Controlling testing machines with digital image correlation

The potential of controlling strains in a mechanical test using a digital image correlation with an ad hoc software called CORRELLICONTROL is presented. The software's description and performance of the correlation algorithm particularly, the correlation parameters and the strain uncertainty is determined a priori. Cascade feedback architecture is introduced, tuned and characterized. A tensile test of a steel was also conducted using the potential of the CORRELLICONTROL software. Using a 10.5-bit CCD camera, a standard displacement uncertainty of 5 × 10-3 pixel and a standard strain uncertainty of the order of 10-5 are achieved so that the two-loop system has performances suited to most material behaviors even in elastic domain. Presently, the strain uncertainty of DIC is only twice grater than that of strain gages.