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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Microstructure and Fatigue Analysis of PM-HIPed Alloys : A Focus on Inconel 625 and High-Nitrogen Tool Steel

Javadzadeh Kalahroudi, Faezeh January 2024 (has links)
Nickel-based superalloys and tool steels are well-known high-performance alloys due to their extensive use in many different industries. Nickel-based superalloys have found their way into aircraft, aerospace, marine, chemical, and petrochemical industries owing to their excellent high-temperature corrosion and oxidation resistance. On the other hand, tool steels could provide a combination of outstanding corrosion and wear resistance. They can play an important role in cutting and wear applications and manufacturing plastic extrusion and food processing components. Near-net shape manufacturing using powder metallurgy (PM) and hot isostatic pressing (HIP) can serve as an efficient manufacturing process to produce these alloys. This technology can successfully tackle conventional manufacturing challenges of highly alloyed materials i.e. segregation during the casting process or cracks during hot working processes of Ni-based superalloys, and carbide segregation and formation of large and irregularly shaped carbides in wrought and hot rolled tool steels. However, the presence of precipitates on prior particle boundaries (PPBs) in Ni-based superalloys, and metallurgical defects like non-metallic inclusions in both Ni-based superalloys and tool steels may affect the fatigue performance of these PM-HIPed products. This licentiate thesis aims to investigate the microstructure and fatigue behavior of two PM-HIPed alloys i.e. Inconel 625 and high-nitrogen tool steel. The results confirm precipitation along PPBs in PM-HIPed Inconel 625; however, no effect was detected in the fractography studies of the high cycle fatigue samples, and tensile properties were comparable with wrought materials reported in the literature. On the other hand, the microstructure of PM-HIPed high-nitrogen tool steel displayed dispersed precipitates and no traces of PPBs. Moreover, in both cases, i.e. very high cycle fatigue of PM-HIPed high-nitrogen tool steel and high cycle fatigue of PM-HIPed Inconel 625, fatigue crack initiation was attributed to the presence of non-metallic inclusions, either individually or agglomerated with precipitates. This underscores the significance of the manufacturing process in fatigue performance. / Near-net shape manufacturing using powder metallurgy (PM) and hot isostatic pressing (HIP) can serve as an efficient manufacturing process to produce high-performance alloys. Among the variety of engineering alloys, Nickel-based superalloys and tool steels stand out as well-known high-performance alloys, widely employed across diverse industries. PM-HIP technology can successfully address conventional manufacturing challenges associated with highly alloyed materials, such as segregation during the casting process or cracks during hot working processes of Ni-based superalloys, and carbide segregation and the formation of large and irregularly shaped carbides in wrought and hot rolled tool steels. However, the presence of precipitates on prior particle boundaries in Ni-based superalloys, and metallurgical defects like non-metallic inclusions in both alloys, may affect the fatigue performance of these PM-HIPed products. The present study aims to assess two PM-HIPed alloys, namely Inconel 625 and high-nitrogen tool steel, with a comprehensive examination of their microstructure and fatigue properties. The objectives include examining the microstructural features introduced by the PM-HIP process and understanding how they influence fatigue failure mechanisms in these alloys.
122

Metallurgical Characterization and Testing of Dissimilar Metal Welds for Service in Hydrogen Containing Environments

Boster, Connor M., Boster 15 August 2018 (has links)
No description available.
123

Optimization and Application of the Strain-To-Fracture Test for Studying Ductility-Dip Cracking in Ni-base Alloys

Kreuter, Verner C., V 20 October 2015 (has links)
No description available.
124

An Adapted Approach to ProcessMapping Across Alloy Systems and Additive Manufacturing Processes

Sheridan, Luke Charles 30 August 2016 (has links)
No description available.
125

Etude de l'Influence de la vapeur d'eau sur l'oxydation à haute température d'un alliage chromino-formeur à base de nickel / Study of water vapor influence in high temperature oxidation for a chromia forming nickel base alloy

Rolland, Raphaël 14 March 2012 (has links)
Ce travail s’inscrit dans un cadre de recherche qui a pour objectif essentiel l’étude de l’influence de la vapeur d’eau sur l’oxydation à haute température d’un alliage formeur de Cr2O3 à base de nickel. L’alliage étudié pour cette étude est le SY 625. L’originalité de cette étude repose sur l’utilisation d’un montage expérimental, mis en oeuvre au laboratoire. Ce montage appelé « montage vapeur d’eau » permet de réaliser l’oxydation du SY 625 à haute température (900-1100°C) en présence de vapeur d’eau (7,5 et 33% de vapeur d’eau) avec différents gaz vecteurs (oxygène, air, argon et azote) en conditions isotherme ou cyclique. Les résultats cinétiques obtenus sous air, ne montrent pas de différences notables que l’oxydation soit réalisée en conditions sèche ou humide (quelque soit le taux de vapeur d’eau). Les résultats n’ont pas montré de breakaway pour les durées d’oxydation allant jusqu’à 48 heures. Ceci est attribué au fait qu’il n’y a pas formation d’oxydes de fer sachant que l’alliage contient seulement 0,23% en masse de fer. Les résultats de DRX montrent la formation des mêmes phases quel-que-soit le gaz vecteur utilisé (en atmosphère sèche ou humide). A 900 et 1000°C, l’oxyde Cr2O3 est détecté ainsi que deux composés intermétalliques : Ni3Mo et NbNi4. En revanche à 1100°C, l’oxyde Cr2O3 est toujours présent mais les composés intermétalliques sont oxydés pour donner un oxyde mixte CrNbO4. L’oxydation du molybdène au dessus de 1000°C conduit à la formation de MoO3 qui est un oxyde volatil. Les analyses morphologiques, ont montré la présence de couches de chromine plus plastiques avec une porosité répartie sur toute l’épaisseur de la couche pour les essais réalisés en présence de vapeur d’eau. Les couches d’oxyde sont alors plus adhérentes. Ceci a été confirmé par des essais d’oxydation en conditions cycliques, qui ont montré notamment à 1100°C, une meilleure tenue mécanique de la couche d’oxyde en présence de vapeur d’eau. Les tests d’oxydation en présence d’un marquage à l’or a aussi permis de mettre en évidence un mécanisme d’oxydation mixte pour les oxydations réalisées en atmosphères riche en oxygène que l’on soit sous atmosphère sèche ou humide. En revanche, le marquage à l’or a montré la présence d’un mécanisme d’oxydation interne pour les atmosphères pauvres en oxygène, avec des couches d’oxydes présentant une adhérence parfaite. Le fait d’ajouter de la vapeur d’eau à ces atmosphères pauvres en oxygène, entraine la réapparition d’un mécanisme de diffusion mixte. / This work is a part of a research project which has for essential objective the study of water vapor influence in high temperature oxidation for a chromia forming nickel base alloy. Alloy studied for this study is the SY 625. Originality of this study is based on an experimental assembly use, create in the laboratory. This assembly called “water vapor assembly” is used for realized SY 625 high temperature oxidation (900-1100°C) in presence of water vapor (7,5 and 33 vol. % water vapor) with various carriers gas (oxygen, air, argon and nitrogen) in isothermal and cyclic conditions. The kinetic results obtained under air, do not show considerable differences that the oxidation is realized in dry or wet conditions (with the various water vapor rate). The results do not show breakaway for the oxidation durations going to 48 hours. This is attributed to the fact that there is no formation of oxides iron knowing that the alloy contains only 0,23 mass % of iron. The XRD results show the formation of the same phases which is the carrier gas used (in dry or wet atmosphere). At 900 and 1000°C, the Cr2O3oxide is detected with two intermetallic compounds : Ni3Mo and NbNi4. On the other hand at 1100°C, the oxide Cr2O3 is always present but the intermetallic compounds are oxidized to give a mixed oxide CrNbO4. The oxidation of the molybdenum above 1000°C leads to the formation of MoO3 which is a volatile oxide. The morphological analyses, showed the presence of more plastic chromia layers with a distributed porosity on all the thickness of the layer for the test realized in water vapor presence. The oxide layers are then more adherents. This was confirmed by oxidation test in cyclic conditions, which showed in particular at 1100°C, a better mechanical behavior of oxide layer in water vapor presence. The oxidation tests with gold marker experiments are also showed a mixed oxidation mechanism for the oxidations realized in rich oxygen atmospheres under dry or wet atmosphere. On the other hand, gold marker experiments showed the presence of a internal oxidation mechanism for poor oxygen atmospheres, with oxides layers showing a perfect adhesion. The fact of adding water vapor to these poor oxygen atmospheres, lead to the reappearance of a mixed diffusion mechanism.
126

Zugbeeinflussungssysteme in Polen, der Slowakei und Tschechien

Dorka, Moritz 31 August 2012 (has links)
In dieser Arbeit sollen die maßgeblichen nationalen Zugbeeinflussungssysteme der Länder Polen (SHP, Radio-Stop, KHP), Slowakei und Tschechien (LS, MIREL VZ1) vorgestellt und miteinander verglichen werden. Der Fokus liegt dabei auf einer funktionellen Betrachtung, wobei auch der technische Hintergrund nicht unberücksichtigt bleibt. Ein Ausblick auf die zukünftigen Bemühungen hinsichtlich ETCS rundet den Überblick ab.:1 Übersicht . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 LS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 Zielstellung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Funktionsweise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 Betriebsmodi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.4 MIREL VZ1-Erweiterungen . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.5 Weitere Entwicklungen in der Slowakei und in Tschechien . . . . . . . . . . 13 3 SHP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.1 Zielstellung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.2 Funktionsweise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.3 KHP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.4 Radio-Stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.5 Weitere Entwicklungen in Polen . . . . . . . . . . . . . . . . . . . . . . . . 19 4 Literaturverzeichnis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 / This paper compares the major national train protection systems of Poland (SHP, Radio-Stop, KHP), the Slovak Republic and Czechia (LS, MIREL VZ1). The emphasis is placed on a functional description, while mentioning the relevant technical background where necessary. An outlook on future developments regarding ETCS in the respective countries concludes each chapter.:1 Übersicht . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 LS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 Zielstellung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Funktionsweise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 Betriebsmodi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.4 MIREL VZ1-Erweiterungen . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.5 Weitere Entwicklungen in der Slowakei und in Tschechien . . . . . . . . . . 13 3 SHP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.1 Zielstellung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.2 Funktionsweise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.3 KHP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.4 Radio-Stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.5 Weitere Entwicklungen in Polen . . . . . . . . . . . . . . . . . . . . . . . . 19 4 Literaturverzeichnis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
127

Modelle zur Beschreibung der Verkehrssicherheit innerörtlicher Hauptverkehrsstraßennetze unter besonderer Berücksichtigung der Umfeldnutzung

Aurich, Allan 17 May 2013 (has links)
In der Arbeit wird eine Methodik einer zusammenhängenden Analyse und modellhaften Beschreibung der Verkehrssicherheit in städtischen Hauptstraßennetzen am Beispiel der Stadt Dresden entwickelt. Die dabei gewonnenen Modelle dienen der Abschätzung von Erwartungswerten von Unfallhäufigkeiten mit und ohne Personenschaden unter Berücksichtigung der Verkehrsbeteiligungsart. Die Grundlage bilden multivariate Regressionsmodelle auf Basis verallgemeinerter linearer Modelle (GLM). Die Verwendung verallgemeinerter Regressionsmodelle erlaubt eine Berücksichtigung von Verteilungen, die besser geeignet sind, den Unfallentstehungsprozess wiederzugeben, als die häufig verwendete Normalverteilung. Im konkreten Fall werden hierzu die Poisson-Verteilung sowie die negative Binomialverteilung verwendet. Um Effekte im Hauptverkehrsstraßennetz möglichst trennscharf abbilden zu können, werden vier grundsätzliche Netzelemente differenziert und das Netz entsprechend zerlegt. Unterschieden werden neben Streckenabschnitten und Hauptverkehrsknotenpunkten auch Annäherungsbereiche und Anschlussknotenpunkte. Die Kollektive der Knotenpunkte werden ferner in signalisierte und nicht-signalisierte unterteilt. Es werden zunächst Modelle unterschiedlicher Unfallkollektive getrennt für alle Kollektive der vier Netzelemente berechnet. Anschließend werden verschiedene Vorgehensweisen für eine Zusammenfassung zu Netzmodellen entwickelt. Neben der Verwendung verkehrstechnischer und infrastruktureller Größen als erklärende Variable werden in der Arbeit auch Kenngrößen zur Beschreibung der Umfeldnutzung ermittelt und im Rahmen der Regression einbezogen. Die Quantifizierung der Umfeldnutzung erfolgt mit Hilfe von Korrelations-, Kontingenz- und von Hauptkomponentenanalysen (PCA). Im Ergebnis werden Modelle präsentiert, die eine multivariate Quantifizierung erwarteter Unfallhäufigkeiten in Hauptverkehrsstraßennetzen erlauben. Die vorgestellte Methodik bildet eine mögliche Grundlage für eine differenzierte Sicherheitsbewertung verkehrsplanerischer Variantenabschätzungen. / A methodology is developed in order to predict the number of accidents within an urban main road network. The analysis was carried out by surveying the road network of Dresden. The resulting models allow the calculation of individual expectancy values for accidents with and without injury involving different traffic modes. The statistical modelling process is based on generalized linear models (GLM). These were chosen due to their ability to take into account certain non-normal distributions. In the specific case of accident counts, both the Poisson distribution and the negative binomial distribution are more suitable for reproducing the origination process than the normal distribution. Thus they were chosen as underlying distributions for the subsequent regressions. In order to differentiate overlaying influences, the main road network is separated into four basic elements: major intersections, road sections, minor intersections and approaches. Furthermore the major and minor intersections are additionally subdivided into signalised and non-signalised intersections. Separate models are calculated for different accident collectives for the various types of elements. Afterwards several methodologies for calculating aggregated network models are developed and analysed. Apart from traffic-related and infrastructural attributes, environmental parameters are derived taking into account the adjacent building structure as well as the surrounding land-use, and incorporated as explanatory variables within the regression. The environmental variables are derived from statistical analyses including correlation matrices, contingency tables and principal components analyses (PCA). As a result, a set of models is introduced which allows a multivariate calculation of expected accident counts for urban main road networks. The methodology developed can serve as a basis for a differentiated safety assessment of varying scenarios within a traffic planning process.
128

[pt] ESTUDO POR MICROSCOPIA ELETRÔNICA ANALÍTICA E EM ALTA RESOLUÇÃO DA SUPERLIGA 625 A BASE DE NI PRODUZIDA POR IMPRESSÃO DIGITAL A LASER / [en] HIGH RESOLUTION ANALYTICAL ELECTRON MICROSCOPY STUDY OF NI- BASE SUPER ALLOY 625 PRODUCED BY DIGITAL LASER PRINTING

CILENE LABRE ALVES DA SILVA DE MEDEIRO 01 July 2020 (has links)
[pt] A presente tese tem como objetivo estudar a estabilidade microestrutural da superliga 625 a base de Ni pelas suas propriedades mecânicas e suas várias aplicações na indústria, em três condições distintas: maciça (placa forjada industrialmente), partículas de pó precursora da peça 3D e uma peça produzida por impressão a laser (Deposição Direta de Metais - DMD). Amostras destas condições foram submetidas a tratamentos de solubilização e envelhecimento isotérmico a 650 graus Celsius e 750 graus Celsius durante 10 horas e 100 horas, de modo a promover fenômeno de precipitação e, assim, correlacionar com as propriedades mecânicas do material. A caracterização microestrutural foi realizada por microscopia ótica (MO), microscopia eletrônica de varredura (MEV), microscopia eletrônica de transmissão (MET) no modo convencional utilizando contraste de difração, na modalidade analítica de transmissão/varredura (STEM), e em alta resolução (HRTEM). Espectroscopias de raios X por dispersão em energia (EDS) e de perdas de energia de elétrons (EELS) foram utilizadas para analisar a composição local da matriz e das fases presentes. Foram realizados ensaios de microdureza para avaliar o efeito dos tratamentos térmicos. A análise microestrutural da amostra maciça na condição como recebida apresentou grãos equiaxiais com fases NbTiC e M6C. Com o tratamento térmico de solubilização a 1100 graus Celsius por 40 minutos houve uma dissolução parcial dos carbetos. O envelhecimento a 650 graus Celsius por 10 horas resultou em carbetos de NbTiC e um aumento da dureza em 5 porcento em relação a amostra como solubilizada. Entretanto no tratamento de envelhecimento a 100 horas ocorreu precipitação homogênea da fase gama aumentando a dureza do material em 45 porcento, se comparada à mesma como solubilizada. A liga maciça envelhecida a 750 graus Celsius por 10 horas apresentou os carbetos NbTiC e M23C6 nos contornos de grãos e dispersos na matriz. Já a liga maciça envelhecida por 100 horas a esta mesma temperatura, apresentou a fase δ dispersa na matriz. A análise microestrutural do pó precursor mostrou ser policristalino constituído predominantemente de grãos colunares da matriz austenítica. Análises das amostras produzidas por DMD como recebida revelou estrutura dendrítica com carbetos de Nb e fase Laves nas regiões interdendríticas. A solubilização das amostras DMD durante 40 minutos por 1100 graus Celsius e 1200 graus Celsius mostrou ser insuficientes para a dissolução dos precipitados. A fim de melhorar a difusão do Nb e a dissolução dos carbetos e da fase Laves, foi realizado o tratamento de solubilização a 1200 graus Celsius por 100 horas. Esta amostra tratada a 650 graus Celsius por 100 horas apresentou carbetos M23C6 precipitados nos contornos de grão e nas interfaces entre matriz CFC e a fase Laves. Entretanto, no envelhecimento a 750 graus Celsius durante 100 horas ocorreu à precipitação dos carbetos M23C6 e M6C nos contornos de grão e dispersos na matriz, aumentando assim a dureza do material em 18 porcento, se comparada à mesma como solubilizada. O aumento da microdureza em 12 porcento após o tratamento térmico está relacionado à precipitação dos carbetos nos contornos de grão e dispersos na matriz resultado dos tratamentos térmicos de envelhecimento. / [en] This thesis studies the microstructural stability of Ni-base Super alloy 625 for its mechanical properties and its varieties of applications in the industry, in three different conditions: bulk (industrially forged plate), precursor powder particles for 3D printing process and a sample produced by laser Direct Metal Deposition (DMD). Aiming at promoting precipitation processes and, therefore, correlate with the mechanical properties of the material, samples of these conditions were submitted to solution annealing and isothermal aging treatments at 650 Celsius degrees and 750 Celsius degrees for 10 hours and 100 hours. Characterization of the microstructure was performed by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), in the conventional diffraction contrast mode, scanning/transmission (STEM) analytical mode, and high resolution microscopy (HRTEM). Energy dispersive X-ray spectrometry (EDXS) and electron energy loss spectroscopy (EELS) were used to analyze the local composition of the matrix and precipitated phases. Micro hardness measurements were performed to evaluate the effect of thermal treatments. The microstructural analysis of the bulk sample in the as-received condition showed an equiaxial grain structure with NbTiC and M6C precipitated phases. Solid solution treatment at 1100 Celsius degrees for 40 minutes allowed partial dissolution of the carbides. Aging at 650 Celsius degrees for 10 hours showed NbTiC carbides and a hardness increase of 5 percent compared to the as-solubilized sample. However, aging at this temperature for 100 hours promoted the homogeneous precipitation of the gama phase, thus increasing the material s hardness by 45 percent, when compared to it as solubilized. The bulk sample aged at 750 Celsius degrees for 10 hours showed grain boundary and homogeneous precipitation of NbTiC and M23C6 carbides. This sample condition upon aging at this temperature for 100 hours shows δ phase homogeneously precipitated in the matrix. The microstructural analysis of the precursor powder showed micrometer size individual particles as polycrystalline, consisting predominantly of columnar grains of the austenitic matrix. Analysis of samples produced by DMD in the as-received condition revealed dendritic microstructure with carbides of Nb and Laves phase in the interdendritic regions. The solution treatment of the DMD samples for 40 minutes at 1100 Celsius degrees and 1200 Celsius degrees proved to be insufficient for the dissolution of the precipitate. In order to enhance diffusion of Nb and so carbide and Laves phase dissolution, a solution anneal was carried out at 1200 Celsius degrees for 100 hours. This sample treated at 650 Celsius degrees for 100 hours showed M23C6 carbides precipitated at grain boundaries and also at the Laves phase/matrix interfaces. However, upon aging at 750 Celsius degrees for 100 hours the precipitation of M23C6 and M6C takes place at the grain boundary and in the austenitic matrix, thus increasing the material s hardness by 18 percent, when compared to it as solubilized. The increase of the hardness by 12 percent after the heat treatment is related to the precipitation of the carbides in the grain boundaries and dispersed in the matrix resulting from the aging thermal treatments.
129

Optimización y análisis de comportamiento de sistemas de sujeción para vías de ferrocarril de alta velocidad española

Carrascal Vaquero, Isidro Alfonso 06 October 2006 (has links)
Los nuevos ferrocarriles de Alta Velocidad Española (AVE) suponen, respecto a su predecesor, la línea Madrid-Sevilla, un incremento en la velocidad máxima, pasando de los 280-300 km/h de la línea original a los 350 km/h que se pretende alcanzar en los nuevos trazados. Este incremento de velocidad origina mayores solicitaciones que afectan a la superestructura de la vía y, por ello, se hace necesario un redimensionado de todos los parámetros de diseño del trazado. Entre los componentes de la superestructura se encuentra el sistema de sujeción. Este sistema está constituido por un conjunto de pequeños elementos de vía que fijan el carril a la traviesa dando continuidad estructural a la vía. El sistema de sujeción cobra mayor importancia debido a este incremento de los esfuerzos originado por el aumento de las velocidades, convirtiéndose en un elemento clave de la superestructura de vía. Esta Tesis, pretende, en primer lugar, encontrar el sistema óptimo de sujeción que se adapte a las exigencias establecidas por la administración en el "Pliego de bases para el suministro de sujeciones" para ferrocarriles de alta velocidad. En segundo lugar, una vez definido el sistema, analizar el comportamiento de la sujeción, tanto desde el punto de vista individual de cada componente, como desde el punto de vista global. Este análisis incluye la totalidad de propiedades importantes del sistema, desde las mecánicas, ya sean estáticas o dinámicas, hasta las eléctricas, pasando, entre otras, por las de durabilidad y deterioro. También, se estudiarán las posibles variaciones sufridas por estas propiedades en función de parámetros externos, como pueden ser los de carácter ambiental, e internos propios del sistema de sujeción. / The new Spanish High Speed Railways (AVE) involve, regarding its predecessor, Madrid-Seville line, an increase in the maximum speed, going from 280-300 km / h of the original line to 350 km / h that expects in the new routes. This speedup produces greater efforts that affect the superstructure of the track and, therefore, resizing of all design parameters of the track is required. The fastening system is among the components of the superstructure. This system is made up of a set of small track pieces that fasten the rail to the sleeper giving structural continuity to the track. The fastening system is becoming more important because of this greater efforts caused by the increased speeds, becoming a key element of the track superstructure. The aim of this thesis is, first, to find the optimum fastening system that well suits the requirements set by the administration in the "Terms for the supply of fasteners" for high speed railways. Secondly, this thesis, once the system has defined; analyzes the behaviour of the fastening, both from the point of view of individual component, and from a global perspective. This analysis includes all the important properties of the system, from the mechanical properties, whether static or dynamic, to the electrical properties, besides the hardness and deterioration. Also, the possible changes undergone for these properties depending of external parameters, such as the environmental measure, and own internal parameters of the fastening system were studied.
130

Desarrollo y análisis de pavimentos industriales desde el punto de vista del acabado superficial

García Hernández, Álvaro 29 January 2008 (has links)
En teoría, el inicio del proceso de flotado de un pavimento de hormigón deberá coincidir con el tiempo de inicio de fraguado. Para resolver este problema, se desarrolló un modelo teórico sobre la evolución de la resistencia a penetración del hormigón antes del inicio de fraguado. Por otra parte, en esta Tesis Doctoral también se ha desarrollado un procedimiento muy sencillo para conocer la energía de activación del hormigón a través de ensayos de Vicat. En esta Tesis se ha hecho también un análisis comparativo de los seis tipos de acabados para pavimentos de hormigón más representativos mediante diferentes tipos de ensayos. Así como un análisis del comportamiento a impacto del pavimento de hormigón. Finalmente, se ha propuesto un modelo para conocer el comportamiento del pavimento sujeto a la abrasión. En él se obtuvo un nuevo modelo estadístico, que puede ser la base de una futura investigación en este campo. / Theoretically, the time of troweling a concrete pavement coincides with the setting time. To solve this problem, a theoretical model of the penetration resistance evolution of concrete during the setting time was developed. A new methodology to know the temperature influence on the setting times of concrete and on the time of toweling the pavement has been also performed.Besides, from six experimental pavements with the most representative type of finishing at the time of carrying out the study, a comparative analysis among them was done by means of different types of tests. Moreover, an analysis of the dynamic behavior of the pavement was carried out to know the protective effect of the type of finishing on the slab. Finally, a model for the dynamic behavior of a concrete pavement subjected to abrasion was made.

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