The Digital Image Correlation System Accuracy Direct Testing Using Strain Gauges

The paper presents an empirical study on the usefulness of the digital image correlation system in determining the Young's and Poisson's ratios for civil engineering materials. The method advantages from a contactless, full surface measurement and can oust established techniques such as mechanical and electrical resistance strain gauges. The limitation is the accuracy and precision of the system, which is studied by comparing three above mentioned measuring methods in one experiment. Results showed the limit for sufficient technical strain readouts for DIC as 350 mu epsilon and for the mechanical strain gauge as 120 mu epsilon. Subset size for minimum relative error is 29x29 pix (increasing it has an insignificant influence) and subset size for minimal relative standard deviation is 57x57 pix (increasing it has a significant influence). Subset step is optimal for 15x15pix. Conclusion: the system is able to determine the Young's and unable to determine the Poisson's modulus for common structural materials.