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Celebrating Applied Sciences Reaches 20,000 Articles Milestone: Invited Papers in Acoustics and Vibrations Section

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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Acoustics and Vibrations".

Deadline for manuscript submissions: closed (20 August 2022) | Viewed by 21590

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Special Issue Editors

Prof. Dr. Dimitrios Aggelis

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Guest Editor

Department of Mechanics of Materials and Constructions, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
Interests: structural health monitoring (shm); non-destructive evaluation (nde); acoustic emission (ae); ultrasonic testing (ut); scattering; dispersion; attenuation; material evaluation; concrete
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Giuseppe Lacidogna

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Guest Editor

Department of Structural, Geotechnical and Building Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin, Italy
Interests: nondestructive testing (NDT); acoustic emission; electromagnetic emission; critical phenomena in structural mechanics; critical phenomena in geophysics; fracture mechanics; static and dynamic analysis of high-rise buildings
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Scientific studies in the field of Acoustics and Vibrations have contributed in recent years to develop non-destructive diagnostic techniques for the assessment of structural safety. The assessment of the quality and mechanical characteristics of structural elements, as well as the monitoring of their stability, without disturbing its material and external appearance, represent a very important technical aspect for the future of structural engineering.

The application of diagnostic techniques based on Acoustics and Vibrations principles supports the increasingly stringent need to intervene on the static and seismic safety of infrastructures and historic buildings, as well as to guarantee and certify structural safety of mechanical components serving transport systems or infrastructures.

To celebrate the recent publication of Applied Sciences’s 20,000th paper and mark this special occasion together with our readers, the journal’s Editorial Board invites researchers in all the areas of interest covered by Acoustics and Vibrations to submit high-quality original research or review articles.

Prof. Dr. Dimitrios Aggelis
Prof. Dr. Giuseppe Lacidogna
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

structural health monitoring
acoustics
vibrations
nondestructive testing
ultrasonic testing
acoustic emission
fracture mechanics
structural monitoring
damage

Published Papers (11 papers)

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Research

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11 pages, 1592 KiB

Open AccessArticle

Effect of Non-Metallic Inclusions on the Fatigue Strength Coefficient of High-Purity Constructional Steel Heated in Industrial Conditions

by Tomasz Lipiński

Appl. Sci. 2022, 12(18), 9292; https://doi.org/10.3390/app12189292 - 16 Sep 2022

Cited by 5 | Viewed by 1128

Abstract

Steel fatigue strength testing is a process that requires large amounts of time, resources and appropriate equipment. The industry seeks to replace cumbersome destructive testing with non-destructive testing. Coefficients were developed that allow the comparison of the parameters of material properties. One such factor is the fatigue strength coefficient, which allows the estimate of fatigue strength using the known hardness of a given material. The fatigue strength factor should be developed for conditions that are as close to the industrial conditions as possible. It should take into account not only the expected properties of the material and the technological process but also its imperfections, e.g., the share of non-metallic inclusions and the steel microstructure. This paper presents the results of research on the influence of non-metallic inclusions on the fatigue strength coefficient of structural steel subjected to rotary bending. The tests were carried out in seven heats obtained in a 140-ton electric furnace under industrial conditions. The steel was desulfurized and refined with argon. The paper presents the bending fatigue strength of hardened and tempered steel at temperatures from 200 °C to 600 °C as a function of the relative volume of inclusions. The non-metallic inclusions occurring in steel were determined qualitatively and quantitatively. The derived fatigue strength coefficient, k, for different tempering temperatures makes it possible to estimate the fatigue strength of the analyzed steel as a function of its hardness for various microstructures represented by the respective tempering temperatures. Full article

(This article belongs to the Special Issue Celebrating Applied Sciences Reaches 20,000 Articles Milestone: Invited Papers in Acoustics and Vibrations Section)

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17 pages, 2955 KiB

Open AccessArticle

Low-Rank Approximation of Frequency Response Analysis of Perforated Cylinders under Uncertainty

by Harri Hakula and Mikael Laaksonen

Appl. Sci. 2022, 12(7), 3559; https://doi.org/10.3390/app12073559 - 31 Mar 2022

Cited by 1 | Viewed by 1607

Abstract

Frequency response analysis under uncertainty is computationally expensive. Low-rank approximation techniques can significantly reduce the solution times. Thin perforated cylinders, as with all shells, have specific features affecting the approximation error. There exists a rich thickness-dependent boundary layer structure, leading to local features becoming dominant as the thickness tends to zero. Related to boundary layers, there is also a connection between eigenmodes and the perforation patterns. The Krylov subspace approach for proportionally damped systems with uncertain Young’s modulus is compared with the full system, and via numerical experiments, it is shown that the relative accuracy of the low-rank approximation of perforated shells measured in energy depends on the dimensionless thickness. In the context of frequency response analysis, it then becomes possible that, at some critical thicknesses, the most energetic response within the observed frequency range is not identified correctly. The reference structure used in the experiments is a trommel screen with a non-regular perforation pattern with two different perforation zones. The low-rank approximation scheme is shown to be feasible in computational asymptotic analysis of trommel designs when the proportional damping model is used. Full article

(This article belongs to the Special Issue Celebrating Applied Sciences Reaches 20,000 Articles Milestone: Invited Papers in Acoustics and Vibrations Section)

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16 pages, 6786 KiB

Open AccessArticle

Relationship between Subjective and Biological Responses to Comfortable and Uncomfortable Sounds

by Takumi Asakura

Appl. Sci. 2022, 12(7), 3417; https://doi.org/10.3390/app12073417 - 27 Mar 2022

Cited by 6 | Viewed by 2139

Abstract

Various kinds of biological sensors are now embedded in wearable devices and data on human biological information have recently become more widespread. Among various environmental stressors, sound has emotional and biological impacts on humans, and it is worthwhile to investigate the relationship between the subjective impressions of and biological responses to such sounds. In this study, the relationship between subjective and biological responses to acoustic stimuli with two contrasting kinds of sounds, a murmuring river sound and white noise, was investigated. The subjective and biological responses were measured during the presentation of the sounds. Compared with the murmuring river sound, the white noise had a significantly decreased EEG-related index of α-EEG and HRV-related index of SD2/SD1. The correlation between each index of subjective and biological responses indicated that α-EEG was highly correlated with the results of subjective evaluation. However, based on a more detailed analysis with clustering, some subjects showed different biological responses in each trial since they felt the sound was powerful when listening to the murmuring river sound, as well as feeling that it was beautiful. It was suggested that biological responses to sound exposure may be affected by the impression of the sound, which varies by individual. Full article

(This article belongs to the Special Issue Celebrating Applied Sciences Reaches 20,000 Articles Milestone: Invited Papers in Acoustics and Vibrations Section)

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11 pages, 3570 KiB

Open AccessArticle

Large Area Detection of Microstructural Defects with Multi-Mode Ultrasonic Signals

by Taeho Ju and Alp T. Findikoglu

Appl. Sci. 2022, 12(4), 2082; https://doi.org/10.3390/app12042082 - 17 Feb 2022

Cited by 3 | Viewed by 1466

Abstract

Cyclic loading or other stresses can lead to development of cracks and crack growth in mechanical structures, leading to eventual failure. While ultrasound imaging can be used for non-destructive testing of such structures, conventional ultrasound techniques are often limited by crack size, density, and areal coverage. An effective characterization of real-world, large-area structures is required at an early damage stage to prevent catastrophic failure and predict remaining life. In this study, a new nonlinear ultrasonic testing (NUT) method is proposed for large-area monitoring of practical structures with arbitrary complexity by using multiple-mode guided-wave ultrasonic signals. The proposed guided-wave NUT technique requires single-element transducers, simple electronics, and a mixed time-frequency domain signal processing. As a proof-of-concept demonstration, numerical simulations and experiments are performed on an A36 carbon steel beam assembly with previously formed microstructural defects that cause nonlinearities in ultrasonic response. The quadratic dependence of the nonlinear wave excitation on the input ultrasonic signal amplitude is shown by numerical simulations, and such a nonlinear ultrasonic response is experimentally observed in the zone with a high density of microstructural defects. Full article

(This article belongs to the Special Issue Celebrating Applied Sciences Reaches 20,000 Articles Milestone: Invited Papers in Acoustics and Vibrations Section)

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13 pages, 2710 KiB

Open AccessArticle

Deep Feature Extraction Based on AE Signals for the Characterization of Loaded Carbon Fiber Epoxy and Glass Fiber Epoxy Composites

by Primož Potočnik, Martin Misson, Roman Šturm, Edvard Govekar and Tomaž Kek

Appl. Sci. 2022, 12(4), 1867; https://doi.org/10.3390/app12041867 - 11 Feb 2022

Cited by 4 | Viewed by 1642

Abstract

Characterization of acoustic emission (AE) signals in loaded materials can reveal structural damage and consequently provide early warnings about product failures. Therefore, extraction of the most informative features from AE signals is an important part of the characterization process. This study considers the characterization of AE signals obtained from bending experiments for carbon fiber epoxy (CFE) and glass fiber epoxy (GFE) composites. The research is focused on the recognition of material structure (CFE or GFE) based on the analysis of AE signals. We propose the extraction of deep features using a convolutional autoencoder (CAE). The deep features are compared with extracted standard AE features. Then, the different feature sets are analyzed through decision trees and discriminant analysis, combined with feature selection, to estimate the predictive potential of various feature sets. Results show that the application of deep features increases recognition accuracy. By using only standard AE-based features, a classification accuracy of around 80% is obtained, and adding deep features improves the classification accuracy to above 90%. Consequently, the application of deep feature extraction is encouraged for the characterization of loaded CFE composites. Full article

(This article belongs to the Special Issue Celebrating Applied Sciences Reaches 20,000 Articles Milestone: Invited Papers in Acoustics and Vibrations Section)

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13 pages, 2826 KiB

Open AccessArticle

A Novel Method to Stimulate Lymphatic Clearance of Beta-Amyloid from Mouse Brain Using Noninvasive Music-Induced Opening of the Blood–Brain Barrier with EEG Markers

by Oxana Semyachkina-Glushkovskaya, Alexander Khorovodov, Ivan Fedosov, Alexey Pavlov, Alexander Shirokov, Ali Esmat Sharif, Alexander Dubrovsky, Inna Blokhina, Andrey Terskov, Nikita Navolokin, Arina Evsukova, Georgy Karandin, Dariya Elovenko, Maria Tzoy, Vasily Ageev, Ilana Agranovich, Valeria Telnova, Anna Tsven, Elena Saranceva, Tatyana Iskra and Jürgen Kurths Show full author list Hide full author list

Appl. Sci. 2021, 11(21), 10287; https://doi.org/10.3390/app112110287 - 02 Nov 2021

Cited by 7 | Viewed by 2190

Abstract

The lymphatic system of the brain meninges and head plays a crucial role in the clearance of amyloid-β protein (Aβ), a peptide thought to be pathogenic in Alzheimer’s disease (AD), from the brain. The development of methods to modulate lymphatic clearance of Aβ from the brain coild be a revolutionary step in the therapy of AD. The opening of the blood–brain barrier (OBBB) by focused ultrasound is considered as a possible tool for stimulation of clearance of Aβ from the brain of humans and animals. Here, we propose an alternative method of noninvasive music-induced OBBB that is accompanied by the activation of clearance of fluorescent Aβ (Fαβ) from the mouse brain. Using confocal imaging, fluorescence microscopy, and magnetic resonance tomography, we clearly demonstrate that OBBB by music stimulates the movement of Fαβ and Omniscan in the cerebrospinal fluid and lymphatic clearance of Fαβ from the brain. We propose the extended detrended fluctuation analysis (EDFA) as a promising method for the identification of OBBB markers in the electroencephalographic (EEG) patterns. These pilot results suggest that music-induced OBBB and the EDFA analysis of EEG can be a noninvasive, low-cost, labeling-free, clinical perspective and completely new approach for the treatment and monitoring of AD. Full article

(This article belongs to the Special Issue Celebrating Applied Sciences Reaches 20,000 Articles Milestone: Invited Papers in Acoustics and Vibrations Section)

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11 pages, 2170 KiB

Open AccessArticle

Identification of Close Modes on Frequency in Rotating Systems

by Rafael A. Figueroa-Díaz, Pedro Cruz-Alcantar and Antonio de J. Balvantín-García

Appl. Sci. 2021, 11(21), 9963; https://doi.org/10.3390/app11219963 - 25 Oct 2021

Viewed by 1174

Abstract

In the area of modal balancing, it is essential to identify the vibration modes to be balanced in order to obtain the different modal parameters that will allow knowing the correction weight and its position in the balance planes. However, in some cases, a single mode is apparently observed in the polar response diagrams used for this process, which actually contains at least two modes and which, when added vectorially, shows only one apparent mode. In these cases, in addition to the intrinsic errors when using a modal parameter extraction tool, there will be errors in determining the correction weight for the modes, as well as for the placement angle. In this work, an identification methodology is presented which, through the use of coordinate transformation and a modal parameter extraction tool, allows identifying characteristic patterns of close modes in frequency and which, when applied in the study of a system in the field, offers robustness and applicability. Full article

(This article belongs to the Special Issue Celebrating Applied Sciences Reaches 20,000 Articles Milestone: Invited Papers in Acoustics and Vibrations Section)

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20 pages, 5209 KiB

Open AccessArticle

Shafting Torsional Vibration Analysis of 1000 MW Unit under Electrical Short-Circuit Fault

by Honggang Pan, Yunshi Wu, Zhiyuan Pang, Yanming Fu and Tianyu Zhao

Appl. Sci. 2021, 11(19), 9205; https://doi.org/10.3390/app11199205 - 03 Oct 2021

Cited by 1 | Viewed by 1592

Abstract

Taking a 1000 MW turbine generator as the research object, the short-circuit fault in electrical disturbance is analyzed. Since it is very difficult to carry out fault analysis experiments and research on actual systems, simulation analysis is one of the more effective means of electrical fault diagnosis; the simulation’s results approach the actual behavior of the system and are ideal tools for power system analysis, and can provide an empirical basis for practical applications. The short-circuit fault model of the SIMULINK power system is built to analyze the two types of faults of generator terminals short-circuit and power grid short-circuit. The impact load spectrum, fault current and speed fluctuation between low-voltage rotors were extracted and analyzed. The conclusion is that the impact value of electromagnetic torque at the generator terminal is greater than that on the power grid side. The impact value of a two-phase short-circuit at the generator terminal is the largest, and that of a three-phase short-circuit on the power grid side is the smallest. The transient impulse current of a three-phase short-circuit at any fault point is greater than that of a two-phase short-circuit; the impulse current of the grid side short-circuit is much greater than that of the generator terminal short-circuit; the speed fluctuation and fluctuation difference caused by the three-phase short-circuit in the grid side are the largest. The alternating frequency of the transient electromagnetic force of the four kinds of faults avoids the natural frequency of the torsional vibration of the shaft system, and the torsional resonance of the shaft system in the time domain of the short-circuit fault will not appear. However, after the fault is removed, the residual small fluctuation torque in the system has a potential impact on the rotor system. This research shows an analysis of the structural integrity and safe operation of turbine generator units after a short-circuit fault, which can not only be applied to engineering practice, but also provide a theoretical basis for subsequent research. Full article

(This article belongs to the Special Issue Celebrating Applied Sciences Reaches 20,000 Articles Milestone: Invited Papers in Acoustics and Vibrations Section)

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16 pages, 4382 KiB

Open AccessArticle

Acoustic and Dynamic Response of Unbaffled Plates of Arbitrary Shape

by Pablo García-Fogeda, Fernando de la Iglesia and Keyvan Salehi

Appl. Sci. 2021, 11(17), 8019; https://doi.org/10.3390/app11178019 - 30 Aug 2021

Viewed by 1480

Abstract

In this study, a method for determining the effects of fluids on the dynamic characteristics of an aerospace structure and the response of the structure when it is excited by the acoustical loads produced during a rocket launch, has been developed. Elevated acoustical loads are critical in the design of large lightweight structures, such as solar arrays and communication reflectors, because of the high acceleration levels. The acoustic field generated during rocket launch can be considered as a diffuse field composed of many uncorrelated incident plane waves traveling in different directions, which impinge on the structure. A boundary element method was used to calculate the pressure jump produced by an incoming plane wave on an unbaffled plate and the fluid–structure coupled loads generated through plate vibration. This method is based on Kirchhoff’s integral formulation of the Helmholtz equation for pressure fields. The generalized force matrix attributed to the fluid loads was then formulated, taking the modes of the plate in vacuum as base functions of the structural displacement. These modes are obtained using a finite-element model. An iteration procedure was developed to calculate the natural frequencies of the fully coupled fluid–plate system. Comparison of the results obtained using the proposed method with those of other theories and experimental data demonstrated its efficiency and accuracy. The proposed method is suitable for analyzing plates of arbitrary shape subjected to any boundary conditions in a diffuse field for low to medium values of the frequency excitation range. Full article

(This article belongs to the Special Issue Celebrating Applied Sciences Reaches 20,000 Articles Milestone: Invited Papers in Acoustics and Vibrations Section)

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18 pages, 16049 KiB

Open AccessArticle

The Possibility to Recreate the Shapes of Objects on the Basis of Printer Vibration in the Additive Printing Process

by Andrzej Stańczak, Ireneusz Kubiak, Artur Przybysz and Anna Witenberg

Appl. Sci. 2021, 11(11), 5305; https://doi.org/10.3390/app11115305 - 07 Jun 2021

Cited by 1 | Viewed by 2476

Abstract

Information protection is an important safety issue in many human activity fields. Technological advances and related ubiquitous computerization bring new challenges in this area. In particular, the problem concerns the protection of devices against non-invasive acquisition processed information in ICT systems. It is known that, e.g., VGA, DVI/HDMI interfaces or laser printer formatter systems that process visual signals are the effective sources of compromising electromagnetic emanations. The emission safety of the more and more commonly used 3D printers is less known. In many cases, the disclosure of information about printed objects might constitute an infringement of the state/industrial/commercial secret, copyright, patent protection, etc. In order to analyze the existing threat, a selected printer using FDM technology was tested. During the tests, simple objects were printed to identify the operation of the stepper motor and the movements of the printer head and the printer platform, which are sources of emissions in the secondary channels. The analyses performed focused on finding the correlation between the recorded vibration signals and the printer head movements when an object was printed. It was shown that the analysis of the registered sensitive signal runtimes and their spectrograms allowed to recreate the printed object shape. Three simple objects (a trihedron, a tube and a tetrahedron) were selected for testing because they include elements that allow the four major movements of the printer head to be easily recognized: along the X axis, along the Y axis, along an arc and diagonally (between the X and Y axes). The paper presents the test results and their analyses. Full article

(This article belongs to the Special Issue Celebrating Applied Sciences Reaches 20,000 Articles Milestone: Invited Papers in Acoustics and Vibrations Section)

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Review

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13 pages, 1270 KiB

Open AccessReview

Review of Computational Mechanics, Optimization, and Machine Learning Tools for Digital Twins Applied to Infrastructures

by Georgios E. Stavroulakis, Barbara G. Charalambidi and Panagiotis Koutsianitis

Appl. Sci. 2022, 12(23), 11997; https://doi.org/10.3390/app122311997 - 24 Nov 2022

Cited by 6 | Viewed by 2793

Abstract

This review discusses the links between the newly introduced concepts of digital twins and more classical finite element modeling, reduced order models, parametric modeling, inverse analysis, machine learning, and parameter identification. The purpose of this article is to demonstrate that development, as almost always is the case, is based on previously developed tools that are currently exploited since the technological tools for their implementation are available and the needs of their usage appear. This fact has rarely been declared clearly in the available literature. The need for digital twins in infrastructures arises due to the extreme loadings applied on energy-related infrastructure and to the higher importance that fatigue effects have. Digital twins promise to provide reliable and affordable models that accompany the structure throughout its whole lifetime, make fatigue and degradation prediction more reliable, and support effective predictive maintenance schemes. Full article

(This article belongs to the Special Issue Celebrating Applied Sciences Reaches 20,000 Articles Milestone: Invited Papers in Acoustics and Vibrations Section)

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