Дисертації з теми "48V hybrid"

In this work, the possible benefits and drawbacks of 48 Volt E/E systems in MotorSport will be analyzed. MotorSport has always been a lauchpad for new technologies, and in recent years the necessity to increase the electrical power on cars has become a key study topic. Increasing the voltage level is one possible solution to mitigate the downsides of increased power. In this dissertation the technologies currently available on the market will be analyzed, with a focus on 48 Volt systems that are already deployed on hybrid vehicles. Subsequently, a real racing car E/E architecture will be analyzed and the impact of an installation of a 48 Volt system will be evaluated. There follows a discussion on vehicle power supply technologies that are already available and the challenges of the supply systems for the future, ending with a set of simulations and considerations about the power supply system of the car under evaluation.

In today's versatile requirements for reducing fuel consumption, a lot of different approaches are in development like hybridization, reducing the amount of cylinders with the same power as before or operating point-independent components and auxiliaries. Within this thesis, one of the approaches is shown: electrified auxiliaries including an operation strategy. Replacing conventional auxiliaries with electrified ones, the need of more electrical power becomes bigger. Due to the limits within the 12V power net, the 48V approach is the logical conclusion in terms of cost benefit and availability of the needed resources to use the electrified components. The 48V power net introduces new or modified parts to the vehicle including a new power net topology. Fuzzy logic was chosen to control the auxiliaries, because of the number of input variables, the flexibility of using it for different cars and being robust during the usage. The results showed a significant improvement of fuel consumption with the developed control strategy for the selected power net topology. This improvement was evident in all cycles, which were discussed within this thesis. In this thesis a new approach for reducing fuel consumption was shown, which includes several electrified auxiliaries and the operation strategy to control them within the vehicle during different cycles. The necessary models for the approach were developed including the auxiliaries, the controller and the needed parts for the power net.
In der heutigen Zeit mit den steigenden Ansprüchen zur Reduzierung des Kraftstoffverbrauchs sind viele verschiedene Ansätze und Technologien in der Entwicklung, wie zum Beispiel Hybridisierung, Zylinderreduktion mit der gleichen Leistungsausbeute wie zuvor oder auch vom Verbrennungsmotor unabhängigen Komponenten und Nebenaggregaten. Innerhalb dieser Arbeit wurde einer dieser Ansätze näher erläutert: elektrifizierte Nebenaggregate inklusive einer Betriebsstrategie. Durch den Austausch der konventionellen Nebenaggregate mit den elektrifizierten Nebenaggregaten steigt der Bedarf an mehr elektrischer Leistung. Durch die Limitierungen im 12V Bordnetz, ist der 48V Ansatz der nächste logische Schritt hinsichtlich des Kosten/Nutzen-Verhältnis und der Ressourcenverfügbarkeit für die Nutzung der elektrifizierten Komponenten. Das 48V Bordnetz benötigt neue bzw. modifizierte Komponenten inclusive einer neuen Bordnetztopologie. Fuzzy-Logik wurde zur Regelung der Nebenaggregate ausgewählt. Grund hierfür waren: Anzahl an Eingangsvariablen, Flexibilität in der Übertragung auf andere Fahrzeuge und dem robusten Verhalten in der Anwendung. Die Ergebnisse zeigten ein signifikantes Einsparpotential durch die Verwendung der entwickelten Betriebsstrategie für die ausgewählte Bordnetztopologie. Die Einsparung war in allen diskutierten Zyklen deutlich zu sehen. In dieser Arbeit wurde ein neuer Ansatz zur Verbrauchsreduktion gezeigt inklusive elektrifizierter Nebenaggregate und der benötigten Betriebsstrategie, um diese im Fahrzeug in verschiedenen Zyklen zu steuern. Die benötigten Modelle wurden entwickelt, wie zum Beispiel die Nebenaggregate, der Regler und den Bordnetzkomponenten.

Transportation electrification has experienced a significant growth in recent years, and the electrification of the powertrain – namely hybridization – is considered the most viable solution seen by car manufacturers to achieve the challenging emission targets. Among the hybrid electrical powertrain topologies, the mild-hybrid configuration with the 48 V battery system offers the best ratio cost versus CO2 improvements. In particular, the 48 V technology does not require electrical shock protection whilst allows to leverage a variety of fuel saving functions such as electrical boost and regenerative braking. The thesis is focused on the electromagnetic and thermal design of a Belt-driven Starter Generator, BSG, for 48 V mild-hybrid powertrains. In the BSG layout, the starter-generator replaces the conventional alternator with a low impact on the engine compartment layout, even if a redesign of the belt tensioner is required. It is noteworthy to keep in mind that the electrical machine shall provide high starting torque and wide constant power speed range, both in motor and generator mode. Furthermore, the application imposes the adoption of low cost materials and the electrical machine is located in a harsh environment. As a consequence, the design is challenging from the electromagnetic, thermal and mechanical point of view. The novelties of the research lie in the 48 V automotive applications, by describing the practical difficulties to fulfill the design specifications through a suitable material selection, the identification of the cooling system and the available technological solutions. The first section of the thesis reports results from a literature review on electrical machine for mild-hybrid application aiming to highlight different criteria for the selection of the electrical machine. In this context the advantages in terms of fault tolerance and stator current splitting of multiphase drives are investigated. Furthermore, in this section the required performances and the constraints imposed by the specific application are analyzed. Among the different motor technologies, a dual three-phase induction machine having two stator winding sets shifted by 60 electrical degrees is selected as a suitable candidate. The second part of the thesis reports electromagnetic and mechanical issues addressed during the design stage, with special focus on stator winding layout, pole number and rotor slot. The adopted six-phase machine uses a four-layer bar stator winding that has been demonstrated as a good solution to improve the slot fill factor and thermal behavior. In addition, the thesis reports a comparison supported by experimental tests between open and closed rotor slots solutions; the focus is to maximize the machine electromagnetic performance according to the mechanical limits imposed by the rotating speed. Finally, predicted and measured performance of the prototypes are reported and discussed for validation purposes. The third part of the thesis deals with the thermal assessment of the BSG with particular emphasis on accurate winding temperature prediction as well as the cooling system selection. Since the stator-winding region is very sensitive to thermal issues and is usually attributed as being the main heat source within the machine body, its thermal modeling is of major importance. In these regards, a simplified stator winding thermal model was developed for the temperature prediction during transient condition. Moreover, considering that the driving cycle is characterized by time variable loss distribution, an effective cooling system must be mandatorily adopted together with high temperature class insulation material. In this context, the development of heat extraction through forced convection is experimentally investigated on the BSG prototype. As a main outcome of this research activity, it has been demonstrated the feasibility of the proposed design solution with respect to electromagnetic and thermal requirements.

Titanium and its alloys are widely used in various engineering applications such as aerospace, biomedical and chemical industries due to their excellent combination of high strength-to weight ratio and good creep, corrosion and fracture resistance. However, these desirable design properties pose a serious challenge to the manufacturing engineers owing to the high temperatures and stresses generated during the machining of titanium alloys. The extremely low thermal conductivity of titanium alloys results in concentration of high temperature close to the tool cutting edge resulting in accelerated thermochemical and mechanical tool wear. Many cooling and lubricating techniques such as high pressure cooling (HPC), minimum quantity lubrication (MQL) and cryogenic machining have been proposed for improving the machinability of titanium alloys. In this study, a hybrid combination of MQL and cryogenic cooling using liquid nitrogen (LN2) is proposed, designed and manufactured as an innovative cooling/lubricating approach for CNC end milling of Ti-6Al-4V titanium alloy. The machining performance of the new hybrid cooling/lubrication technique is investigated in terms of tool wear and surface finish and compared to that of flood cooling, MQL and cryogenic cooling. The proposed hybrid cooling/lubrication technique demonstrated the best machining performance among all cooling/lubricating conditions and recorded more the 30 fold increased tool life over conventional flood cooling. In addition, 28% reduction in surface roughness was recorded for hybrid cooling/lubrication method as compared to flood cooling. The improvement in surface roughness was 50% for MQL when compared to flood cooling. The outstanding improvement in tool life with hybrid cooling/lubricating strategies is encouraging for the wide spread of this cooling/lubricating technique for industrial adoption.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Friction Riveting is an innovative spot joining technology for metal-polymer hybrid structures. This MSc thesis provided for the first time in the literature, a fundamental understanding on the Friction Riveting process for metal-thermoset composites joints. Joints of Ti-6Al-4V rivet and pultruded glass fiber reinforced thermoset polyester part were produced under three joining conditions with different heat input. Thorough analytical techniques were used to understand the physics of the process and the effect of the energy input on the final microstructure of the joined parts, the physico-chemical changes in the composite and the local and global mechanical properties of the joints. The process temperature reached values up to 761 ± 2°C indicating intrinsic degradation of the composite, formation of a softened/molten glass interlayer between the rivet and the composite and complex metallurgical transformations in the metallic rivet. Through monitoring of the process temperature and torque, an unstable friction regime was observed for FricRiveting of pultruded thermoset composites leading to distinguished extents of composite degradation. The microstructure of the Ti-6Al-4V alloy changed across the length of the rivet, from the equiaxed morphology to acicular structures in the rivet tip, where plastic deformation occurred. Three microstructural zones were proposed for each joint part including two thermo-mechanically affected zones and a heat affected zone. Microhardness mapping was performed in the metallic rivet evidencing an increase from the center to the tip of the rivet, with a hardness increment of over 20% compared to the base material (HVTi6Al4V= 300- 320 HV). The glass interphase consolidated in the metallic surface reached values of up to 974 HV followed by a drastic decrease to 24 HV in the polyester matrix located out of the joint area. The ultimate bearing strength ranged between 60 MPa and 166 MPa. Lesser composite degraded areas led to stronger joints. Two failure modes were observed combining initial composite bearing followed by final failure through shear of the rivet with partial rivet pullout or by full rivet pull-out. Complex failure micro-mechanisms were observed including the combination of cohesive and adhesive failures through the glass layer and the damaged composite interface. Friction-riveted joints achieved an ultimate lap shear strength of up to 80% to that of a similar bolted joint. A case study for a presumptive truss bridge application of friction-riveted joints showed a necessary of 92 rivets per truss node, 43% less than previous studies and with potential for further optimization.
Rebitagem por Fricção é uma tecnologia de união pontual inovadora para estruturas híbridas metal-polímero. Esta tese de mestrado apresenta pela primeira vez na literatura um entendimento aprofundado do processo de Rebitagem por Fricção para juntas de metal e compósito termofixo. Juntas de rebite de Ti-6Al-4V e componente pultrudado de poliéster termofixo reforçado com fibra de vidro foram produzidas seguindo três condições de processo com diferentes aportes térmicos. Diversas técnicas analíticas foram utilizadas para entender a física do processo e o efeito do aporte térmico na microestrutura final dos componentes unidos, mudanças físico-químicas no compósito, formação de camada vítrea intermediária entre o compósito e o rebite metálico e transformações metalúrgicas. Através do monitoramento da temperatura processual e do torque, um regime friccional não estável foi observado para a Rebitagem por Fricção de compósito pultrudado termofixo resultando em distintas extensões da degradação do compósito. A microestrutura da liga de Ti-6Al-4V transforma-se ao longo da secção transversal do rebite, de uma morfologia equiaxial no centro do rebite para uma estrutura acicular em sua extremidade, onde ocorre deformação plástica. Três zonas microestruturais foram propostas para cada componente da junta incluindo duas zonas termo mecanicamente afetadas e uma termicamente afetada. Mapa de microdureza foi realizado no rebite metálico evidenciando um aumento do centro para a extremidade do mesmo, próximo a 20% comparado com o material de base (HVTi6Al4V= 300-320 HV). A interfase vítrea consolidada na superfície do rebite metálico apresentou dureza em torno de 974 HV seguido de um drástico decaimento para 24 HV na matriz de poliéster localizada fora da região de união. A tensão máxima de apoio variou entre 60 e 166 MPa. Juntas com menor área degradada apresentaram os melhores desempenhos mecânicos em ensaio quase estático de cisalhamento. Dois modos de falha foram observados combinando um modo de falha inicial por deformação plástica severa no compósito seguida de falha final por cisalhamento no rebite metálico com parcial remoção do mesmo ou por remoção completa do rebite. Complexos micro mecanismos de falha foram observados incluindo a combinação de falha adesiva e coesiva através da interface entre interfase vítrea e compósito degradado. Juntas rebitadas por fricção atingiram resistência ao cisalhamento de 80% da obtida para juntas parafusadas. O estudo de caso para uma ponte hipotética treliçada revelou um número necessário de rebites de até 92 rebites por nó da ponte, 43% a menos que o encontrado em trabalhos anteriores, com potencial para futuras optimizações.

Trabalho na área de História e Historiografia da Educação que se propõe a conhecer, reconhecer, registrar e refletir a respeito das formas lúdicas em contexto de comunidade quilombola, sob perspectiva de um estudo de caso apoiado em elementos etnográficos. O campo de pesquisa é a comunidade de Bombas, situada em Iporanga, São Paulo, que atualmente busca reconhecimento como remanescente de quilombo. A periodização reside no tempo de ocupação do território pelos ancestrais dos atuais habitantes da região, ou seja, aproximadamente um século (1910 até os dias de hoje). Toma por referência a noção de quilombos contemporâneos. Bombas é um lugar peculiar para estudo: cravado na floresta, não conta com estrada, água encanada, telefones ou luz elétrica. Assumindo o lúdico como elemento da cultura (HUIZINGA, 1996) e a cultura como objeto da História e da Educação, investigam-se no cotidiano os brinquedos, brincadeiras, jogos e outras manifestações lúdicas como festividades, que são praticadas ou fazem parte da memória do grupo. Os sujeitos da pesquisa são jovens, adultos e crianças, observando-se o processo educativo nas relações estabelecidas e não apenas na instituição escola. No campo da metodologia o texto recorre à triangulação de fontes, observando o que Cambi (1999) chamou de pluralismo tipológico de documentos a fim de apreender o objeto (o lúdico) e suas relações com a cultura, História e Educação, propondo, entre elas, um exercício dialógico. São considerados como fontes os registros de campo, imagens do local e das situações tidas como lúdicas, bem como depoimentos e entrevistas dos habitantes e colaboradores, além de alguns documentos escritos oriundos de outros trabalhos. A cada grupo de fontes coube tratamento adequado a sua tipologia, como, por exemplo, no caso das entrevistas, recorre-se a recursos próprios da história oral. Rompendo com a dicotomia habitual que polariza campo/cidade, urbano/rural, ócio/trabalho, culto/popular, tradicional/moderno, dentre outras denominações, o trabalho afirma como pertinente a condição teórica proposta como Culturas Híbridas (GARCIA CANCLINI). Assume como constante o fluxo de idéias, cultura, educação, discursos, produções, enfim, a História em sociedade plural. Desemboca, na área de Educação, nos preceitos que consideram a diversidade como elemento fundamental no trato educativo em qualquer contexto, apontando a necessidade de se desfazer dos modelos que tendem a homogeneizar (e branquear) as relações e padronizar o conhecimento, apontando a urgência em se adotar abordagens e práticas inspiradas pelo multiculturalismo.
A History and Historiography of Education case study project supported by ethnographic elements and intended to understand, acknowledge, record and think about forms of play in a black community. The research is conducted in the community of Bombas, located in Iporanga, São Paulo, which is currently attempting to be recognized as a remnant quilombo (ancient autonomous slave community). The study includes the one hundred year period (from 1910 up to today) of territorial occupation by the ancestors of the current inhabitants of the region, and is based on the notion of contemporary quilombos. Bombas is an unusual location for this study as it is thrust deep in the middle of the forest and has no road, drinking water, telephone or power supply infrastructure. By assuming that playful behavior was an element of the culture (HUIZINGA, 2000), and that this culture was an appropriate subject for History and Education research, the daily use of toys, entertainment and games was studied, as were other manifestations of play, such as festivals and celebrations that are still commemorated or remembered by members of the group. The research subjects included adolescents, adults and children, and the education process within the established relationships, not only in the school institutions, was observed. The study text uses the triangulation of sources methodology and observes what Cambi (1999) has called the typological pluralism of documents to comprehend the objective (playful behavior) and its relationship with culture, history and education, and then to propose a dialogue between them. Field records, images and photos and playful situations were used as sources, as were anecdotal information and interviews with inhabitants and collaborators, and written documents selected from other studies. Each source of study received appropriate treatment for its type; for instance, the interviews relied on oral history resources. By breaking away from the customary dichotomy that polarizes the designations of field/city, urban/rural, leisure/work, erudite/popular, traditional/modern, among others, the study affirms the relevance of the proposed Hybrid Cultures theoretical condition (GARCIA CANCLINI, 2006). It also assumes that the flow of ideas, culture, education, discourse, productions, in short, the History in a pluralistic society, is a constant. In the area of Education, this study follows the principles that consider diversity to be a fundamental educational element in any context by pointing out the necessity to eliminate models that tend to homogenize (and whiten) the relationships and standardize the knowledge, and highlights the urgency of adopting approaches and practices inspired by multiculturalism.

Tucídides, ateniense, pensador político do quinto século antes de Cristo, narrou, em sua única obra, grande parte da história da Guerra do Peloponeso. Convicto de que ela seria grande e mais importante que todas as anteriores (TUCÍDIDES, I.1), o historiador antigo, seguindo o critério da própria razão, reuniu relatos, dados e informações gerais sobre a contenda e as nações envolvidas, selecionou personagens, acontecimentos e discursos para compor sua obra de criação (ROMILLY, 1998). O resultado disso é a impressão, por parte dos leitores, de que acompanharam a guerra, compreenderam suas motivações e entenderam o impacto das ações de seus personagens no desenrolar da contenda. Tal papel foi criteriosamente analisado por Tucídides, que buscou indicar ao longo de sua narrativa histórica a força da physis anthropon na condução da polis. Explorar a natureza humana como causadora da crise e da derrota de Atenas é a resposta de Tucídides para compreender o fim do Império Ateniense e marca o rompimento com a justificativa fantasiosa ou divina que constava, até então, nos registros do passado. Para mostrar isso, fizemos uso do personagem Alcibíades no contexto do debate siciliano (TUCÍDIDES, VI.9-23). Ambientado na assembleia que buscava definir os passos seguintes da Expedição à Sicília, esse debate se originou da negativa de Nícias, um dos comandantes da expedição, de os atenienses partirem em auxílio aos aliados, empregando as forças atenienses contra a Sicília; e se consumou com a resposta de Alcibíades, que ao subir à tribuna, fez a sua grande defesa diante da ekklesia. Deste debate depreende-se a figura de Alcibíades: a do orador que reúne as habilidades para conquistar a confiança de seus ouvintes e para convencê-los sobre o que é benéfico ou não à polis, incitando o medo e inflamando os ânimos dentro de uma lógica argumentativa que atravessou os impulsos e os desejos dos atenienses. As palavras que Tucídides selecionou para o discurso de Alcibíades formam a imagem de um homem intemperante, dominado pela hybris, que se propôs a governar os outros sem antes ter governado a si mesmo. Aliado a esta reflexão, tornou-se possível alargar o quadro proporcionado pelo historiador antigo, tendo em vista as conexões observadas ao longo da pesquisa entre a narrativa histórica tucidideana e as leis de Sólon e a formação do cidadão, proposta pelo Sócrates platônico. A preocupação de Sócrates é a mesma que Sólon explorou em seus versos e na elaboração das leis e é a mesma que Tucídides retratou em sua obra. Enquanto Sólon versou sobre as leis da comunidade social e política (JAEGER, 2010), Sócrates empreendeu uma missão de formar o verdadeiro cidadão para evitar que a mais justa forma de governo se degenerasse.
Thucydides, an Athenian, political thinker of the fifth century before Christ, narrated, in his only work, much of The Peloponnesian War history. Convinced that it would be great and more important than all the previous ones (THUCYDIDES, I. 1), the ancient historian, according to the criteria of his own reason, collected reports, data and general information about the strife and the nations involved, selected characters, events and speeches to compose his work of creation (ROMILLY, 1998). The result of this is the impression on the part of the readers, who accompanied the war, understood its motivations and perceived the impact of the actions of his characters in the unfolding of the strife. This role has been carefully analyzed by Thucydides, who sought to demonstrate over the course of its historical narrative the strength of the physis anthropon leading the polis. Exploring the human nature as the cause of the crisis and Athenss defeat is the response from Thucydides to understand the end of the Athenian Empire, and marks a break with the unrealistic or divine justification that was, until then, in records of the past. To demonstrate this, we have made use of the character Alcibíades in the context of the Sicilian debate (THUCYDIDES, VI.9 -23). Set up in the assembly that sought setting the following steps to the Sicilian Expedition, this debate is originated from the negative of Nícias, a commander of the expedition, from the Athenians breaking in aid to allies, undertaking the Athenian forces against the Sicily; and was consummated with Alcibíadess answer, who climbing up the tribune, made his great defense before the ekklesia. This debate makes it clear that the figure of Alcibíades: the speaker that brings together the skills to win the trust and confidence of his listeners and to convince them of what is beneficial or not to the polis, inciting fear and by exaggerating within a logical argument that crossed the impulses and the desires of the Athenians. The words that Thucydides selected for the Alcibíadess speech constituted the image of an intemperate man, dominated by hybris, who proposed governing others without having governed himself first. Allied to this reflection, it has become possible to extend the framework provided by the ancient historian, having in mind the connections observed along the research between the Thucydidess historical narrative and the Solons laws and the formation of the citizen, proposed by the platonic Socrates. Socratess concern is the same that Solon explored in his lyrics and in the drafting of laws and it is the same as Thucydides portrayed in his work. While Solon focused on the community\'s laws and social policy (JAEGER, 2010), Socrates embarked on a mission to form the true citizen to prevent the most fair form of government of degenerating.

Após uma revisão de trabalhos que se dedicam a investigar as relações entre a docência e a tecnologia em suas múltiplas formas apresentamos uma série de redimensionamentos das ações docentes no contato com tecnologias digitais. Partindo dos quatro verbos fundamentais propostos por Nílson Machado como forma de caracterizar e expressar a natureza das ações docentes mapear, mediar, tecer e narrar discutimos o redimensionamento da docência no contato com aparatos tecnológicos em contextos permeados por tecnologias ou constituídos digitalmente a partir delas, sobretudo em modalidades de educação híbridas e online considerando, portanto, a Educação a Distância (EAD) de variadas formas. Em nossa tese buscamos, além de examinar e apresentar um conjunto de ações e estudos, oferecer subsídios e ideias que possam contribuir para a prática docente, na esperança de ampliar a compreensão das ações do professor no ciberespaço e das relações mediadas por dispositivos digitais examinando diferentes abordagens e formas possíveis de interação com os alunos no interior de uma comunidades de aprendizagem num paradigma ecossistêmico de educação online.
After a review of works devoted to understand the relationships between teaching and technology in its many forms we present a series of teachers\' actions redefined in contact with digital technologies. Based on four key verbs proposed by Nílson Machado as a way to characterize and express the nature of teaching practices mapping, mediating, weaving and storytelling we discourse about the new dimensions of teaching in contact with technology devices in contexts permeated or digitally made by technology, especially in hybrid and online education modalities therefore considering Distance Education (DE) in different perspectives. Besides an examination and after presents a set of researches and proposals, this work seeks to provide insights and ideas that can contribute to the teaching practices, hoping to broaden the understanding of the teacher\'s actions in cyberspace and about the relationships mediated by digital devices examining different forms and approaches of interacting with students inside a learning community in an ecosystem paradigm of online education.

Workshop cluster 1 (WC1) molecules are exclusively expressed on the surface of gamma delta T cells and act as co-receptors and bind pathogens thus also functioning as pattern recognition receptors. The aim was to obtain cDNA evidence to support the recent caprine genome annotation of the WC1 multigene family conducted by a colleague. To get cDNA sequences three strategies were used. Strategy 'I' was used to obtain three clones that corresponded to WC1 SRCR domain d9 through the intracytoplasmic tail sequence. Strategy 'II' was used to obtain 6 clones. A PCR was conducted using SRCR domain b7 through the intracytoplasmic tail sequence. A third strategy obtained full-length WC1 transcripts. The three sequences that extended from SRCR domain d9 to the intracytoplasmic tail matched closely with predicted goat Gene 1 or 14. Another 3 sequences that extended from the SRCR b7 domain through SRCR domain d11 or through the intracytoplasmic tail matched with the predicted Genes 1, 2 and 14, respectively. Two additional full-length cDNA clones CH-MA-03 and 41 were completely sequenced in stages which involved a PCR amplication of the internal domains to complete the sequencing. The a1 domain of CH-MA41 was 100% similar to the annotated and predicted Gene 4 while CH-MA03 also was closest to Gene 4 with a 99% similarity. However, the intracytoplasmic tail sequence of these two cDNA clones was a Type II tail while Gene 4 had a Type I tail. Because of this difference in tails these two cDNA clones had a greater overall similarity with Genes 7 and 15 which had Type II tails. These results suggest that the genome assembly may have errors.

碩士
國立臺灣大學
機械工程學研究所
93
Titanium alloy is well known as one of the typical difficult-to-cut materials. This thesis focuses on the effect of various cooling and lubricating methods on machinability in turning Ti-6Al-4V titanium alloy. The appropriate cutting fluid and its associated flow rate of the minimum quantity lubrication (MQL) applied in the cutting process are determined first. Thereafter, four types of cooling and lubrication methods during cutting are compared. They are machining with the MQL technique, machining with flooded cutting fluid, machining with a heat pipe embedded beneath the insert for heat removal, and machining with the MQL technique together with the assistance of a heat pipe. The most appropriate cooling and lubrication method is determined based on the analysis of the resulting tool wear, cutting force, tool temperature, surface finish and the chip morphology in cutting. It is found that 20% water-based cutting fluid and a flow rate of 20ml/hr are the proper combination of MQL. The use of MQL incorporates with a heat pipe assisting heat removal results in minimum tool wear. The cutting speed in turning Ti-6Al-4V titanium alloy can be increased from the normally recommended 50-70 m/min to 90m/min. Hence improvement of machining efficiency is expected.