Modal Parameter Estimation of a Compliant Panel Using Phase-based Motion Magnification and Stereoscopic Digital Image Co
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S.I. : COMPUTER VISION AND SCANNING LASER VIBROMETRY METHODS
Modal Parameter Estimation of a Compliant Panel Using Phase-based Motion Magnification and Stereoscopic Digital Image Correlation M. Eitner1
· M. Musta1 · L. Vanstone1 · J. Sirohi1 · N. Clemens1
Received: 19 April 2020 / Accepted: 4 August 2020 © The Society for Experimental Mechanics, Inc 2020
Abstract This paper demonstrates the use of broad-band phase based motion magnification (PMM) to improve the modal parameter estimation from high-speed stereoscopic digital image correlation (DIC). PMM is used as a diagnostic technique to investigate the free vibration response of a panel. The compliant panel, consisting of a thin polycarbonate sheet, forms a test section wall in a supersonic blow-down wind tunnel, where it is used to investigate supersonic fluid-structure interaction in the presence of shock wave boundary layer interaction. The panel is excited by an impact hammer and the transient deformation is captured using high-speed cameras. The original and motion-magnified images are input to a digital image correlation algorithm to calculate the out-of-plane deformation of the panel. The measured deformation is used to extract the modal parameters of the compliant panel. By using PMM as a preprocessing tool in a broad frequency band containing multiple structural modes, the signal to noise ratio of the measured deformation is improved. The use of PMM improves the estimated mode shapes, increasing the MAC value of the first mode compared to FEM predictions from 0.29 to 0.99. Motion magnification also improves the coherence between measured input force and panel deformation by up to 13% if suitable parameters are chosen. Keywords Modal analysis · Phase-based motion magnification · Digital image correlation · Impact testing · Fluid-structure interaction
Introduction The analysis of fluid-structure interaction (FSI) in supersonic flow is of increasing importance in the context of supersonic vehicle design, where shock waves impinging on lightweight structures can lead to large aero-thermal and structural loads, potentially leading to destructive instabilities. Computational modeling of shock wave boundary layer interactions is very expensive due to the unsteadiness and highly coupled nature of these processes [1]. Therefore in recent years, several researchers have investigated supersonic panel FSI experimentally, using high-speed optical methods to measure the deformation of compliant panels with impinging shocks, see for example [2, 3]. Especially M. Eitner
[email protected] 1
Department of Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin, Austin, TX, USA
the use of high-speed stereoscopic DIC has been well established in this community to record the full-field structural responses [4, 5]. The present work is part of a larger project that investigates the FSI induced by shock-induced separation over a compliant panel in supersonic flow. Experiments were performed in a Mach 2 wind tunnel in which one part of the
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