Bridge static and dynamic vibration monitoring is a key activity for both safety and maintenance purposes. The development of vision-based systems allows to use this type of devices for remote estimation of a bridge vibration, simplifying the measuring system installation. The uncertainty of this type of measurements is strongly related to the experimental conditions (mainly the pixel-to-millimeters conversion, the target texture, the camera characteristics and the image processing technique). In this paper two different types of cameras are used to monitor the response of a bridge to a train pass-by. The acquired images are analyzed using three different image processing techniques (Pattern Matching, Edge Detection and Digital Image Correlation) and the results are compared with a reference measurement, obtained by a laser interferometer providing single point measurements. Tests with different zoom levels are shown and the corresponding uncertainty values are estimated. As the zoom level decreases it is possible not only to measure the displacement of one point of the bridge, but also to grab images from a wide structure portion in order to recover displacements of a large number of points in the field of view. The extreme final solution would be having wide area measurements with no targets, to make measurements really easy, with clear advantages, but also with some drawbacks in terms of uncertainty to be fully comprehended.

Vibration Monitoring of Multiple Bridge Points by Means of a Unique Vision-Based Measuring System

Digital sinusoidal fringe pattern generation: Defocusing binary patterns VS focusing sinusoidal patterns

Author(s): Bonnassieux, Y; Brabec, CJ; Cao, Y; Carmichael, TB; Chabinyc, ML; Cheng, KT; Cho, G; Chung, A; Cobb, CL; Distler, A; Egelhaaf, HJ; Grau, G; Guo, X; Haghiashtiani, G; Huang, TC; Hussain, MM; Iniguez, B; Lee, TM; Li, L; Ma, Y; Ma, D; McAlpine, MC; Ng, TN; Osterbacka, R; Patel, SN; Peng, J; Peng, H; Rivnay, J; Shao, L; Steingart, D; Street, RA; Subramanian, V; Torsi, L; Wu, Y | Abstract: This roadmap includes the perspectives and visions of leading researchers in the key areas of flexible and printable electronics. The covered topics are broadly organized by the device technologies (sections 1–9), fabrication techniques (sections 10–12), and design and modeling approaches (sections 13 and 14) essential to the future development of new applications leveraging flexible electronics (FE). The interdisciplinary nature of this field involves everything from fundamental scientific discoveries to engineering challenges; from design and synthesis of new materials via novel device design to modelling and digital manufacturing of integrated systems. As such, this roadmap aims to serve as a resource on the current status and future challenges in the areas covered by the roadmap and to highlight the breadth and wide-ranging opportunities made available by FE technologies.

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The 2021 flexible and printed electronics roadmap

Around the world are continued attempts to use the vibroacoustic phenomena for purposes of diagnosis of machine condition. Particularly important becomes non-invasive methods including methods based on vibration and acoustic signals. Vibroacoustic phenomena, which relates to the working of technical objects, includes all necessary information connected with the technical condition. The biggest difficulty is the transformation of registered vibroacoustic signals and creation on their basic measures, which will be non-sensitive to any type of interference occurring during the operation of objects and recording signals. To the group of technical objects, for which are already conducted numerous studies all over the world, connected with use of vibroacoustic phenomena for diagnostic purposes which relates to the automotive drive systems, including combustion engines. Combustion engines during its working generate a whole range of vibroacoustic phenomena bringing information on the proper operation of the engine, as well as on condition of each of its elements. In a combustion engine, there are many sources of vibroacoustic phenomena, which contributes to the disruption of diagnostic information. The development of appropriate methods for vibroacoustic signal processing and complete diagnostic systems may allow future extension of the on-board diagnostics OBD system – currently in used cars. The most interesting would be the development of complex system for diagnosing the condition of the individual elements of the car engine operating by basing on information from vibroacoustic signals. In this article are shown results of research, which aim is to diagnose damages of mechanical elements of car combustion engine using vibration signals and artificial neural networks.

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Application of the discrete wavelet transform and probabilistic neural networks in IC engine fault diagnostics

We propose an application for a bidimensional empirical mode decomposition and a Hilbert transform algorithm (BEMD-HT) in processing amplitude modulated fringe patterns. In numerical studies we investigate the influence of parameters of the algorithm and a fringe pattern under study on the demodulation results to optimize the procedure. A spiral phase method and the angle-oriented partial Hilbert transform are introduced to the BEMD-HT and tested. A postprocessing filtration method for BEMD-HT is proposed. Results of processing experimental data, such as vibration mode patterns obtained by time-average interferometry, correspond richly with numerical findings. They compare very well with the results of our previous investigations using the temporal phase-shifting (TPS) method and the continuous wavelet transform (CWT). Not needing to perform phase-shifting represents significant simplification of the experimental procedure in comparison with the TPS method.

Evaluation of amplitude encoded fringe patterns using the bidimensional empirical mode decomposition and the 2D Hilbert transform generalizations

Investigation of dynamic displacements of lithographic press rubber roller by time average geometric moiré

Contrast enhancement of time-averaged fringes based on moving average mapping functions

Geometric moiré is a powerful experimental technique applicable for the determination of in-plane displacements of various structures. Time average geometric moiré is a technique providing insight into dynamic displacements of vibrating elastic structures. Though there exist advanced techniques for formation of moiré gratings on even microscopic surfaces, applicability of time average techniques in such cases is rather problematic first of all due to the fact that microscopic areas of macroscopic objects tend to vibrate as non-deformable bodies. Then the following question rises—would it be possible to exploit the natural, stochastic structure of the object’s surface for identification of its in-plane vibrations? In case if the answer is positive, a simple cost-effective inverse engineering technique could be developed.

Identification of in‐plane vibrations using time average stochastic moiré

G eometric moiré 1,2 is a classical in-plane whole-field non-destructive optical experimental technique based on analysis of visual patterns produced by superposition of two regular gratings that geometrically interfere. Examples of gratings are equispaced parallel lines, concentric circles, and arrays of dots. The gratings can be superposed by double-exposure photography, by reflection, by shadowing, or by direct contact. Moiré patterns are used to measure variables such as displacements, rotations, curvature, and strain throughout the viewed area. In-plane moiré is typically conducted with gratings of equispaced, parallel lines.2,4

Rimas Maskeliunas

Papers

Investigation of dynamic displacements of lithographic press rubber roller by time average geometric moiré

Contrast enhancement of time-averaged fringes based on moving average mapping functions

Identification of in‐plane vibrations using time average stochastic moiré

The structure of moiré grating lines and its influence to time-averaged fringes

Plotting Moiré fringes for circular structures from FEM results