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Contribuição ao estudo da integridade superficial de um aço inoxidável super-duplex após usinagem. / Contribution to study effects of the turning operations in the surface integrity in a super duplex stainless steel.Éd Claudio Bordinassi 26 May 2006 (has links)
Este trabalho teve por objetivo estudar os efeitos da operação de torneamento na integridade superficial do aço inoxidável super-duplex ASTM A890 - Gr 6A. O foco do trabalho foram as operações de acabamento, porém também foram realizados alguns estudos com operações de desbaste, ambas utilizando planejamentos fatoriais completos com 2 níveis e 5 fatores. Os ensaios foram realizados em centros de torneamento com ferramentas de metal duro e tiveram como variáveis: a geometria da ferramenta / classe da pastilha, avanço, profundidade de corte, velocidade de corte e utilização ou não de fluido de corte. As respostas estudadas foram: análise microestrutural óptica e por difração de raios-X, medição de forças através de um dinamômetro piezoelétrico, rugosidade superficial, micro-dureza, tensão residual através de difração de raios-x e estabilidade dimensional. Os resultados não mostraram alterações microestruturais no material mesmo nas operações de desbaste que foram as mais severas. As outras respostas foram correlacionadas com os parâmetros de corte e a melhor combinação destes foi encontrada para a obtenção da melhor integridade superficial. O menor avanço (0,1mm/v), a menor velocidade de corte (110m/min) e a maior profundidade de corte (0,5mm) obtiveram os menores valores para a tensão residual, a menor rugosidade e o maior valor de micro-dureza. A correlação entre as respostas foi bastante difícil de ser estabelecida, uma vez que as interações tiveram grande influência nas análises, porém para algumas combinações estas correlações se mostraram possíveis de serem estabelecidas. / The objective of this work was to study the effects of the turning operations in the surface integrity in a super duplex stainless steel (SDSS) ASTM A890-Gr6A. The focus of the work was the finishing operations but some tests in rough operations were carried out. A complete factorial planning was used for both, with 2 levels and 5 factors. The tests were conducted on turning centers with carbide tools and the main input variables were: tool geometry / tool material class, feed rate, cutting depth, cutting speed and the cutting fluid utilization. The analyzed answers were: microstructure analysis by optical microscopy and x-ray diffraction, cutting measurements by a piezoelectric dynamometer, surface roughness, micro-hardness, residual stress by x-ray diffraction technique and dimensional stability. The results do not showed any changes in the microstructure of the material, even when the greater cutting values were used. All the other answers were correlated with the cutting parameters and the best combination of cutting parameters was founded for the best surface integrity. The smaller feed rate (0,1mm/v), smaller cutting speed (110m/min) and greater cutting depth (0,5mm) provided the smaller values for the tension residual stress, the smaller roughness and the greater micro-hardness. The correlation between all the answers was very difficult to analyze because there was great interaction between the factors, but for some data groups it was possible. Read more
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Desenvolvimento de um controlador PID para aplicação em uma mesa angular rotativa / Application of a PID controller for a piezoelectric tilt stageJosé Antonio Pinheiro 24 April 2009 (has links)
Trata do desenvolvimento de um controlador Proporcional-Integral-Derivativo (PID) para uma Mesa Angular Rotativa (MAR) destinada à usinagem de ultraprecisão. O sistema de controle tem como objetivo efetuar posicionamento angular de alta resolução e repetibilidade antes e durante a usinagem de ultraprecisão, propiciando fabricar peças complexas através de torneamento. A MAR faz uso de elementos como mancais de flexão, atuadores piezelétricos, juntamente com o sistema de controle PID. A estratégia de controle é baseada na aquisição de dados na plataforma de desenvolvimento LabVIEW®, para gerar curvas tensão de saída do tesatronic versus deslocamento da MAR e no processamento dos sinais adquiridos ao longo do microposicionamento da MAR em tempo real para realimentação de posição. Constatou-se que o sistema suporta deslocamentos da MAR correspondendo a expansão do atuador piezelétrico de até 24 µm com freqüência de acionamento de até 3 Hz. O uso de filtro Chebyshev provocou atraso na resposta e forte instabilidade no sistema. Conclui-se que para a melhora do desempenho do sistema em termos de freqüência pode ser conseguida através do uso de filtro do tipo FIR (Finite Impulse Response). / A Micro Tilt Stage (MTS) was developed in the Precision Engineering Laboratory (University of São Paulo) to be used in commercial diamond turning machines. The MTS has the aim of positioning workpieces angularly with high resolution and repeatability before and during ultraprecision machining. The use of flexural bearings and piezoelectric actuators together with a PID control system provided improved dynamic performance. The control strategy is based on data acquisition using LabView to create standard curves and perform the correction of positioning errors. Experimental tests are performed with displacement of the (MTS), up to 24 µm, with frequency, up to 3 Hz. The use of a Chebyshev filter caused a delay and a strong instability in the system. In conclusion, in order to improve the performance of the system in terms of frequency, the use of a FIR filter (Finite Impulse Response) may be indicated. Read more
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Reduzindo chatter em processos de torneamento através do uso de material piezoelétrico considerando aspectos não-lineares / Chatter avoidance using piezoelectric material considering non-linear aspects in turning operationsGiuliana Sardi Venter 06 March 2015 (has links)
Chatter é uma vibração auto-excitada que ocorre durante usinagens e limita a produtividade do processo. Esta instabilidade causa qualidade superficial inaceitável, diminuição da vida da ferramenta e ruído. Estratégias para definição de modelos e controle desta vibração são importantes, devendo ser avaliadas e implementadas. Neste trabalho foram realizados experimentos e características como frequências naturais, respostas em frequência e respostas temporais foram obtidas. Analisando tais resultados é possível a visualização do acoplamento existente nas duas direções de vibração. Uma estratégia de redução de chatter foi implementada, através do uso de shunts passivos conectados ao sistema mecânico por meio de material piezoelétrico, e sua viabilidade foi verificada. A estratégia foi adaptada para ser utilizada nas duas direções de vibração e o resultado da redução da vibração se provou mais eficiente após esta adaptação. Diagramas de fase, respostas temporais e espectros foram obtidos durante a usinagem e um comportamento não-linear se mostrou presente. Após a validação do uso de material piezoelétrico para o controle de chatter, existe a necessidade de modelos numéricos para a descrição do fenômeno, para que controles ativos e mais efetivos possam ser desenvolvidos. Devido ao acoplamento entre as duas direções de vibração e ao comportamento não linear do fenômeno, modelos que contenham tais características foram estudados, modificados e adaptados. Os resultados numéricos obtidos pelos modelos estudados foram então comparados aos resultados experimentais e conclusões sobre similaridades foram apresentadas. Considerando os resultados obtidos, acredita-se que o modelo que melhor representa o sistema real pode ser utilizado para o desenvolvimento de controles ativos, que garantam uma redução mais efetiva do chatter. / Chatter is a self-excited vibration that leads to instability during ongoing machining, which affects productivity. Chatter instability causes poor surface quality, diminishes the tool\'s life and may cause clatter. Therefore, strategies to control chatter and chatter models are highly necessary, and must be evaluated and implemented. In an experimental campaign done during this work, characteristics such as natural frequencies, frequency responses and temporal responses were obtained. Trough these analysis, it was observed that the system presents a coupling in its two normal directions of vibration. One strategy for chatter reduction was then implemented, in which a passive shunt using piezoelectric material was used. The feasibility of this chatter reduction strategy for one direction could be verified. In addition, the strategy was adapted in order to be utilized in both main vibration directions and the results confirmed that this approach grants better results for the reduction of chatter. Phase-planes, temporal responses and spectras could also be derived from the turning experiments and a nonlinear behavior could be seen present. Being verified the possibility of using a piezoelectric material in chatter control, numerical models that describe the phenomena should be pursued, so that more effective active control could be developed. Because the experiments show the mode coupling between two directions and a nonlinear behavior, models that represent such characteristics were studied, modified and adapted. The numerical results from this models were then compared to the experiments and conclusions were drawn. Considering the obtained results, it is believed that the most similar model should be used in the development of active control that could guarantee a better chatter reduction. Read more
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Contribuição ao estudo do torneamento do aço inoxidável superduplex empregando ferramentas de metal duro com revestimentos / Contribution to study of turning stainless steel super duplex using carbide tools with coatingsAguiar, Herbert César Gonçalves de 21 August 2018 (has links)
Orientador: Amauri Hassui / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-21T02:22:26Z (GMT). No. of bitstreams: 1
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Previous issue date: 2012 / Resumo: Os aços inoxidáveis superduplex são materiais de estrutura bifásica contendo ferrita e austenita, que garantem ao material boa resistência à corrosão por pitting, resistência mecânica e outras características que tornam o material atrativo para as indústrias: petrolífera, óleo/gás, papel/ celulose e química. As mesmas características que tornam o aço inoxidável superduplex mais resistente dificultam a sua usinagem. Portanto, a definição dos parâmetros de usinagem deve atender ao compromisso de por um lado garantir alta produtividade e por outro não comprometer as características do material na sua aplicação. O presente trabalho consiste no torneamento com lubrificação do aço inoxidável superduplex, variando os parâmetros de usinagem e utilizando ferramentas de metal duro da classe M05-M20 revestidas com TiN/Al2O3/TiCN, Al2O3/TiCN e TiAlN, com o objetivo de investigar os efeitos dos parâmetros de usinagem sobre o mecanismo de desgaste da ferramenta através de micrografias obtidas por microscopia eletrônica de varredura (MEV) e de micro-análise semi-quantitativa através do sistema de espectroscopia de energia dispersiva (EDS), a tensão residual induzida no material usinado medida por difração raio-X e a rugosidade na peça. As análises do desgaste da ferramenta mostraram a predominância do mecanismo de adesão/attrition com surgimento de entalhe causado pelo martelamento da rebarba gerada no cavaco durante o torneamento. Isso por sua vez contribuiu ainda mais com a adesão dificultando a remoção do material que aumentou os esforços de corte gerando tensões residuais superficiais compressivas. A ferramenta revestida com TiN/Al2O3/TiCN se destacou por apresentar melhor resultado em termos de vida da ferramenta e menores tensões residuais superficiais de tração no início de vida da ferramenta em relação às ferramentas revestidas com TiAlN e Al2O3/TiCN. A condição de vc = 80 m/min e f = 0,4 mm/rev se destacou dentre todas as classes testadas em termos de produtividade. No entanto, o f = 0,4 mm/rev é prejudicial à integridade superficial gerando tensões trativas e maiores rugosidades / Abstract: The super duplex stainless steels are materials of biphasic structure containing ferrite and austenite, which guarantee a good pitting corrosion resistance, mechanical resistance and other characteristics that make the material attractive to industries: petroleum, oil/gas, paper/cellulose and chemical. The same characteristics that make the super duplex stainless steel more resistant make its machining more difficult. Therefore, the definition of machining parameters should comply with the commitment on the one hand of guaranteeing high productivity and on the other of not compromising the characteristics of the material in its application. This work consists on the turning with lubrication of the super duplex stainless steel, varying the machining parameters and using carbide tools of the grade M05-M20 coated with TiN/Al2O3/TiCN, TiAlN and Al2O3/TiCN, with the objective of investigating the effects of the machining parameters over the tools wear mechanism was also analyzed through micrographs obtained by scanning electron microscopy (SEM) and by semi-quantitative micro-analysis through the system energy dispersive spectroscopy (EDS), the residual stress induced into machined material measured by X-ray diffraction and the parts roughness. The tool wear analysis showed a predominance of the adherence/attrition mechanism with the appearance of grooves caused by the hammering of the burr generated in the chip during the turning. This, in its turn, contributed even more with the adhesion, making it difficult to remove the material which increased the effort in cutting, generating superficial compressive residual stress. The tool coated with TiN/Al2O3/TiCN highlighted itself for presenting better result in terms of the life of the tool and lower surface residual stresses of tensile at the beginning of tool life in relation to the tools coated with TiAlN and Al2O3/TiCN. The condition of vc = 80 m/min and f = 0,4 mm/rev highlighted itself among all the tested classes in terms of productivity. However, the f = 0,4 mm/rev is prejudicial to the superficial integrity, generating tensile stress and greater roughness / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica Read more
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Alternative binder hardmetals for steel turningToller, Lisa January 2017 (has links)
The goal of this work is to understand how the wear and deformation mechanisms of hardmetalinserts change when the cobalt binder phase is replaced with a dierent metal or analloy. The focus is on inserts for steel turning. The work presented in this licentiate thesisconsists of the rst steps.Cobalt is the most common binder phase in hardmetal tools based on tungsten carbide asthe hard phase. Metallic cobalt powder, present during the manufacturing, has been associatedwith lung diseases and an increased risk for lung cancer if inhaled. Therefore it is importantto investigate alternative binders as one possible solution.This work studies binder phase alloys from the iron-nickel-cobalt system. These alloyscan be either austenitic, martensitic or a mixture of the two phases. By changing the binderphase composition to change the crystal structure it is possible to tailor the macroscopic mechanicalproperties of the material. It is also possible to tailor the composition in such a waythat the binder is transformation toughening, forming martensite as a response to mechanicaldeformation.The majority of inserts for steel turning are coated, and it is important to investigate if thehardmetals with alternative binder can be coated and if the coating adhesion is sucient forsteel turning.Four dierent alternative binder alloys and one reference with cobalt binder coated bychemical vapour deposition were investigated by scratch testing to determine the adhesion.The scratch test adhesion was sucient on all samples, but signicant variations in coatingadhesion were found.One alternative binder with 86wt%Ni and 14wt%Fe and a reference with cobalt binder manufacturedto mimic state of the art turning inserts were tested in steel turning. The alternativebinder grades had a lower resistance to plastic deformation and this was attributed to earlyaking of the coating due to a lower coating adhesion. Focused ion beam and scanning electronmicroscopy were used to study the deformation of the hard metal in the used cuttinginserts. Read more
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Improvements in ultrasonically assisted turning of TI 15V3Al3Cr3SnMaurotto, Agostino January 2013 (has links)
Titanium alloys have outstanding mechanical properties such as high hardness, a good strength-to-weight ratio and high corrosion resistance. However, their low thermal conductivity and high chemical affinity to tool materials severely impairs their machinability with conventional techniques. Conventional machining of Ti-based alloys is typically characterized by low depth of cuts and relatively low feed rates, thus adversely affecting the material removal rates (MRR) during the machining process. Ultrasonically assisted turning (UAT) is an advanced machining technique, in which ultrasonic vibration is superimposed on a cutting tool. UAT was shown to improve machinability of difficult-to-machine materials, such as ceramics, glass or hard metals. UAT employment in the industry is, however, currently lacking due to imperfect comprehensive knowledge on materials' response and difficulties in obtaining consistent results. In this work, significant improvements in the design of a UAT system were performed to increase dynamic and static stiffness of the cutting head. Concurrent improvements on depth-of-cut controls allowed precise and accurate machining operations that were not possible before. Effects of depth of cut and cutting speed were investigated and their influence on the ultrasonic cutting process evaluated. Different cutting conditions -from low turning speeds to higher recommended levelwere analysed. Thermal evolution of cutting process was assessed, and the obtained results compared with FE simulations to gain knowledge on the temperatures reached in the cutting zone. The developed process appeared to improve dry turning of Ti-15-3-3-3 with significant reduction of average cutting forces. Improved surface quality of the finished work-piece was also observed. Comparative analyses with a conventional turning (CT) process at a cutting speed of 10 m/min showed that UAT reduced the average cutting forces by 60-65% for all levels of ap considered. Temperature profiles were obtained for CT and UAT of the studied alloy. A comparative study of surface and sub-surface layers was performed for CT- and UAT-processed work-pieces with notable improvements for the UAT-machined ones. Two- to three-fold reductions of surface roughness and improvements of other surface parameters were observed for the UAT- machined surfaces. Surface hardness for both the CT- and UAT-machined surfaces was investigated by microindentation. The intermittent cutting of the UAT-process resulted in reduction of hardening of the sub-surface layers. Optical and electronic metallographic analyses of cross-sectioned work-pieces investigated the effect of UAT on the grain structure in material's sub-surface layers. Backscatter electron microscopy was also used to evaluate the formation of α-Ti during the UAT cutting process. No grain changes or α-precipitation were observed in both the CT- and UAT-machined work-pieces. Read more
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Men at work : an ethnography of drug markets and youth transitions in times of austeritySalinas Edwards, Michael Antonio January 2014 (has links)
Based on six-years ethnographic research, this thesis provides an in-depth account of a contemporary British drug market. The study follows a group of twenty-five friends, termed The Lads, during their transition from late-adolescence (16-22) through to early adulthood (22-28). This was a critical stage in their life course; it was a time when many had begun advancing into the world of work and business entrepreneurship, in search of their chosen career. Yet it was during this time that two key developments occurred: bulk volumes of illicit drugs became available to The Lads through credit and the UK experienced several years of economic recession and stagnation. The economic constraints The Lads encountered during this time prompted many to become involved in the trafficking of illegal drugs. Though their entry into the markets was not necessarily motivated out of absolute need or poverty, the experience of low-paying salaries, the loss of work and income, and the inability to secure legitimate investment capital, all made drug dealing an alluring source of untaxed revenue, available as and when needed. This study assesses the practices of this cohort of closed-market drug dealers, who capitalised on their expansive social networks as a means of trafficking a variety of illegal substances at the time of these two developments. During the course of the research their involvement came to span several stages of the supply chain, including: mid-level wholesale brokerage, import/export, wholesale, and retail (i.e. to the end-users). The study addresses various structural elements of their trade, including drug purchasing and selling, the assessment and mitigation of risks in relation to law enforcement, and the use of informal credit (i.e. ‘fronting’) as one of the principle facilitating factors of The Lads’ various trade networks. A variety of data collection methods were employed over many years to garner a depth of understanding and appreciation difficult to achieve in the study of active offenders. The data comprises of life narratives, observations, interview data and economic data. The findings offer some new insight into: the kinds of people who deal drugs; what characteristics they share; how they function as traders; what motivates them to either enter or exit the trade, and what social structures influence their offending careers?These young men were not the archetypal drug dealer: they were neither predatory nor territorial. They were ambitious and hard working. Drug dealing was simply a shortcut to the lifestyle they aspired to; it was a source of capital; a means of funding their studies; a ‘means to an end’. To these young men, drug dealing was just another form of work: a bad job that paid a good salary. Read more
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Podnikatelský záměr - Business Jet / Business Plan – Private jet airlines establishmentMajerčin, Jakub January 2012 (has links)
The aim of this thesis is to develop a business plan for the establishment of private airlines in the Czech Republic, based in Prague. The first part describes the theoretical part of the business plan. Its contents are facts that business plan should include, describes the practical meaning of this work and the reason for its assembly. Theoretical part describes in detail each part of the business plan and defines methods which are used in the practical part. The second part of this thesis deals with the transfer of theory into practical application. The practical part describes a preparation of the business plan, the establishment of private airlines. The content of the business plan is the executive summary, organizational structure, description of services offered, operation and analysis of competition and market. There are also accurately described activities of business, risk analysis and financial plan. The financial plan is created for five years in business and it has three possible variants of development. The conclusion contains a summary of the project and recommendations.
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Att lämna den kriminella livsstilen - En kvalitativ studie om de avgörande faktorernaAndersson, Lina, Elbayrouti, Ahmad January 2020 (has links)
Syftet med studien är att undersöka vilka som är de avgörande faktorerna till att individen lämnar den kriminella livsstilen samt upprätthåller den prosociala livsstilen. Studien har använt en kvalitativ metod i form av semistrukturerade intervjuer. För att besvara studiens syfte har fem respondenter inkluderats från föreningen KRIS-Kriminellas Revansch I Samhället i Malmö. Alla fem respondenter har suttit i fängelset och haft en tidigare kriminell livsstil. Resultatet påvisade att fyra faktorer var avgörande för att lämna den kriminella livsstilen: avslutande av missbruk, familj, påföljd och hälsa. Där missbruksproblematiken hade en stark koppling till deras kriminalitet. Gällande den prosociala livsstilen menade respondenterna att relationer, förändrat konsekvenstänk, sysselsättning och avslutande av missbruk var drivkraften till upprätthållandet. Avslutningsvis menade respondenterna att det oftast inte finns endast en specifik faktor till avslutandet eller upprätthållandet, utan viljan att förändra sin livsstil måste finnas där. / This study aims to investigate what the crucial factors for an individual leaving the criminal lifestyle and maintaining the prosocial lifestyle are. The study has used a qualitative method in the form of semi-structured interviews. To respond to the purpose of the study, five respondents have been included from the association KRIS-Kriminellas Revansch I Samhället in Malmö. All five respondents have been in prison and had a previous criminal lifestyle. The results showed that there were four crucial factors to leaving the criminal lifestyle: the termination of addiction, family, penalty and health. Where the problem of abuse had a strong connection to their crime. Regarding the prosocial lifestyle respondents argued that relationships, mindfulness of consequences, employment and termination of addiction were the driving force for maintaining a prosocial lifestyle. In conclusion the respondents expressed that there is often not only a specific factor that dictates if one is able to maintain nor end criminal behavior, but instead the will to change lifestyle is what must be prominent. Read more
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Atypické využití karuselového soustruhu / Atypical use of a carousel latheOndráček, Ivo January 2018 (has links)
The first part of the diploma thesis deals with a brief research of turning operations and the characteristic of vertical lathes with description of individual parts. There are described possibilities and a typical vertical lathe assortment and also representatives of Czech manufacturers of vertical lathes. In the second part, the thesis deals with elaboration of the design technology production of the selected component, including the NC program. First, a component and material is selected, a semi-finished product is designed, suitable machines and tools are selected and finally a technological process of production is developed. The conclusion of the thesis contains the technical–economic evaluation, where the total costs of production are solved.
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