Micromechanical Applications of Digital Image Correlation Techniques
Résumé
Digital image correlation (DIC) is applied to images obtained with a scanning electron microscope (SEM) in order to determine the local strain field in a heterogeneous material on a representative domain of the microstructure, millimetric in size, the local contrast being provided by a microgrid deposited on the surface of the sample, with a typical 5μm step. The specific difficulties encountered when applying this classical technique for CCD images to SEM images are discussed. They are related to geometric images defects, high noise levels or imperfect scanning or to the non optimal local contrast, which are all potential sources of loss of accuracy. Several procedures to correct such imperfections are presented. The investigation of the residual strain field in a ferritic-martensitic steel after 1% total strain under uniaxial traction is then shortly presented.
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