CORRELI STC ®, a software dedicated to metrology of mechanical deformations
Software stéréocorrélation CORRELISTC
® is a partnership between the LMT Laboratory of Mechanics and Technology of the Ecole Normale Supérieure de Cachan, EADS-IW and HOLO3. It was developed in the project VULCOMP supported by the ANR and dedicated to the vulnerability of composites.
Latest developments of the software team of HOLO3, the image correlation software (DIC : Digital Image Correlation) allows, from a simple pair of digital cameras to map a very fine displacement field on the surface of a mechanical part (or any other object) subject to external stress (mechanical stress, heat ,..). It also allows several post treatments such as the creation of virtual gauges, profiles. Recordings can be made in quasi-static mode (standard cameras) or in dynamic.
Besides the development of an interface-oriented to industrial use, a significant effort has been devoted to the metrological aspect. The basic information provided by a system is a mapping of movement which is pixel unit . The move to millimeter data is achieved through a rigorous calibration phase but still relatively simple to implement. The displacements at any point on the surface can easily be measured with a resolution of ten microns for a field analysis of 800x800 mm.
The other quantity of interest to the designer of a mechanical part is the mechanical strain under stress. In the case of DIC it is obtained by derivation of at the first order of the displacement field. One can get the complete mapping of all components of the strain tensor. Of course, wellknow strain gauge, has been included in the software CORRELSTC
®, this is a virtual gauge that can be place a posteriori (after testing) at any point the surface and anywanted direction. The strain in the direction of the gauge but also provides : X, Y, Z, displacement strain in the direction perpendicular to the gauge, main directions. The metrological aspect of deformation has also been widely studied: numerous comparisons between the information gauge "virtual" and real gauges bonded to the surface showed differences not exceeding 0.02%, even for large deformations .... why real gauges come off sometimes.
Finally, the big advantage of this technology is the ability to comprehensively compare experimental data with data from finite element simulation and allow a late registration of simulation models updating.
HOLO3 is the Centre for Technology Transfer (CRITT) that takes innovation from the world of research in the field of optics, such as 3D scanning / speckle interferometry / multi-spectral imaging / Virtual Reality / Tracking / video LIBS / Infrared Imaging / Image Correlation. The center develops industrial equipment based on optical, conducts applied research, and carried out daily metrological services on demand.
Longitudinal deformations of a specimen of aluminium