A space–time approach in digital image correlation: Movie-DIC

• Published in: Optics and lasers in engineering Vol. 49; no. 1; pp. 71 - 81
• Main Authors: Besnard, Gilles, Guérard, Sandra, Roux, Stéphane, Hild, François
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 2011; Elsevier
• Subjects: Computers in experimental physics; Correlation; Digital; Digital image correlation; Displacement field; Engineering Sciences; Estimates; Exact sciences and technology; Image processing; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Lasers; Mathematical analysis; Mechanics; Mechanics of materials; Physics; Shape functions; Spatial resolution; Strain field; Strain rate field; Tensile tests; Velocity field; Strain rate field; Strain field; Displacement field; Digital image correlation; Velocity field; Strains; Displacement measurement; Digital image; Velocity fields; Spatial resolution; Video
• ISSN: 0143-8166; 1873-0302
• DOI: 10.1016/j.optlaseng.2010.08.012

A new method is proposed to estimate arbitrary velocity fields from a time series of images acquired by a single camera. This approach, here focused on a single spatial plus a time dimension, is specialized to the decomposition of the velocity field over rectangular shaped (finite-element) bilinear shape functions. It is therefore assumed that the velocity field is essentially aligned along one direction. The use of a time sequence over which the velocity is assumed to have a smooth temporal change allows one to use elements whose spatial extension is much smaller than in traditional digital image correlation based on successive image pairs. This method is first qualified by using synthetic numerical test cases, and then applied to a dynamic tensile test performed on a tantalum specimen. Improvements with respect to classical digital image correlation techniques are observed in terms of spatial resolution.