3D mode shapes characterisation using phase-based motion magnification in large structures using stereoscopic DIC

Molina-Viedma, Ángel J.; Felipe-Sesé, Luis; López‐Alba, Elías; Díaz, Francisco

doi:10.1016/j.ymssp.2018.02.006

Cited by 58 publications

(16 citation statements)

References 32 publications

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“…Hence, the algorithm inputs are the image sequence, the desired frequency band, and the magnification factor. For subsequent measurements using 3D-DIC, the sequence from each camera must be magnified using the same parameters [18]. Unlike sinusoidal excitation, many significant modes are now present in the images simultaneously.…”

Section: Image Processingmentioning

confidence: 99%

“…It is only suitable to visualise in-plane motions and, thus, only for 2D displacements. Considering that, the authors evaluated the validity of the measurement on magnified images from a stereoscopic system using 3D-DIC [18]. Under analogous conditions, the obtained ODSs were compared with numerical simulations for a cantilever beam and it was demonstrated that no distortion occurred as a consequence of separate magnification of the images from each camera.…”

Section: Introductionmentioning

confidence: 99%

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Operational Deflection Shape Extraction from Broadband Events of an Aircraft Component Using 3D‐DIC in Magnified Images

Molina-Viedma

López‐Alba

Felipe-Sesé

et al. 2019

Shock and Vibration

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Recently, many works have shown the capabilities of noninterferometric optical techniques, such as digital image correlation, to characterise modal behaviour. They provide a global insight into the structure or component behaviour which implies massive spatial information, unaffordable by traditional sensor instrumentation. Moreover, phase-based motion magnification (PMM) is a methodology which, based on a sequence of images, magnifies a periodic motion encoded in phase time-domain signals of the complex steerable pyramid filters employed to decompose the images. It provides a powerful tool to interpret deformation. However, the interpretation is just qualitative and should be avoided if out-plane motion is recorded as only one camera is employed. To overcome this issue, 3D digital image correlation (3D-DIC) has been linked with PMM to provide measurements from stereoscopic sets of images, providing full-field displacement maps to magnified images. In this work, the combination of PMM and 3D-DIC has been employed to evaluate the modal behaviour of an aircraft cabin under random excitation. The study was focused on the passenger window area due to its significance to the structural integrity as a discontinuity of the peel. Operational deflection shapes at different resonances were characterised by magnifying a single resonance in the spectrum and then measuring with 3D-DIC. These measurements were validated with those obtained in forced normal mode tests. Motion and displacement videos improved the understanding of the identified resonance deformation. Actually, a relevant behaviour was noticed in the window’s frame, a quite narrow area where using traditional sensors would not provide such a detailed 3D information.

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Section: Image Processingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Operational Deflection Shape Extraction from Broadband Events of an Aircraft Component Using 3D‐DIC in Magnified Images

Molina-Viedma

López‐Alba

Felipe-Sesé

et al. 2019

Shock and Vibration

Self Cite

View full text Add to dashboard Cite

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“…In a review of 3D high-speed DIC for vibration measurement, Beberniss and Ehrhardt [4] pointed to a difficulty at high frequency because of low out-of-plane sensitivity. This was overcome separately by Poozesh et al [5] and Molina-Viedma et al [6] using phase-based motion magnification and results are reported in [7] for 3D operational deflection shapes in the range from 1500 Hz to 6710 Hz without the need for high levels of excitation. Poozesh et al [8] and Patil et al [9] developed methods for the stitching of DIC images of sub-areas of very large structures to obtain complete images of vibration modes.…”

Section: Introductionmentioning

confidence: 99%

Basis-updating for data compression of displacement maps from dynamic DIC measurements

Chang

Wang

Siebert

et al. 2019

Mechanical Systems and Signal Processing

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The extraction of useful information and removal of redundant noise from data has become a major research topic in recent years. Data compression is necessary for all kinds of analysis, and the demand for efficient compression techniques has gained much attention. Digital image correlation is a camera-based measuring system, which has been widely applied in strain analysis because of the convenience of measuring displacement fields by simply selecting a region of interest. Currently, there is interest in applying such methods to engineering structures in dynamics. However, one of the major issues related to the integration of camera-based systems with dynamic measurement is the generation of huge amounts of data, typically extending to many thousands of data points, because of the requirements of high sampling rate, spatial resolution, and long duration of recording. In this paper a new algorithm is presented that addresses the need for efficiency in full-field data processing. By making use of the data itself and combining the concept of sparse representation with Gram-Schmidt orthogonalisation, the number of basis function used to represent the data can be reduced and a concise decomposition established. In both simulated and experimental cases, the compression ratios for data size and number of signals used in operational modal analysis are substantially diminished, thereby demonstrating the effectiveness of the proposed algorithm. A reduced number of new basis functions is determined for the representation of data under the condition that the reconstructed displacement map reproduces the raw measured data to within a chosen threshold on the coefficient of correlation.

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“…Recently, the out-of-plane vibrations of cantilever beams were tracked via a new camera technology, namely light field imagers, by Chesebrough et al [ 35 ]. To the best of the authors’ knowledge, studies in three-dimensions with imperceptible motion employing PBMM are currently limited to the use of the 3D-DIC technique [ 36 , 37 ]. Particle tracking velocimetry (PTV) was proposed by the authors as an alternative technique to obtain dynamic displacements for SHM applications, in both 2D [ 38 ] and 3D [ 39 , 40 ], as well as a performance comparison with optical flow [ 19 ].…”

Section: Introductionmentioning

confidence: 99%

A Novel Approach for 3D-Structural Identification through Video Recording: Magnified Tracking

Harmanci

Gülan

Holzner

et al. 2019

Sensors

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Advancements in optical imaging devices and computer vision algorithms allow the exploration of novel diagnostic techniques for use within engineering systems. A recent field of application lies in the adoption of such devices for non-contact vibrational response recordings of structures, allowing high spatial density measurements without the burden of heavy cabling associated with conventional technologies. This, however, is not a straightforward task due to the typically low-amplitude displacement response of structures under ambient operational conditions. A novel framework, namely Magnified Tracking (MT), is proposed herein to overcome this limitation through the synergistic use of two computer vision techniques. The recently proposed phase-based motion magnification (PBMM) framework, for amplifying motion in a video within a defined frequency band, is coupled with motion tracking by means of particle tracking velocimetry (PTV). An experimental campaign was conducted to validate a proof-of-concept, where the dynamic response of a shear frame was measured both by conventional sensors as well as a video camera setup, and cross-compared to prove the feasibility of the proposed non-contact approach. The methodology was explored both in 2D and 3D configurations, with PTV revealing a powerful tool for the measurement of perceptible motion. When MT is utilized for tracking “imperceptible” structural responses (i.e., below PTV sensitivity), via the use of PBMM around the resonant frequencies of the structure, the amplified motion reveals the operational deflection shapes, which are otherwise intractable. The modal results extracted from the magnified videos, using PTV, demonstrate MT to be a viable non-contact alternative for 3D modal identification with the benefit of a spatially dense measurement grid.

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3D mode shapes characterisation using phase-based motion magnification in large structures using stereoscopic DIC

Cited by 58 publications

References 32 publications

Operational Deflection Shape Extraction from Broadband Events of an Aircraft Component Using 3D‐DIC in Magnified Images

Operational Deflection Shape Extraction from Broadband Events of an Aircraft Component Using 3D‐DIC in Magnified Images

Basis-updating for data compression of displacement maps from dynamic DIC measurements

A Novel Approach for 3D-Structural Identification through Video Recording: Magnified Tracking

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