A technique for measuring displacement and strain fields on the surface of an object by tracking changes in digital images. It operates by comparing a series of images captured before, during, and after deformation. Features, or subsets of pixels, within a reference image are identified and tracked across subsequent images. By analyzing the movement of these features, the displacement field, revealing how different points on the surface have moved, is determined. From the displacement field, strain, indicating the degree of deformation, can be calculated.
The technique offers several advantages over traditional measurement methods. It is a full-field technique, meaning it provides data for the entire surface of interest, rather than at discrete points. It is also non-contact, which is particularly beneficial for testing fragile or sensitive materials, or for applications where access is limited. Originally developed in the 1980s, its applications have expanded significantly with advancements in digital imaging and computational power, evolving from primarily two-dimensional analysis to include three-dimensional and volumetric capabilities. The insights gained are valuable in validating numerical simulations, optimizing designs, and understanding material behavior under various loading conditions.
