Vibration Analyses of a Gantry Structure by Mobile Phone Digital Image Correlation and Interferometric Radar

The study presents results from applying the Real Aperture Radar interferometry technique and Digital Image Correlation through a mobile phone camera to identify static and dynamic deformations of a gantry during surveying operations on the Michelangelo’s David at the Galleria dell’Accademia di Firenze Museum in Florence. The statue has considerable size and reaches an elevation of more than seven meters on its pedestal. An ad-hoc gantry was designed and deployed, given the cramped operating area around the statue. The scanner had a stability control system that forbid surveying in instrument movements. However, considering the unicity of the survey and its rare occurrence, the previous survey had been carried out in the year 2000; verifying stability and recording deformations is a crucial task, and necessary for validation. As the gantry does not have an on-board stability sensor, and considering the hi-survey accuracy requested, a redundant, contactless, remote monitoring system of the gantry and the statue stability was chosen to guarantee the maximum freedom of movement around the David to avoid any interference during scanning operations. Thanks to the TInRAR technique, the gantry and the statue were monitored with an accuracy of 0.01 mm. At the same time, a Digital Image Correlation analysis was performed on the gantry, which can be considered a Multi-Degree-Of-Freedom (MDOF) system, to accurately calculate the vibration frequency and amplitude. A comparison between TInRAR and DIC results reported substantial accordance in detecting gantry’s oscillating frequencies; a predominant oscillation frequency of 1.33 Hz was identified on the gantry structure by TinSAR and DIC analysis.

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Inverse problems with the digital image correlation: approach and applications

Frattura ed Integrità Strutturale ◽

10.3221/igf-esis.57.22 ◽

2021 ◽

Vol 15 (57) ◽

pp. 300-320

Author(s):

Emanuele Sgambitterra ◽

Fabrizio Niccoli

Keyword(s):

Digital Image Correlation ◽

Inverse Problems ◽

Digital Image ◽

Ad Hoc ◽

Solid Mechanics ◽

Iterative Algorithms ◽

Image Correlation ◽

Estimation Errors ◽

Pipe Coupling ◽

Viable Approach

A viable approach to solve inverse problems in elasticity is proposed. It is based on regression algorithms to estimate materials and/or loading parameters by fitting the experimentally-evaluated displacement field to representative analytical solutions. Displacements are measured by the digital image correlation (DIC) technique and they are used as input for numerical procedures able to minimize the estimation errors of the unknowns and to quantify the unavoidable rigid body motions of the samples/components. In addition, thanks to ad-hoc developed iterative algorithms, non-linear phenomena related to high and localized stress/strain states, can be captured successfully. This latter represents a relevant novelty of the methodology as it allows to investigate plasticity-induced mechanisms in solid mechanics which are impossible to analyze with more traditional DIC-based approaches. Three different case studies are considered: 1) estimation of the stress intensity factor in fracture mechanics problems, 2) estimation of the elastic properties of a material by the Brazilian tests, 3) estimation of the contact pressure generated by thermally activated shape memory alloy (SMA) rings used for pipe coupling. The reliability and the accuracy of the method is demonstrated through systematic comparisons of the results with conventional techniques in experimental mechanics.

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A Novel Method of Vein Detection with the Use of Digital Image Correlation

Entropy ◽

10.3390/e23040401 ◽

2021 ◽

Vol 23 (4) ◽

pp. 401

Author(s):

Zbigniew Lutowski ◽

Sławomir Bujnowski ◽

Beata Marciniak ◽

Sylwester Kloska ◽

Anna Marciniak ◽

...

Keyword(s):

Digital Image Correlation ◽

Adverse Events ◽

Mobile Phone ◽

Digital Image ◽

Image Correlation ◽

Blood Collection ◽

Novel Technique ◽

Specialized Equipment ◽

Novel Method ◽

Mobile Phone Camera

Digital image correlation may be useful in many different fields of science, one of which is medicine. In this paper, the authors present the results of research aimed at detecting skin micro-shifts caused by pulsation of the veins. A novel technique using digital image correlation (DIC) and filtering the resulting shifts map to detect pulsating veins was proposed. After applying the proposed method, the veins in the forearm were visualized. The proposed technique may be used in the diagnosis of venous stenosis and may also contribute to reducing the number of adverse events during blood collection. The great advantage of the proposed method is the lack of the need to have specialized equipment, only a typical mobile phone camera is needed to perform the test.

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DIGITAL IMAGE CORRELATION IN ASSESSING STRUCTURED-LIGHT 3D SCANNER’S GANTRY STABILITY: PERFORMING DAVID’S (MICHELANGELO) HIGH-ACCURACY 3D SURVEY

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xlvi-m-1-2021-463-2021 ◽

2021 ◽

Vol XLVI-M-1-2021 ◽

pp. 463-469

Author(s):

F. Mugnai ◽

G. Tucci ◽

A. Da Re

Keyword(s):

Digital Image Correlation ◽

Digital Image ◽

Ad Hoc ◽

Structured Light ◽

Image Correlation ◽

3D Scanner ◽

Freedom Of Movement ◽

Stability Threshold ◽

Deformation Patterns ◽

Dic Technique

Abstract. The paper presents results from applying Digital Image Correlation (DIC) technique to determine deformations and verify stability on a gantry during surveying operations on the Michelangelo’s David at the Galleria dell’Accademia di Firenze museum in Florence. An advanced hi-resolution Structured-light 3D scanner has been used to create a hi-detailed digital twin of the masterpiece. Considering the high scanner sensitivity, a contactless, remote and passive monitoring system of the gantry stability has been chosen to guarantee maximum freedom of movement around the David and avoid any interference during scanning operations. Due to the remarkable elevation of the statue, which reaches almost 7 meters on his pedestal, and considering the cramped operating area around the statue, an ad-hoc gantry has been designed and deployed. The sophisticated scanner’s technique and the extreme hi-resolution required for the survey needed firm gantry stability during scanning operations from one side. The complex geometries and the considerable extension of the statue surface impose extended flexibility and a nimble elevation platform from the other side. Thanks to the DIC technique the gantry stability has been constantly monitored with an accuracy of 0.03 ÷ 0,04 pixels, optimising scanning scheduling and, consequently, operations efficiency. A comparison of scans with post-processed deformation patterns allowed to optimise the scanning schedule, minimising downtime, and maintaining the needed platform stability threshold for effective scanning.

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