Refractive devices for acoustical and flexural waves

The aim of this work has been the design and demonstration of refractive devices, not only for acoustic waves, but also for flexural waves in thin plates. Mathematically these problems have been treated by means of the multiple scattering theory, because the geometries of the problems were mainly circular and such theory is the best one in these cases. The multiple scattering theory, previously stated, is here explained. Additionally, a multilayer scattering theory for flexural waves is here introduced and successfully used to numerically simulate their behavior. Therefore, this PhD thesis is divided in two parts. The first part is devoted to describe two acoustic refractive devices: a gradient index lens and an omnidirectional broadband acoustic absorber, or “acoustic black hole”. Both are based on sonic crystals consisting of of rigid cylinders immersed in a fluid background. As the homogenization method states, the desired refractive index can be obtained by tailoring the radii of the cylinders. Thereafter, numerical simulations and measurements were conducted to test the behavior of each device. For this purpose, two specific measuring systems were developed: the two-dimensional chamber and the impedance chamber. Both are here explained in detail. The second part describes the design of refractive devices for flexural waves. Instead of using “platonic crystals”, we made use of the peculiar dispersion relationship of flexural waves. As the equation states, the wave speed is modified not only by the elastic properties of the plate, but also from its thickness. Using the latest approach a set of numerical simulations of known circularly symmetrical gradient index lenses have been performed. Additionally, an omnidirectional broadband insulating device for flexural waves has been designed. It consist of a well-like thickness profile in an annular region of the plate, that mimics the combination of an attractive and repulsive potentials. The waves are focused at its bottom and dissipated by means of an absorptive layer placed on top. Numerical simulations are here presented and discussed. Finally, we present an in-plane flexural resonator, consisting of a hole in a thin plate traversed by a beam. Here, a closed form of the transfer matrix is obtained by coupling the Kirchhoff-Love and the Euler-Bernoulli motion equations. Numerical simulations, tested against a commercial finite element simulator, prove its efficiencyClimente Alarcón, A. (2015). Refractive devices for acoustical and flexural waves [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48536TESI

Analysis of flexural wave cloaks

This work presents a comprehensive study of the cloak for bending waves theoretically proposed by Farhat et al. [see Phys. Rev. Lett. 103, 024301 (2009)] and later on experimentally realized by Stenger et al. [see Phys. Rev. Lett. 108, 014301 (2012)]. This study uses a semi-analytical approach, the multilayer scattering method, which is based in the Kirchoff-Love wave equation for flexural waves in thin plates. Our approach was unable to reproduce the predicted behavior of the theoretically proposed cloak. This disagreement is here explained in terms of the simplified wave equation employed in the cloak design, which employed unusual boundary conditions for the cloaking shell. However, our approach reproduces fairly well the measured displacement maps for the fabricated cloak, indicating the validity of our approach. Also, the cloak quality has been here analyzed using the so called averaged visibility and the scattering cross section. The results obtained from both analysis let us to conclude that there is room for further improvements of this type of flexural wave cloak by using better design procedures. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).This work has been supported by the Spanish Ministerio de Economia y Competitividad and the European Union Fondo Europeo para el Desarrollo Regional (FEDER) under Grant with Ref. TEC2014-53088-C3-1-R. We gratefully acknowledge Nicolas Stenger for providing us the parameters listed in Table I.Climente Alarcón, A.; Torrent Martí, D.; Sánchez-Dehesa Moreno-Cid, J. (2016). Analysis of flexural wave cloaks. AIP Advances. 6(12):121704-1-121705-16. https://doi.org/10.1063/1.4968611S121704-1121705-1661

Single-phase metamaterial plates for broadband vibration suppression at low frequencies

[EN] By studying platonic crystals based on lattices of cavities containing N-beam resonators, we conclude that crystals made of 1-beam resonators easily produce low-frequency omnidirectional bandgaps. Based on this favorable property, hardly obtained for resonant cavities containing a higher number of beams N >= 2, we have designed single-phase metamaterial plates for the suppression of low frequency flexural waves in a broad range of frequencies. These metamaterials are obtained by using resonant cavities containing a multiple number M of identical 1-beam resonators uniformly distributed in the cavity. Square lattices of this type of resonators have been studied by using the impedance matrix approach and the multiple scattering method. This semi-analytical method has been employed to show the existence of complete bandgaps whose width can be optimized by increasing M. For the case M = 4, the largest number of resonators studied here, three complete bandgaps separated by two narrow passbands appear in the band structure. The formation of these complete bandgaps originates from the dynamic interaction between different local resonators as well as their interaction with the propagating waves in the host plate. By using composite structures consisting of platonic crystal slabs with complementary bandgaps, these separated bandgaps easily merge into a broadband wave attenuation region. The normalized width, defined as the percentage of the bandwidth to its central frequency, reaches 95.3%, representing an enhancement of about one order of magnitude compared with the absolute bandwidth obtained for the case of a single 1-beam resonator in the cavity. It is shown that the gaps can be easily tuned to lower frequencies by changing the geometrical parameters, such as the length of the beam, the radius and thickness of the smaller circular plate. Since the metamaterial is made of a single-phase material without attaching heavy masses, the work reported here provides a simple approach to construct low-cost structures with potential applications in aeronautic and astronautic industries for broadband vibration suppression at low frequencies. (C) 2018 Published by Elsevier Ltd.This work was supported by the Ministerio de Economia y Competitividad of the Spanish government and the European Union Fondo Europeo de Desarrollo Regional (FEDER) [Grant No. TEC2014-53088-C3-1-R], and the National Natural Science Foundation of China [Grant Nos. 11432004 and 11421091]. Penglin Gao acknowledges a scholarship provided by China Scholarship Council [Grant No. 201606120070].Gao, P.; Climente Alarcón, A.; Sánchez-Dehesa Moreno-Cid, J.; Wu, L. (2019). Single-phase metamaterial plates for broadband vibration suppression at low frequencies. Journal of Sound and Vibration. 444:108-126. https://doi.org/10.1016/j.jsv.2018.12.022S10812644

Theoretical study of platonic crystals with periodically structured N-beam resonators

[EN] A multiple scattering theory is applied to study the properties of flexural waves propagating in a plate with periodically structured N-beam resonators. Each resonator consists of a circular hole containing an inner disk connected to background plate with N rectangular beams. The Bloch theorem is employed to obtain the band structure of a two-dimensional lattice containing a single resonator per unit cell. Also, a numerical algorithm has been developed to get the transmittance through resonator slabs infinitely long in the direction perpendicular to the incident wave. For the numerical validation, a square lattice of 2-beam resonators has been comprehensively analyzed. Its band structure exhibits several flat bands, indicating the existence of local resonances embedded in the structure. Particularly, the one featured as the fundamental mode of the inner disk opens a bandgap at low frequencies. This mode has been fully described in terms of a simple spring-mass model. As a practical application of the results obtained, a homogenization approach has been employed to design a focusing lens for flexural waves, where the index gradient is obtained by adjusting the orientation of the resonators beams. Numerical experiments performed within the framework of a three-dimensional finite element method have been employed to discuss the accuracy of the models described here. Published by AIP Publishing.This work was supported by the Ministerio de Economia y Competitividad of the Spanish government and the European Union Fondo Europeo de Desarrollo Regional (FEDER) through Project No. TEC2014-53088-C3-1-R, and the National Science Foundation of China under Grant No. 11432004. Penglin Gao acknowledges a scholarship with No. 201606120070 provided by China Scholarship Council.Gao, P.; Climente Alarcón, A.; Sánchez-Dehesa Moreno-Cid, J.; Wu, L. (2018). Theoretical study of platonic crystals with periodically structured N-beam resonators. Journal of Applied Physics. 123(9). https://doi.org/10.1063/1.5009170S123

Recent Educational Experiences in Electric Machine Maintenance Teaching

[EN] Maintenance of electric machines and installations is a particularly important area; eventual faults in these devices may lead to significant losses in terms of time and money. The investment and concern in developing proper maintenance protocols have been gradually increasing over recent decades. As a consequence, there is a need to instruct future engineers in the electric machines and installations maintenance area. The subject ¿Maintenance of Electric Machines and Installations¿ has been designed under this idea. It is taught within an official master degree in Maintenance Engineering. This work describes the educational experiences reached during the initial years of the teaching of the subject. Aspects such as student profiles, subject approaches, design of the syllabus, methodology and structure of the laboratory sessions are remarked in the work. In addition, the paper discusses other educational strategies which are being introduced to increase the interest in the subject, such as integration of Information and Communication Technologies (ICT), promotion of the collaborative work, inclusion of the possibility of remote learning or development of new assessment systems.This work was supported by the Conselleria d’Educació, Formació i Ocupació of the Generalitat Valenciana, in the framework of the ‘‘Ayudas para la Realización de Proyectos de I+D para Grupos de Investigación Emergentes’’, project reference GV/2012/020.Antonino Daviu, JA.; Pons Llinares, J.; Climente Alarcón, V. (2013). Recent Educational Experiences in Electric Machine Maintenance Teaching. International Journal of Engineering Pedagogy. 3(3):21-26. https://doi.org/10.3991/ijep.v3iS3.2742S21263

Gradient index lenses for flexural waves based on thickness variations

Copyright (2014) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics along with the following message: The following article appeared in Applied Physics Letters 105, (6) and may be found at http://dx.doi.org/10.1063/1.4893153. Authors own version of final article on e-print serversThis work presents a method for the realization of gradient index devices for flexural waves in thin plates. Unlike recent approaches based on phononic crystals, the present approach is based on the thickness-dependence of the dispersion relation of flexural waves, which is used to create gradient index devices by means of local variations of the plate's thickness. Numerical simulations of known circularly symmetrical gradient index lenses have been performed. These simulations have been done using the multilayer multiple scattering method and the results prove their broadband efficiency and omnidirectional properties. Finally, finite element simulations employing the full three-dimensional elasticity equations also support the validity of the designed approach. (c) 2014 AIP Publishing LLC.This work has been supported by the U.S. Office of Naval Research under Grant No. N000140910554.Climente Alarcón, A.; Torrent Martí, D.; Sánchez-Dehesa Moreno-Cid, J. (2014). Gradient index lenses for flexural waves based on thickness variations. Applied Physics Letters. 105(6). https://doi.org/10.1063/1.4893153S1056Norris, A. N., & Vemula, C. (1995). Scattering of flexural waves on thin plates. Journal of Sound and Vibration, 181(1), 115-125. doi:10.1006/jsvi.1995.0129SQUIRE, V. A., & DIXON, T. W. (2000). SCATTERING OF FLEXURAL WAVES FROM A COATED CYLINDRICAL ANOMALY IN A THIN PLATE. Journal of Sound and Vibration, 236(2), 367-373. doi:10.1006/jsvi.2000.2953Movchan, A. ., Movchan, N. ., & McPhedran, R. . (2007). Bloch–Floquet bending waves in perforated thin plates. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 463(2086), 2505-2518. doi:10.1098/rspa.2007.1886Lee, W.-M., & Chen, J.-T. (2010). Scattering of flexural wave in a thin plate with multiple circular holes by using the multipole Trefftz method. International Journal of Solids and Structures, 47(9), 1118-1129. doi:10.1016/j.ijsolstr.2009.12.002Parnell, W. J., & Martin, P. A. (2011). Multiple scattering of flexural waves by random configurations of inclusions in thin plates. Wave Motion, 48(2), 161-175. doi:10.1016/j.wavemoti.2010.10.004McPhedran, R. C., Movchan, A. B., & Movchan, N. V. (2009). Platonic crystals: Bloch bands, neutrality and defects. Mechanics of Materials, 41(4), 356-363. doi:10.1016/j.mechmat.2009.01.005Hsu, J.-C., & Wu, T.-T. (2006). Efficient formulation for band-structure calculations of two-dimensional phononic-crystal plates. Physical Review B, 74(14). doi:10.1103/physrevb.74.144303Huang, C.-Y., Sun, J.-H., & Wu, T.-T. (2010). A two-port ZnO/silicon Lamb wave resonator using phononic crystals. Applied Physics Letters, 97(3), 031913. doi:10.1063/1.3467145Farhat, M., Guenneau, S., & Enoch, S. (2010). High directivity and confinement of flexural waves through ultra-refraction in thin perforated plates. EPL (Europhysics Letters), 91(5), 54003. doi:10.1209/0295-5075/91/54003Wu, T.-T., Chen, Y.-T., Sun, J.-H., Lin, S.-C. S., & Huang, T. J. (2011). Focusing of the lowest antisymmetric Lamb wave in a gradient-index phononic crystal plate. Applied Physics Letters, 98(17), 171911. doi:10.1063/1.3583660Pierre, J., Boyko, O., Belliard, L., Vasseur, J. O., & Bonello, B. (2010). Negative refraction of zero order flexural Lamb waves through a two-dimensional phononic crystal. Applied Physics Letters, 97(12), 121919. doi:10.1063/1.3491290Farhat, M., Guenneau, S., Enoch, S., Movchan, A. B., & Petursson, G. G. (2010). Focussing bending waves via negative refraction in perforated thin plates. Applied Physics Letters, 96(8), 081909. doi:10.1063/1.3327813Bramhavar, S., Prada, C., Maznev, A. A., Every, A. G., Norris, T. B., & Murray, T. W. (2011). Negative refraction and focusing of elastic Lamb waves at an interface. Physical Review B, 83(1). doi:10.1103/physrevb.83.014106Wang, C. H. (2003). Plate-Wave Diffraction Tomography for Structural Health Monitoring. AIP Conference Proceedings. doi:10.1063/1.1570323Fromme, P., Wilcox, P. D., Lowe, M. J. S., & Cawley, P. (2006). On the development and testing of a guided ultrasonic wave array for structural integrity monitoring. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 53(4), 777-785. doi:10.1109/tuffc.2006.1621505Berryman, J. G. (1980). Long‐wavelength propagation in composite elastic media I. Spherical inclusions. The Journal of the Acoustical Society of America, 68(6), 1809-1819. doi:10.1121/1.385171Krokhin, A. A., Arriaga, J., & Gumen, L. N. (2003). Speed of Sound in Periodic Elastic Composites. Physical Review Letters, 91(26). doi:10.1103/physrevlett.91.264302Torrent, D., Håkansson, A., Cervera, F., & Sánchez-Dehesa, J. (2006). Homogenization of Two-Dimensional Clusters of Rigid Rods in Air. Physical Review Letters, 96(20). doi:10.1103/physrevlett.96.204302Stenger, N., Wilhelm, M., & Wegener, M. (2012). Experiments on Elastic Cloaking in Thin Plates. Physical Review Letters, 108(1). doi:10.1103/physrevlett.108.014301Krylov, V. V., & Tilman, F. J. B. S. (2004). Acoustic ‘black holes’ for flexural waves as effective vibration dampers. Journal of Sound and Vibration, 274(3-5), 605-619. doi:10.1016/j.jsv.2003.05.010O’Boy, D. J., Krylov, V. V., & Kralovic, V. (2010). Damping of flexural vibrations in rectangular plates using the acoustic black hole effect. Journal of Sound and Vibration, 329(22), 4672-4688. doi:10.1016/j.jsv.2010.05.019Krylov, V. V., & Winward, R. E. T. B. (2007). Experimental investigation of the acoustic black hole effect for flexural waves in tapered plates. Journal of Sound and Vibration, 300(1-2), 43-49. doi:10.1016/j.jsv.2006.07.035Georgiev, V. B., Cuenca, J., Gautier, F., Simon, L., & Krylov, V. V. (2011). Damping of structural vibrations in beams and elliptical plates using the acoustic black hole effect. Journal of Sound and Vibration, 330(11), 2497-2508. doi:10.1016/j.jsv.2010.12.001Climente, A., Torrent, D., & Sánchez-Dehesa, J. (2013). Omnidirectional broadband insulating device for flexural waves in thin plates. Journal of Applied Physics, 114(21), 214903. doi:10.1063/1.4839375Šarbort, M., & Tyc, T. (2012). Spherical media and geodesic lenses in geometrical optics. Journal of Optics, 14(7), 075705. doi:10.1088/2040-8978/14/7/075705Narimanov, E. E., & Kildishev, A. V. (2009). Optical black hole: Broadband omnidirectional light absorber. Applied Physics Letters, 95(4), 041106. doi:10.1063/1.3184594Climente, A., Torrent, D., & Sánchez-Dehesa, J. (2012). Omnidirectional broadband acoustic absorber based on metamaterials. Applied Physics Letters, 100(14), 144103. doi:10.1063/1.370161

CITRINE: Common Intelligence and Traceability for Rescue and Identification Operations

The Master Thesis is part of the European project CITRINE. A command and control system for crisis management has been build making use of DSS and a civil version of the military standar C2IEDM. The system uses sensors such as GPS recievers and video cameras to achief an artificial vision of the operation field.Climente Alarcón, A. (2009). CITRINE: Common Intelligence and Traceability for Rescue and Identification Operations. http://hdl.handle.net/10251/14323Archivo delegad

Designing collaborative working laboratory sessions for induction machine fault diagnosis learning

In this paper, two laboratory sessions, specially designed to instruct students on the operational methodology of different induction motors fault diagnosis techniques, are presented and explained. The sessions are taught within the context of a subject dealing with predictive maintenance of electrical installations and machines. During the laboratory sessions, the students apply the different condition monitoring techniques, using special educational laboratory test benches built to this end. These test benches allow the students to easily capture the necessary current signals in motors with rather different constructive characteristics, operating conditions and faults. Next, the students must process the captured signals by using available software programs. While stationary current signals are analyzed using the Fast Fourier Transform (FFT) conventional diagnosis approach the startup current signals are processed using the Discrete Wavelet Transform (DWT) modern transient-based diagnosis method. The laboratory sessions have been developed from a collaborative perspective, so that the students are encouraged to work in groups in the experimental part with further collective discussion on their diagnostic conclusions, all within an open framework for information sharing.This work was supported by the Conselleria d'Educacio, Formacio i Ocupacio of the Generalitat Valenciana, in the framework of the 'Ayudas para la Realizacion de Proyectos de I+D para Grupos de Investigacion Emergentes', project reference GV/2012/020.Antonino Daviu, JA.; Climente Alarcón, V.; Pons Llinares, J. (2014). Designing collaborative working laboratory sessions for induction machine fault diagnosis learning. International Journal of Electrical Engineering Education. 51(1):68-81. https://doi.org/10.7227/IJEEE.51.1.6S6881511Antonino-Daviu, J. A., Riera-Guasp, M., Folch, J. R., & Palomares, M. P. M. (2006). Validation of a new method for the diagnosis of rotor bar failures via wavelet transform in industrial induction machines. IEEE Transactions on Industry Applications, 42(4), 990-996. doi:10.1109/tia.2006.876082Riera-Guasp, M., Antonino-Daviu, J. A., Pineda-Sanchez, M., Puche-Panadero, R., & Perez-Cruz, J. (2008). A General Approach for the Transient Detection of Slip-Dependent Fault Components Based on the Discrete Wavelet Transform. IEEE Transactions on Industrial Electronics, 55(12), 4167-4180. doi:10.1109/tie.2008.2004378Benveniste, R., & Ünsalan, C. (2012). Hands-On DSP Education through Experiments. International Journal of Electrical Engineering & Education, 49(3), 302-309. doi:10.7227/ijeee.49.3.

Omnidirectional broadband acoustic absorber based on metamaterials

We present the design, construction, and experimental characterization of the acoustic analogue of the so called photonic black-hole. The fabricated sample has cylindrical symmetry and consists of two parts, a shell that bends the sound towards the center and a core that dissipates its energy. The shell is made of a metamaterial that perfectly matches the acoustic impedance of air and behaves like a gradient index lens. The experimental data obtained in a multi-modal impedance chamber demonstrate that the proposed acoustic black-hole acts like an onmidirectional broadband absorber with strong absorbing efficiency. © 2012 American Institute of Physics.Work supported by the U.S. Office of Naval Research. The authors acknowledge V.M. Garcia-Chocano and F. Cervera for useful discussions and technical help. D.T. acknowledges a fellowship provided by the program Campus de Excelencia Internacional 2010 UPV.Climente Alarcón, A.; Torrent Martí, D.; Sánchez-Dehesa Moreno-Cid, J. (2012). Omnidirectional broadband acoustic absorber based on metamaterials. Applied Physics Letters. 100(14):1-4. doi:10.1063/1.3701611S141001

Particle Filter-Based Estimation of Instantaneous Frequency for the Diagnosis of Electrical Asymmetries in Induction Machines

"© 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.” Upon publication, authors are asked to include either a link to the abstract of the published article in IEEE Xplore®, or the article’s Digital Object Identifier (DOI).Fault diagnosis of induction machines operating under variable load conditions is still an unsolved matter. Under those regimes, the application of conventional diagnostic techniques is not suitable, since they are adapted to the analysis of stationary quantities. In this context, modern transient-based methodologies become very appropriate. This paper improves a technique, based on the application of Wigner Ville distribution as time frequency decomposition tool, using a particle filtering method as feature extraction procedure, to diagnose and quantify electrical asymmetries in induction machines, such as wound- rotor induction generators used in wind farms. The combination of both tools allows tracking several variable frequency harmon- ics simultaneously and computing their energy with high accu- racy, yielding magnitudes and values similar to those obtained by the application of the fast Fourier transform in stationary operation. The experimental results show the validity of the approach for rapid speed variations, independently of any speed sensor.Climente Alarcon, V.; Antonino Daviu, JA.; Haavisto, A.; Arkkio, A. (2014). Particle Filter-Based Estimation of Instantaneous Frequency for the Diagnosis of Electrical Asymmetries in Induction Machines. IEEE Transactions on Instrumentation and Measurement. 63(10):2454-2463. doi:10.1109/TIM.2014.2310113S24542463631