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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.
1

Procedur för delning av casing offshore med hjälp av vattenskärning / Casing splitting procedure offshore with waterjet cutting

Söderwall, Patrik January 2015 (has links)
Within the oil and gas industry on offshore installations in the North Sea, several oil wells are closing in on the brink where they no longer are being profitable to keep producing from. When that day comes the oil wells are closed off and the boreholes are plugged with cement. Before the holes can be cemented shut the companies need to remove all their equipment that has been used for underwater exploitations of the well and if applicable remove the above water installation as well. This includes removing the casing that the holes are lined with which main purpose is to prevent the hole from collapsing on the production line and to prevent oil and gas leaks into the surroundings. This thesis focuses on removal of the borehole casing.  When performing this task problems have been raised regarding corrosion on the casing couplings, making them very hard to separate. When this problem occurs, the need for an alternative method to split them is necessary. As of today this operation is performed by cold cut sawing or with a beveling machine. This is a highly time consuming task and an alternative method to perform a faster cut is wanted. This degree work investigates the possibilities of doing this using the benefits of abrasive water jet (AWJ) cutting. The major concerns on using this technic is whether it is fast enough and if it is possible to perform in accordance with the fire and explosive hazards on a hydrocarbon producing installation. As a reference the maximum cut time is set to one minute. Calculations on theoretical cutting speeds as well as physical testing on the AWJ method has been performed and evaluated. The investigations show that the method does have the possibilities of making the cut within the target time.  The work also contains a simple concept model on how the equipment could be constructed. / Inom olje- och gasindustrin på offshoreanläggningar i Nordsjön, närmar sig flera reservoarer randen där de inte längre är lönsamma att fortsätta producera från. När den dagen kommer pensioneras borrhålen och pluggas med en cementblandning. Innan hålen pluggas måste företagen ta bort all utrustning som har använts vid utvinningen av brunnen, både ovan och under ytan. Detta innefattar avlägsnande av casingen, som hålen är fodrade med, och vars huvudsakliga syfte är att förhindra att hålet kollapsar och skadar produktionsledningen, men även för att förhindra olje- och gasläckor till omgivningen. Denna avhandling fokuserar på borttagandet av casingen. När detta görs upplevs problem med att casingskarvarna är kraftigt korroderade vilket gör dem mycket svåra att separera. Detta är ett problem som efterfrågar en alternativ delningsmetod. I dag utförs den här operationen med antingen kallsågning eller med en avfasningsmaskin. Detta är en mycket tidskrävande uppgift och en metod för att utföra en snabbare delning önskas. Detta examensarbete är tänkt att undersöka möjligheterna att göra detta genom att använda fördelarna med abrasiv vattenskärning för att kapa rören. De största frågorna gällande denna metod är om den är tillräckligt snabb och om det är möjligt att utföra i enlighet med de brand- och explosionsrisker som finns på en kolväteproducerande installation. Som referens är målet för maximal skärtid satt till en minut. Beräkningar på teoretiska skärhastigheter samt fysiska tester på metoden har utförts och utvärderats. Undersökningarna visar på att metoden har möjligheter att göra snittet inom utsatt tid. Arbetet innehåller också en enkel konceptmodell på hur utrustningen skulle kunna konstrueras.
2

MULTI-MODELLING of ABRASIVE WATERJET MACHINING

Hale, Patrick 10 1900 (has links)
<p>Abrasive waterjet (AWJ) machining is a complex, non-conventional machining process involving numerous input parameters including hydraulic, abrasive, mixing and cutting that must be accurately manipulated to guarantee precise cutting and quality. Currently, available models are empirical or require continuous calibration, or extensive experimental work. To reduce the calibration and experimental time required for accurate prediction of AWJ cutting, computational fluid dynamics (CFD) is being utilized to model the nozzle flow interaction; high pressure water is pushed through the orifice into the mixing chamber, pulling the abrasive into the flow and cohering in the focus tube. Initial research worked towards understanding the effect that input parameters - such as pressure, particle size and shape, focus tube length and volume fraction of air in fluid mixture - have on the velocity profile through the nozzle and upon exit to the atmosphere. Once understood, the CFD model can be utilized to vary mass-inlet, mixing head, orifice and focus tube dimensions to optimize velocity profile of abrasive material including magnitude and jet coherency. Primarily focused on pump pressure, which is limited by technology - an optimized AWJ nozzle will increase material removal rate and/or enhance cut quality without making changes to any other AWJM components.</p> <p>Utilizing the velocity output information from the CFD model, a depth of penetration erosion prediction model was generated. Based on methodology from Finnie, and modified by Hashish and ElTobgy, a multi-particle erosion model of an impacted work piece is developed. With an updated formulation for the specific cutting resistance of a work piece, dependent on particle velocity and nozzle traverse speed, the erosion prediction over the sixty-five different setups modelled and tested experimentally, reduced error on average 41.8%. Moreover, the development of this model created multi-layered surface plots, illustrating for quick reference, the erosion of a work piece for a given set of parameters albeit mass flow rate, pump pressure and traverse rate.</p> <p>Further, a database of quick reference guides, including variable input settings, nozzle types, garnet types and work piece materials can easily be developed. Finally, a new methodology for the leading edge of the waterjet is described and can be incorporated into the erosion simulation by making use of the ``top-hat`` profile generated in the CFD model. This would reduce reliance on model constants to account for secondary cutting, or when particles do not contribute to cutting but are simply entrained in the fluid flow.</p> <p>Both models demonstrated good correlation with experiments or literature. The use of these models will increase understanding of the complex abrasive waterjet process and reduce the need for costly experiments moving forward.</p> / Master of Applied Science (MASc)
3

A Study of the Cutting Performance in Abrasive Waterjet Contouring of Alumina Ceramics and Associated Jet Dynamic Characteristics

Liu, Hua January 2004 (has links)
Abrasive waterjet (AWJ) cutting is one of the most recently developed nontraditional manufacturing technologies. It has been increasingly used in industry owing to its various distinct advantages over the other cutting technologies. However, many aspects of this technology require to be fully understood in order to increase its capability and cutting performance as well as to optimize the cutting process. This thesis contains an extensive literature review on the investigations of the various aspects in AWJ machining. It shows that while considerable work has been carried out, very little reported research has been found on the AWJ contouring process although it is a common AWJ cutting application. Because of the very nature of the AWJ cutting process, the changing nozzle traverse direction involved in AWJ contouring results in kerf geometrical or shape errors. A thorough understanding of the AWJ contouring process is essential for the reduction or elimination of these shape errors. It also shows that a lack of understanding of the AWJ hydrodynamic characteristics has limited the development of cutting performance models that are required for process control and optimization. Accordingly, a detailed experimental investigation is presented in this thesis to study the various cutting performance measures in AWJ contouring of an 87% alumina ceramic over a wide range of process parameters. For a comparison purpose, the study also considers AWJ straight-slit cutting. The effects of process parameters on the major cutting performance measures in AWJ contouring have been comprehensively discussed and plausible trends are amply analysed. It finds that the taper angles on the two kerf walls are in different magnitudes in AWJ contouring. The kerf taper on the outer kerf wall increases with the arc radius (or profile curvature), while that on the inner kerf wall decreases. Moreover, the depth of cut increases with an increase in arc radius and approaches the maximum in straight cutting for a given combination of parameters. The other process variables affect the AWJ contouring process in a way similar to that in straight cutting. The analysis has provided a guideline for the selection of process parameters in the AWJ contouring of alumina ceramics. In order to predict the cutting performance in process planning and ultimately optimize the cutting process, mathematical models for the major cutting performance measures in both straight-slit cutting and contouring are developed using a dimensional analysis technique. The models are then verified by assessing both qualitatively and quantitatively the model predictions with respect to the corresponding experimental data. It shows that the models can adequately predict the cutting performance measures and form the essential basis for developing strategies for selecting the optimum process parameters in AWJ cutting. To achieve an in-depth understanding of the jet dynamic characteristics such as the velocity and pressure distributions inside a jet, a Computational Fluid Dynamics (CFD) simulation is carried out using a Fluent6 flow solver and the simulation results are validated by an experimental investigation. The water and particle velocities in the jet are obtained under different input and boundary conditions to provide an insight into the jet characteristics and a good understanding of the kerf formation process in AWJ cutting. Various plausible trends and characteristics of the water and particle velocities are analysed and discussed, which provides the essential knowledge for optimizing the jet performance through optimizing the jetting and abrasive parameters. Mathematical models for the water and particle velocity distributions in an AWJ are finally developed and verified by comparing the predicted jet characteristics with the corresponding CFD simulation data. It shows that the jet characteristics models can yield good predictions for both water and particle velocity distributions in an AWJ. The successful development of these jet dynamic characteristics models is an essential step towards developing more comprehensive mathematical cutting performance models for AWJ cutting and eventually developing the optimization strategies for the effective and efficient use of this advanced manufacturing technology.
4

Advanced hybrid manufacturing process for high precision ring of a planetary gear – main focus on Abrasive Waterjet Machining

GOTIA, BOGDAN, LOYA MUCINO, JORGE January 2016 (has links)
Under år 2008 uppskattades den totala produktionen av kugghjul inom bilindustrin till 2000 – 2500 miljoner detaljer, varav 1000 - 1400 miljoner av dessa är av hög kvalité [1]. För precisionskugghjul med modul under 1 mm kan tidsbegränsning och kostnader kopplade till design av skärverktyget elimineras genom att tillämpa en flexibel tillverkningsmetod som tillexempel abrasiv vattenskärning (AWJM). Denna studie undersöker designen av ett hybridtillverkningssystem konfigurerat kring AWJM samt föreslår finbearbetningsprocess via konventionella bearbetningsmetoder. Den tekniska möjligheten att producera kuggring av hög precision testas med en 5-axlig vattenjetmaskin och utvärderas enligt kvalitets nivåer för DIN-standard. För detta ändamål studerades ett kugghjul med modul 0,55 mm, 199 tänder, 110 mm i ytterdiameter och 72 mm i innerdiameter samt en tjocklek på 6 mm gjord av Armox T500, höghållfast stål. Resultaten visar på hög potential att uppnå ISO standardkvalité för kugghjul. Vissa kvalitetsegenskaper, definierade i DIN- och ISO-standarder, till exempel ytfinhet med låga värden; Ra 0,8 μm, uppnås vid användning av AWJM. Andra kvalitetskännetecken som profilavvikelse är relaterade till parametrar som skäreffekt, matningshastighet, mängd abrasivmedel, etc. Framtagna värden sträcker sig från Q10 och Q11 enligt DIN3967 vilket möjliggör slutoperationer som till exempel slipning. Geometrisk avvikelse, på ovansidan, gav en maximalt värde på 7 μm med en standardavvikelse på 4 μm. Jetstrålens eftersläpning observerades och kan kompenseras för medan resultatet av rundade hörn existerar i alla skärning med AWJ. Radiell förskjutning, tandtjocklek och index avvikelser visar värden som kan förbättras tillsammans med processoptimering, maskinkalibrering och eliminering av inneboende positionsavvikelser i maskinen. Varje enskild geometri kräver specifika processparametrar och CAM-programmens algoritmer behöver vidare optimeras för arbeten med tämligen små geometrier. / Production of gears for the automotive industry during 2008 is estimated to have been between 2000 – 2500 million pieces, from which 1000 to 1400 million pieces were high quality gears [1]. For precision gears with module below 1 mm, the time limitations and costs associated with the design of the cutting tool can be eliminated by using a flexible manufacturing technology such as Abrasive WaterJet Machining (AWJM). This project investigates the design of a hybrid manufacturing system configured by use of AWJM and proposed finishing processes using conventional machining methods. The technical feasibility is analysed to produce high precision ring gears using a 5-axes AWJM system to achieve DIN standards quality levels. For this purpose, a gear with a module of 0.55 mm, 199 teeth and 110 mm in the outer diameter and 130 teeth and 72 mm in the inner diameter with a thickness of 6 mm is studied; the selected material is Armox T500, a high strength steel. The results indicate high potential of producing ISO quality standard gears. Certain quality characteristics defined in DIN and ISO standards, for instance surface roughness – values as low as Ra 0.8 μm, are possible to achieve accurately by using AWJM. Others quality features as profile deviation, are related to parameters as cutting power, feed rate, abrasive feed rate, etc. The displayed values ranged Q10 and Q11 according to DIN3967 which allows for use of further finishing operations such as grinding. The top geometry deviations of a 0.3 mm cut, display a maximum value of 7 μm with an average value of 4 μm. Observed jet lag effects can be improved. Rounded corner effect exists in all AWJ cuts. Runout, tooth thickness and index deviations show values that can be improved together with process optimization, machine calibration and elimination of machine inherent positioning deviations. Each particular geometry needs specific process parameters and CAM software algorithms need further optimization for working with rather small design geometries.
5

Modelling the cutting process and cutting performance in abrasive waterjet machining with controlled nozzle oscillation

Xu, Shunli January 2006 (has links)
Abrasive waterjet (AWJ) cutting is one of the most recently developed manufacturing technologies. It is superior to many other cutting techniques in processing various materials, particularly in processing difficult-to-cut materials. This technology is being increasingly used in various industries. However, its cutting capability in terms of the depth of jet penetration and kerf quality is the major obstruction limiting its further applications. More work is required to fully understand the cutting process and cutting mechanism, and to optimise cutting performance. This thesis presents a comprehensive study on the controlled nozzle oscillation technique aiming at increasing the cutting performance in AWJ machining. In order to understand the current state and development in AWJ cutting, an extensive literature review is carried out. It has found that the reported studies on controlled nozzle oscillation cutting are primarily about the use of large oscillation angles of 10 degrees or more. Nozzle oscillation in the cutting plane with such large oscillation angles results in theoretical geometrical errors on the component profile in contouring. No published attempt has been found on the study of oscillation cutting under small angles although it is a common application in practice. Particularly, there is no reported research on the integration of nozzle oscillation technique into AWJ multipass cutting, which is expected to significantly enhance the cutting performance. An experimental investigation is first undertaken to study the major cutting performance measures in AWJ single pass cutting of an 87% alumina ceramic with controlled nozzle oscillation at small angles. The trends and characteristics of cutting performance quantities with respect to the process parameters as well as the science behind which nozzle oscillation affects the cutting performance have been analysed. It has been shown that as with oscillation cutting at large angles, oscillation at small angles can have an equally significant impact on the cutting performance. When the optimum cutting parameters are used for both nozzle oscillation and normal cutting, the former can statistically increase the depth of cut by 23% and smooth depth of cut by 30.8%, and reduce kerf surface roughness by 11.7% and kerf taper by 54%. It has also been found that if the cutting parameters are not selected properly, nozzle oscillation can reduce some major cutting performance measures. In order to correctly select the process parameters and to optimise the cutting process, the mathematical models for major cutting performance measures have then been developed. The predictive models for the depth of cut in both normal cutting and oscillation cutting are developed by using a dimensional analysis technique. Mathematical models for other major cutting performance measures are also developed with the aid of empirical approach. These mathematical models are verified both qualitatively and quantitatively based on the experimental data. The assessment reveals that the developed models conform well to the experimental results and can provide an effective means for the optimum selection of process variables in AWJ cutting with nozzle oscillation. A further experimental investigation of AWJ cutting of alumina ceramics is carried out in order to study the application of AWJ oscillation technique in multipass cutting. While high nozzle traverse speed with multipass can achieve overall better cutting performance than low traverse speed with single pass in the same elapsed time, it has been found that the different combination of nozzle traverse speed with the number of passes significantly affects cutting process. Optimum combination of nozzle traverse speed with the number of passes is determined to achieve maximum depth of cut. It has also demonstrated that the multipass cutting with low nozzle traverse speed in the first pass and a comparatively high traverse speed for the following passes is a sensible choice for a small kerf taper requirement. When nozzle oscillation is incorporated into multipass cutting, it can greatly increase the depth of cut and reduce kerf taper. The predictive models for the depth of cut in both multipass normal cutting and multipass oscillation cutting are finally developed. With the help of dimensional analysis, the models of the incremental cutting depth for individual pass are derived based on the developed depth of cut models for single pass cutting. The models of depth of cut for a multipass cutting operation are then established by the sum of the incremental cutting depth from each pass. A numerical analysis has verified the models and demonstrated the adequacy of the models' predictions. The models provide an essential basis for the development of optimization strategies for the effective use of the AWJ cutting technology when the multipass cutting technique is used with controlled nozzle oscillation.
6

Rock cutting by abrasive water jet: an energy approach / Corte de rocha com jato d\'água abrasivo: uma abordagem baseada em energia

Arab, Paola Bruno 20 March 2017 (has links)
Abrasive waterjet (AWJ) cutting is a versatile technique which has been effectively applied to rock cutting since the late 1980s. The complexity of the interaction between the waterjet and the rocks complicates the thorough understanding of the phenomena involved in AWJ rock cutting. On one hand, rocks are complex materials which are generated through different processes in an uncontrolled environment without human interference. On the other hand, the AWJ acts with high velocity and turbulence, complicating direct observation and the perception of details. In this respect, the present research aims to contribute to the study of AWJ cutting applied to rocks, including the analysis of qualitative and quantitative information, both of great importance regarding the study of complex materials. Concerning quantitative data, special attention is given to the investigation of the cutting efficiency, which can be analyzed by observing conditions in which the higher cutting rate is associated with the minimum energy provided by the AWJ machine per removed volume of rock. Moreover, the real efficiency can be analyzed through the investigation of the conditions in which the major part of the energy provided by the AWJ machine is used effectively for rock cutting, deducting dissipation losses. The effects of varying traverse velocity and pump pressure on cutting parameters were also investigated, in addition to the influence of rock properties on the effective energy of cutting. The effective energy was calculated based both on the specific energy and specific destruction work of the materials. With respect to the qualitative investigation, petrographic and scanning electron microscopy (SEM) analyses were conducted in order to visualize and better understand the different effects of cutting on the studied rocks. Cutting tests with a traverse velocity of 200 mm/min and a pump pressure of 400 MPa presented the most efficient rock cutting regarding both methods of efficiency analysis. Dry density and tensile strength presented fair correlations with the effective cutting energy, while the modulus ratio presented the best correlations. It was observed that brittleness plays a key role in the understanding of the phenomena involved in AWJ rock cutting. / O jato d\'água abrasivo (AWJ) é uma técnica versátil que tem sido efetivamente aplicada ao corte de rochas desde o fim da década de 1980. A complexidade da interação entre o jato e as rochas dificulta a compreensão detalhada dos fenômenos envolvidos no corte de rochas com AWJ. Por um lado, rochas são materiais complexos gerados em ambientes sem interferência humana. Por outro lado, o AWJ age com alta velocidade e turbulência, dificultando a observação direta do procedimento. Assim, a presente tese de doutorado visa a contribuir com o estudo do corte de rochas com AWJ, incluindo análises de dados qualitativos e quantitativos, ambos de grande importância em estudos de materiais complexos. A análise quantitativa possui foco na investigação da eficiência de corte, a qual pode ser analisada por meio da observação das condições em que há a maior taxa de corte associada à mínima energia fornecida pelo AWJ por volume de rocha removido. Além disso, a eficiência real do corte pode ser analisada a partir da investigação das condições em que a maior parte da energia fornecida pelo AWJ é usada para efetivamente cortar a rocha, descontando perdas por dissipação. Os efeitos da variação da velocidade transversal de corte e da pressão da bomba nos parâmetros de corte também foram investigados, além da influência das propriedades das rochas na energia efetiva de corte. A energia efetiva de corte, denominada energia relativa de formação da ranhura (EKR), foi calculada com base na energia específica e no trabalho de destruição específico dos materiais. Análises de microscopia eletrônica de varredura (SEM) e petrografia foram conduzidas para visualizar e compreender melhor os diferentes efeitos do corte nas rochas estudadas. Os testes de corte realizados com velocidade transversal do bocal de 200 mm/min e pressão da bomba de 400 MPa apresentaram as melhores eficiências de corte considerando-se ambos os métodos de análise de eficiência. Dentre as propriedades das rochas investigadas, a massa específica e a resistência à tração por compressão diametral apresentaram correlações razoáveis com EKR, enquanto que o modulus ratio apresentou as melhores correlações. Observou-se que a ruptibilidade possui papel fundamental na compreensão dos fenômenos envolvidos no corte de rochas com AWJ.
7

A study of the cutting performance in multipass abrasive waterjet machining of alumina ceramics with controlled nozzle oscillation

Zhong, Yu, Mechanical & Manufacturing Engineering, Faculty of Engineering, UNSW January 2008 (has links)
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.
8

A study of the cutting performance in multipass abrasive waterjet machining of alumina ceramics with controlled nozzle oscillation

Zhong, Yu, Mechanical & Manufacturing Engineering, Faculty of Engineering, UNSW January 2008 (has links)
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.
9

Rock cutting by abrasive water jet: an energy approach / Corte de rocha com jato d\'água abrasivo: uma abordagem baseada em energia

Paola Bruno Arab 20 March 2017 (has links)
Abrasive waterjet (AWJ) cutting is a versatile technique which has been effectively applied to rock cutting since the late 1980s. The complexity of the interaction between the waterjet and the rocks complicates the thorough understanding of the phenomena involved in AWJ rock cutting. On one hand, rocks are complex materials which are generated through different processes in an uncontrolled environment without human interference. On the other hand, the AWJ acts with high velocity and turbulence, complicating direct observation and the perception of details. In this respect, the present research aims to contribute to the study of AWJ cutting applied to rocks, including the analysis of qualitative and quantitative information, both of great importance regarding the study of complex materials. Concerning quantitative data, special attention is given to the investigation of the cutting efficiency, which can be analyzed by observing conditions in which the higher cutting rate is associated with the minimum energy provided by the AWJ machine per removed volume of rock. Moreover, the real efficiency can be analyzed through the investigation of the conditions in which the major part of the energy provided by the AWJ machine is used effectively for rock cutting, deducting dissipation losses. The effects of varying traverse velocity and pump pressure on cutting parameters were also investigated, in addition to the influence of rock properties on the effective energy of cutting. The effective energy was calculated based both on the specific energy and specific destruction work of the materials. With respect to the qualitative investigation, petrographic and scanning electron microscopy (SEM) analyses were conducted in order to visualize and better understand the different effects of cutting on the studied rocks. Cutting tests with a traverse velocity of 200 mm/min and a pump pressure of 400 MPa presented the most efficient rock cutting regarding both methods of efficiency analysis. Dry density and tensile strength presented fair correlations with the effective cutting energy, while the modulus ratio presented the best correlations. It was observed that brittleness plays a key role in the understanding of the phenomena involved in AWJ rock cutting. / O jato d\'água abrasivo (AWJ) é uma técnica versátil que tem sido efetivamente aplicada ao corte de rochas desde o fim da década de 1980. A complexidade da interação entre o jato e as rochas dificulta a compreensão detalhada dos fenômenos envolvidos no corte de rochas com AWJ. Por um lado, rochas são materiais complexos gerados em ambientes sem interferência humana. Por outro lado, o AWJ age com alta velocidade e turbulência, dificultando a observação direta do procedimento. Assim, a presente tese de doutorado visa a contribuir com o estudo do corte de rochas com AWJ, incluindo análises de dados qualitativos e quantitativos, ambos de grande importância em estudos de materiais complexos. A análise quantitativa possui foco na investigação da eficiência de corte, a qual pode ser analisada por meio da observação das condições em que há a maior taxa de corte associada à mínima energia fornecida pelo AWJ por volume de rocha removido. Além disso, a eficiência real do corte pode ser analisada a partir da investigação das condições em que a maior parte da energia fornecida pelo AWJ é usada para efetivamente cortar a rocha, descontando perdas por dissipação. Os efeitos da variação da velocidade transversal de corte e da pressão da bomba nos parâmetros de corte também foram investigados, além da influência das propriedades das rochas na energia efetiva de corte. A energia efetiva de corte, denominada energia relativa de formação da ranhura (EKR), foi calculada com base na energia específica e no trabalho de destruição específico dos materiais. Análises de microscopia eletrônica de varredura (SEM) e petrografia foram conduzidas para visualizar e compreender melhor os diferentes efeitos do corte nas rochas estudadas. Os testes de corte realizados com velocidade transversal do bocal de 200 mm/min e pressão da bomba de 400 MPa apresentaram as melhores eficiências de corte considerando-se ambos os métodos de análise de eficiência. Dentre as propriedades das rochas investigadas, a massa específica e a resistência à tração por compressão diametral apresentaram correlações razoáveis com EKR, enquanto que o modulus ratio apresentou as melhores correlações. Observou-se que a ruptibilidade possui papel fundamental na compreensão dos fenômenos envolvidos no corte de rochas com AWJ.
10

Vodní paprsek ve strojírenství / A water jet in engineering

Kadlček, František January 2021 (has links)
This diploma thesis deals with the principle of the abrasive jet and describes the devices needed to create it. The thesis presents an analysis of technological parameters and their impact on the quality of the cut. Subsequently, this thesis deals with an experiment, which consists in the design of technology for a sample component, followed by evaluation of surface quality and the economic evaluation.

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