Bidimensional strain measurement using digital images

This paper proposes a method that allows a strain field on plane samples to be determined using the digital image correlation method. The displacement field is approximated by an iterative process attempting to optimize the correlation between two pictures, the first one before strain and the second one after strain. The precision obtained on the displacement field can be better than 0.01 pixel. This precision makes it possible to calculate the strains in a large range, from elastic strains (+/- 0.01 per cent) to large strains (> 200 per cent), with or without a strain gradient.