Scanner-Based Digital Image Correlation Method for Mechanical Characterization of Rubber

Abstract

The digital image correlation (DIC) method coupled with a moveable camera has been widely used for large in-plane displacement measurement in elastomeric materials. However, this method has the limitation due to the limited field-of-view (FOV) of the camera. In this paper, a novel scanner based digital image correlation (SBDIC) method which enables acquisition of a large FOV of speckle pattern image on the specimen has been developed. The entire information of the deformation was obtained and analyzed up to 350% strain. The correlation between the images at successive stages was computed using incremental cross correlation (CC) tracking algorithm. The Young’s modulus and Poisson’s ratio of vulcanized natural rubber (VNR) up to 350% axial strain were determined simultaneously using the same set of data. Tangent and secant modulus of the rubber at axial strains of 50% to 350% in 50% increments obtained from the scanner-based DIC method was compared with those obtained from a universal tensile test machine (UTM). In addition, the Poisson’s ratios show that the experimental data fitted well with the theoretical result up to an axial stretch ratio of 2.0. The SBDIC method was found to be a potential tool for low cost measurement of mechanical characteristics of polymeric materials. Keywords: DIC, large deformation, cross-correlation, axial strain, Poisson ratio