Monitoring distant structures using a high-speed camera frequently relies on modal parameters. Even with high-dynamic-range sensors (e.g. accelerometers) damping identification is not trivial. With high-speed cameras the dynamic range is relatively small and contaminated with a relatively high level of noise. Image-based techniques have the advantage of providing contact-less full-field structural identification. While the damping is a modal parameter and theoretically not spatially dependent, this study looks at the potential to use the spatial over-determination, provided by the high-speed camera to increase the accuracy of the contact-less damping identification. High-speed cameras provide thousands of measurement locations, and identify the damping with noise-resistant methods like those based on the Continuous Wavelet Transform is numerically demanding. This research is built on the the Morlet Wave Damping Identification method, which is based on the Continuous Wavelet Transform, but is also significantly faster. Finally, the full-field damping parameters were averaged with regard to the identified deflection shapes. The theory is extended with an experiment, where damping is identified for a simple structure at frequencies up to 2.5\,kHz. It was found that the proposed method resulted in damping identification that was comparably accurate to the damping identified from high-dynamic-range and low-noise piezoelectric accelerometers. This research confirms that damping can be accurately identified from high-speed-camera measurements, only.
Ladisk, Faculty of Mechanical Engineering, University of Ljubljana
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