Measurement of Small-Sized Objects Based on the Multi-Camera DIC Test System

Digital Image Correlation (DIC) technology is a powerful tool in the field of experimental mechanics to obtain the full-field deformation/strain information of an object. It has been rapidly applied in industry in recent years. However, for the large-angle full-field strain measurement of small-sized cylindrical objects, it’s still a challenge to the DIC accurate measurement due to its small size and curved surface. In this paper, a measurement method based on the multi-camera DIC system is proposed to study the compressive performance of small-sized cylindrical materials. Three cameras form two stereo DIC measurement systems (1 and 2 cameras, and 2 and 3 cameras), each of which measures a part of the object. By calibrating three cameras at the same time, two stereos DIC coordinate systems can be unified to one coordinate system. Then match the two sets of DIC measurement data together to achieve large-angle measurement of the cylindrical surface. For improving the spatial resolution of small-sized objects in the camera, the minimum length of field of view is calculated and compared for different focus length lenses. The most suitable lens is selected based on the calculation result. The compressive test is used to verify the feasibility of the proposed system, and the 3D full-filed strain distribution can be extracted for further analysis.