Noncontact vibration measurement and modal analysis system based on fringe-pattern thin films

XU Zong-huang, ZHONG Shun-cong, LIN Yun-lin, LIU Feng, CHEN Man
(School of Mechanical Engineering and Automation, Fuzhou University, Fuzhou 350108, China)

Abstract: Aiming at the influence of the weight of the sensors on the modal parameters of the structure, a fringe patternbased testing theory and methodology were proposed in this work to noncontact measure vibration of the structures. The effects of shape, material, thickness, diameter, print quality and initial density of the fringe patterns on the measurement performance and sampling resolution of the fringe patterns were investigated using finite element simulations and experiment validations. The Fourier transform was employed to analyze the fringe pattern signal, combining with the frequency spectrum correction method to correct the frequency of the signal. Subsequently, the proposed testing system was applied for noncontact experimental modal analysis of beamlike structures. The results indicate that the first three resonance frequencies of the beams measured by the fringe pattern was consistent with the simulation results. The measuring principle of the proposed method is simple but effective and therefore, it could be recommended for real engineering applications.
Key words: fringe pattern; low-frequency vibration measurement; spectral correction method; modal analysis