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RESEARCH PRODUCT

Digital Correlation Method Based on Microgeometrical Texture Patterns for Strain Fields Measurements

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International audience; Digital correlation method is widely used in experimental mechanics to obtain the deformation field. Currently this method is applied with digital images of the initial and deformed surface sprayed with black or white painting. Speckle patterns are then captured and the correlation can be made with high 0.01 pixel accuracy in 2D-cases. In three-dimensions, the stereo-correlation can be used with a lower accuracy. The work presented in this paper, is a first approach based on the use of a 3D laser scanner in the objective of three-dimensional strain field measurement. The digital speckle patterns are not given by gray level but from the micro-geometrical surface texture. We consider that the waviness and the roughness remain sufficiently small in the deformation motion to give a good estimation of the displacement particle. The principle of the measurement is described notably the methodology to obtain digital images from measured points clouds. Next the different texture parameters, giving the sensitivity of the method, are introduced. We discuss the best correlation choice in taking into account of the S/N ratio. Some experimental results are presented for 2D-displacement and 2D-strain fields of bi-dimensional objects. Finally, we suggest different improvements to use this method in complete 3D-strain field measurement.