Full-Field Modal Analysis by Using Digital Image Correlation Technique

Digital Image Correlation (DIC) is a non-contact full-field image analysis technique which allows to retrieve strains and displacements in three dimensions at the surface of any type of material and under arbitrary loading. In recent years, high-speed and high-resolution cameras have been developed for static as well as for dynamic applications. As consequence, the application fields for DIC have broadened and it has proven to be a flexible and very accurate measurement solution for deformation analysis and material characterization. In this work DIC technique is used to get the full-field displacement of the structure under test. This information could then be used to derive the modal characteristic of the structure (e.g. natural frequencies, damping ratios and full-field mode shapes). These results can be validated by using classical sensors (e.g. strain gauges, accelerometers) or other optical methods (e.g. laser doppler vibrometers). Several test cases are discussed, and two different approaches are used for combining the data obtained during the vibration tests. The most obvious approach would be the alignment of the time histories of input (shaker) and output based on reference signals for Frequency Response Functions (FRFs) calculation prior to perform any further processing. An alternative in case of broadband excitation, requires processing time data into auto and crosspowers and identify the modal parameters by using Operational Modal Analysis (OMA).