• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 13
  • 3
  • 2
  • 2
  • 2
  • 2
  • 1
  • Tagged with
  • 27
  • 27
  • 8
  • 6
  • 5
  • 4
  • 4
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 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.
21

Grundlagen zur Optimierung der Rütteldruckverdichtung

Hell, Marylin 24 June 2024 (has links)
Das Thema der Optimierung der Rütteldruckverdichtung ist seit vielen Jahrzehnten Gegenstand der Forschung. In dieser Arbeit werden die bisher untersuchten Mechanismen und Erkenntnisse zusammengefasst. Es ergeben sich jedoch einige Fragestellungen, aus denen sich die Forschungsfragen der vorliegenden Arbeit ableiten lassen. Die meisten Erkenntnisse sind theoretischer Natur und vieles wurde in der Praxis noch nicht nachgewiesen. Aus diesem Grund wurde ein Modellversuchsstand aufgebaut, der die Rütteldruckverdichtung mit einem Modellrüttler realitätsnah abbilden kann. Die darin eingebaute Sensorik wird im Rahmen einer Parameterstudie eingesetzt, bei der Standardversuche zur Rütteldruckverdichtung mit Parametervariationen durchgeführt werden. Durch die Parameterstudie konnten einige Vermutungen, die bisher nur theoretischer Natur waren oder aus der praktischen Anwendung stammen, erstmals nachgewiesen werden. Dazu gehören ein großer Einfluss der Schwingwegamplitude auf die Verdichtung sowie ein starker Einfluss der eingestellten Verdichtungsfrequenz. Diese Parameter sollten optimiert und nicht maximiert werden, da dies die Verdichtung wieder verschlechtern kann. Darüber hinaus hat sich der Vorlaufwinkel als geeigneter Regelparameter erwiesen, da er ein reproduzierbares Verhalten in gleichen Tiefenlagen zeigt. Weiter zeigt er das Ende eines Verdichtungsschritts in der jeweiligen Tiefenlage an, wenn er einen nahezu konstanten Wert erreicht. Zudem konnte durch den Vergleich verschiedener Verdichtungsverfahren die schrittweise Verdichtung gegenüber dem Pilgerschrittverfahren und dem konstanten Ziehen als beste Methode identifiziert werden. Auf Basis der Auswertungen wurde ein neuer Regelparameter eingeführt. Mit Hilfe des Sensorphasenwinkels kann das Bewegungsverhalten des Rüttlers erfasst und ein unrundes Bewegungsverhalten erkannt werden. Des Weiteren konnte ein Einfluss der Spülmethode, des Spüldurchsatzes und der Kornzertrümmerung festgestellt werden. Eine optimierte Verdichtungskontrolle und ein optisches Verfahren zur qualitativen Bewertung der Verdichtung wurden erstmals eingesetzt. Kern der vorliegenden Arbeit ist die Optimierung der Rütteldruckverdichtung. Hierzu konnten geeignete Regelparameter identifiziert und in Form eines multikriteriellen Regelalgorithmus umgesetzt werden. Dieser wurde für das Eindringen und Heben vorgeschlagen und erstmals für die Verdichtung angewendet. Der Modellrüttler passte seine Frequenz anhand der aufgezeichneten Sensordaten an die umgebenden Bodeneigenschaften an. Die dabei verwendeten Regelparameter wurden variiert und mit Großversuchen verglichen, um Wege und Potentiale aufzuzeigen, die im Großgerät Anwendung finden sollten. Die vorliegende Arbeit legt den Grundstein, um die gewonnenen Erkenntnisse in weiteren Modellversuchen anzuwenden und die neu entstandenen Forschungsfragen zu beantworten. Dadurch kann die Rütteldruckverdichtung optimiert werden, um in Zukunft ressourcenschonender und intelligenter eingesetzt zu werden.
22

Métodos e processos para a análise experimental de sistemas oceânicos de produção de petróleo e gás. / Methods and procedures for the experimental analysis of offshore systems for oil and gas production.

Malta, Edgard Borges 09 April 2010 (has links)
O aumento na complexidade das operações de sistemas de produção de petróleo e gás no mar e um fato concreto. Atualmente, a necessidade de avaliar o comportamento no mar destes sistemas requer a compreensão de fenômenos, até então, pouco explorados e que tornam imprescindível uma investigação apoiada em experimentos com modelos reduzidos. Resultados obtidos em tanques de provas, por sua vez, requerem metodologias que contam com a experiência do pesquisador e que, em muitos casos, não são encontradas de maneira detalhada o suficiente na literatura. Ou seja, muitas destas metodologias normalmente são encontradas, no entanto, não em nível para que pesquisadores iniciantes desenvolvam atividades experimentais minimamente pertinentes as eventuais tomadas de decisão ou confrontação com outras linhas de abordagem como a analítica e/ou a numérica. Portanto, e exatamente neste contexto que se insere a presente dissertação de mestrado, buscando descrever em detalhes a teoria e prática envolvida nos procedimentos experimentais para o estudo de comportamento no mar típico de uma plataforma padrão, perfeitamente adaptáveis a outras geometrias mais complexas de sistemas navais e oceânicos. Esses procedimentos envolvem desde o planejamento dos ensaios necessários, passando pelos cuidados durante sua execução, culminando nos métodos de análise dos resultados e formas usuais de documentação. Para facilitar o processo de compreensão, além do próprio texto, este trabalho também contemplou a construção de uma ferramenta matemática dedicada a condução das atividades acima, destacando-se a avaliação e obtenção de parâmetros a partir de ensaios de decaimento e o levantamento expedito das curvas de resposta em ondas regulares, transientes e irregulares. / The increasing complexity of o shore system operations for oil and gas production is a reality. Currently, the need to evaluate the seakeeping of these systems requires understanding some phenomena not yet explored and, for that reason, researches using experiments with small scale models become indispensable. Results obtained in model basins require methodologies that rely on the researchers experience and, most of the time, they are not found detailed enough in the literature. When many of these methodologies are usually found, however, they are not ready for beginner researchers to develop experimental activities minimally relevant to any decision and/or confrontation with other lines, such as the analytical and/or numerical approaches. Therefore, the context of this dissertation describes in detail the theory and involved practice in an experimental procedure for the study of seakeeping of a standard platform, perfectly adaptable to other complex geometries and naval systems. These procedures involve the planning of the necessary tests, through the care during their execution, culminating in the methods of result analyses and usual forms of documentation. In order to facilitate the process of understanding, the construction of a dedicated mathematical tool to conduct the activities described above is provided, emphasizing the assessment and quick obtaining parameters from decay tests, curves response in regular and transient waves, among many others.
23

Métodos e processos para a análise experimental de sistemas oceânicos de produção de petróleo e gás. / Methods and procedures for the experimental analysis of offshore systems for oil and gas production.

Edgard Borges Malta 09 April 2010 (has links)
O aumento na complexidade das operações de sistemas de produção de petróleo e gás no mar e um fato concreto. Atualmente, a necessidade de avaliar o comportamento no mar destes sistemas requer a compreensão de fenômenos, até então, pouco explorados e que tornam imprescindível uma investigação apoiada em experimentos com modelos reduzidos. Resultados obtidos em tanques de provas, por sua vez, requerem metodologias que contam com a experiência do pesquisador e que, em muitos casos, não são encontradas de maneira detalhada o suficiente na literatura. Ou seja, muitas destas metodologias normalmente são encontradas, no entanto, não em nível para que pesquisadores iniciantes desenvolvam atividades experimentais minimamente pertinentes as eventuais tomadas de decisão ou confrontação com outras linhas de abordagem como a analítica e/ou a numérica. Portanto, e exatamente neste contexto que se insere a presente dissertação de mestrado, buscando descrever em detalhes a teoria e prática envolvida nos procedimentos experimentais para o estudo de comportamento no mar típico de uma plataforma padrão, perfeitamente adaptáveis a outras geometrias mais complexas de sistemas navais e oceânicos. Esses procedimentos envolvem desde o planejamento dos ensaios necessários, passando pelos cuidados durante sua execução, culminando nos métodos de análise dos resultados e formas usuais de documentação. Para facilitar o processo de compreensão, além do próprio texto, este trabalho também contemplou a construção de uma ferramenta matemática dedicada a condução das atividades acima, destacando-se a avaliação e obtenção de parâmetros a partir de ensaios de decaimento e o levantamento expedito das curvas de resposta em ondas regulares, transientes e irregulares. / The increasing complexity of o shore system operations for oil and gas production is a reality. Currently, the need to evaluate the seakeeping of these systems requires understanding some phenomena not yet explored and, for that reason, researches using experiments with small scale models become indispensable. Results obtained in model basins require methodologies that rely on the researchers experience and, most of the time, they are not found detailed enough in the literature. When many of these methodologies are usually found, however, they are not ready for beginner researchers to develop experimental activities minimally relevant to any decision and/or confrontation with other lines, such as the analytical and/or numerical approaches. Therefore, the context of this dissertation describes in detail the theory and involved practice in an experimental procedure for the study of seakeeping of a standard platform, perfectly adaptable to other complex geometries and naval systems. These procedures involve the planning of the necessary tests, through the care during their execution, culminating in the methods of result analyses and usual forms of documentation. In order to facilitate the process of understanding, the construction of a dedicated mathematical tool to conduct the activities described above is provided, emphasizing the assessment and quick obtaining parameters from decay tests, curves response in regular and transient waves, among many others.
24

Lávky pro pěší tvořené plochým obloukem / Pedestrian bridges formed by a flat arch

Jurík, Michal January 2012 (has links)
This doctoral thesis focuses on the research of the pedestrian bridges formed by the flat arch. To understand the basic static behaviour of the flat arch it was necessary to make a study of the development of the direct flat arch as footbridge with large span and the impact of stiffness on its camber. For the mathematical modeling FEM software ANSYS were used. The calculation has shown that a design of purely concrete flat arch would demand enormous bending stiffness, which can be achieved only through a massive cross-section. The findings gained in this chapter were further used to design a unique pedestrian bridge formed by the curved in plan flat arch, where to transfer of the large bending moments a steel pipe was designed. Several variants with different span and rise of the arch in plan were tested. From the tested variants was then selected footbridge with a span of 45 m and with the rise of the arch 10 m, which seemed to be the best solution according to the calculations and it was further analyzed in detail. The studied structure is formed by curved concrete slab that is stiffened through the steel brackets on the inner side of a steel tube with a graded thickness. The external cables that are situated in the handrail pipe balance the dead load torsional moment. Designed structure and the static analysis procedure were verified on a fully functional 1:6 scale model. The thesis describes the model analogy used for the design of the model, its structural design and its implementation. Load tests on the model confirmed correctness of the design of the proposed curved in plan pedestrian bridge, its high carrying capacity and the accuracy of the developed procedure of static analysis. Results and experiences acquired from the design and the realization of model are the basis for a practical realization of studied structures. The last part of the thesis deals with the possibility of replacement of the steel components with concrete in pedestrian bridges formed
25

Analýza půdorysně zakřivených závěsných a visutých lávek / Analysis of a plan curved cable stayed and suspension footbridges

Koláček, Jan January 2013 (has links)
The aim of the doctoral thesis focuses on the static and dynamic analysis of a plan curved cable stayed and suspension pedestrian bridges suspended on a single-side of their deck. The first part of this thesis deals with an analysis of the equilibrium in the transversal direction of a deck cross section suspended on a single-side. The section and its arrangement should be designed so that the torsion caused by the deck self-weight and dead load would be minimal. This theory was verified on a simple study of a single-sided suspended section with and without prestressing. Second part of the thesis deals with the design of a study of a plan curved cable stayed pedestrian bridge. The study describes in detail a finding of an initial state of the structure and the static and dynamic analysis performed by software ANSYS. The static analysis describes the response of the structure on the most frequent variable loads only, but not design of dimensioning according to the valid codes. The dynamic analysis verifies a predisposition of the structure to the vibrations and others harmful oscillation effects. The next objective of the thesis was to design a study of a plan curved suspension pedestrian bridge suspended on a single-side. A process of an analysis of these structures has not found in any available references. Especially, the finding of an initial state of a suspension cable has not been documented anywhere and by anybody. The study was analyzed with the same geometry as the cable stayed variation in order to compare both structures. The static and dynamic analysis was performed, too. The last part of the thesis describes the verification of structural solution on a fully functional model in a 1:10 scale, proposed process of the initial state finding, response of the structures on the loading and ultimate load test. The important step is the comparison of the results of the completed physical model and the calculation model.
26

Půdorysně zakřivená konstrukce z předpjatého pásu. / Stress ribbon curved structure

Kocourek, Petr January 2013 (has links)
The theme of this doctoral thesis is research of footbridges curved in plan that are formed by stress ribbon. Recently, several noteworthy curved pedestrian bridges, which decks are suspended on their inner edges on suspension or stay cables, have been constructed. However, curved stress ribbon bridges have not been built so far. The goal of this study was to answer the question whether the use of curved stress ribbon structures is even possible. For this reason, in the first stage feasibility study of these structures has been prepared. Knowledge of both curved pedestrian bridges, which decks are suspended on their inner edge and straight stress ribbon has been used. For the mathematical modeling FEM software ANSYS was used. The obtained findings were further used to design a new type of a modern, aesthetic curved bridge for pedestrians. The structure is formed by slender reinforced deck, which is through the steel brackets on the inner side stiffened by steel section. Torsion of the deck, caused by curved structure and asymmetrical cross-section, is reduced by cable situated in the handrail. Footbridge span is 45 m, arc camber in plan is 10 m, free bridge width is 3 m. Described is a general structure effect, detail static and dynamic analysis was carried out. Designed structure including construction stages were experimentally verified on a fully physical functional 1:6 scale model. The thesis describes the model analogy used for the design of the model, its structural design and its implementation. The model was subjected to a series of load tests including the final ultimate strength test. Performed tests confirmed the good match of calculation with the reality, correctness of the design and high resistance of designed construction. Acquired results and experiences from design and realization of model form the basis for practical realization of studied structures.
27

Modelling and Design of a Test Rig to investigate the dynamic behaviour of a Servo driven Powertrain

Wittwer, Max 14 December 2017 (has links)
In the present work a simulation model for examining the fundamental dynamic behaviour of a servo driven powertrain is developed. This powertrain consists of a permanent magnet synchronous motor, a cycloidal gearbox and a torque motor to apply a load. On basis of this model the selection of components for the design of a test rig is possible. This leads to the constructive draft of the test rig. In order to model the system, the fundamentals give a brief overview of the components incorporated in the test rig system. With ais of the specified task the simulation purpose is defined and the modelling process enabled. The subsequent system analysis is performed intensively to decompose the system into subsystems, which are then investigated to find the optimal modelling approach for the given simulation task. Particular emphasis is put on the investigation of the cycloidal gearbox subsystem and it shows, that approaches for modelling the dynamic behaviour of the gearbox as a whole have only been published partially. Therefore, the available modelling approaches are analysed and suitable models are developed as conceptual models. Those will be formalised and implemented in Matlab/Simulink. The model is verified and simulation experiments are performed, that help in the selection of suitable test rig components. On basis of a flexible test rig, finally the constructive draft is presented.:1 Introduction 1.1 Motivation 1.2 Procedure 2 Fundamentals 2.1 Definitions 2.2 Modelling 2.3 Servo Drive 2.3.1 Introduction 2.3.2 Permanent Magnet Synchronous Motor 2.3.3 Servo Inverter 2.3.4 Control System 2.4 Torque Motor 2.5 Gearbox 3 Specified Task 4 System Analysis 4.1 Introduction 4.2 Servo Inverter 4.3 Control System 4.4 Servo Motor 4.5 Transmission Elements 4.6 Cycloidal Gearbox 5 Model Formalisation 5.1 Introduction 5.2 Servo Inverter 5.3 Control System 5.4 Servo Motor 5.5 Transmission Elements 5.6 Cycloidal Gearbox 6 Model Implementation 6.1 Introduction 6.2 Servo Inverter 6.3 Control System 6.4 Servo Motor 6.5 Transmission Elements 6.6 Cycloidal Gearbox 7 Simulation 7.1 Introduction 7.2 Solver 7.3 Verification 7.4 System Evaluation 7.4.1 Sensitivity Analysis 7.4.2 Stability Analysis 8 Design of the Test Rig 8.1 Selection of the components 8.2 Constructive Draft 9 Summary and Outlook

Page generated in 0.0397 seconds