Rotating Vibration Measurement Using 3D Digital Image Correlation

Background Dynamic measurement and analysis of rotating components is an arduous and complex task that has always attracted great attention from the engineering community. Objective In order to propose a low-cost, efficient, high-precision, and high temporal and spatial resolution rotating vibration measurement scheme, three-dimensional Digital Image Correlation (3D DIC) combined with down-sampling technology is employed. Two defects of this scheme hinder its wide application: the additional initial shape function estimation in rotation correlation of DIC and the cumbersome experimental operation process of traditional down-sampling. Therefore, an extension of down-sampling technology and a comparative study on efficient initial value estimation algorithms were researched. Methods Comparative experiments of extended down-sampling proposed in this paper and high-frequency sampling were carried out on a rotating disc for its vibration Operational Deflection Shapes (ODSs) measurement. During the data processing procedure, an efficient initial value estimation algorithm is recommended by comparing the efficiency and accuracy of Fourier-Mellin Transform-based (FMT-based), Scale Invariant Feature Transform-based (SIFT-based), and Hough Transform-based (HT-based) algorithms. Results The experimental results indicate that the FMT-based algorithm is the most efficient, and its estimation accuracy guarantees accurate and efficient convergence of the sub-pixel iteration process, though slightly lower than that of the SIFT-based algorithm; The harmonic response and natural response ODSs of the disc were obtained in the high-frequency sampling experiment, and the corresponding harmonic response ODSs were obtained in the extended down-sampling experiment. The precision of the amplitude of obtained ODSs is on the order of submicron. Conclusions The proposed extended down-sampling technology has been verified to circumvent the limitation of the Nyquist-Shannon sampling theorem, and accurately restore different orders of harmonic response ODSs with sampling once at a low frequency. Combined with extended down-sampling technology, 3D DIC becomes an efficient, submicron precision, full-field rotating vibration measurement scheme with high temporal and spatial resolution using low-cost conventional cameras. Simultaneously, the FMT-based rotation parameters estimation algorithm can efficiently provide accurate initial value estimation for 3D DIC.