Made available in DSpace on 2014-06-11T19:27:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-12-09Bitstream added on 2014-06-13T20:16:12Z : No. of bitstreams: 1 nascimento_fa_me_guara.pdf: 1927608 bytes, checksum: 45dad02510529469f0740b83b9ea94d2 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os aços inoxidáveis martensíticos, essencialmente ligas Fe – Cr – C, são largamente utilizados na fabricação de componentes de Turbinas Hidráulicas devido à elevada resistência ao ataque químico e a sua maior resistência mecânica, quando comparado aos outros tipos de aços inoxidáveis. A proposta deste trabalho é estudar o acabamento superficial do aço inoxidável AISI 410 sob diferentes condições de corte, visto que este requisito é de suma importância para o funcionamento de alguns componentes de Turbinas Hidráulicas. Serão avaliados também os diferentes tipos de cavacos obtidos, os desgastes nas ferramentas de corte e comparados os resultados de rugosidade obtidos experimentalmente com os valores obtidos através da utilização da equação proposta pela literatura. Durante os ensaios foram variados os parâmetros de corte, sendo eles a velocidade de corte, o avanço por volta, a profundidade de corte e o tipo de pastilha, e medida a rugosidade para cada condição. Com os valores de rugosidade obtidos experimentalmente foi possível, através de uma regressão linear, propor uma equação para o seu cálculo e comparar estatisticamente os erros encontrados da utilização de ambas as equações. Os resultados mostraram que as condições de acabamento não são severas a ponto de desgastar as pastilhas, que a formação da APC influencia diretamente na rugosidade, que a pastilha com geometria Wiper fornece baixos valores de rugosidade quando empregados altas taxas de avanço e que são observadas grandes variações quando comparados os resultados de rugosidade obtidos nos ensaios com os calculados pela equação teórica da rugosidade. / The martensitic stainless steel, essentially alloys Fe – Cr – C, are widely used for the manufacture of Hydraulic Turbines components due to its high resistance to chemical attack and its greater mechanical resistance, when compared to other stainless steels. The proposal of this work is to study surface roughness on the AISI 410 stainless steel under different cutting conditions, since this requirement is very important to the correct functioning of some components of Hydraulic Turbines, the different types of chips, the wears on the cutting tools and to compare the results of roughness obtained experimentally and calculated by using the equation proposed by the literature. During the tests was varied the cutting parameters, witch were the cutting speed, the feed rate, the depth of cut and the tool, measuring the superficial roughness for each condition. With the values of roughness obtained experimentally was possible, using a linear regression, to purpose an equation to calculate the surface roughness and the comparison between the errors when used both equation. The results has shown that the finishing conditions are not severe enough to initiate the wear on cutting tools, the BUE influences the roughness, the Wiper geometry results in low values of roughness when using high feed rates and it is observed great variations when compared roughness results obtained experimentally and the results from the theoretical equation for roughness calculation.

No description available.

No description available.

An overall framework to provide a complete tool management solution to an existing or specified manufacturing system is constructed, and prototype software provided, for a hierarchy of levels of tool flow automation. The work is targeted at the design and operation of tooling systems for prismatic parts flexible machining systems ranging from stand-alone unmanned machining stations to highly automated multi-machine multi-cell configurations. The research work moves from identification and category definition of a tool flow network appropriate for the manufacturing requirements, through the careful selection and definition of operating rules and strategies to the evaluation of the options available for tool issue and assignment. Two main computer aids (design facilities) to provide support in a systems thinking approach to tool flow management have been developed and tested with the aid of case studies. The essential role of these design facilities is the timely scheduling of tools to satisfy a short to medium term manufacturing task, and to examine the cost and number of captive tools under selected rules and strategies.

No description available.

Electrochemical machining (ECM) is a non-conventional machining technique capable of machining any conductive substrate, regardless of its physical properties e.g. hardness. ECM became an attractive method due to its ability to machine substrates without creating a defective surface layer. ECM utilises electrolysis; a small gap is maintained between two electrodes whilst a favourable potential is applied between them to remove material from the workpiece. The parameters are adjusted to obtain the desired machining results i.e. surface finish, machining resolution and machining rate. Much work has been conducted for the anodic dissolution of stainless steels and brass but little work outside of these materials is available. This work demonstrates the applicability of ECM for a new range of materials; superconductors and semiconductors, along with the application of ECM for medical needle production and an alteration to the machine set up to anodically dissolve titanium metal at reduced potentials. Through a series of electrochemical techniques, namely polarisation curves, machining potentials were defined for a cuprate superconductor and a semiconductor. These were then demonstrated as suitable settings by completing tests on an electrochemical machine. Hypodermic needles were created on an electrochemical machine and polarisation curves of titanium with the addition of ultrasonic vibrations were used to demonstrate the anodic dissolution of titanium at much reduced potentials.

The University of Manchester,Mohamad Farizal RAJEMI,Doctor of Philosophy,Energy analysis in turning and milling,2010.Energy generation as driven by consumption demand is a key contributor to carbon dioxide emissions and climate change. Hence reducing energy usage is an essential consideration in sustainable manufacturing. In addition, the world is experiencing a higher demand and cost of energy, hence reducing energy usage is an important factor for cost control and economic sustainability. Energy availability and security is now recognised as a key aspect to the socio-political sustainability of nations. Thus, reducing energy demand can be associated with the three; economic, environmental and social sustainability pillars. The manufacturing sector is a key industry that relies on the use of energy in driving value adding manufacturing processes. A widely used process is mechanical machining. This PhD was focussed on an investigation of energy consumption in machining processes and the energy footprints of machined products. A literature review had indicated that despite decades of optimising of machining operations based on cost and productivity, optimising energy use had not received significant attention. In the study a current monitoring device was used to evaluate current requirements and hence power and energy needs for machining processes. The study was done for (i) a range of workpiece materials and (ii) the turning and milling process. This enabled the definition of energy distribution for a machining process and identification of key areas of focus in order to reduce the energy used by a machine tool. The study was then focused on an energy intensive material in terms of machining requirements (titanium alloys) and an in-depth characterisation of the impacts of conventional compared to high speed machining was undertaken. From the study it was clear that a methodology was needed to ensure that energy use can be reduced or optimised. Thus an energy footprint model for a machined component was developed. This model was then used to derive an optimum tool life equation that satisfies the minimum energy criterion. A methodology for selection of optimum cutting conditions was then developed and tested on a component. Thus, the Thesis presents a new and novel model and methodology for selecting optimum cutting conditions for machining, based on minimum energy requirements. The energy savings associated with using such methodologies are quantified and found to be very significant. This work makes a distinct and important contribution to the machining science for reducing the energy and carbon footprints of machined products.

Mechanical micro machining is an emerging material removal process in precision manufacturing industries. There are challenges involved in micro drilling of difficult to cut alloys. These relate to the development of a feasible and reliable manufacturing process given the fragile nature of the micro drill and the poor machinability of difficult to cut materials. Moreover, the established knowledge of macro scale machining may not be directly transferable into micro machining domain. Therefore, mechanical micro machining needs to be adapted to a specific application. Currently, electrical discharge machining (EDM) is an established industrial process for making micro holes in nickel alloys. The mechanical micro drilling process is at present being considered for improved surface integrity, better hole definition and high productivity. Considering the potential of mechanical micro drilling process in nickel based super alloys, the research presented in this thesis focused on developing a novel micro drilling strategy and a process window. Having developed the process window and selected optimum tool geometry, workpiece surface integrity was evaluated at various cutting conditions. Mechanical and microstructural characterization of the modified layers was conducted using electron backscatter diffraction (EBSD), focused ion beam (FIB), backscatter election (BSE), transmission electron microscopy (TEM) and nano-indentation techniques. The mechanisms behind the generation of these modified layers were revealed. The effects of various feedrates, cutting speeds and tool edge radius were analyzed under dry and wet cutting conditions. A new and novel contribution to modified material microstructure analysis was presented in dry and wet drilling conditions. Furthermore, important findings were presented on the tool-chip and tool-workpiece cutting zones. This research provides a comprehensive picture of the surface integrity definition of the micro hole features in drilling nickel based super alloys. Since nickel based super alloys are known for their poor machinability, tool life becomes an important economic variable. For this purpose, tool wear was studied in the micro machining domain. A new tool wear map was developed on a feed-speed plane, identifying low tool wear zones at high productivity. Wear mechanisms were identified which contributed to better understanding of tool-workpiece interactions. A range of different heat resistant and wear resistant coatings were tested which helped identifying the critical material requirements of machining these alloys. Finally, after having developed a complete set of requirements for the mechanical micro drilling process in terms of process window, suitable tool geometry, workpiece surface integrity, tool wear evaluation and selection of suitable coatings for the micro drilling process; the surface integrity produced by mechanical drilling was compared with EDM and laser drilling processes. Mechanical and microstructural character of surface and subsurface layers was assessed. Comparison of surface integrity parameters showed that the mechanical micro drilling process has the potential to benefit industry making micro size holes with better hole definition and surface integrity. This work is an important contribution to industry in that it presents process feasibility assessment and characterization and is regarded by the industrial partners as having achieved Manufacturing Capability Readiness Level (MCRL) 3.

The adoption of Electrical Discharge Machining (EDM) technologies to mainstream manufacturing saw dramatic advances in the process starting in the 1980's. Wire Electrical Discharge Machining (WEDM) in particular achieved enhancements in cutting speed of over 800% between 1980 and 1992 due to improvements in generator and wire technology. Since then, increases in cutting speed have been gradual. To achieve dramatic improvements to the process once again, a paradigm shift, from improving upon existing technologies to introducing and developing new one is required. In this light, an investigation into the proof-to-concept and development of a novel hybrid machining process based upon Wire Electrical Discharge Machining (WEDM) and abrasive technologies is presented. In the process termed Abrasive Wire Electrical Discharge Machining (AWEDM), material removal is shown to occur by the simultaneous action of electrical erosion and abrasion. Through experimental evaluation, this combination is shown to bring about a manyfold improvement in the material removal rate and to generate machined surfaces with minimal recast layer, in comparison to conventional WEDM processes. To understand the operation of the process and to control the proportion of abrasion and EDM taking place, the effect of varying the process conditions is studied. The servo-reference voltage and peak discharge current, in particular, provide effective means to control the process. Practical implementation of the process presents several challenges, such as accurately guiding an abrasive wire; a discussion of some of these issues and possible solutions is included. The need for a wire that is specially suited to AWEDM is demonstrated with a discussion of the requirements and possible designs for such a wire. Whether or not a manufacturing process sees practical industrial use is chiefly dictated by economics. By considering the increase in both productivity and wire cost, AWEDM is shown to be economically feasible and offer potentially substantial benefits. This work ultimately serves as the basis for future work with respect to AWEDM. The work herein covers a broad range of topics in hopes of guiding future areas of research. / Thesis / Master of Applied Science (MASc)

Water-repellent behaviour, known as hydrophobicity, has recently attracted a great deal of interest due to its applications, such as anti-icing and self-cleaning. The phenomenon of hydrophobicity found in surfaces like lotus leaves is manifest by a hierarchical structure on low-energy surfaces. Fabrication of hydrophobic surfaces has thus far been largely accomplished on polymers and colloidal materials, which are limited by poor mechanical strength that leads to performance degradation over time. To this end, fabrication of a robust metallic hydrophobic surface is the focus of this research. Sink electrical discharge machining is demonstrated to generate hydrophobic surfaces in 7075 aluminum alloy with water contact angles in excess of 150˚. / Thesis / Master of Applied Science (MASc)