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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.
61

Pokrokové metody dělení materiálů se zaměřením na laser, vodní paprsek, elektroerosivní řezání drátem a hloubení / Advanced methods of material division focusing on laser, water jet, electroerosive wire cutting and drilling

JANOVÁ, Jana January 2017 (has links)
In the introductory part of the work carried out the theoretical research of advanced methods of cutting. Chosen methods are laser, water jet and EDM wire cutting and trenching the wire. There is described the history, the principle of separation and classification. The practical part of these methods are discussed in detail with emphasis on their use in practice. The text is supplemented with illustrative examples of products. Finally, the work focuses on the comparison of the described methods. Overall, the work is conceived as a methodological text useful in teaching this topic.
62

Diagnostika vlastností betonů vystavených působení vysokých teplot / Diagnostic properties of concrete exposed to high temperatures

Hudský, Petr January 2014 (has links)
This master’s thesis studies the problems of high temperatures on cement concretes, their following diagnostics from pre-treatment to rehabilitation, the emphasis was on the use of high-speed water jet. In the experimental part of the design of a concrete composition with basalt aggregate. Were reviewed the physico-mechanical properties after thermal loading. The influence of pressure water jet on the thermal load on concrete, pull-off test, the volume of the removed concrete with a strength evaluation and comparison.
63

Gravação de materiais de engenharia com jato d\'água abrasivo. / Etching on engennering material with abrasives water jet.

Valena Hennies Lauand 16 December 2009 (has links)
O presente trabalho descreve a utilização do jato d\'água abrasivo como ferramenta de gravação em ladrilhos de Mármore Branco de Cachoeiro de Itapemirim e em placas de vidro plano comum. São apresentadas as variações de desempenho do processo de gravação, assim como as várias geometrias de ranhuras obtidas com a variação de diversos parâmetros do equipamento. Os resultados da gravação em diversas amostras foram digitalizadas e fotografadas. Além disso apresenta o resultado da gravação, em mármore e vidro de um desenho de geometria complexa. Finalmente discussões e conclusões a respeito dos resultados obtidos são apresentadas. / The current thesis describes the use of abrasive water jet as an etching tool in Branco de Cachoeiro de Itapemirim Marble plate and in float glass plate. Etching process performance variations are introduced as well as different kerf geometries obtained with variation of many processes parameters. The results of the etching in several samples have been photographed and scanned. Furthermore the results of the etching of a complex drawing in marble and glass is shown. Finally conclusions and discussions over the achieved results are described.
64

Approches expérimentales et numériques de l’usinage assisté jet d'eau haute pression : étude des mécanismes d'usure et contribution à la modélisation multi-physiques de la coupe / Experimental and numerical approaches to high pressure water jet assisted machining : a study of tool wear mechanisms and contribution to the multi-physical modeling of cutting

Ayed, Yessine 05 December 2013 (has links)
Cette étude porte sur l'usinage de l'alliage de titane Ti17 avec une assistance jet d'eau haute pression. Une attention particulière a été portée à l'analyse des mécanismes de dégradation et d'usure des outils lors de l'usinage avec et sans assistance. Le suivi de l'usure est réalisé par des observations régulières au microscope électronique à balayage (MEB) et par des analyses chimiques (technique EDS) afin de déterminer les zones de dépôt de matière sur l'outil. Toutes ces observations ont permis d'expliquer les mécanismes d'usure pour une opération d'ébauche et de finition. Il a été montré que les mécanismes d'usure sont différents entre l'usinage conventionnel et l'usinage assisté. En effet, lors de l'assistance jet d'eau haute pression, certains mécanismes ne sont plus activités mais d'autres mécanismes sont accélérés. Il existe donc une pression de jet d'eau optimale pour minimiser l'usure de l'outil.Afin de mettre en évidence l'effet du jet d'eau sur les phénomènes thermomécaniques dans les zones de formation du copeau, une modélisation par éléments finis est réalisée. Un couplage fluide / structure a dû être mis en place afin de prendre en compte les actions mécaniques et thermiques du jet d'eau sur la zone de coupe. Pour cela, la loi de comportement et le modèle d'endommagement de Johnson-Cook, ont été identifiés pour le Ti17 dans des conditions extrêmes sur une large gamme de températures et de vitesses de déformation. Cette modélisation a permis de mettre en évidence, pour l'usinage assisté haute pression, la diminution de la zone de contact outil/copeau, de retrouver la fragmentation du copeau et de quantifier le refroidissement des différentes zones de cisaillement.En revanche, cette modélisation ne permet pas de connaître l'effet de l'hétérogénéité microstructurale du matériau sur la zone de coupe. Ce constat est d'autant plus important que le matériau étudié présente une taille de grain importante (de l'ordre du millimètre). Pour cela, une nouvelle modélisation (multi-échelle) a été développée afin de prendre en compte la microstructure du matériau. Le matériau est donc modélisé comme un polycristal qui prend en compte des lois de la plasticité cristalline. Cette nouvelle approche permet alors de simuler la formation du copeau en prenant en compte les orientations cristallines des grains et les changements de phase qui apparaissent lors de l'usinage. / This study focuses on the machining of the Ti17 titanium alloy using high-pressure water jet assistance. Special emphasis is placed on the analysis of degradation mechanisms and tool wear during machining, with and without assistance. Wear monitoring was achieved by regular observations using both scanning electron microscope (SEM) and chemical analysis (EDS technique) to determine the areas of material deposition on the tool. These observations made it possible to explain the wear mechanisms for roughing and finishing conditions. Wear mechanisms for conventional machining and for assisted machining were found to be significantly different. Indeed, with high-pressure water jet assistance, some tool wear mechanisms are no longer activated, whereas others are accelerated. Hence, there exists an optimum water jet pressure which minimizes tool wear.To highlight the effect of water jet assistance on the thermomechanical phenomena in the chip formation zone, finite-element modeling has been performed. Fluid/structure coupling was developed to take into account the mechanical and thermal effects of the water jet. For this to be possible, the Johnson-Cook constitutive law and damage model have been identified for the Ti17 titanium alloy, under extreme conditions, over a wide range of temperatures and strain rates. This modeling has highlighted the fact that, for high-pressure assisted machining, the tool/chip contact zone is reduced. In addition, the simulation of chip fragmentation as well as the cooling effect on the tool and workpiece is possible.However, this model does not shed light on the effect of the microstructural heterogeneity of the material in the cutting zone. This is an important observation because the material studied has a very large grain size (of the order of a millimeter). For this reason, a new (multi-scale) modeling approach has been developed to take into consideration the microstructure of the material. The material is subsequently modeled as a polycrystal which obeys crystal plasticity constitutive laws. This new approach is then used to simulate chip formation, taking into account the grain orientations and phase changes that occur during the machining process.
65

The physical and microstructural properties of peened austenitic stainless steel

Clitheroe, Linda Suzanne January 2011 (has links)
Surface treatments used to improve the life of a material known as peening are already extensively used in industry. The main aim of peening is to introduce compressive resiudal stress to the surface and subsurface of a metallic material, however literature also includes a number of microstructural and mechanical effects that peening introduces to a material when the compressive residual stress is established. The aim of this dissertation is compare and contrast the mechanical and microstructural effects of a current industrial peening method called shot peening, with three new increasingly competitive surface treatments. These are laser shock peening, ultrasonic impact treatment and water jet cavitation peening. The surface finish, and changes in microstructure, hardness depth profile, residual stress depth profile and plastic work depth profile of the four surface treatments are analysed. The effect of the peening parameters on the material is also determined, such as length of time of treatment, shot size, step size, direction of treatment, and irradiance per centimetre squared. The effect of peening on the residual stress depth profile of a gas tungsten eight pass grooved weld is also determined. Welding is a known region of early failure of material, with one of the factors affecting this being the introduction of tensile residual stress to the surface and near surface of the weld. An analysis to determine if peening the welded region alters the residual stress was carried out. In all experiments in this dissertation, the material that was used was austenitic stainless steel, as this material is highly used, especially within the nuclear industry. The results of this dissertation show that different peening types and peenign parameters produce a variety of surface, microstructural and mechanical effects to austenitic stainless steel. Peening of an aaustenitic stainless steel welded region results in teh near surface tensile residual stress to alter to ccompressive residual stress.
66

Parametry laserového paprsku / Parameters of the laser beam

Hort, Zbyněk January 2017 (has links)
The diploma thesis consists of the three main parts. The first part deals with the theoretical description of the laser technology and other unconventional technologies. In the second part, the thesis is focused on testing the parameters of the laser and evaluating the most suitable parameters. In the last part the diploma thesis deals with comparison of unconventional technologies in terms of cut quality
67

Obrábění těžkoobrobitelných materiálů pomocí vodního paprsku s abrazivem / Abrasive water jet machining of hard-to-machine materials

Kubín, Matěj January 2019 (has links)
The diploma thesis deals with unconventional technology of material separation by water jet with abrasive. It describes the influence and specification of technological parameters of the water jet on the quality of the cutting surface. The work contains an experiment, where the aim was to achieve from the theory the influence of tech-nological parameters on surface roughness on composite materials from glass fiber and carbon fiber.
68

Racionalizace malosériové výroby výpalků v podmínkách firmy PARS Nova a.s. / Rationalization of small-lot production of slops in conditions of company PARS Nova a.s.

Jurka, Pavel January 2008 (has links)
Analysis of the technological possibility ray methods of protoplasm, laser and water jet on the part of needs company Pars Nova a.s.. Propsal concrete of unconventional method. Process layout and exigencies of working designed method. Security and ecological diversification of designed method. Technical – economics evaluation contribution designed of unconventional technology.
69

Současný stav a budoucnost nekonvenční technologie vodního paprsku v podmínkách průmyslu České republiky / Status quo and future of unconventional technology water jet in conditions of industry Czech republic

Steiner, Martin January 2008 (has links)
Description of basic principle of water jet unconventional method. Description and characteristics of water jet machining. Analysis of technological potential and operation severity. Status quo and future in the Czech Republic industry condition. Comparison of water jet to other jet methods.
70

Abrazivní vodní paprsek / Abrasive Water Jet

Kopečný, Libor January 2011 (has links)
This dissertation thesis is focused on explaining the broad issue of the non-conventional machining by an abrasive water jet. Introductory chapters deal with various techniques and methods of water-jet cutting and analyze them. Then the following text provides us with a detailed description of the machine itself so that people can understand the way how this technology works. The third chapter is focused on the quality of the resulting surface and the possibility of affecting it by technological parameters. This part is connected with the practical part of my thesis, in which the resultant surfaces of various materials made by different cutting parameters were compared. Subsequent section outlines the development of this technology. The last chapter contains technical and economic evaluation.

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