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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.

The goals of this work are a design and implementation of a new vision system, integrated with the waterjet machine. This system combines two commercial webcams applied on an industrial dedicated platform. A main purpose of the vision system is to detect the position and rotation of a workpiece placed on the machine table. The used object recognition algorithm consists of edge detection, standard math processing functions and noise filters. The Hough transform technique is used to extract lines and their intersections of a workpiece. Metric rectification method is used, in order to obtain a top view of the workspace and to adjust an image coordinate system, accordingly to the waterjet machine coordinates. In situ calibration procedures of the booth webcams are developed and implemented. Experimental results of the proposed new vision system prototype confirm required performance and precision of the element detection.

The diploma thesis is focused on waterjet technology, dimensional and shape accuracy of manufactured parts. In the theoretical section, the principle of technlogy and its use in engineering industry at the present time, are described. Moreover, the theoretical section includes discription of every single parts of the machine of waterjet cutting, that are nowadays used. The biggest part of diploma thesis focuses on 3D cutting technology and on attachments for elimination of undercutting. Practical section focuses on dimensional and shape accuracy of manufactured parts manufactured by waterjet technology that makes use of 3D head and different cutting speed. The practical section also includes operating and maintenance cost of the machine. In terms of maintenance, real service life of components is compared there with a lifespan declarated by machine producer.

No description available.

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.

Este trabalho tem por objetivo o design e a fabricação de superfícies tácteis a partir de padrões modulares encaixáveis. Estas superfícies foram construídas em diferentes materiais naturais (minerais e madeiras) e em distintos processos de fabricação inovadores (usinagem por jato de água, usinagem por controle numérico computadorizado ou CNC e corte a laser). A intenção foi desenvolver uma metodologia de design & tecnologia para aplicá-la em painéis de revestimento que possam ser produzidos em baixa escala de forma semi-industrial. A grande variedade de materiais naturais encontrados no estado do Rio Grande do Sul; a carência de design associado a estes materiais quando do produto final e o volume de rejeitos oriundos deste beneficiamento, foram os principais motivadores para a utilização destas matérias primas. O estudo de diferentes técnicas de design de superfície auxilia na transformação destes materiais, para que os mesmos passem a ter o formato de módulo. Dentro deste contexto, foram estudadas as técnicas desenvolvidas pelo artista Maurits Cornelis Escher. Ele dedicou boa parte de sua vida profissional à composição de desenhos que, justamente, partem da utilização da simetria, modularidade, continuidade e encaixe. Neste sentido, após a compreensão das técnicas utilizadas por Escher, alguns de seus desenhos foram aplicados nos materiais selecionados através dos processos de fabricação adequados, possibilitando a construção das diferentes superfícies tácteis. Os resultados obtidos identificam que a utilização de processos de fabricação inovadores para interferência nos materiais naturais são ferramentas importantes para a promoção de uma nova geração de produtos locais. Conclui-se que estas interferências viabilizam a fabricação de produtos com maior valor estético, social e econômico. / This work aims at the design and the manufacturing of tactile surfaces from modular plug patterns. These surfaces were built in different natural materials (mineral and wood) and in distinct innovative manufacturing processes (waterjet machining, computerized numerical control machining or CNC and laser cutting). The objective was to develop a design & technology methodology for applying it in coating panels that can be produced on a semiindustrial small scale. The huge variety of natural materials found in Rio Grande do Sul State, the lack of design associated to these materials as to the final product and the volume of waste from this processing were the main motivators for the use of these raw materials. The study of these different techniques of surface design helps the transformation of these materials in order that they start to have the modular format. Within this context, the techniques developed by the artist Maurits Cornelis Escher were studied. He devoted much of his professional life to the composition of drawings beginning exactly with the use of symmetry, modularity continuity and joint. In this sense, after understanding the techniques used by Escher, some of his drawings were applied in the materials selected through suitable manufacturing processes, enabling the construction of different tactile surfaces. The results obtained identify that the utilization of innovative manufacturing processes to interfere in the natural materials are important tools for the promotion of a new generation of local products. It is conclude that these interferences enable the manufacture of products with greater aesthetic, social and economic value.

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.

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.

The purpose of this rapport/paper is to summarize and compare three different reparation methods, which can be used in repairing damaged concrete dams, which are one of the most important parts of electricity production in Sweden. Most of big dams in Sweden built between1900- 1960 are in a great need of restoration. Time, harsh winter conditions and constant presence of water have caused great damages to these dams. There are numerous restoration methods, which can be used in dam reconstruction.  However, choosing the right method plays a crucial role in terms of economy and quality for the power plant companies. Due to negatively impacting global warming, carbon dioxide emissions can also be another concern for power plant companies when selecting a reparation method. Sometimes determining and choosing the “right” method is rather difficult when facing different reparation methods.  When deciding which method to choose, comparisons are made in terms of economy, quality, and carbon dioxide emissions causing global warming. The methods compared in this rapport are applying waterjet mechanical chiseling, and Chesterton filler.  Accordingly, some boundaries are set and some, but not all, factors are taken into account.  For example, winter expenses and transportation are not included in this rapport. The method which has been used in this study is both qualitative and quantitative. In the qualitative method, interviews, literature studies and experience of experts are gathered and used. The quantitative method used for calculation of costs and CO2 (e) emissions to the air. The study shows that in a minor spalled concrete damage, the waterjet method and Chesterton filler are appropriate with regards to quality.  Mechanical chiseling is the cheapest method, and the Chesterton filler method releases the least amount of carbon dioxide to the air of all methods. Hopefully, the comparison in this rapport can aid those who want to choose a reparation method based on the criterias for the outcome/method. / Dammkonstruktioner är en av de viktigaste delarna av elproduktionen i Sverige. De flesta av de stora betongdammarna i Sverige som är byggda mellan 1900 och 1960 är i behov av reparation. Åldern, svåra vinterförhållanden och ständig närvaron av vatten påverkar dammarna negativt och orsakar skador i betongen. Det finns gott om olika reparationsmetoder som kan användas vid dammreparationer. Att välja rätt metod vid reparationer kan spela en avgörande roll när det gäller ekonomi och kvalitet för kraftverksbolagen. Då de olika metoderna resulterar i olika mycket koldioxidutsläpp till luften och därmed effekt på den globala uppvärmningen är just koldioxidutsläppen en annan faktor som kan beaktas av elbolagen när de vill välja en reparationsmetod. Valet av reparationsmetod är inte lätt. Ofta går det att välja mellan flera olika metoder. Syftet med denna rapport att upprätta sammanfattningar för tre olika reparationsmetoder vid reparation av betongdammar, samt en jämförelse mellan dessa metoder. Jämförelser har gjorts i förhållande till ekonomi, kvalitet och koldioxidutsläpp till luften. De reparationsmetoder som har jämförts i denna rapport är vattenbilning, mekanisk bilning och Chesterton spackel. För att möjliggöra jämförelsen i denna studie har några avgränsningar gjorts i för de faktorer som jämförts, bland annat har vinterkostnader och transporter inte inkluderats i jämförelsen.   Metoden i denna uppsats bygger på kvalitativ och kvantitativ studie. Den kvalitativa studien består av litteraturstudier och intervjuer genom samtal och email, och den kvantitativa studien består av beräkningar för kostnader och CO2 (e)-utsläpp med hjälp av grundvärden och faktorer för 1 m² betongyta. Studien visar att vid en enkel frostskada så är vattenbilningsmetoden och Chestertonspackel lämpligast med avseende på kvalitet. Mekanisk bilning är billigast och Chestertonspackel släpper ut minst koldioxid till luften. Förhoppningsvis kan jämförelsen i denna rapport hjälpa de som vill välja reperationsmetod baserat på önskade kriterier för slutresultatet. / <p>2017-06-27</p>