1,721,079 research outputs found
Structural Monitoring and Maintenance (SMM), An International Journal
No full textThe Structural Monitoring and Maintenance, An International Journal, aims at the valuable source of information and excellent publication channel for the global community of structural monitoring and maintenance of structures
Applied Sciences
No full textApplied Sciences (ISSN 2076-3417) provides an advanced forum on all aspects of applied natural sciences. It publishes reviews, research papers and communications. Our aim is to encourage scientists to publish their experimental and theoretical results in as much detail as possible. There is no restriction on the length of the papers. The full experimental details must be provided so that the results can be reproduced. Electronic files and software regarding the full details of the calculation or experimental procedure, if unable to be published in a normal way, can be deposited as supplementary electronic material
Journal of Applied Mathematics
No full textJournal of Applied Mathematics is a refereed journal devoted to the publication of original research papers and review articles in all areas of applied, computational, and industrial mathematics
Sviluppo di una Smart Platform (SmartBench) per la sicurezza integrata degli stabilimenti industriali ad Alta Affidabilità
No full textSmartBench mette insieme diverse applicazioni verticali, accomunate dall’impiego di sensoristica avanzata per migliorare la sicurezza dei lavoratori e degli impianti. Non è solo un ombrello per progetti diversi, ma è una vera piattaforma che ambisce a diventare uno standard di riferimento anche per applicazioni future. Lo scopo è far si che le singole applicazioni «smart» possano parlare fra di loro e contribuire tutte a migliorare il sistema di gestione della sicurezza. L’integrazione di SmartBench non finisce con la condivisione di risorse e servizi informatici e tecnologici (banche dati, protocolli di comunicazione, eccetera) ma punta a riportare tutto al sistema di gestione della sicurezza del lavoro. Il sistema di gestione della sicurezza nella visione INAIL è il motore che regola all’interno di uno stabilimento tutte le attività che hanno a che fare con la prevenzione degli infortuni e degli incidenti. Il simbolo degli ingranaggi utilizzato nel logo di SmartBench è stato scelto proprio perché un sistema smart integrato con la gestione dinamica della sicurezza è come la ruota di un ingranaggio perfetto. I sistemi automatizzati in colloquio fra loro vanno a sovrapporsi alle stesse istruzioni operative e procedure, rendendole di immediata applicazione per l’intero sistema di gestione
Seismic metasurfaces for Love waves control
No full textElastic metasurfaces consist of resonant inclusions or resonant oscillators, placed at the free surface of an
elastic medium, which collectively interact with surface elastic waves to redirect, steer or absorb their energy.
Metasurfaces of vertical oscillators over homogeneous elastic half-spaces can inhibit the propagation of vertical
polarized waves (i.e. Rayleigh waves) creating band-gaps at selected frequencies [1]. Such ability has inspired the
design of meter-scale metabarriers to protect buildings and infrastructures from harmful seismic Rayleigh waves
[2].
In this work, we extend the study of metasurfaces to in-plane polarized surface waves, i.e. Love waves, travelling
on a soft elastic layer overlaying a stiffer substrate. We derive an original dispersion relation for the Love type
waves existing on a bi-layer coupled on its free surface with a metasurface of horizontal resonators [3]. By tuning
the mass and the frequency of the resonators we show the possibility of manipulating the phase velocity of the
fundamental Love wave, and thus the related metasurface’s refractive index at specific frequencies.We exploit this
ability to design gradient index lenses (i.e. Luneburg and Maxwell lenses) for Love waves redirection. We analyse
the performance of the designed lenses using full 3D FE simulations confirming the analytical predictions. Our
work can serve as a guide for the design of meter-scale Love waves barriers for seismic or anthropic vibrations
attenuation.
References
[1] N. Boechler, J. K. Eliason, A. Kumar, A. A. Maznev, K. A. Nelson, and N. Fang, Phys. Rev. Lett. 111, (2013).
[2] A. Palermo, S. Krödel, A. Marzani, and C. Daraio, Sci. Rep. 6, 39356 (2016).
[3] A. Palermo and A. Marzani, submitted to Sci. Rep.
Rayleigh waves bandgap tuning via inertial amplified metasurfaces
No full textElastic metasurfaces are thin interfaces composed of locally resonant structures placed at the free surface or across the boundaries of elastic waveguides. The units which form this interface have sub-wavelength feature size and exploit their resonances to manipulate the dispersive properties of the hosting medium. When metasurfaces are constructed over an elastic half-space, they can be used to control the propagation of Surface Acoustic Waves. In particular, the collective resonant modes of the metasurface can open narrow bandgaps in the spectrum of Rayleigh Waves, which are filtered out as shear modes propagating in the medium bulk.
One of the current limitations in the exploitation of such resonant band gaps is the need for large masses to widen their bandwidth. To overcome this drawback, we here investigate the possibility of designing an inertial amplified mechanism able to tune the natural frequency of the metasurface resonators. Our resonant unit exploits two lateral inerters, i.e., kinematical devices made by two inclined rigid links connected to an additional mass to modify the inertia of the resonator.
After discussing the dynamic of the proposed resonator, here named as the Inertial Amplification Resonator (IAR), we unveil the properties of a metasurface composed by an array of IARs. By employing an effective medium approach, we investigate the interaction between Rayleigh waves and the metasurface deriving its closed-form analytical dispersion law. We show that the dynamic response of inertially amplified metasurfaces can be controlled by the added mass and geometrical configuration of the IARs and highlight the possibility of shifting the bandgap spectrum of the metasurfaces by modifying their design parameters without changing the mass and stiffness of the oscillators. We take advantage of the tunability feature of inertially amplified metasurfaces for designing multi-frequency (metawedges) metasurfaces to achieve broadband attenuation of Rayleigh waves. We analyze the transmission performance of the metasurface using 2D FE simulations and confirm the analytical predictions
Metodi e tecnologie per ispezioni con onde ultrasoniche guidate di piastre e gusci in composito
No full textTra le tecnologie proposte per il monitoraggio strutturale (in inglese Structural Health Monitoring o SHM), quelle che usano onde ultrasoniche guidate sono considerate tra le più promettenti e versatili per le applicazioni che riguardano i materiali compositi. Con onde guidate ci si riferisce ad onde meccaniche che si propagano in strutture o in elementi strutturali, le guide d’onda, con almeno una dimensione caratteristica paragonabile alla lunghezza d’onda delle onde stesse. L’interazione tra la lunghezza d’onda e la geometria della guida d’onda dà luogo all’esistenza di svariate onde meccaniche. Tali onde variano in numero e mutano le loro caratteristiche di propagazione quali lunghezza d’onda, velocità, attenuazione e forma d’onda, al variare della frequenza (comportamento dispersivo).
Le implementazioni tipiche di questi sistemi prevedono un sistema software/hardware che controlla una rete di trasduttori piezoelettrici posti sulla struttura da controllare, attraverso i quali si generano e ricevono onde guidate che sondano la struttura stessa. Mediante procedure di analisi dei segnali registrati ai trasduttori, le metodologie cercano di risalire allo stato di integrità del componente.
La concreta possibilità di integrare una simile tecnologia di monitoraggio ad onde guidate in strutture in composito è attualmente limitata da: (i) scarsità di strumenti per la modellazione della propagazione in materiale composito; (ii) ingombro della strumentazione e cablature non compatibili con il monitoraggio permanente; (iii) limitata validazione delle tecnologie in condizioni operative ambientali (iv) elevati costi di integrazione. Per superare queste limitazioni sono allo studio nuovi trasduttori piezoelettrici e tecniche avanzate di elaborazione di segnale
A resonant metasurface for Love waves
No full textElastic metamaterials comprise a broad class of artificially engineered media designed to
control the propagation of elastic waves at sub-wavelength scales. This unique ability stems from
the presence of resonant inclusions embedded in an elastic matrix which affect the wave
propagation at specific frequency ranges. Elastic metasurfaces are a special class of metamaterials,
realized by arranging an array of resonant structures at the free surface of the medium or at an
interface between two media. Metasurfaces of vertical resonators over an elastic half-space have
been successfully utilized to control the propagation of in-plane surface waves, i.e., Rayleigh
waves, for various applications across different length scales, as waveguiding or wave
filtering.
In this talk, we present an extension of the metasurface concept to Love waves, anti-plane
surface waves existing in semi-infinite layered media. We investigate the interaction between
Love waves and a metasurface of horizontal oscillators deriving an original analytical solution for
its dispersion relation. By tuning the mass and the frequency of the resonators we achieve full
control of the Love wave phase velocity, and thus on the related metasurface refractive index. We
exploit the ability to manipulate the metasurface refractive index to design gradient index lenses
(i,e. Luneburg and Maxwell lenses) for Love waves redirection. We analyse the performance of
the designed lenses using full 3D FE simulations confirming the analytical predictions. Our work
can serve as a guide for advanced Love wave-based devices and sensors as well as for the design
of meter-scale barriers for low-frequency vibrations attenuation
Fast guided waves inspection using compressive sensing and wavenumber domain analysis
No full textMany nondestructive evaluations and structural health monitoring techniques for plate like structures rely on the full field analysis related to stress guided waves propagation. Such techniques can be quite slow as in general the acquisition of the full wave field and its processing, aimed at extracting damage related information, are time consuming processes. Therefore, strategies to reduce the acquisition time and improve the damage detection and quantification are sought. This research describes a method based on Compressive Sensing (CS) and a wavenumber estimation technique that can lead to fast scanning and improved damage detection. The proposed technique exploits the full wavefields which are rapidly reconstructed by applying the CS technique. Then, frequency wavenumber processing is performed to identify the maximum wavelength. Finally a dedicated masking procedure is implemented to enhance the defect-induced scattering. To demonstrate the effectiveness of the proposed techniques, several experiments were performed on aluminum structure, emulating defect with a mass. In the experiments, guided waves are excited with a piezoelectric transducer bonded to the inspected structure and sensed by an air-coupled probe mounted on a CNC machine. The results demonstrate that the proposed technique allows to reduce the amount of measurements needed and therefore the needed scanning time, as just the 20% of the Nyquist scanpoints were measured, and improves the performance of damage imaging tasks by removing automatically noise artifacts
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