Analysis of Digital Speckle‐Pattern Interferometry Fringe Patterns Issued from Transitory Mechanical Loadings

Abstract

Abstract: During a dynamic mechanical loading, we cannot use a phase‐shifting technique because the mechanical parameters evolve according to the time. This problem can be avoided by the development of algorithms which can extract the mechanical information from only one fringe pattern. In this way, we present two algorithms, the modulated phase correlation (MPC) and the polynomial modulated phase correlation (pMPC). These processes are based on the use of the virtual fringe pattern which locally approaches the real fringe morphology. The similarity degree between real and virtual fringe pattern is estimated by digital correlation technique. When the best similarity is obtained, we suppose that the virtual phase function is very close to the real phase function. Some examples are presented to show the low noise sensitivity of these techniques. So, we propose to use the MPC or the pMPC algorithms to extract the relief from a single interferogram obtained by digital speckle‐pattern interferometry. In this paper, we present experimental tests of impact loading on plates. The frame rate is adapted to the dynamic conditions of loading. Recorded fringe patterns and results of the unwrapped phase demodulated with our algorithms are shown.