Multiscale FE-Based DIC for enhanced measurements and constitutive parameter identification

Abstract

Since they provide a large amount of information, full-field measurement techniques like Digital Image Correlation (DIC) allow the identification of several material parameters from a single non-homogeneous test. However the level of uncertainty associated with the identified parameters depends on the displacement measurement uncertainties, which are related to the spatial resolution of the measurement. To overcome the well-known compromise between spatial resolution and uncertainty, a multiscale approach to Finite Element DIC (FE-DIC) is proposed by considering additional nearfield images to improve locally the resolution of the measurement. An accurate estimation of the nearfield/farfield transformation is obtained by a dedicated global DIC method to bridge precisely the measurements at both scales. This multiscale FE-DIC measurement is then associated to a multiscale Finite Element Model Updating (FEMU) identification technique. After being validated on synthetic test cases, the method is applied to a tensile test carried out on an open-hole specimen made of glass/epoxy laminate. The four in-plane orthotropic elastic parameters are identified. Results show that the multiscale approach greatly improves the uncertainties of both the measured displacements and the identified material parameters.