High speed water jets have un-substitutable place in unconventional technologies in the machining of materials. Indeed its larger spreading is limited above all by its really high purchase price and also high costs of the operation. Certain possibility is represented by high-speed pulsating jets, which don’t put such a high pretension on arrangement of generating the pressure during the comparable operation. Probably the most effective method of the generating of pulsating water jets is ultrasonic modulation. This work could benefit to understanding spreading of pressure impulses between ultrasonic generator and output nozzle. Pulsating is solved by the numerical calculation using transfer matrix method.

Master's thesis, elaborated within Master's degree, submits a proposal of suitable technology for manufacturing “column foot“ part, which attaches filtration unit to the ground. Material is 6 mm thick sheet steel in accordance with ČSN 41 1375 norm. Run (/production batch) of the part is 4 000 pieces per year. On the basis of literary study about unconventional technologies for flat sheet metal production 3 technologies were suggested: plasma cutting, water jet cutting and laser cutting. These technologies were technologically and economically analyzed. At the end thesis evaluates whether purchase of respective machine would pay out for the firm or they should continue to buy parts from cooperation company.

This master thesis deals with the use and technological capabilities of abrasive water jet in the application of 3D cutting head. One part of this thesis is the description of waterjet technology and its other applications. The experimental comparison of the effect of the parameters was carried out for different materials Mach 4 equipment Flow International Corporation in company AWAC, spol. s.r.o. and subsequently the workpieces were subjected to evaluation of the shape and dimensional accuracy.

Cavitation is a phenomenon that occurs in liquids when the pressure drops below the vapor pressure of the liquid. Previous research has verified that cavitation bubble collapse is a dynamic and destructive process. An understanding of the behavior of cavitation is necessary to implement this destructive mechanism from an axisymmetric jet for underwater material removal. This work investigates the influence of jet pressure and nozzle diameter on the behavior of a cloud of cavitation bubbles generated by a submerged high-pressure water jet. First, this investigation is put into context with a condensed historical background of cavitation research. Second, a description of the cavitation-generating apparatus is given. Next, the experimental methods used to explore the behavior of the cavitation clouds are explained. Finally, the results of the investigation, including propagation distance, cloud width and area, pulsation frequency, and cloud front velocity are presented. Among the results is a discussion of the significant experimental factors affecting the behavior of the cavitation clouds. It is shown that the Reynolds number, specifically the diameter of the nozzle, has a significant effect on the measurements. In some cases the jet pressure, and subsequent jet velocity, had a less significant effect than was expected. Overall, this research describes the cavitation cloud formed when a submerged high-speed water jet discharges.

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.

Les revêtements organiques déposés en surface de tuyaux en fonte ductile ont pour vocation d’assurer une protection (notamment la résistance chimique, la tenue à la corrosion) vis-à-vis des effluents agressifs transportés. Pour assurer l’adhérence entre le revêtement (époxy) et son substrat, une préparation de surface est souvent nécessaire. Parmi les procédés conventionnels, le grenaillage est la solution la plus utilisée. Simple à mettre en œuvre et d’efficacité prouvée, il permet d’assurer le décapage de la surface tout en générant une rugosité adaptée. Si la solution est approuvée, des questions subsistent néanmoins quant à l’influence respective de la topographie et de la physico-chimie des surfaces. De plus, encouragées par les nouvelles réglementations environnementales, de nouvelles techniques de préparation de surface se développent.Le travail présenté s’est alors attaché à évaluer l’effet de nouvelles techniques de préparation comme le laser de structuration et le jet d’eau à ultra haute pression à comparer à d’autres procédés conventionnels tels que le brossage et le sablage. Ces nouvelles alternatives vont permettre alors de mieux comprendre l’influence du décapage et de la rugosité de surface avant la mise en peinture.Enfin, les différents résultats obtenus ont été alors spécifiquement analysés pour permettre la compréhension des phénomènes ou mécanismes d’adhésion se produisant à l’interface du couple époxy/substrat, d’un point de vue mécanique et physico-chimique. Divers moyens d’analyses ont alors pu être mis en œuvre pour caractériser les surfaces d’un point de vue morphologique (ratio de surface) et chimique (spectroscopies Raman et photoélectronique à rayons X (XPS)) pour évaluer la tenue interfaciale (test de traction adhérence). / Organic coatings applied on the surface of cast iron pipes ensure very good chemical and anti-corrosion protection against aggressive effluents. To improve adherence between coating (epoxy) and substrate, a surface preparation is required. Among conventional processes shot blasting has emerged as the most efficient and cheapest solution for ensuring stripping while generating adapted roughness. However, as it may enhance both mechanical anchorage and chemical bonding a better understanding of these phenomena should be developed. Besides new eco-friendly alternatives were investigated.Indeed, new techniques were evaluated, i.e. laser structuring and an ultra-high pressure water jet whose major benefits are understanding the effect of ablation and surface roughness prior to applying a coating. Moreover, two other conventional processes (sand blasting and brushing) were introduced to obtain a various roughness.Results obtained were then analyzed to further understand bonding mechanisms at the interface.Several processes were then implemented to evaluate the surface morphology as well as the surface chemistry (spectroscopy Raman and XPS) correlated to the adhesion mechanisms

An experimental investigation has been undertaken to study the depth of cut in multipass abrasive waterjet (AWJ) cutting of an 87% alumina ceramic with controlled nozzle oscillation. The experimental data have been statistically analysed to study the trends of the depth of cut with respect to the process parameters. It has been found that multipass cutting with controlled nozzle oscillation can significantly increase the depth of cut. Within the same cutting time and using the same cutting parameters other than the jet traverse speed, it has been found that multipass cutting with nozzle oscillation can increase the depth of cut by an average of 74.6% as compared to single pass cutting without nozzle oscillation. Furthermore, a multipass cutting with higher nozzle traverse speeds can achieve a larger depth of cut than a single pass cutting at a low traverse speed within the same cutting time. A recommendation has been made for the selection of appropriate process parameters for multipass cutting with nozzle oscillation. In order to estimate the depth of cut on a mathematical basis, predictive models for the depth of cut in multipass cutting with and without nozzle oscillation have been developed using a dimensional analysis technique. The model development starts with the models for single pass cutting which are then extended to multipass cutting where considerations are given to the change of the actual standoff distance after each pass and the variation of kerf width. These predictive models has been numerically studied for their plausibility by assessing their predicted trends with respect to the various process variables, and verified qualitatively and quantitatively based on the experimental data. The model assessment reveals that the developed models correlate very well with the experimental results and can give adequate predictions of this cutting performance measure in process planning.

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Oil Jet Cavitation Peening in Air (OPA) is capable of inducing compressive residual stress in standard aerospace materials. This paper demonstrates the process capabilities of OPA on Al 2024-T3. Specifically, changes in the workpiece residual stress, microhardness, mass loss and surface roughness are investigated as a function of the control parameters for the system. Additionally, the paper identifies a method to monitor the process in situ through the use of high frequency acoustic emission sensors. The results indicate the OPA process is capable of generating residual stresses comparable to those of standard shot peening, up to 60% of the yield strength of the material, at similar depths, around 300 µm. Finally, the acoustic emission signal may be utilized to monitor the process, specifically in predicting the microhardness and mass loss of the system.

An experimental investigation has been undertaken to study the depth of cut in multipass abrasive waterjet (AWJ) cutting of an 87% alumina ceramic with controlled nozzle oscillation. The experimental data have been statistically analysed to study the trends of the depth of cut with respect to the process parameters. It has been found that multipass cutting with controlled nozzle oscillation can significantly increase the depth of cut. Within the same cutting time and using the same cutting parameters other than the jet traverse speed, it has been found that multipass cutting with nozzle oscillation can increase the depth of cut by an average of 74.6% as compared to single pass cutting without nozzle oscillation. Furthermore, a multipass cutting with higher nozzle traverse speeds can achieve a larger depth of cut than a single pass cutting at a low traverse speed within the same cutting time. A recommendation has been made for the selection of appropriate process parameters for multipass cutting with nozzle oscillation. In order to estimate the depth of cut on a mathematical basis, predictive models for the depth of cut in multipass cutting with and without nozzle oscillation have been developed using a dimensional analysis technique. The model development starts with the models for single pass cutting which are then extended to multipass cutting where considerations are given to the change of the actual standoff distance after each pass and the variation of kerf width. These predictive models has been numerically studied for their plausibility by assessing their predicted trends with respect to the various process variables, and verified qualitatively and quantitatively based on the experimental data. The model assessment reveals that the developed models correlate very well with the experimental results and can give adequate predictions of this cutting performance measure in process planning.