Comparative of conventional and alternative Digital Image Correlation techniques for 3D modal characterisation

Abstract

The integration of Fringe Projection and 2D-DIC is a low-cost optical technique which employs a single camera for full-field 3D displacement measurements using RGB colour encoding to filter coexisting fringe and speckle patterns out from a single image. In this work, this technique was explored together with conventional 3D-DIC for challenging modal analysis on a large aeronautical panel under random excitation. Modal identification was performed using the Least-Squares Complex Exponential approach. Multiple degree-of-freedom methods have been avoided in previous works or just employed in one direction due to high memory requirements to process 3D full-field data. In this work, the 3D modal characterisation was addressed with especial mention to mode shapes. Hardware limitations makes FP + DIC less sensitive than 3D-DIC and hence more suitable for lower frequencies. Nevertheless, the obtained modal parameters showed high agreement and hence FP + DIC demonstrated to be a cost-effective alternative for 3D modal analyses.