Although the study of the interaction of acoustic and elastic waves with periodic surfaces and structures has a rich history dating back to Lord Rayleigh, it has recently been attracting new research efforts due to its value in the study of phononic crystals and in methods for ultrasonic non-destructive evaluation (NDE). The objective of the research described in this thesis is to provide new numerical and experimental tools capable of capturing important features that occur due to the diffraction of ultrasound on periodic solid surfaces. This thesis is divided into four main parts. First, the Rayleigh-Fourier (R-F) method will be used to simulate diffracted fields generated by structures containing multiple periodic surfaces and/or multiple solid layers. The second part of this thesis examines diffraction effects and compares ultrasonic NDE techniques for surfaces with imperfect periodicities. The third portion of this thesis focuses on one unusual phenomenon that has been observed on periodic surfaces, namely the lateral backward displacement of a bounded ultrasonic beam along the surface. This effect is currently understood to occur due to backward propagating surface waves that result from diffraction and mode conversion on the surface. The fourth and final part of this thesis describes the diffraction of bulk ultrasonic waves that can occur on the surfaces of phononic crystals.

Submitted by Izabel Franco (izabel-franco@ufscar.br) on 2016-10-06T20:50:11Z No. of bitstreams: 1 DissMOS.pdf: 8901062 bytes, checksum: 08b58e3ccf045cae12fa956cafaba68c (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-20T19:37:55Z (GMT) No. of bitstreams: 1 DissMOS.pdf: 8901062 bytes, checksum: 08b58e3ccf045cae12fa956cafaba68c (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-20T19:38:01Z (GMT) No. of bitstreams: 1 DissMOS.pdf: 8901062 bytes, checksum: 08b58e3ccf045cae12fa956cafaba68c (MD5) / Made available in DSpace on 2016-10-20T19:38:06Z (GMT). No. of bitstreams: 1 DissMOS.pdf: 8901062 bytes, checksum: 08b58e3ccf045cae12fa956cafaba68c (MD5) Previous issue date: 2016-02-02 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / The present study delas with nondestructive evaluation of modern masonry built with hollow concrete blocks, through the flatjack technique. The technique is already used to evaluate masonry structures with solid bricks and stones and it is considered as efficient to obtain in situ mechanical properties, without any permanent damages. The tests in solid unit masonry using flatjack is included in international standards and recommendations as: ASTM C 1196 e 1197-09 e RILEM MDT.D.4 e MDT.D.5-04. The current standards and the practical applications deal with masonry with brick or stones elements only. Nondestructive evaluation in modern hollow block masonry is demanded and the flatjack can be used in these cases. However, the current available jack can be used only on solid units, due to its geometrical limitations. Therefore, this research proposes to adapt the flatjack technique for nondestructive evaluation in modern masonry built with hollow concrete blocks. The analyzed test is the deformability one, which the modulus of elasticity and an estimative of the compressive strength is wanted. In this research, a new flatjack equipment was developed to allow its application on hollow blocks and it was tested in modern masonry samples. The new equipment was successfully developed and it was used in flatjack tests on hollow concrete block masonry. As main results, masonry properties obtained from the flatjack technique was close to the expected ones, indicating the great potentiality of the technique for hollow blocks also. / O presente trabalho trata da avaliação não destrutiva em alvenarias estruturais de blocos de concreto, através da técnica de macacos planos. A técnica já é utilizada em análises de estruturas de alvenaria de tijolos maciços e de pedras, sendo considerada bastante eficiente para a obtenção de propriedades mecânicas, no próprio local, sem causar danos permanentes. Os testes com macacos planos em alvenarias de unidades maciças já fazem parte de normas e recomendações internacionais como: ASTM C 1196 e 1197-09 e RILEM MDT.D.4 e MDT.D.5-04. As normas e as aplicações práticas já realizadas tratam apenas de alvenarias com elementos de tijolos ou pedras. Existe uma demanda para avaliação estrutural não destrutiva em alvenarias modernas, na maioria compostas por blocos vazados, de maneira que a técnica poderia ser utilizada. Entretanto, os macacos atualmente disponíveis podem ser aplicados em unidades maciças apenas, devido a limitações geométricas. Portanto, este estudo visa adaptar a técnica de macacos planos para análise não destrutiva em alvenarias modernas, compostas por blocos vazados de concreto. O teste adaptado é o teste de deformabilidade, em que se visa obter o módulo de elasticidade e uma estimativa da resistência à compressão. Para a realização deste trabalho, um novo modelo de macaco foi desenvolvido, possibilitando sua aplicação em blocos vazados, sendo testado em amostras de paredes. O equipamento foi desenvolvido com sucesso e utilizado em testes de deformabilidade em paredes com blocos de concreto. Como resultado, propriedades foram obtidas com boa proximidade com os valores esperados, indicando potencialidade da técnica para esse tipo de aplicação. Palavras-chave: Macacos planos; teste de deformabilidade; avaliação não destrutiva; blocos vazados de concreto.

The wet pressing process represents a new production method for carbon fibre-reinforced plastics components. Due to the low cycle times, it is suitable for use in the automotive industry. Therefore, a sufficient degree of industrialisation needs to be achieved, which is characterised by a stable process. The knowledge about relevant process parameters, their interactions, and influence on the part quality builds the basis of an economic process. This is a major challenge, since in the early stage of process development the available amount of recorded process data is small and the data sets are not complete. As the implementation of time-, material-, and cost-intensive experiments represents no acceptable alternative, a theoretical approach is chosen. This article describes a theoretical procedure to define the critical factors of the wet pressing process with significantly less resource input.

[pt] Ondas ultrassônicas podem ser usadas para ensaios não destrutivos. Elas são geradas e adquiridas por transdutores. Transdutores acústicos eletromagnéticos (EMATs) possuem algumas vantagens em relação a transdutores tradicionais piezoelétricos, principalmente a capacidade de gerar ondas ultrassônicas sem necessidade de contato físico com o meio em teste. No entanto, sua principal desvantagem é a menor eficiência, que resulta em uma relação sinal-ruído mais baixa. Técnicas de casamento de impedância podem ser utilizadas para combater isso. A rede de casamento de impedância do tipo circuito L é comumente utilizada para garantir a transferência máxima de potência da eletrônica de excitação para o EMAT. Existem diversas variáveis que podem afetar a impedância de um EMAT além do próprio transdutor, como as propriedades e distância do material, a temperatura e a frequência de excitação. Portanto, para garantir a transferência máxima de potência, o circuito de casamento de impedância precisa ser reconfigurado e ter seus valores ajustados sempre que um dos fatores mencionados acima sofrer alteração. O processo de ajuste manual desta rede é trabalhoso e demorado, portanto, sua automação pode trazer grandes benefícios para o uso de transdutores EMAT. Esta dissertação propõe um circuito simplificado, com um único elemento, para casamento de impedância de EMATs. Os valores teóricos ideais para circuitos mono-elemento foram obtidos. Simulações confirmaram sua viabilidade em aumentar a eficiência do EMAT. Circuitos de casamento manual e automáticos foram projetados e construídas. Configurações experimentais foram elaboradas e postas em prática. Experimentos com dois transdutores EMATs distintos foram conduzidos utilizando várias frequências. O sistema automático foi capaz de determinar a melhor configuração para o circuito mono-elemento de casamento de impedância e forneceu um ganho de até 5,6 dB, similar à solução manual. A configuração automática foi mais de duas vezes mais rápida do que a manual. / [en] Ultrasonic waves can be used for nondestructive testing. They are generated and acquired by transducers. Electromagnetic acoustic transducers (EMATs) have some advantages over traditional piezoelectric transducers. Mainly, the ability to generate ultrasonic waves without requiring physical contact with the medium under test. Nevertheless, they present a main drawback of less efficiency, which leads to a lower signal-to-noise ratio. To overcome this, impedance matching techniques can be used. The L-network impedance matching network is often used in order to ensure maximum power transfer to the EMAT from the excitation electronics. There is a wide range of variables that can affect an EMAT s impedance besides the transducer itself, namely, the properties and distance to the specimen material, the temperature, and the excitation frequency. Therefore, to ensure optimal power transfer, the Lnetwork s configuration needs to be tuned whenever one of the factors that affect impedance changes. The process of manually adjusting the impedance matching network is a laborious and time-consuming task, therefore, its automation can be of great benefit to the use of EMAT transducers. In this work, a simplified one-element automatic matching network is proposed. The theoretical optimal values for the one-element matching networks are derived. Simulations confirmed their effectiveness to increase EMAT efficiency. Manual and automatic networks were designed and built. Experiments were performed with two dierent EMATs at several frequencies. The automatic system was able to determine the best conguration for the one-element matching network and provided up to 5.6 dB gain, similar to the manual solution. The automatic setup was more than two-fold faster than the manual one.

No description available.

Although several studies have proven the accuracy of using a non-contact, air-coupled receiver in nonlinear ultrasonic (NLU) Rayleigh wave measurements, inconsistent results have been observed when working with narrow specimens. The objectives of this research are first, to develop a 3D numerical finite element (FE) model which predicts nonlinear ultrasonic measurements and second, to apply the validated model on the narrow waveguide to determine causes of the previously observed experimental issues. The commercial FE-solver ABAQUS is used to perform these simulations. Constitutive law and excitation source properties are adjusted to match experiments conducted, considering inherent effects of the non-contact detection, such as frequency dependent pressure wave attenuation and signal averaging. Comparison of “infinite” and narrow width simulations outlines various influences which impair the nonlinear Rayleigh wave measurements. When the wave expansion is restricted, amplitudes of the fundamental and second harmonic components decrease more significantly and the Rayleigh wavefronts show an oscillating interaction with the boundary. Because of the air-coupled receiver’s finite width, it is sensitive to these edge effects which alter the observed signal. Thus, the narrow specimen adversely affects key factors needed for consistent measurement of material nonlinearity with an air-coupled, non-contact receiver.

De nombreuses études ont été menées jusqu’ici afin d’analyser l’apport de la technique de génération acoustique par micro-ondes dans le domaine de l’évaluation et du contrôle non destructifs des structures mécaniques. Le caractère entièrement sans contact de cette nouvelle technique en ferait un moyen pouvant être adopté pour générer aisément des ondes acoustiques dans les matériaux diélectriques absorbants. Ce travail porte d’abord sur l’étude des vibrations latérales engendrées dans les barreaux viscoélastiques placés dans un guide d’ondes électromagnétiques contenant une ouverture sur l’une des faces latérales et soumis à de brèves excitations de micro-ondes. Un modèle paramétrique prédit la forme de l’élévation de la température à l’intérieur de l’échantillon. Ses résultats soulignent que l’utilisation des guides partiellement ouverts provoque une distribution asymétrique de la température générant ainsi des modes de flexion. Par ailleurs, un modèle numérique tridimensionnel par éléments finis a permis de mettre en évidence l’existence d’autres modes liés aux déformations des sections-droites lorsqu’elles sont soumises à une brusque dilatation thermique. Ensuite, l’élaboration de méthodes directes pour compléter l’évaluation des propriétés viscoélastiques des mêmes barreaux placés dans les guides conventionnels est considérée. Différents modèles analytiques sont construits pour analyser l’effet du coefficient de Poisson sur le rapport des vibrations induites dans les directions latérale et longitudinale d’une part, et sur la dispersion des ondes acoustiques de type traction compression d’autre part. Un algorithme d’optimisation permettant d’estimer le coefficient de Poisson et la partie réelle de la lenteur à valeurs complexes par une méthode inverse est élaboré puis appliqué dans le cas concret de deux barreaux polymériques. Enfin, une étude analytique et numérique par éléments finis est menée afin d’analyser les vibrations générées sur un défaut circulaire (trou) contenu dans une plaque et chauffé localement par des micro-ondes. Deux approches acoustiques sont construites pour prédire la forme de la zone chauffée par une température uniforme ou gaussienne. Une relation directe entre la taille du défaut et les fréquences de certains pics qui apparaissent sur les spectres des vibrations de la plaque ont été mises en évidence. Celle-ci conviendrait à l’élaboration d’une méthode inverse permettant de dimensionner ces types de défauts. / Many studies in the field of both nondestructive evaluation and testing of mechanical structures have been conducted so far by analyzing the contribution of the microwaves induce acoustic technique. This new non-contact technique can be easily adopted to generate acoustic waves in non-conducting materials. This work begins with studying the lateral vibrations generated within viscoelastic bars hold inside grooved electromagnetic waveguides and subjected to short microwave irradiations. A parametrical model is established in order to predict the shape of the temperature rise within the sample. Results emphasize the fact that these types of waveguides generate a sudden asymmetric temperature rise, which produces some flexural modes. Besides, the development of a 3D numerical model allow the prediction of new vibration modes which are related to the deformations of the bar cross-sections during the sudden thermal heating. Then, direct methods are developed to complete the assessment of the viscoelastic properties of bars placed inside conventional electromagnetic waveguides. Different analytical models are proposed to study the effects of the Poisson ratio either on the ratio between lateral and longitudinal vibrations or on the dispersion of longitudinal waves. An optimization algorithm that allows the Poisson ratio and the real part of the complex slowness evaluation by means of dispersion curves is elaborate before being applied in the specific case of two polymeric bars. Finally, analytical and numerical finite element methods are conducted to analyze the acoustic waves generated by a circular defect (hole) contained in a plate and heated locally by microwaves. Two acoustic approaches are performed to predict the temperature rise form. Furthermore, a nondestructive testing method is highlighted by a direct relationship between the size of the defect and the frequencies of some peaks that appear on the velocity spectra of the plate. This method could be applied to set up an inverse procedure that can be used to size these kinds of defects.

Ultrasonic guided wave imaging methods offer a cost-effective mechanism to perform in situ structural health monitoring (SHM) of large plate-like structures, such as commercial aircraft skins, ship hulls, storage tanks, and civil structures. However, current limits in imaging quality, environmental sensitivities, and implementation costs, among other things, are preventing widespread commercial adoption. The research presented here significantly advances state of the art guided wave imaging techniques using inexpensive, spatially distributed arrays of piezoelectric transducers. Novel adaptive imaging techniques are combined with in situ estimation and compensation of propagation parameters; e.g., dispersion curves and transducer transfer functions, to reduce sensitivity to unavoidable measurement inaccuracies and significantly improve resolution and reduce artifacts in guided wave images. The techniques can be used not only to detect and locate defects or damage, but also to characterize the type of damage. The improved ability to detect, locate, and now characterize defects or damage using a sparse array of ultrasonic transducers is intended to assist in the establishment of in situ guided wave imaging as a technically and economically viable tool for long-term monitoring of plate-like engineering structures.

No description available.

[EN] The test for determining the resonance frequencies has traditionally been used to investigate the mechanical integrity of concrete cores, to assess the conformity of concrete constituents in different accelerated durability tests, and to ascertain constitutive properties such as the elastic modulus and the damping factor. This nondestructive technique has been quite appealed for evaluation of mechanical properties in all kinds of durability tests. The damage evolution is commonly assessed from the reduction of dynamic modulus which is produced as a result of any cracking process. However, the mechanical behavior of concrete is intrinsically nonlinear and hysteretic. As a result of a hysteretic stress-strain behavior, the elastic modulus is a function of the strain. In dynamic tests, the nonlinearity of the material is manifested by a decrease of the resonance frequencies, which is inversely proportional to the excitation amplitude. This phenomenon is commonly referred as fast dynamic effect. Once the dynamic excitation ceases, the material undergoes a relaxation process whereby the elastic modulus is restored to that at rest. This phenomenon is termed as slow dynamics. These phenomena (fast and slow dynamics) find their origin in the internal friction of the material. Therefore, in cement-based materials, the presence of microcracks and interfaces between its constituents plays an important role in the material nonlinearity. In the context of the assessment of concrete durability, the damage evolution is based on the increase of hysteresis, as a result of any cracking process. In this thesis three different nondestructive techniques are investigated, which use impacts for exciting the resonant frequencies. The first technique consists in determining the resonance frequencies over a range of impact forces. The technique is termed Nonlinear Impact Resonant Acoustic Spectroscopy (NIRAS). It consists in ascertaining the downward resonant frequency shift that the material undergoes upon increasing excitation amplitude. The second technique consists in investigating the nonlinear behavior by analyzing the signal corresponding to a single impact. This is, to determine the instantaneous frequency, amplitude and attenuation variations corresponding to a single impact event. This technique is termed as Nonlinear Resonant Acoustic Single Impact Spectroscopy (NSIRAS). Two techniques are proposed to extract the nonlinear behavior by analyzing the instantaneous frequency variations and attenuation over the signal ring down. The first technique consists in discretizing the frequency variation with time through a Short-Time Fourier Transform (STFT) based analysis. The second technique consists of a least-squares fit of the vibration signals to a model that considers the frequency and attenuation variations over time. The third technique used in this thesis can be used for on-site evaluation of structures. The technique is based on the Dynamic Acousto- Elastic Test (DAET). The variations of elastic modulus as derived through NIRAS and NSIRAS techniques provide an average behavior and do not allow derivation of the elastic modulus variations over one vibration cycle. Currently, DAET technique is the only one capable to investigate the entire range of nonlinear phenomena in the material. Moreover, unlike other DAET approaches, this study uses a continuous wave source as probe. The use of a continuous wave allows investigation of the relative variations of the elastic modulus, as produced by an impact. Moreover, the experimental configuration allows one-sided inspection. / [ES] El ensayo de determinación de las frecuencias de resonancia ha sido tradicionalmente empleado para determinar la integridad mecánica de testigos de hormigón, en la evaluación de la conformidad de mezclas de hormigón en diversos ensayos de durabilidad, y en la terminación de propiedades constitutivas como son el módulo elástico y el factor de amortiguamiento. Esta técnica no destructiva ha sido ampliamente apelada para la evaluación de las propiedades mecánicas en todo tipo de ensayos de durabilidad. La evolución del daño es comúnmente evaluada a partir de la reducción del módulo dinámico, producido como resultado de cualquier proceso de fisuración. Sin embargo, el comportamiento mecánico del hormigón es intrínsecamente no lineal y presenta histéresis. Como resultado de un comportamiento tensión-deformación con histéresis, el módulo elástico depende de la deformación. En ensayos dinámicos, la no linealidad del material se manifiesta por una disminución de las frecuencias de resonancia, la cual es inversamente proporcional a la amplitud de excitación. Este fenómeno es normalmente denominado como dinámica rápida. Una vez la excitación cesa, el material experimenta un proceso de relajación por el cual, el módulo elástico es restaurado a aquel en situación de reposo. Este fenómeno es denominado como dinámica lenta. Estos fenómenos ¿dinámicas rápida y lenta¿ encuentran su origen en la fricción interna del material. Por tanto, en materiales basados en cemento, la presencia de microfisuras y las interfaces entre sus constituyentes juegan un rol importante en la no linealidad mecánica del material. En el contexto de evaluación de la durabilidad del hormigón, la evolución del daño está basada en el incremento de histéresis, como resultado de cualquier proceso de fisuración. En esta tesis se investigan tres técnicas diferentes las cuales utilizan el impacto como medio de excitación de las frecuencias de resonancia. La primera técnica consiste en determinar las frecuencias de resonancia a diferentes energías de impacto. La técnica es denominada en inglés: Nonlinear Impact Resonant Acoustic Spectroscopy (NIRAS). Ésta consiste en relacionar el detrimento que el material experimenta en sus frecuencias de resonancia, con el aumento de la amplitud de la excitación. La segunda técnica consiste en investigar el comportamiento no lineal mediante el análisis de la señal correspondiente a un solo impacto. Ésta consiste en determinar las propiedades instantáneas de frecuencia, atenuación y amplitud. Esta técnica se denomina, en inglés, Nonlinear Single Impact Resonant Acoustic Spectroscopy (NSIRAS). Se proponen dos técnicas de extracción del comportamiento no lineal mediante el análisis de las variaciones instantáneas de frecuencia y atenuación. La primera técnica consiste en la discretización de la variación de la frecuencia con el tiempo, mediante un análisis basado en Short-Time Fourier Transform (STFT). La segunda técnica consiste en un ajuste por mínimos cuadrados de las señales de vibración a un modelo que considera las variaciones de frecuencia y atenuación con el tiempo. La tercera técnica empleada en esta tesis puede ser empleada para la evaluación de estructuras in situ. La técnica se trata de un ensayo acusto-elástico en régimen dinámico. En inglés Dynamic Acousto-Elastic Test (DAET). Las variaciones del módulo elástico obtenidas mediante los métodos NIRAS y NSIRAS proporcionan un comportamiento promedio y no permiten derivar las variaciones del módulo elástico en un solo ciclo de vibración. Actualmente, la técnica DAET es la única que permite investigar todo el rango de fenómenos no lineales en el material. Por otra parte, a diferencia de otras técnicas DAET, en este estudio se emplea como contraste una onda continua. El uso de una onda continua permite investigar las variaciones relativas del módulo elástico, para una señal transito / [CA] L'assaig de determinació de les freqüències de ressonància ha sigut tradicionalment empleat per a determinar la integritat mecànica de testimonis de formigó, en l'avaluació de la conformitat de mescles de formigó en diversos assajos de durabilitat, i en la terminació de propietats constitutives com són el mòdul elàstic i el factor d'amortiment. Esta tècnica no destructiva ha sigut àmpliament apel·lada per a l'avaluació de les propietats mecàniques en tot tipus d'assajos de durabilitat. L'evolució del dany és comunament avaluada a partir de la reducció del mòdul dinàmic, produït com resultat de qualsevol procés de fisuración. No obstant això, el comportament mecànic del formigó és intrínsecament no lineal i presenta histèresi. Com resultat d'un comportament tensió-deformació amb histèresi, el mòdul elàstic depén de la deformació. En assajos dinàmics, la no linealitat del material es manifesta per una disminució de les freqüències de ressonància, la qual és inversament proporcional a l'amplitud d'excitació. Este fenomen és normalment denominat com a dinàmica ràpida. Una vegada l'excitació cessa, el material experimenta un procés de relaxació pel qual, el mòdul elàstic és restaurat a aquell en situació de repòs. Este fenomen és denominat com a dinàmica lenta. Estos fenòmens --dinámicas ràpida i lenta troben el seu origen en la fricció interna del material. Per tant, en materials basats en ciment, la presència de microfissures i les interfícies entre els seus constituents juguen un rol important en la no linealitat mecànica del material. En el context d'avaluació de la durabilitat del formigó, l'evolució del dany està basada en l'increment d'histèresi, com resultat de qualsevol procés de fisuración. En esta tesi s'investiguen tres tècniques diferents les quals utilitzen l'impacte com a mitjà d'excitació de les freqüències de ressonància. La primera tècnica consistix a determinar les freqüències de ressonància a diferents energies d'impacte. La tècnica és denominada en anglés: Nonlinear Impact Resonant Acoustic Spectroscopy (NIRAS). Esta consistix a relacionar el detriment que el material experimenta en les seues freqüències de ressonància, amb l'augment de l'amplitud de l'excitació. La segona tècnica consistix a investigar el comportament no lineal per mitjà de l'anàlisi del senyal corresponent a un sol impacte. Esta consistix a determinar les propietats instantànies de freqüència, atenuació i amplitud. Esta tècnica es denomina, en anglés, Nonlinear Single Impact Resonant Acoustic Spectroscopy (NSIRAS). Es proposen dos tècniques d'extracció del comportament no lineal per mitjà de l'anàlisi de les variacions instantànies de freqüència i atenuació. La primera tècnica consistix en la discretización de la variació de la freqüència amb el temps, per mitjà d'una anàlisi basat en Short-Time Fourier Transform (STFT). La segona tècnica consistix en un ajust per mínims quadrats dels senyals de vibració a un model que considera les variacions de freqüència i atenuació amb el temps. La tercera tècnica empleada en esta tesi pot ser empleada per a l'avaluació d'estructures in situ. La tècnica es tracta d'un assaig acusto-elástico en règim dinàmic. En anglés Dynamic Acousto-Elastic Test (DAET). Les variacions del mòdul elàstic obtingudes per mitjà dels mètodes NIRAS i NSIRAS proporcionen un comportament mitjà i no permeten derivar les variacions del mòdul elàstic en un sol cicle de vibració. Actualment, la tècnica DAET és l'única que permet investigar tot el rang de fenòmens no lineals en el material. D'altra banda, a diferència d'altres tècniques DAET, en este estudi s'empra com contrast una ona contínua. L'ús d'una ona contínua permet investigar les variacions relatives del mòdul elàstic, per a un senyal transitori. A més, permet la inspecció d'elements per mitjà de l'accés per una sola cara. / Eiras Fernández, JN. (2016). Studies on nonlinear mechanical wave behavior to characterize cement based materials and its durability [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/71439 / TESIS / Premios Extraordinarios de tesis doctorales