Materials which are both lighter and stronger have faced an increased demand over the past decades to fulfil the requirements across a range of industrial applications. More specifically, demands for titanium alloys have increased significantly due to its high strength to weight ratio which is particularly attractive for increasing fuel efficiency in aircrafts and cars and is also used in biomedical implants. Despite the increasing demand for titanium made products, machining titanium alloys remains a significant challenge. High material strength and hardness lead to excessive heat generation at the cutting zone which accumulates and results in high cutting temperatures due to the poor thermal conductivity. The high cutting temperatures together with inherent material properties of titanium are responsible for short tool life and poor surface finish. Despite the environmental and health drawbacks, a generous amount of cutting fluids is commonly used to control the cutting temperature in machining titanium alloys. However, conventional cutting fluids evaporate at high cutting temperatures which isolate the cutting zone by forming a vapour cushion resulting in further increases in cutting temperatures. This research investigates the effects of cryogenic cooling on machinability of Ti-6Al-4V alloy in CNC milling as compared to conventional dry and wet machining environments. Two literature reviews were conducted and a methodology has been developed and implemented consisting of three experimental stages of i) design and manufacture of a cryogenic cooling system, ii) comparative study of cryogenic cooling with dry and wet machining and iii) optimisation of cutting parameters for cryogenic machining. The major contribution of this research can be summarised as design, realisation and assessment of a novel cryogenic cooling system for CNC milling, termed cryogenic shower, which is retrofitable to an existing CNC machining centre. In addition, the research provides a thorough study on the effects of cryogenic cooling on machinability of Ti-6Al-4V alloy in comparison with dry and wet machining. The studies range from power consumption and tool wear through to surface topography and surface integrity. Furthermore, the optimum cutting parameters for cryogenic machining are identified. The research demonstrates that using the cryogenic shower has significantly improved machinability of Ti-6Al-4V through realisation of higher material removal rates, reduced tool wear and improved surface finish, surface topography and surface integrity.

The main objective of this thesis is to apply new ideas to achieve innovation and attractive design of bridge machining center. The final concept should correspond to the technical, ergonomic and aesthetic requirements and at the same time it should fulfil the social and psychological function. Another objective is to impress as many potential users of this machine as possible.

The main objective of this thesis is to apply new ideas to achieve innovation and attractive design of bridge machining center. The final concept should correspond to the technical, ergonomic and aesthetic requirements and at the same time it should fulfil the social and psychological function. Another objective is to impress as many potential users of this machine as possible.

No description available.

The trends of rapid manufacturing (RM) have influenced numerous developments of technologies mainly in additive processes. However, the material compatibility and accuracy problems of additive techniques have limited the ability to manufacture end-user products. More established manufacturing methods such as Computer Numerical Controlled (CNC) machining can be adapted for RM under some circumstances. The use of a 3-axis CNC milling machine with an indexing device increases tool accessibility and overcomes most of the process constraints. However, more work is required to enhance the application of CNC for RM, and this thesis focuses on the improvement of roughing and finishing operations and the integration of cutting tools in CNC machining to make it viable for RM applications. The purpose of this research is to further adapt CNC machining to rapid manufacturing, and it is believed that implementing the suggested approaches will speed up production, enhance part quality and make the process more suitable for RM. A feasible approach to improving roughing operations is investigated through the adoption of different cutting orientations. Simulation analyses are performed to manipulate the values of the orientations and to generate estimated cutting times. An orientations set with minimum machining time is selected to execute roughing processes. Further development is carried out to integrate different tool geometries; flat and ball nose end mill in the finishing processes. A surface classification method is formulated to assist the integration and to define the cutting regions. To realise a rapid machining system, the advancement of Computer Aided Manufacturing (CAM) is exploited. This allows CNC process planning to be handled through customised programming codes. The findings from simulation studies are supported by the machining experiment results. First, roughing through four independent orientations minimized the cutting time and prevents any susceptibility to tool failure. Secondly, the integration of end mill tools improves surface quality of the machined parts. Lastly, the process planning programs manage to control the simulation analyses and construct machining operations effectively.

Finite element simulation of metal cutting processes offers a cost-effective method to optimize the cutting conditions and to select the right tool material and geometry. A key input to such simulations is a constitutive model that describes material behavior during severe plastic deformation. However, the vast majority of material models used in prior work are phenomenological in nature and are usually obtained by fitting a non-physically based mathematical equation to the macro-scale stress-strain response of the material. Moreover, the deformation range covered by the stress-strain response used in the model calibration process usually falls short of the ranges typically observed in metal cutting. This thesis seeks to develop a unified material model that explicitly incorporates microstructure evolution into the constitutive law to describe the macro-scale plastic deformation response of the material valid over the range of strains, strain rates and temperatures experienced in machining. The proposed unified model is based on the underlying physics of interactions of mobile dislocations with different short and long range barriers and accounts for various physical mechanisms such as dynamic recovery and dynamic recrystallization. In addition, the inclusion of microstructure evolution into the constitutive model enables the prediction of microstructure in the chip and the machined surface. In this study, the unified material model is calibrated and validated in the severe plastic deformation regime characteristic of metal machining and is then implemented in finite element simulations to evaluate its ability to predict continuous and segmented chip formation in machining of pure metals such as OHFC copper and commercially-pure titanium (CP-Ti). Due to the physical basis of the proposed unified material model, the continuous chip formation observed in orthogonal cutting of OFHC copper is shown to be successfully predicted by the finite element model utilizing a version of the unified material model that explicitly accounts for microstructure evolution as well as dislocation drag as a plausible deformation mechanism applicable at the high strain rates common in metal cutting operations. The segmented or shear localized chip formation in orthogonal cutting of CP-Ti is also shown to be successfully simulated by the unified model after incorporating the inverse Hall-Petch effect arising from the ultrafine grain structure within the shear band. For both metals, the model is experimentally validated using flow stress data as well as machining data including cutting and thrust forces and relevant chip morphology parameters. Machining simulations carried out using the unified material model also yield useful insights into the microstructure evolution during the machining process, which is shown to be consistent with the available experimental data and the known physical understanding of severe plastic deformation behavior of the metals.

No description available.

The development of prescription methods and evaluation of biomechanical performance of bespoke orthoses has been a source of research for the last 40 years. What started as anecdotal and experience–led knowledge has evolved into a more quantifiable paradigm utilising state of the art technologies commonly found in other high-precision industries. The manufacturing challenges associated with such customised products have been driven by the requirement to produce small (often one-off) batches, bespoke for the end user. The introduction of precise scanning equipment and CAD/CAM systems to the podiatry community is enabling the accurate and repeatable manufacture of orthoses that were previously predominantly hand crafted and shaped. Although these traditional production methods are still in use today, the advantages that scanning and CAD/CAM provide mean they are rapidly being adopted. Today, CNC machining and additive manufacture provide state of the art manufacturing methods for bespoke insoles prescribed and modelled in a CAD environment. However, the limitations of both these manufacturing methods relate to the materials that can be processed, which becomes problematic when manufacturing soft or semi-rigid orthoses. Hence an opportunity exists to develop a new and innovative method for processing foamed polymer materials that are typically vacuum formed today. This research explores the prescription and analysis methods attributed to insole design for sporting applications using specific sports shoes. The insole designs encompass material selection to deliver a product that provides control and function whilst also providing a degree of impact attenuation, recognising the dynamic and high-impact nature of the sportsspecific movements. Consideration is also given to the types of activities that function with the device. This research analyses characteristic plantar pressures experienced whilst undertaking sports-specific movements to aid in the prescription of bespoke insoles for the chosen sport. A design methodology encompassing state of the art scanning technologies and anthropometric measurements provides a repeatable and accurate means to produce the required geometry for a bespoke sport and symptom-specific insole. The research also presents the concept of cryogenic machining, a novel manufacturing method for the CNC machining of foamed polymers. The materials are cooled with the use of a liquid cryogen to below their glass transition temperature at which point relative motion at a molecular level is significantly reduced, providing a rigid and machineable form. This, along with a bespoke cryogenic facility encompassing a vertical 3 axis CNC machining centre, a pressurised liquid nitrogen dewar connected to a bespoke-designed fixture by a vacuum jacketed pipe, enables the dual-sided machining of an amorphous material, something which is not possible with conventional processes. The major contributions of this work are the design methodology to prescribe a sport and symptom-specific insole using state of the art scanning and CAM methods, the design and manufacture of a fixture to facilitate the dual-sided machining of a customised insole and the subsequent testing of the designs in a laboratory environment. In addition the research utilises motion analysis, force plate data and pressure measurement to explore the effects of the insoles on the kinetics, kinematics and peak plantar pressures at discrete anatomical regions during sport-specific manoeuvres.

Orientador: Alessandro Roger Rodrigues / Co-orientador: Hidekasu Matsumoto / Banca: Juno Gallego / Banca: Warley Augusto Pereira / Resumo: Este trabalho tem por objetivo geral realizar um levantamento dos principais tipos de desgaste que ocorrem na usinagem das ligas de alumínio-silício. Como metas específicas, visa-se executar canais em pistões automotivos com duas composições químicas diferentes verificando a influência da velocidade de corte (v c ), avanço (f) e teor de silício contido na liga na vida de um bedame de classe N, além de verificar o efeito do aumento da velocidade de corte, do avanço e do percentual de silício da liga Al-Si na produtividade de canais para bedames de classe N. Para tanto foi utilizado um centro de torneamento Romi GL-240M. Foi adotado como critério de fim de vida do bedame o desgaste de flanco V b = 0,3 mm. A evolução do desgaste foi acompanhado em um estéreo-microscópio Zeiss Discovery V8. Para analisar a influência e o efeito de cada variável citado, foi utilizado a análise de variância (ANOVA). O principal mecanismo de desgaste observado foi a adesão da liga na ferramenta e a abrasão da liga devido à presença do silício. O teor de silício foi o fator de maior influência, onde a liga com menor porcentagem de silício proporcionou maior vida do bedame. A velocidade de corte (v c ) também teve forte influência, sendo que o seu aumento causou diminuição da vida da ferramenta. O avanço (f) também teve influência, no entanto, o seu aumento prolongou a vida da ferramenta / Abstract: This research aims to monitoring the tool wear when turning aluminum-silicon alloys. The specific goal is to turn channels in automotive pistons with two different chemical compositions by checking the influence of the control factors cutting speed (v c ), tool feed (f) and workpiece silicon content on response N-Class chisel life. As well as to study the effect of the same aforementioned variables on channels productivity. A turning center Romi GL-240M was used. 0.3 mm flank wear was adopted as a criterion of tool life. Chisel flank wear was monitored and measured by using a stereo-microscope Zeiss Discovery V8. Analysis of Variance (ANOVA) was used to quantify statistical influences of the control factors upon response. Adhesion and abrasion of the part material over tools were observed. Silicon content was the most influential factor on the channels productivity so that the lower silicon content, the greater tool productivity. Cutting speed and tool feed has influenced on channels productivity strongly. The first one is inversely proportional to tool life whereas the latter is directly proportional to channels productivity / Mestre

Orientador: Marcos Valério Ribeiro / Banca: Humberto Lopes Rodrigues / Banca: Jose Vitor Candido de Souza / Resumo: A usinagem de superligas de níquel e ligas resistentes a altas temperaturas como o inconel 718 sempre representou uma tarefa difícil no chão-de-fábrica. Mas as aplicações industriais desses materiais passaram por rápida evolução nos últimos anos. Na indústria aeroespacial, o crescimento da popularidade destes materiais tem sido evidenciado na forma de palhetas de turbina, peças de compressor, suportes e elementos de conjuntos para aviação. Devido a suas propriedades e aos benefícios que trazem à indústria, o uso destes materiais se expandiu aos setores automotivo, médico, químico, indústria de miniaturas e outras indústrias. Para as superligas e ligas resistentes a altas temperaturas estima-se que a dificuldade na usinagem vai da combinação de forças de corte relativamente altas, combinadas com altas temperaturas que se desenvolvem durante o processo de usinagem. Estes níveis de calor podem causar a deterioração da aresta de corte, com quebras ou deformações. Os tipos comuns de desgaste de ferramenta para estes materiais são primeiramente reconhecidos como desgaste do flanco, entalhes e formação de arestas postiças. O presente trabalho consiste no torneamento cilíndrico externo da liga a base de níquel inconel 718, utilizando ferramenta cerâmica (Si3N4) visando à otimização da usinagem desta liga e buscando proporcionar aumentos reais de produtividade sem a necessidade de investimentos em novos meios de produção. Os ensaios de usinagem foram realizados em um corpo de prova da liga, considerando os parâmetros de usinagem: velocidade de corte, profundidade de usinagem e avanços próprios de acabamento. Os ensaios foram realizados em um torno CNC e ferramentas com pastilha de cerâmica à base de Nitreto de Silício Si3N4. Após cada etapa do torneamento foram realizadas as medidas do comprimento de corte, do desgaste das ferramentas e a rugosidade... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The nickel superalloys and resistant alloys machining to discharges temperatures as the inconel 718 always represented a difficult task in the job-shop. But the industrial applications of those materials went by fast evolution in the last years. In the aerospace industry, the growth of the popularity of these materials has been evidenced in the form of turbine blades, compressor parts, holders and elements of parts for aviation. Due to its properties and to the benefits that bring to the industry, the use of these materials expanded to the automotive sector, medical, chemical, in the industry of miniatures and other industries. For the superalloys and resistant alloys to high temperatures is considered that the difficulty in the machining is going relatively of the combination of high cutting forces, combined with high temperatures that grow during the machining process. These levels of heat can cause to deterioration of the cutting edge, with breaks or deformations. The types common of tool wear for these materials are recognized firstly as flank wear, incisions and formation of build up edge. The present work seeks to develop study of the machining for external cylindrical turning of the nickel base alloy inconel 718, using ceramic tool (Si3N4) seeking to the optimization of machining of this alloy and looking for to provide real increases of productivity without the need of investments in new production means. The machining tests were accomplished in a sample of the alloy, considering the machining parameters: cutting speed, cutting depth and own progresses of finish. The rehearsals were accomplished in a lathe CNC and tools with ceramic insert of Silicon Nitride. After each stage of the turning the measures of the cutting length were accomplished, of the tool wear and the roughness of the pieces (appraised in each phase of the process), with the aid of a portable roughness meter... (Complete abstract click electronic access below) / Mestre