Dissertations / Theses on the topic 'Cooling and Lubrication'

The manufacturing sector is one of the most rapidly growing sectors in the industrialized world today. Manufacturing industry is concerned with being more competitive and profitable. Profit margins are directly related to the productivity of the company, and productivity improvements can be achieved by making manufacturing processes more efficient and sustainable. Knowledge of cutting conditions and their impact on machined surface and tool life enable productivity improvement.  These days the main emphasis is not only to increase productivity, but also to make processes cleaner and more environmental friendly.  This research aims to study machinability of difficult to cut, titanium alloys, in close reference to the application of different cooling/ lubrication strategies and their environmental impact. Total energy consumed (kWh) and carbon dioxide (CO2) emissions produced in machining are common environmental indicators. In this research project environmental implications of the cutting process were calculated in terms of carbon dioxide (CO2) emissions and energy consumption analysis. The experimental work consisted of controlled machining tests with cutting force, surface roughness, power, and flank wear measurements under dry, mist, combination of vegetable oil mist and cooled air (MQL+CA) and flood cutting environments. The current study provides better understanding of the cutting performance of TiAlN coated and uncoated carbide tools. The study also investigated tool failure modes, tool wear mechanisms, surface roughness and energy consumption to improve machinability of Titanium alloys.  The study revealed the promising behaviour of minimum quantity lubrication (MQL) under specific ranges of cutting speed for both coated and uncoated tools.  Variation in the cutting force showed close link with built up edge (BUE) formation. MQL based systems have huge potential to improve machinability of Titanium alloys and should be investigated further.

QC 20140407

Modern machining involves more dependence on green manufacturing techniques. Minimum Quantity Cooling Lubrication (MQCL) of machining processes has replaced conventional flood cooling in many applications, involving various materials and cutting conditions. The use of this technique results in considerable reductions in the quantity of lubricant used, reducing manufacturing costs as well as the impact of the process on the environment. With the objective of achieving a fuller understanding of this technology, an interest has been taken in the properties of the aerosol, and their impact on machining performance. This study presents an attempt to understand these properties through the use of experimental and numerical flow visualization techniques, followed by machining experiments. The Particle Image Velocimetry study revealed how the MQCL nozzle geometry and the injection parameters (air and lubricant flow rates) which control the Sauter Mean Diameter (SMD) of the resulting droplets, affect the flow, and that droplets with smaller SMD are more capable of following the air flow. Computational Fluid Dynamics simulations showed that a single-phase (air only) simulation is sufficient in describing the flow, when comparing the simulation and experimental (real flow) PIV results. They also revealed that the potential thermal benefits of the air flow can be achieved if the nozzle orientation vis-à-vis a model tool is exploited. Comparisons of MQCL with conventional flood cooling and dry machining modes in milling of Carbon-Fibre Reinforced Plastics (CFRP) revealed that the benefit of MQCL (namely lower tool wear and higher geometric accuracy of the machined part), can be achieved if the atomization parameters are set for appropriate lubrication and SMD size.
L'usinage moderne implique plus de dépendance des techniques de manufacture verte. La micro-lubrification (Minimum Quantity Cooling Lubrication) des processus d'usinage a remplacé l'arrosage conventionnel dans le cas de plusieurs applications, impliquant des matériaux et des conditions d'usinage variés. L'usage de cette méthode mène à des réductions considérables de la quantité de lubrifiant utilisé, réduisant ainsi les coûts de fabrication ainsi que l'impact du processus sur l'environnement. Un intérêt a été porté aux propriétés de l'aérosol, et leurs effets sur la qualité de l'usinage, ayant pour objectif une meilleure compréhension de cette technologie. Cette étude est une tentative de mieux comprendre ces propriétés à travers l'usage des techniques de visualisation de débit expérimentaux et numériques, suivis par des essais d'usinage. L'étude Particle Image Velocimetry (PIV) a démontré comment la géométrie de la buse el les paramètres d'injection (débits d'air et de lubrifiant) qui contrôlent la taille du diamètre moyen de Sauter (SMD) des gouttelettes résultantes, affectent le débit, mais aussi que les bulles ayants les tailles SMD les plus petites sont les plus efficace lorsqu'il s'agit de suivre le débit de l'air. Des essais numériques (Computational Fluid Dynamics) ont démontré que des simulations monophasiques (air seulement) sont suffisantes pour bien décrire le débit, en comparant avec les résultats du PIV (débit réel). Ils ont aussi démontré que les avantages thermiques de l'air peuvent être obtenus si la position de la buse vis à vis de l'outil est exploitée. Des comparaisons entre l'MQCL et de arrosage conventionnel et usinage à sec lors d'essais de fraisage de plastique à renfort fibre de carbone (PRFC) ont montré que les avantages de l'MQCL, notamment un usage réduit et une plus grande efficacité géométrique de la pièce usinée, peuvent être obtenus si les paramètres d'atomisation sont choisis pour une lubrification suffisante et taille SMD appropriée.

Titanium alloys are widely utilized in the aerospace, biomedical,marine, petro-chemical and other demanding industries due to theirdurability, high fatigue resistance and ability to sustain elevateoperating temperature. As titanium alloys are difficult to machine, dueto which machining of these alloys ends up with higher environmentalburden. The industry is now embracing the sustainable philosophy inorder to reduce their carbon footprint. This means that the bestsustainable practices have to be used in machining of titanium alloys aswell as in an effort to reduce the carbon footprint and greenhouse gas(GHG) emissions.In this thesis, a better understanding towards the feasibility of shiftingfrom conventional (dry and flood) cooling techniques to the vegetableoil based minimum quantity cooling lubrication (MQCL) wasestablished. Machining performance of MQCL cooling strategies wasencouraging as in most cases the tool life was found close to floodstrategy or sometimes even better. The study revealed that theinfluence of the MQCL (Internal) application method on overallmachining performance was more evident at higher cutting speeds. Inaddition to the experimental machinability investigations, FiniteElement Modeling (FEM) and Computational Fluid Dynamic (CFD)Modeling was also employed to prediction of energy consumed inmachining and cutting temperature distribution on the cutting tool. Allnumerical results were found in close agreement to the experimentaldata. The contribution of the thesis should be of interest to those whowork in the areas of sustainable machining.

QC 20150915

Next generation defense and commercial applications for structural steels require new alloys that eliminate or reduce critical elements from their composition to lower cost and improve manufacturability, while maintaining or exceeding high strength and toughness requirements. A new alloy, denoted as AF9628, has recently been developed for this purpose and its manufacturing characteristics and the material response in component manufacturing must be fully understood. In the present study, hardened AF9628 alloy was turned with a coated carbide cutting tool under fixed cutting speed, feed rate, and depth of cut parameters. This work focuses on chip-form and tool-wear analysis to understand, for the first time with AF9628, these fundamental aspects of the turning process and their relationship to productivity and part quality. Current industry standard practice of flood-cooled machining for AF9628 was used during machining experiments. Dry, minimum quantity lubrication (MQL), and cryogenic machining were investigated as alternative cooling and lubrication conditions. High-speed imaging during AF9628 turning experiments provides a new insight into the chip formation process, while the use of optical microscopy and scanning white light interferometry allowed for further characterization of chip-form and tool-wear. Chip-form is favorable as short, arc-shaped chips with new tools under all of the tested cooling and lubrication conditions. As a result of rapid wear at the end of the tool-life in all of the experimental conditions, chip-form evolves to unfavorably long, snarled ribbon-like chips and the resultant cutting force increased by as much as 64% under flood-cooled conditions. Tool-wear types that were observed during experiments include a combination of nose wear, built-up edge, plastic deformation, and groove wear on the rake face. Due to the fixed cutting parameters and cutting tool selected for this study, which were designed for flood-cooled machining in a prior study, undesirable failure of the cutting tools under dry, MQL, and cryogenic machining occurred. Future work requires experimentation across a wider processing space, and with different cutting tools, to thoroughly evaluate alternative cooling and lubrication techniques for machining AF9628.

The use of cutting fluids in machining process is very essential for achieving desired machining performance. Due to the strict environmental protection laws now in effect, there is a wide-scale evaluation of the use of cutting fluids in machining. Consequently, minimal quantity lubrication (MQL), which uses very small quantity of cutting fluids and still offers the same functionality as flood cooling, can be considered as an alternative solution. This thesis presents an experimental study of face milling of automotive aluminum alloy A380 under four different lubrication/cooling conditions: dry cutting, flood cooling, MQL (Oil), and MQL (Water). Experiments were design using Taguchi method for design of experiments. Empirical models for predicting surface roughness and cutting forces were developed for these four conditions in terms of cutting speed, feed and depth of cut. Optimization technique using Genetic Algorithms (GA) was used to optimize performance measures under different lubrication/cooling conditions, based on a comprehensive optimization criterion integrating the effects of all major machining performance measures. Case studies are also presented for two pass face milling operation comparing flood cooling condition with MQL. The comparison of the results predicted by the models developed in this work shows that the cutting force for MQL (Oil) is either lower or equal to flood cooling. The surface roughness for MQL (Oil) is comparable to flood cooling for higher range of feed and depth of cut. A comparison of the optimized results from the case studies, based on value of utility function, shows that the optimum point for two pass face milling operation having MQL (Oil) as finish pass has highest utility function value.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
É analisada a influência das técnicas de mínima quantidade de lubrificante (MQL), refrigeração otimizada e refrigeração convencional, com diferentes vazões e velocidade de aplicação do fluido de corte, na qualidade das peças produzidas (acabamento, erros de forma, trincas, queima, perda da dureza) com aços endurecidos, no processo de retificação cilíndrica externa de mergulho com a utilização de rebolos superabrasivos com baixa concentração de CBN. Utilizou-se fluidos de corte de origem vegetal, que representam menos riscos à saúde e ao meio. A análise da qualidade das peças foi realizada através da avaliação das variáveis de saída do processo como o comportamento da força tangencial de corte, energia específica de retificação, rugosidade, desvio de circularidade, emissão acústica, tensão residual, análise de microscopias eletrônicas de varredura e microdureza. Com a análise das formas de aplicação e das várias vazões e velocidades do fluido de corte utilizadas encontraram-se condições de lubri-refrigeração que propiciam a diminuição do volume de fluido de corte, diminuição do tempo de usinagem sem prejudicar os parâmetros geométicos, dimensionais, o acabamento superficial e a integridade superficial dos componentes. Em relação as diferentes formas de aplicação do fluido de corte notou-se o melhor desempenho da aplicação otimizada para maiores velocidades mostrando a eficiência de um novo conceito de bocal utilizado. O processo otimizado e o processo MQL foram capazes de manter a dureza superficial e a integridade superficial das peças produzidas. Exceção somente para a condição MQL com vazão de fluido de corte de 40ml/h que produziu trincas e retêmpera superficial. O desvio de circularidade e a rugosidade proporcionada pelos métodos estão dentro de valores recomendados para a retificação sendo que a técnica otimizada...
The influences on surface integrity of the parts (finishing, geometrical errors, cracks, burn, microhardness) and grinding wheel (wear) have been analyzed in this research by employing the minimum quantity of lubrication (MQL), optimized and conventional cooling for hardened parts of steel and superabrasives grinding wheel in the cylindrical plunge grinding process. This study was carried out through the assessment of the process output variables such as the behavior of the tangential cutting force, specific energy, surface roughness, circularity errors, acoustic emission, residual stress, scanning electronic microscopy (SEM) and microhardness. The cutting fluid derived from vegetal oil has been utilized in order to comply with the environmental requirements and thus offering less risk to the health. It could be observed from the analysis on different ways of cutting fluid applications that there are cooling conditions which facilitate the decrease in cutting fluid volume, decrease in grinding time without impairing the geometrical and dimensional parameters, the surface finish and surface integrity of the parts. It could be noted the optimized application for higher velocities has presented the best performance regarding the different applications of cutting fluids. The optimized and MQL processes were able to maintain the hardness and surface integrity of the ground parts. Exception occurend only for MQL condition with flow rate of 40ml/h, which led to cracks and quench on the workpiece surface. Roundness errors and surface roughness are within recommended valus for grinding with the best results obtained for the optimized method (2'mü' for roundness error and 0.5'mü'm for surface roughness) compared with the MQL technique (6.8'mü'm for roundness error and 1.2'mü'm for surface roughness). The process of minimum quantity of lubrication, however, has showed possible... (Complete abstract click electronic access below)

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Atualmente há por parte das empresas uma constante preocupação com a atualidade de seus sistemas produtivos, buscando a melhoria da eficiência dos processos respeitando as leis de preservação ambiental. Dentro desse contexto e considerando que o segmento das cerâmicas corresponde a aproximadamente 1% do PIB brasileiro, com perspectiva de crescimento, inúmeros estudos têm sido feitos nesse campo de pesquisa. Contudo, ainda se tem um alto custo agregado ao acabamento da peça, o qual é feito, na maioria dos casos, pelo processo de retificação. Além do alto custo do processamento, o uso de fluidos de corte tem se tornado um problema para a indústria devido à dificuldade de descarte imposta pela rígida Legislação Ambiental. Face ao exposto, o presente trabalho propõe o estudo de métodos alternativos de lubri-refrigeração para o processo de retificação externa de mergulho de cerâmica avançado com rebolo diamantado. Tais métodos visam diminuir os gastos com fluido de corte, sendo eles: a técnica de lubri-refrigeração otimizada e a de mínima quantidade de lubrificação (MQL). A avaliação das técnicas foi feita através do monitoramento do processo e da quantidade final da peça retificada. Mais especificamente, foram analisados: força tangencial de corte, rugosidade, relação G, desvio de circularidade, microestrutura e tensão residual por difração de raios X. Os resultados obtidos mostram que as duas técnicas propostas podem substituir o método convencional de lubri-refrigeração, destacando-se que a técnica otimizada reduziu o desgaste do rebolo e produziu pelas com melhor acabamento geométrico e dimensional, enquanto a técnica de MQL reduziu significativamente a quantidade de fluido utilizado no processo
During the last years there has been a constant concern by the companies about the modernization of their manufacturing methods, seeking to improve the process efficiency and environmental preservation. In this context, and considering the ceramic segment corresponds to approximatelly 1% of Brazilian GDP, with growing perspective, many studies have been done in this area. Nevertheless, the work piece finishing is still expensive, mainly because it has been usually made by the grinding process. Besides of the high cost of the process, the use of cutting fluids has become a problem for the industry because of the discard dificulty imposed by the rigorous environmental laws. In this way, the present work proposes alternative methods for the lubrification and cooling in the external cylindrical plunge grinding of advanced ceramic with diamond wheels, which aims to reduce the costs with cutting fluid. These methods are: the optimized cooling and the Minimal Quantity Lubrication (MQL) techniques. The evaluation of these techniques has been made by the process monitoring and the work piece final quality. In the present work the following analysis techniques were used: tangential cut force, roughness, G relation, circularity deviation, microstructure and residual stress by X ray diffraction measurements. The results show both proposed techniques can replace the conventional cooling method. The main result is that the optimized technique reduced the cutting tool consuming and produced work pieces with better dimensional finishing, while the MQL techniques significantly reduced the volume of cutting fluid in the process

Orientador: Eduardo Carlos Bianchi
Coorientador: Paulo Roberto de Aguiar
Banca: Dayse Iara dos Santos
Banca: Roosevelt Droppa Junior
Banca: Leonardo Roberto da Silva
Banca: Jaime Gilberto Duduch
Resumo: Atualmente há por parte das empresas uma constante preocupação com a atualidade de seus sistemas produtivos, buscando a melhoria da eficiência dos processos respeitando as leis de preservação ambiental. Dentro desse contexto e considerando que o segmento das cerâmicas corresponde a aproximadamente 1% do PIB brasileiro, com perspectiva de crescimento, inúmeros estudos têm sido feitos nesse campo de pesquisa. Contudo, ainda se tem um alto custo agregado ao acabamento da peça, o qual é feito, na maioria dos casos, pelo processo de retificação. Além do alto custo do processamento, o uso de fluidos de corte tem se tornado um problema para a indústria devido à dificuldade de descarte imposta pela rígida Legislação Ambiental. Face ao exposto, o presente trabalho propõe o estudo de métodos alternativos de lubri-refrigeração para o processo de retificação externa de mergulho de cerâmica avançado com rebolo diamantado. Tais métodos visam diminuir os gastos com fluido de corte, sendo eles: a técnica de lubri-refrigeração otimizada e a de mínima quantidade de lubrificação (MQL). A avaliação das técnicas foi feita através do monitoramento do processo e da quantidade final da peça retificada. Mais especificamente, foram analisados: força tangencial de corte, rugosidade, relação G, desvio de circularidade, microestrutura e tensão residual por difração de raios X. Os resultados obtidos mostram que as duas técnicas propostas podem substituir o método convencional de lubri-refrigeração, destacando-se que a técnica otimizada reduziu o desgaste do rebolo e produziu pelas com melhor acabamento geométrico e dimensional, enquanto a técnica de MQL reduziu significativamente a quantidade de fluido utilizado no processo
Abstract: During the last years there has been a constant concern by the companies about the modernization of their manufacturing methods, seeking to improve the process efficiency and environmental preservation. In this context, and considering the ceramic segment corresponds to approximatelly 1% of Brazilian GDP, with growing perspective, many studies have been done in this area. Nevertheless, the work piece finishing is still expensive, mainly because it has been usually made by the grinding process. Besides of the high cost of the process, the use of cutting fluids has become a problem for the industry because of the discard dificulty imposed by the rigorous environmental laws. In this way, the present work proposes alternative methods for the lubrification and cooling in the external cylindrical plunge grinding of advanced ceramic with diamond wheels, which aims to reduce the costs with cutting fluid. These methods are: the optimized cooling and the Minimal Quantity Lubrication (MQL) techniques. The evaluation of these techniques has been made by the process monitoring and the work piece final quality. In the present work the following analysis techniques were used: tangential cut force, roughness, G relation, circularity deviation, microstructure and residual stress by X ray diffraction measurements. The results show both proposed techniques can replace the conventional cooling method. The main result is that the optimized technique reduced the cutting tool consuming and produced work pieces with better dimensional finishing, while the MQL techniques significantly reduced the volume of cutting fluid in the process
Doutor

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.

Diploma thesis deals with a topic of lubrication and cooling of the ball screw rotary nuts. The first part is focused on a research behind the theory of ball screws and ball screw rotary-nuts. The three types of construction were developed in the second half of the thesis. Each construction is designed as an external attachable cooling and lubrication unit, which can be installed on an existing, slightly modified ball screw rotary-nut. For cooling and lubrication, only one type of medium is used and that is a cooled oil. External unit provides medium flow to ball screws working space. On top of diploma thesis tasks a design concept of ball screw rotary-nut with an integrated cooling and lubrication is introduced itself. Both described designs could become interesting for an industrial market.

Le développement de l’industrie du transport conduit la conception de transmissions mécaniques de puissance toujours plus légères et efficientes. Les composants de ces transmissions doivent supporter des efforts transmis dans des environnements de plus en plus restreints. Du fait que les carters soient devenus de plus en plus compacts, les systèmes de refroidissement se sont aussi complexifiés. C’est dans ce contexte que les paliers à roulement, plus communément appelés roulements, doivent produire moins de chaleur, opérer dans des espaces plus proches des engrènements, tout en ayant des durées de vie plus grandes. Le calcul des pertes énergétiques des roulements est essentiel pour quantifier la quantité d’huile à injecter pour refroidir ces composants. L’objectif de cette étude est donc de fournir des outils pour modéliser les pertes dans les roulements et leur comportement thermique. Dans un premier temps, une analyse bibliographique a été menée sur les pertes de puissance dans les roulements, incluant des modèles locaux et globaux de pertes de puissance. Un banc d’essais dédié a été utilisé afin d’analyser les puissances dissipées et la thermique de roulements à billes à gorge profonde. Les influences de la vitesse de rotation, du chargement, de la température d’injection, du débit d’huile injecté, des techniques de lubrification ont été examinées. Les modèles globaux précédemment investigués ont été comparés aux données expérimentales. Enfin, un modèle thermique a été développé pour comprendre l’influence des transferts de chaleur dans les pertes de puissance générées par les roulements. Des comparaisons entre différentes lubrifications et différentes géométries ont été faites. Une nouvelle formule du couple résistif a été proposée pour mieux prendre en compte la géométrie du roulement considéré
The development of the transport industry has led to design lighter and more efficient transmission systems. The components within these transmissions have to withstand the transmitted loads in closer environments. As the housing has become more compact than ever, the cooling system has also become more complex. In that context, Rolling Element Bearings (REBs) are required to produce less heat, to work closer to the gear meshes while having higher life-expectancies. The calculation of REB power loss is essential to quantity the amount of injected oil to cool off these components. This study therefore aims at providing tools to model REB power loss and their thermal behaviour. As a first step, a bibliographical survey was conducted on REB power losses, including local and global models. A dedicated test rig has been used to analyse the power losses and the thermal behaviour of Deep Groove Ball Bearings. The influence of rotational speed, load, oil injection temperature, oil flow rate and lubrication design has been investigated. The above-mentioned global models have been compared to the experimental data. Finally, a REB thermal model has been developed in order to understand the influence of heat-transfer within REBs on power losses. Comparisons between different lubrication designs and between different geometries have been done. A new formulation to better take into account the REB geometry in the global models has been proposed

Content of this thesis is design of one-housing condensing steam turbine with two uncontrolled extractions. First part is describing design of balance scheme. Including cycle joints calculation, design of equipment for whole steam and condense cycle. Thesis continues with preliminary and detail design of regulativ stage. Main goal of this part is thermodynamic calculation of flow channel. Second part is describing lubricating oil and cooling system. Contains process description of lubricating oil scheme including calculation, specification of components and pipe branches design. Diploma thesis is finished with detail lubricating oil scheme.

La technologie du palier à feuilles (GFB) est l’un des facteurs clés pour la transition envisagée vers des machines tournantes sans huile dans les futurs moyens de transport. Outre les nombreux avantages en termes de taille, de poids, d’efficacité et de propreté, les GFBs offrent la possibilité unique d’être lubrifiés par des fluides de travail tels que les réfrigérants. Cependant, l’analyse numérique des systèmes GFB–rotor lubrifiés par réfrigérant représente un problème interdisciplinaire d’une énorme complexité et d’intérêts contradictoires entre des approches de modélisation et de résolution exhaustives mais performantes. Dans ce mémoire de thèse, il est possible d’explorer et de surmonter les limites de faisabilité actuelles, ce qui permet d’établir une nouvelle stratégie permettant des analyses de stabilité et de bifurcation
The gas foil bearing (GFB) technology is considered one of the key factors for the intended transition to oil-free rotating machinery in future transportation systems. Besides numerous advantages in terms of size, weight, efficiency, and cleanliness, GFBs offer the unique ability to be lubricated with working fluids such as refrigerants. However, the computational analysis of refrigerant-lubricated GFB–rotor systems represents an interdisciplinary problem of enormous complexity and with conflicting interests between all-encompassing but efficient modeling and solution approaches. This thesis succeeds in exploring and pushing forward existing limits of feasibility and thereby establishes a new strategy that enables stability and bifurcation analyses

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.

碩士
國立虎尾科技大學
創意工程與精密科技研究所
99
Along with widening applications of titanium alloy, the requirement to the machining quality of related parts has been heightened, and their functions could be fulfilled only through grinding process. Due to the low thermal conductivity and high chemical activity of titanium alloy, the high temperature of grinding would be concentrated on the surface layer, which would cause the grinding wheel adhesion and loading, as well as heat damage on the ground surface. Numerous difficulties have become the major factors resulting in its failure of extensive application. For this reason, this study investigated the grinding performance and grinding quality in combination of the green manufacturing technology under hot research both at home and abroad. This study conducted the grinding experiment on titanium alloy by two kinds of green manufacturing technologies (minimum quantity lubrication and liquid nitrogen cooling), and the conventional coolant by CBN grinding wheel. Dynamometer and spectrum analyzer were used in the grinding experiment to monitor the grinding force and vibration, respectively. The chips under different process parameters, surface morphology and surface roughness were observed to conduct analysis and discussion of the experimental data. The result showed that compared with the conventional coolant grinding, the minimum quantity oil mist provided lubrication for the grinding zone, as well as cooling effect of compressed air to reduce grinding wheel adhesion so as to reduce the grinding force. Observation on the flowing-type chip found that the minimum quantity oil mist improved the grinding conditions, and achieved a better ground surface quality than that of the conventional coolant grinding. Processing by cryogenic cooling has exhibited the cooling advantages and characteristics to maintain the grinding area at a low-temperature state, which could help to reduce material toughness of the workpiece and the grinding wheel adhesion resulted by chemical activity. Moreover, it could also maintain the abrasive grit under a sharp status to improve the grinding performance, and keep the grinding force, vibration magnitude and surface quality controlled under a lower and stable level. From the synthesis results and investigations, it shows that when increasing wheel speed and decreasing depth of cut that will be reduced the grinding force and grinding wheel adhesion, and the quality of ground surface will thus be improved.

碩士
國立虎尾科技大學
機械與電腦輔助工程系碩士班
101
In the recent year, the glass substrate has become gradually the most important material of the development in the information technology enterprise, its demanding quantity is increasing higher and higher, the quality of various processing have been requested more severer. For the time being, the enterprise of glass processing is mainly on cutting and edge seaming, the process flow is complicated and the cost is higher, therefore , the important topics of the current processing technology are seeking for the breakthrough of short process and the efficient cost saving . Because the glass possesses the quality of high intensity, high stiffness and low thermal conductivity, it is easy to make the cutting tool have the fast abrasion in the processing period and have imperfections like cracks and edge/corner collapse on the processing surface. To improve the above problems, the high rotation speed and low cutting depth and cooling fluild are employed in this study, also collocates the suitable feed rate and proceed the side milling/cutting, control the tough and brittle milling/cutting transformation model hopefully, thus, improve the processing efficiency of the glass substrate. The study employs large and medium water- soluble cutting fluid and green Production technique MQL and uses the diamond Tungsten Carbide (WC) cutting tool to proceed the milling/cutting experiment of the glass substrate. During the milling/cutting experiment, dynamometer and spectrum analyzer are employed to monitor the cutting force and vibration quantity, respectively. Also, observing the quality of edge surface of glass and the abrasion of cutting tool under different experiment parameters by tool-microscope off-line. The experimental data are analyzed under numerical analysis. Results show that the comparison between the traditional medium quantity of pouring wet milling/cutting and MQL, large quantity of pouring wet milling/cutting provide a good quenching effect on processing zone, thus, reduce the abrasion of the cutting tool and contribute to lower the cutting force. Observing from the cutting dynamic vibration quantity reveals that adding the water- soluble cutting fluid will contribute to improve and lower the cutting vibration and provide the stable action of cutting. Another observing from the damage of the raw material edge reveals that the better surface quality of the glass edge is obtained under high cutting speed, low feed rate and shallow path cutting. Adding the water- soluble cutting fluid can lower effectively the large amount of heat which is generated in the processing period of the glass surface. The high temperature difference between the surface and the inner layer of the glass is avoided, thus, the internal stress of the glass increases and over the limited intensity of the glass itself, then, leads to the break of the glass. Observing from the abrasion quantity of the cutting tool reveals that adding the water- soluble cutting fluid in the milling/cutting period, when increasing the cutting depth, the apparent dent damage will appear on the abdomen part of the cutting tool as the feed rate is increasing. Applying the MQL processing will make the cutting tool collapse the edge and shell off on its front end. Making a comprehensive survey of all the performance of milling/cutting, raising the cutting speed, lowering both of the cutting depth and the feed rate will reduce the occurrence of damage of glass substrate edge effectively, upgrade the cutting tool life and obtain the better quality of edge surface.

碩士
國立成功大學
機械工程學系碩博士班
98
This thesis discussed surface roughness and tool wear in milling tool steel material with different cutting fluid supply conditions. SKD11(HRc60) and SKD61(HRc40) were milled on the condition of high pressure air cooling and ultrasonic lubrication. The milling force was analyzed to identify both the cutting coefficients of shearing and plowing effects individually. The experiment results showed that less tool wear and better roughness of milling surface can be found on the condition of ultrasonic lubrication and less radial cutting depth. Even on the condition of higher radial cutting depth, the influences of the ultrasonic lubrication to the milling performance were superior to that of the high pressure air cooling.According to the cutting coefficients identified from the milling force, the plowing coefficient in tangential direction mostly reduced while supplying the ultrasonic lubricant. Moreover, the ultrasonic lubrication can suppress the rapid growth of milling temperature more efficiently than the high pressure air cooling when cutting load was increased in milling the high hardness tool steel.