Volume 21, Issue 1 (January 2021)                   Modares Mechanical Engineering 2021, 21(1): 39-53 | Back to browse issues page

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Afsanehbekrpoushideh@gmail.com. Modal Identification of Structures via Processing of Recorded Videos and Output-only Algorithms. Modares Mechanical Engineering. 2021; 21 (1) :39-53
URL: http://mme.modares.ac.ir/article-15-49390-en.html
Abstract:   (351 Views)
One of the measurement systems for the identification of modal parameters of the structure is digital video cameras. Modal analysis based on video measurements, despite the many advantages, is associated with some challenges due to its dependence on high contrast markers. In the present study, a new algorithm is presented to use only the measured full-field responses, without additional preparation of the structural surface. This algorithm is phase-based and is implemented using the blind source separation method and motion magnification technique. It uses a multi-scale pyramid analysis technique to extract the full-field spatiotemporal pixel phases. To validate this algorithm, the free and random vibration videos of two cantilever and simple beams with known modal parameters were reconstructed in MATLAB. The average difference between the values identified and the theoretical values for the frequencies of the first to fourth modes is less than 2% and less than 0/1 for damping. The results obtained in this section also confirm the ability of the algorithm to identification closely-spaced modes of the structure. Also, to evaluate the performance of the algorithm in laboratory conditions, a free and random vibration video of an aluminum cantilever beam, prepared in the laboratory using a high-speed camera, is examined. Comparing the results with theoretical values or case study reports shows that using the techniques introduced in this article is a suitable and promising solution to identify the modal parameters of the structure.
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Article Type: Original Research | Subject: Impact Mechanics
Received: 2021/01/21 | Accepted: 2021/01/19 | Published: 2021/01/19

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