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Ghadimzadeh, Seyed Reza. "Machining of hypereutectic aluminium-silicon alloy." Thesis, Coventry University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281726.
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Quinn, R. W. "Machining damage in silicon nitride ceramics." Thesis, University of Surrey, 1992. http://epubs.surrey.ac.uk/843210/.
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This Thesis is primarily concerned with the effects of abrasive machining (diamond grinding) and diamond indentation on the fracture properties of a range of silicon nitride materials. Test specimens machined to surface finishes representative of those found on Aero Gas Turbine components were produced for Modulus of Rupture (MOR) testing, and variations in the fracture strengths were assessed. Optical and Scanning Electron Microscopy (SEM) were performed as a means of identifying the nature of the defects found within these materials. Having determined the dependence of strength and reliability on the machined surface finish, attempts were made to palliate the machining damage by thermal annealing and Nitrogen Ion Implantation. X-ray diffraction residual stress measurements were performed in order to quantify the magnitude of the near surface stresses in both the "as machined" and annealed conditions.* Diamond indentation techniques (Vickers and Knoop) were employed in order to determine the hardness of the materials studied and to quantify the extent of the Indentation Size Effect (ISE). These studies were then extended to the point of indentation fracture as a means of assessing the materials fracture toughness (KIC) and the nature of the crack systems beneath the indentation. *Residual stress measurements were carried out on a sub contract basis at the CEGB Central Laboratories by P E J Flewitt and D Lonsdale, their help throughout this work is gratefully acknowledged.
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Nicholson, Garth Martyn John. "The ultrasonic machining of silicon carbide/alumina composites." Thesis, Sheffield Hallam University, 1998. http://shura.shu.ac.uk/20119/.
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Silicon carbide fibre reinforced alumina is a ceramic composite which was developed in conjunction with the Rolls-Royce Aerospace Group. The material is intended for use in the latest generation of jet engines, specifically for high temperature applications such as flame holders, combustor barrel segments and turbine blade tip seals. The material in question has properties which have been engineered by optimizing fibre volume fractions, weaves and fibre interface materials to meet the following main requirements : high thermal resistance, high thermal shock resistance and low density. Components intended for manufacture using this material will use the "direct metal oxidation" (DIMOX) method. This process involves manufacturing a near net shape component from the woven fibre matting, and infiltrating the matting with the alumina matrix material. Some of the components outlined require high tolerance features to be included in their design. The combustor barrel segments for example require slots to be formed within them for sealing purposes, the dimensions of these features preclude their formation using DIMOX, and therefore require a secondary process to be performed. Conventional machining techniques such as drilling, turning and milling cannot be used because of the brittle nature of the material. Electrodischarge machining (E.D.M.) cannot be used since the material is an insulator. Electrochemical machining (E.C.M.) cannot be used since the material is chemically inert. One machining method which could be used is ultrasonic machining (U.S.M.).The research programme investigated the feasibility of using ultrasonic machining as a manufacturing method for this new fibre reinforced composite. Two variations of ultrasonic machining were used : ultrasonic drilling and ultrasonic milling. Factors such as dimensional accuracy, surface roughness and delamination effects were examined. Previously performed ultrasonic machining experimental programmes were reviewed, as well as process models which have been developed. The process models were found to contain empirical constants which usually require specific material data for their calculation. Since a limited amount of the composite was available, and ultrasonic machining has many process variables, a Taguchi factorial experiment was conducted in order to ascertain the most relevant factors in machining. A full factorial experiment was then performed using the relevant factors. Techniques used in the research included both optical and scanning electron microscopy, surface roughness analysis, x-ray analysis and finite element stress analysis. A full set of machining data was obtained including relationships between the factors examined and both material removal rates, and surface roughness values. An attempt was made to explain these findings by examining established brittle fracture mechanisms. These established mechanisms did not seem to apply entirely to this material, an alternative method of material removal is therefore proposed. It is hoped that the data obtained from this research programme may contribute to the development of a more realistic mathematical model.
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Crawford, Gregory Allan. "Process characterization of Electrical Discharge Machining of highly doped silicon." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74893.
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Thesis (Nav. E. and S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 107).
Electrical Discharge Machining (EDM) is an advanced machining process that removes material via thermal erosion through a plasma arc. The machining process is accomplished through the application of high frequency current (typically through a fine wire or some other electrode) to a conductive workpiece. The electrode is physically separated from the workpiece by some small distance and the potential difference is commonly discharged through an insulating dielectric material such as deionized water or oil. This short duration application of current produces a spark across the gap between the electrode and workpiece, causing vaporization and melting of local material in both the electrode and workpiece. The EDM process is most frequently used for conductive substrates (i.e. metals); however, research has shown that the process may be successfully used on semiconductor substrates such as doped silicon wafers'. The purpose of this research was to characterize the EDM process using Design of Experiments (DOE) statistical methodology on highly doped silicon wafer workpieces for material removal rate (MRR) and surface roughness (Ra) for both Wire EDM (WEDM) and die sinker EDM machines. Once process characterization was completed, confirmation testing was conducted for each machine. The applied spark energy had a significant impact on processing speed for both machines as expected, with the WEDM processing also heavily dependent on selected control speed. Surface roughness was also found to be highly dependent on spark energy for both machines. Evaluation of minimum obtainable feature sizes for some specific geometries as well as evaluation of various effects on the processing of silicon were also conducted.
by Gregory Allan Crawford.
Nav.E.and S.M.
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Kirwan, M. A. Q. "Diamond machining in 5 wt% Y2O3 sinter hipped silicon nitride." Thesis, University of Surrey, 1992. http://epubs.surrey.ac.uk/843045/.
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A collaborative research project was set up to study peripheral diamond wheel machining damage in silicon nitride ceramics. The objective of the work to be carried out at the University of Surrey was to study the nature and depth of machining damage in 3 point flexural rupture test bars made from 5 wt% Y2O3 sintered hot isostatically pressed silicon nitride. The bars were machined to three surface finishes. The work carried out at Rolls-Royce by Mr R Quinn concentrated on the effects the machining damage had on the fracture strengths of the test bars. Work at the University of Surrey has identified in detail the nature and depth of machining damage in "coarse" 0. 4mum centre line average roughness surfaces. Deep grooves up to 2mum depth, 18mum width are found to have been superimposed on the general surface roughness by singularly large diamonds in the 350 grit diamond wheel. Sub-surface median cracks normal to the machining direction were clearly identified in bar cross-sections using oblique, diffuse "penumbra" illumination in an optical microscope, an as yet undocumented technique. Cross-section views of the machined surface and sub-surface were made possible by the very difficult and delicate technique of producing sandwich cross-sections of the machined bars. An analysis of machining-induced median cracks has not been carried out in such detail before. Semi-elliptical in shape the median cracks extend from 6mum - 45mum below the machined surface, and range from 19mum to 101mum in length parallel to the machining direction. They initiate at the focal point of a tributary system of microcracks at an average depth of 4mum - 5mum below the machined surface. It is believed that the median cracks initiate at the plastic/elastic boundary of a plastically deformed surface layer. Therefore a residual compressive layer, formed by the overlap of localised residual stresses from multi-particle contact events. and bound by an underlying tensile field, is thought to have an average depth of 4mum - 5mum. A very innovative technique was used to reveal sub-surface deformation, where TEM X-ray microdiffraction spots were distorted by mechanical damage in the ceramic grain structure. The "arcing" or "streaking" of the diffraction spots tended to disappear at a depth of 4mum - 5mum below the machined surface. This is further evidence of the existence of a thin layer in residual compression, which has an average depth of 4mum - 5mum. This technique is not known to have been used before. Fine diamond machining with a 600 grit wheel produced a centre line average roughness of 0.01/0.02 mum. However, evidence of machining damage is still present in the form of "remnant tracks" which lie parallel to the machining direction and consist of material pull-out. They are remnants of machining damage under grinding grooves introduced in previous machining stages. Single point Vickers pyramid diamond scratches were implemented at different loads on a polished surface. The morphology of the grooves and material fragmentation and the sub-surface median cracks were examined. Many features were found to resemble the deformation/fracture formed under a deep grinding groove in the coarse machined surface. Work carried out at Rolls-Royce by R Quinn showed that an increase in the quality of surface finish is accompanied by an increase in the mean strength and Weibull modulus of the machined bars. Furthermore a distinct anisotropy in the fracture strengths parallel and normal to the "coarse" machining direction is evidence of anisotropy in machining damage formed by a peripheral diamond grinding wheel. X-ray diffraction tests carried out at the CEGB by P E J Flewitt showed that machining damage produces a long range biaxial residual compressive field with the highest component acting normal to the machining direction. These results are consistent with the nature of machining damage identified at the University of Surrey, namely the strength-controlling median cracks which lie parallel to the machining direction and the residual compressive stress which exists as a thin 4mum - 5mum layer below the machined surface. Processing flaws were discovered in the as-hipped billets received for the project. Their elemental composition and likely origin were examined. A three dimensional "cellular network" flaw ranging from 400mum to 2.1mm in size (in different production batches) is believed to have been formed as a result of flocculation clustering during processing. Clusters of 1mum - 3mum metallic particles were also identified. They range from 5mum - 45mum in size. The contaminant particles are steel and were introduced as a result of the original ceramic powder ball milling process which employed a steel ball mill.
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Cannon, Bennion Rhead. "Design and Analysis of End-Effector Systems for Scribing on Silicon." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/95.
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This thesis investigates end-effector systems used in a chemomechanical scribing process. Chemomechanical scribing is a method of patterning silicon to selectively deposit a monolayer of material on the surface of the silicon. This thesis details the development of a unique end-effector for chemomechanical scribing using a compliant mechanism solution. The end-effector is developed to scribe lines that have uniform geometry and produce less chipping on the surface of the silicon. The resulting scribing mechanism is passively controlled, has high lateral stiffness, and low axial stiffness. The mechanism is analyzed using the pseudo-rigid-body model and linear-elastic beam method to determine the axial stiffness, finite element methods to determine the lateral stiffness, and fatigue analysis to determine mechanism cycle life. This thesis also investigates the significance of mechanical factors on the chemomechanical scribing process using the compliant end-effector. The factors examined are scribing force, scribing speed, tip geometry, wafer orientation, and wetting liquid. The factors are analyzed using a two-step approach: first, an analysis of the influence of the mechanical factors on line characteristics and second, an analysis of the influence of line characteristics on line performance.
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Guo, Lei. "Modelling of microstructure development in silicon-containing bainitic free-machining steels." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/264766.
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This research aims to model the microstructure development of Si-containing bainitic free-machining steel, including allotriomorphic ferrite, idiomorphic ferrite, pearlite, Widmanstatten ferrite, bainite and martensite. The effect of recalescence has been included to give a better estimation of the cooling curve under natural cooling conditions. A model for estimating retained austenite size distribution in the carbide-free bainitic microstructure has been developed. Manganese sulphide particles are used in the free-machining steel to break chips during machining; its effect on the prior austenite grain size has been investigated, taking account of the sulphide shape. The theories of all the major solid state phase transformations involved in steel are reviewed in chapter 2. The theory of the simultaneous transformation model is presented in chapter 3.uu A recalescence model dealing with the heat of reaction has been developed in chapter 5 for bar-shaped products. The model is based on the integration of a heat transfer model, considering latent heat generation, into the simultaneous transformation framework. It has been found that latent heat can greatly affect the transformation, especially in the case of pearlite and Widmanstatten ferrite. Chapter 6 presents the model for estimating the size distribution of retained austenite regions. The model builds on the random division of an austenite grain by bainite sheaves, which means the sizes of the two new compartments generated by the division of an austenite grain by a bainite sheaf are allocated randomly. The next compartment to be divided is also chosen at random. Good agreement between prediction and experiment has been achieved for high carbon carbide-free bainitic microstructures. The transition temperature from upper to lower bainite is modelled in chapter 7. The model compares the time required for decarburising a supersaturated bainitic ferrite platelet and that for cementite precipitation within the ferrite platelet. Manganese, silicon and chromium are considered in the model. It is suggested that carbon and manganese favour lower bainite, whereas silicon promotes upper bainite. The effect of manganese sulphide particles on austenite grain boundary motion has been studied in chapter 8. These rod-shaped particles span many austenite grains; the result shows that the long rod-shaped particles are more effective in pinning the austenite grain boundary than spheres of the same volume, or even strings of identical spheres with the same total volume. Experimental work is presented in chapters 9 and 10. In situ synchrotron X-ray study of the bainite transformation reveals that the distribution of carbon in the residual austenite becomes heterogeneous as transformation progresses. Low carbon regions transform preferentially into martensite during cooling after isothermal bainite transformation. The partitioning of carbon was found to lag behind the bainite transformation; more time is needed as the transformation temperature is reduced. Tetragonality was not observed in either the bainitic ferrite or martensite, because the carbon content of the alloy is relatively low, and the Zener ordering temperature is below the bainite and martensite transformation temperature. No significant difference was observed in the kinetics of bainite transformation between the high sulphur and low sulphur steel.
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Shen, Xinwei. "Numerical modeling and experimental investigation of laser-assisted machining of silicon nitride ceramics." Diss., Kansas State University, 2010. http://hdl.handle.net/2097/6645.
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Doctor of PhilosophyDepartment of Industrial & Manufacturing Systems Engineering
Shuting Lei
Laser-assisted machining (LAM) is a promising non-conventional machining technique for advanced ceramics. However, the fundamental machining mechanism which governs the LAM process is not well understood so far. Hence, the main objective of this study is to explore the machining mechanism and provide guidance for future LAM operations. In this study, laser-assisted milling (LAMill) of silicon nitride ceramics is focused. Experimental experience reveals that workpiece temperature in LAM of silicon nitride ceramics determines the surface quality of the machined workpiece. Thus, in order to know the thermal features of the workpiece in LAM, the laser-silicon nitride interaction mechanism is investigated via heating experiments. The trends of temperature affected by the key parameters (laser power, laser beam diameter, feed rate, and preheat time) are obtained through a parametric study. Experimental results show that high operating temperature leads to low cutting force, good surface finish, small edge chipping, and low residual stress. The temperature range for brittle-to-ductile transition should be avoided due to the rapid increase of fracture toughness. In order to know the temperature distribution at the cutting zone in the workpiece, a transient three-dimensional thermal model is developed using finite element analysis (FEA) and validated through experiments. Heat generation associated with machining is considered and demonstrated to have little impact on LAM. The model indicates that laser power is one critical parameter for successful operation of LAM. Feed and cutting speed can indirectly affect the operating temperatures. Furthermore, a machining model is established with the distinct element method (or discrete element method, DEM) to simulate the dynamic process of LAM. In the microstructural modeling of a β-type silicon nitride ceramic, clusters are used to simulate the rod-like grains of the silicon nitride ceramic and parallel bonds act as the intergranular glass phase between grains. The resulting temperature-dependent synthetic materials for LAM are calibrated through the numerical compression, bending and fracture toughness tests. The machining model is also validated through experiments in terms of cutting forces, chip size and depth of subsurface damage.
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Rivero, Paz Ive. "The effect of key microstructure features on the machining of an aluminum-silicon casting alloy /." View online, 2010. http://ecommons.txstate.edu/engttad/1.
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Velasco, Ivann Civi Lomas-E. "Dynamic Body Armor Shape Sensing Using Fiber Bragg Gratings and Photoassisted Silicon Wire-EDM Machining." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/9201.
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In this thesis, a method to improve survivability is developed for fiber Bragg gratings under high velocity impact in dynamic body armor shape sensing applications by encasing the fiber in silicone. Utilizing the slipping of the fiber within the silicone channel, a proportionality relationship between the strain of the fiber to the acceleration of the impacting projectile is found and is used to obtain the rate of the back-face deformation. A hybrid model is developed to handle errors caused by the stick-slip of the fiber by fitting an inverse exponential to stuck sections found in a captured strain profile and double integrated to transform the stuck section to its equivalent slipping. Displacement errors below 10% was achieved using the hybrid model. A graphical user interface with a step-by-step walkthrough and a fiber Bragg grating interrogation system was designed for test engineers to utilize this technology. Test engineers from the Army Test Center in Aberdeen, MD were trained on this technology and successfully captured and processed shots using this technology. A method for cutting Silicon through wire-EDM machining is developed by utilizing the photoconductive properties of Silicon. Cut rates for unilluminated and illuminated Silicon was compared and a 3x faster cut was achieved on the illuminated cuts.
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Churi, Nikhil. "Rotary ultrasonic machining of hard-to-machine materials." Diss., Manhattan, Kan. : Kansas State University, 2010. http://hdl.handle.net/2097/2509.
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Cali, Serdal. "An Experimental Study On Single Crystal Diamond Turning Of Optical Quality Silicon." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12609235/index.pdf.
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Silicon is commonly used in infrared (IR) imaging systems. The surface quality is
an important issue in optics manufacturing since surface roughness affects optical
performance of imaging systems. Surface quality of an optical component is
determined by number of factor, including cutting parameterscutting speed, depth of cut and feed in radial direction. In this thesis, an experimental study has been performed to investigate the relation between cutting parameters and average roughness of the surface of silicon. In the experiments, silicon specimens, which have a diameter of 50 mm, were face turned by using a 2-axis CNC single point diamond turning machine. The specimens were machined by using either constant spindle speed or constant cutting speed. Two different tools with rake angles of -15 degrees and -25 degrees were used. The attained surfaces were measured by using a white light interferometer, which has a resolution of 0.1nm. The experiments were designed according to the factorial design method, considering cutting parameters. The effects of cutting parameters and tool rake angles on surface quality of silicon were observed. The best average surface roughness obtained was about 1 nm which is quite better than the acceptable average surface roughness level of 25 nm.
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Skokan, Jan. "Vliv plastifikátoru na technologii zpracování a vlastnosti slinovaného keramického mateiálu na bázi SiC." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231997.
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This master’s thesis deals with an influence of physical properties and machining technology at adjustment to the basic composition granules and production of technical ceramics. Selected series of experiments have been applied to the different phases of production. Composition of the granules vary according to the used plasticizer and ranks to RTP (ready-to-press) materials. The goal of this thesis is recomendation to the production of RTP granules and next experiments.
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Jesus, Edilson Rosa Barbosa de. "OBTENÇÃO, USINAGEM E DESGASTE DE MATERIAIS COMPÓSITOS DE MATRIZ METÁLICA PROCESSADOS VIA METALURGIA DO PÓ." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/85/85132/tde-25052007-163032/.
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O objetivo deste trabalho foi a obtenção de compósitos de matriz metálica (CMM) pela rota da metalurgia do pó, e a avaliação destes quanto às suas características de usinagem e desgaste. Inicialmente foram obtidos materiais compósitos de matriz de alumínio comercialmente puro, com frações volumétricas de partículas de reforço de carboneto de silício iguais a 5, 10 e 15 %. Foi obtida também uma quantidade de material somente com o material da matriz (sem partículas de reforço) para que se pudesse durante o trabalho, verificar por comparação a influência da adição de material de reforço na matriz. O material obtido foi caracterizado física (densidade hidrostática), mecânica (dureza, ensaios de tração) e microestruturalmente (microscopia óptica e microscopia eletrônica de varredura). Os resultados mostraram para os materiais compósitos uma distribuição homogênea das partículas de reforço e melhoria das propriedades mecânicas principalmente o limite de resistência (LR) em relação ao material sem reforço. Na etapa seguinte foram realizados ensaios para verificação do comportamento dos materiais frente à usinagem, e avaliação de desempenho de diversos materiais de ferramenta (carboneto cementado, cerâmica e diamante policristalino). Nestes ensaios foram coletados valores de força de corte a partir de porta-ferramentas instrumentados com medidores de deformação. Fenômenos tais como desgaste da ferramenta, formação ou não de aresta postiça de corte e formação de cavaco também foram observados e avaliados. Os resultados encontrados nos ensaios com ferramenta de carboneto duro sinterizado foram utilizados para a determinação dos índices de usinabilidade de cada material; estes valores foram ainda aplicados na equação de Taylor e as constantes da equação para os materiais e condições de ensaio foram também determinadas. Os resultados mostraram que a inclusão de partículas de reforço cerâmico torna extremamente difícil a usinagem desses materiais e, somente com ferramenta de diamante foi possível obter resultados satisfatórios. Na fase final foram realizados testes de desgaste de efeito comparativo para verificação da influência da adição de partículas de reforço nas características de resistência ao desgaste do material. Neste caso a adição de partículas de reforço mostrou ser eficiente na melhoria da resistência ao desgaste de todos os materiais compósitos em relação ao material sem reforço.The aim of this investigation was the obtainment of metal matrix composites (MMC) by the route of powder metallurgy, and the valuation of these materials with relation to their machining and wear characteristics. Firstly, were obtained pure comercial aluminium matrix composites materials, with 5, 10 and 15% volumectric fraction of silicon carbide particles. Was also obtained a material without reinforcement particles in order to verify by comparison, the influence of adittion of reinforcement particles. The obtained materials were characterized physics (hidrostatic density), mechanics (hardness and tensile tests) and microstructurally (optical microscopy and scanning electron microscopy). The results showed a homogeneous distribution of reinforcement particles in the composite, and improvement in the mechanical properties, mainly tensile strength (UTS) in comparison to the unreinforced material. After, tests were made to verify the materials behavior during machining and to check the performance of several tool materials (cemented carbide, ceramics and polycrystalline diamond). In these tests, values of the cutting force were measured by instrumented tool-holders. Phenomena such as tool wear, built-up edge formation and mechanism of chip formation were also observed and evaluated. The results from the cemented carbide tool tests, were utilisated for the machinability index determination of each material. These results were applied to the Taylor equation and the equation constants for each material and test conditions were determinated. The results showed that the inclusion of silicon carbide particles made extremely difficult the machining of the composites, and only with diamond tool, satisfactory results were obtained. At last, wear tests were performed to verify the influence of the reinforcement particles in the characteristics of wear resistance of the materials. The results obtained were utilized in the wear coefficient determination for each material. The results showed an improvement in wear resistance, with the increase in volume fraction of reinforcement particles.
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Kudrna, Tomáš. "Elektroerozivní hloubení technické keramiky." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417445.
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The master’s thesis deals with the topic of electrical discharge machining. The first part of the thesis contains a study of the die-sinking EDM. The die-sinking EDM of the silicon carbide ceramic is realized in the experimental part of the thesis. The result of this work was to explore the influence of the EDM sinking parameters, specifically pulse current, open-voltage and pulse on-time, on the machined surface. Furthermore, the analysis of the tool electrode was made. This analysis was focused on the wear in the corners, which has key influence on accuracy of the machining. The machining time was also examined.
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Bellaredj, Mohamed Lamine Fayçal. "Méthodes et outils pour la fabrication de transducteurs ultrasonores en silicium." Phd thesis, Université de Franche-Comté, 2013. http://tel.archives-ouvertes.fr/tel-00937560.
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L'utilisation des ultrasons pour l'imagerie présente plusieurs avantages : elle est extrêmement sure car ellen'utilise pas de radiations ionisantes et ne présente pas d'effets néfastes sur la santé. D'autre part, elle donne desrésultats d'excellente qualité avec un coût relativement faible. Historiquement, les matériaux piézoélectriques et leurscomposites ont été très tôt utilisés pour la génération d'ultrasons. Les transducteurs fabriqués à partir de ces matériauxdominent actuellement le marché des sondes ultrasonores. Cependant, pour certaines applications, ils ne peuvent pasêtre utilisés pour des raisons de dimensionnement et de limitations dues aux propriétés des matériaux. Une solutionpeut être apportée par l'utilisation des transducteurs ultrasonores capacitifs micro-usinés dits CMUTs. Ces dernierssuscitent un intérêt croissant dans le milieu de l'imagerie ultrasonore et sont considérés comme une alternativepotentielle et viable aux transducteurs piézoélectriques. Cette nouvelle technologie CMUTs est caractérisée par uneplus large bande passante, une sensibilité élevée, une facilité de fabrication et une réduction des coûts de production.Cette thèse est consacrée à la mise en place d'un certain nombre d'outils théoriques et expérimentaux permettant lamodélisation/conception, la fabrication et la caractérisation de transducteurs CMUTs à membrane circulaire pourl'émission des ultrasons. Nous commençons par développer des outils de simulation à base de calculs par élémentsfinis, permettant la compréhension et la modélisation du comportement électromécanique des CMUTs pour laconception et le dimensionnement des cellules élémentaires et des réseaux. Nous proposons par la suite un nouveauprocédé de fabrication de transducteurs CMUTs basé sur le collage anodique d'une couche de silicium monocristallind'épaisseur fixe d'une plaquette de SOI sur un substrat de verre. L'évolution du procédé de fabrication est détailléepour chaque étape technologique en soulignant à chaque fois les améliorations/modifications apportées pour unefiabilité et une répétitivité accrue associées à une connaissance des limites de faisabilité. Dans la dernière partie de cetravail, on s'intéresse à la mise en œuvre de plusieurs plateformes expérimentales permettant différentescaractérisations électromécaniques statiques et dynamiques des dispositifs CMUTs fabriqués
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Holmberg, Patrik. "Laser processing of Silica based glass." Doctoral thesis, KTH, Laserfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-173929.
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The main topic of this thesis work is photosensitivity and photo-structuring of optical fibers and bulk glass. Although research in the field of photosensitivity in glass and optical fibers has been ongoing for more than three decades, the underlying mechanisms are still not well understood. The objective was to gain a better understanding of the photo-response by studying photosensitivity from a thermodynamic perspective, as opposed to established research focusing on point defects and structural changes, and strain and stress in optical fibers. Optical fibers was mainly used for experimental studies for two reasons; first, photosensitivity in fibers is more pronounced and more elusive compared to its bulk counterpart, and secondly, fibers provide a simplified structure to study as they experimentally can be seen as one-dimensional.Initially, ablation experiments on bulk glass were performed using picosecond infrared pulses. With a design cross section of 40x40 μm, straight channels were fabricated on the top (facing incident light) and bottom side of the sample and the resulting geometries were analyzed. The results show a higher sensitivity to experimental parameters for bottom side ablation which was ascribed to material incubation effects. Moreover, on the top side, the resulting geometry has a V-shape, independent of experimental parameters, related to the numerical aperture of the focusing lens, which was ascribed to shadowing effects.After this work, the focus shifted towards optical fibers, UV-induced fiber Bragg gratings (FBGs) and thermal processing with conventional oven and with a CO2 laser as a source of radiant heat.First, a system for CO2 laser heating of optical fibers was constructed. For measuring the temperature of the processed fibers, a special type of FBG with high temperature stability, referred to as "Chemical Composition Grating" (CCG) was used. A thorough characterization and temperature calibration was performed and the results show the temperature dynamics with a temporal resolution of less than one millisecond. The temperature profile of the fiber and the laser beam intensity profile could be measured with a spatial resolution limited by the grating length and diameter of the fiber. Temperatures as high as ~ 1750 °C could be measured with corresponding heating and cooling rates of 10.500 K/s and 6.500 K/s.Subsequently, a thorough investigation of annealing and thermal regeneration of FBGs in standard telecommunication fibers was performed. The results show that thermal grating regeneration involves several mechanisms. For strong regeneration, an optimum annealing temperature near 900 C was found. Two different activation energies could be extracted from an Arrhenius of index modulation and Braggv iwavelength, having a crossing point also around 900 °C, indication a balance of two opposing mechanisms.Finally, the thermal dynamics and spectral evolution during formation of long period fiber gratings (LPGs) were investigated. The gratings were fabricated using the CO2 laser system by periodically grooving the fibers by thermal ablation. Transmission losses were reduced by carefully selecting the proper processing conditions. These parameters were identified by mapping groove depth and transmission loss to laser intensity and exposure time.Huvudtemana i denna avhandling är fotokänslighet och fotostrukturering av optiska fibrer och bulk glas. Trots att forskning inom fotokänslighet i glas och optiska fibrer har pågått under mer än tre decennier är de bakomliggande mekanismerna ännu inte klarlagda. Syftet var att få en bättre förståelse för fotoresponsen genom att studera fotokäsligheten ur ett termodynamiskt perspektiv, i motsats till etablerad forskning med fokus på punktdefekter och strukturförändringar, samt mekaniska spännings effekter i optiska fibrer. Optiska fibrer användes för flertalet av de experimentella studierna av två skäl; för det första är fotokänsligheten i fibrer större och dessutom vet man mindre om bakomliggande mekanismer jämfört med motsvarande bulk glas, och för det andra kan fibrer vara enklare att studera eftersom de experimentellt kan ses som en endimensionell struktur.Inledningsvis utfördes ablaherings experiment på bulk glas med en infraröd laser med pikosekund pulser. Raka kanaler med ett designtvärsnitt på 40x40 μm tillverkades på ovansidan (mot infallande ljus) och bottensidan av provet och de resulterande geometrierna analyserades. Resultaten visar en högre känslighet för variationer i experimentella parametrar vid ablahering på undersidan vilket kan förklaras av inkubations effekter i materialet. Dessutom är den resulterande geometrin på ovansidan V-formad, oavsett experimentella parametrar, vilket kunde relateras till den numeriska aperturen hos den fokuserande linsen, vilket förklaras av skuggningseffekter.Efter detta arbete flyttades fokus mot optiska fibrer, UV inducerade fiber Bragg gitter (FBG), och termisk bearbetning med konventionell ugn samt även med en CO2-laser som källa för strålningsvärme.Först konstruerades ett system för CO2-laservärmning av fibrer. För mätning av temperaturen hos bearbetade fibrer användes en speciell sorts FBG med hög temperaturstabilitet, kallade ”Chemical Composition Gratings” (CCG). En grundlig karaktärisering och temperaturkalibrering utfördes och temperaturdynamiken mättes med en tidsupplösning på under en millisekund. Temperaturprofilen i fibern, och laserns strålprofil, kunde mätas med en spatiell upplösning begränsad av gitterlängden och fiberns diameter. Temperaturer upp till ~1750 °C, vilket är högre än mjukpunktstemperaturen, kunde mätas med korresponderande uppvärmnings- och avsvalningshastighet på 10.500 K/s och 6.500 K/s.Därefter gjordes en omfattande undersökning av värmebearbetning och termisk regenerering av FBG:er i telekomfiber. Resultaten visar att termisk gitter-regenerering aktiveras av flera olika mekanismer. Värmebearbetning vid en temperatur omkring 900 °C resulterade i starka gitter efter en regenerering vid en temperatur på 1100 °C. Två olika aktiveringsenergier kunde extraheras från en Arrhenius plot avseende brytningsindexmodulation och Braggvåglängd, med en skärningspunkt tillika runt 900 °C, vilket indikerar en avvägning mellan två motverkande mekanismer vid denna temperatur.Slutligen undersöktes temperaturdynamiken och de spektrala egenskaperna under tillverkning av långperiodiga fibergitter (LPG). Gittren tillverkades med CO2-vi iilasersystemet genom att skapa en periodisk urgröpning medelst termisk ablahering. Transmissionsförluster kunde reduceras med noggrant valda processparametrar. Dessa parametrar identifierades genom mätningar av ablaherat djup och transmissionsförlust som funktion av laserintensitet och exponeringstid.
QC 20150924
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Chin, Shih-chieh, and 秦仕杰. "The machining characteristic of poly-silicon by WEDM." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/51629001715703922195.
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碩士國立中央大學
機械工程研究所
97
Electrical discharge machining (EDM) has been developed for over half a century, and there have been numerous materials machined by means of this technology. However, little research is conducted on poly-silicon. The current study investigated the effects of operation parameters on feedrate, machining groove width, and surface roughness, utilizing the technology of WEDM to process poly-silicon, in hopes of having a breakthrough in the technology of WEDM on poly-silicon. The results showed that the longer on-time or the larger the open-voltage was, the faster the feedrate was, the wider the machining groove width was, and the coarser the surface roughness was. The off-time suggested a contrast effect. Moreover, increasing the wire tension might modify the machining groove width, but might lower the feedrate, revealing a tendency of worsening the surface roughness. As for other factors causing effects on the manufacturing process, a larger flush flow rate, helped amend the feedrate, the machining groove width, and surface roughness while wire speed could only partially improve the feedrate, the machining groove width and had limited impact on the surface roughness. The results from the second part of the experiment also indicated that processing poly-silicon by means of double-pulse power supply could actually modify the phenomenon of ignition delay and increase the discharge frequency, promoting the machining efficiency. The present study successfully showed that WEDM can be applied to poly-silicon wafers slicing. This manufacturing process is believed to be competitive if used in industries related to solar cell.
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Huai, Yu-Po, and 游博淮. "Machining characteristics of polycrystalline silicon by wire electrical discharge machining and surface quality improvement." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/55639891258755767148.
Full textAbstract:
博士國立中央大學
機械工程研究所
99
In recent years, the application of solar cell is very popular since the significant improvements on cost and electrical transfer efficiency. Accordingly, there is a big shortage on the raw material. Hence, how to minimize the kerf loss during machining so as to reduce cost for solar cell production has currently become an important research issue. This study examines the use of wire electrical discharge machining (WEDM) in machining polycrystalline silicon with resistivity of 2-3 Ωcm. The effects of different WEDM parameters on cutting speed, machining groove width, and surface roughness are explored. Experimental results indicate that open voltage is the critical parameter in breaking the insulation of polycrystalline silicon. The experimental results show that WEDM can be practically applied to machining polycrystalline silicon. Hence, applications of WEDM to manufacturing of solar cell can lead to significant enhancement in production efficiency. However, WEDM material removal mechanism involves heat generation. Cracks and craters are also formed on the workpiece surface under high-temperature melting and rapid cooling. All these undermine the surface quality of the WEDMed workpiece, which in turn affect both precision and life of the final product. Therefore, the improvement of surface defects by electrolytic machining (EM) to enhance surface quality will also introduce in this study. The experiment results show the surface roughness improvement rate up to 33 %.
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Chang, Hao-wei, and 張皓瑋. "The Analysis and Research of Machining P-type Silicon in different Electrolytes by Electrochemical Machining." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/06291101986569266022.
Full textAbstract:
碩士國立中央大學
機械工程學系
101
In numerous non-traditional machinings, the electrochemical machining (ECM) has the advantage of quick processing speed, good convergence in surface stress, and nice smoothness on the workpiece surface with enormous potentialities and highly added value. Single-crystal p-Si is machined by ECM. Tungsten carbide cylinders with diameter of 50 and 100 micro-meter are selected as the electrode tools. In this research, four kinds of solution, namely ammonium fluoride, hydrofluoric acid, ammonium fluoride added with hydrogen chloride and ammonium fluoride added with sulfuric acid are used as electrolytes. The effects of machining diameter and depth by different electrolytes, and other machining parameters are investigated to identify a relatively better diameter. From experimental results, it shows that the machining performance is poor when machined with ammonium fluoride and ammonium fluoride added with hydrogen chloride on p-type silicon plates. And the machining diameter in ammonium fluoride added with sulfuric acid is better then that in hydrofluoric acid. Finally, under the best parameter of machining, the diameter reaches only 108.7μm.
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Lin, Chung-Wei, and 林忠緯. "A study of Laser Micro-Machining on the Silicon Wafer." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/00266999452027389378.
Full textAbstract:
碩士國立中正大學
機械工程所
95
Wafer means the semiconductor integrated circuit to need material. Taiwan takes the place of one of the works important country in silicon wafer for the world at present, so there is its necessity in the technology of probing into silicon wafer processing. Silicon wafer is a fragility material, traditional mechanical processing method is limited to the diameter of cutter that the corners and small characteristics can’t be processed. To focus the laser spot size very small can overcome above disadvantages. Laser processing that photothermal material removing and photochemical ablation will make heat affect zone and recasting that influence the quality of processing. In this research, utilize Pico-second laser, UV laser and Nd : YAG laser to micro-machining on the silicon wafer, adjusts the laser parameters and additional assist equipment to improve and observe its processing result and confer with different laser’s processing mechanism and correlate with each other. The planning of the micro-structure, for the micro-structure of this kind of saw tooth structure of probe card that the industry uses now. Using different lasers to process silicon wafer, adjustment of parameter receives better processing results, how to understand processing characteristic of three kinds of lasers and find to correlations for each other is key point in this research. Among this thesis, we utilize laser to process a micro-structure of good quality successfully. According to process results, we understand the quality of micro-structure to correlate with pulse width, wavelength absorption depth each other. To Supply a basis to select a laser while processing different materials in the future. Key word：silicon wafer、Pico-second laser、UV laser、Nd：YAG laser、 Micro-machining、pulse width、wavelength absorption depth
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Ji, Chao-Jie, and 紀朝傑. "The Analysis and Investigation on Silicon Plate by Electrochemical Machining." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/01028837803131117818.
Full textAbstract:
碩士國立中央大學
機械工程研究所
96
In numerous non-traditional machining, the electrochemical machining (ECM) has the advantage of quick processing speed, good convergence in surface stress, and nice smoothness in workpiece surface with enormous potentialities and highly added value. Single-crystal p-Si is machined by ECM. A tungsten carbide cylinder with diameter of 100 micro-meter is selected as the electrode tool. Hydrofluoric acid is selected as the electrolyte. In this research, the single variable method and Taguchi statistical method are used to analyze the influence of the parameters (such as applied voltage, concentration of electrolyte, initial inter electrode gap, rotational speed of the tool, tool feeding rate, etc) on the overcut of the drilling and the relative importance among parameters. From experimental results, it shows that the feeding rate and the rotating rate of the electrode have only slightly influence on machining. Finally, the best parameters are taken for drilling the silicon substrate, and a hole with diameter of about 300μm is obtained.
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Sugadev, Prasath Mungundu. "Numerical Controlled Electrochemical Machining Of Silicon Carbide/Aluminum Metal Matrix Composites." Thesis, 2004. http://hdl.handle.net/10125/10490.
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Chang, Kuang-hua, and 張光華. "Study on texturing of mono-silicon by using Electrochemical Discharge Machining." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/20830703287553681299.
Full textAbstract:
碩士國立中央大學
機械工程學系在職專班
102
In order to improve the light conversion efficiency of solar cells, recently processing method use the strong chemical substances to etch silicon surface. Although acid or alkaline texturing can increase the frequency of the light reflecting, this kind of texturing process not only has long processing time but also is harmful to the environment. Compared with the conventional surface texturing process which generates chemical etched pyramid structure or crater structure , this study proposes texturing P type mono-crystalline silicon by electrochemical discharge machining (ECDM). ECDM method has the advantage of short processing time and can generate a higher surface roughness and the porous structure. In this study, stainless steel was used as negative electrode. The graphite was used as the positive electrode acting as the auxiliary electrode. The potassium hydroxide was used as the electrolyte. The processing parameters include the machining voltage, the processing time, the machining gap, the electrolyte concentration, the additive agent concentration, pulse frequency and duty factor, etc. The surface roughness was measured using surface roughness tester. The surface morphology was observed using SEM and three-dimensional laser scanning microscope. The result of experiments reveals that appropriate concentrations of ethanol can expand the size of the pores and enhance surface roughening effect. The appropriate processing parameters are a machining gap of 200μm, voltage of 48V, concentration of potassium hydroxide of 3M, concentration of ethanol of 4%. The electrochemical discharge machined surface roughness was increased from 0.417μm to 0.915μm using one minute processing time. The average reflectance rate of the textured surface was decreased from 29.6% to 12.7% measuring by using integration spectroscopic reflectometer.
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Chen, Jian-Hao, and 陳建豪. "The Study of Machining Microstructure of the Silicon Wafer by Picosecond Laser." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/32549047808591981107.
Full textAbstract:
碩士義守大學
機械與自動化工程學系碩士班
96
The study is to examine how picosecond laser affects the microstructure of the thin silicon wafer. Traditionally diamond cutters are chosen to cut grooves on the silicon wafers. The method, if applied carelessly, would cause cracks at the cutting edges. In addition, extra material will be needed to compensate the material lost at the place of cut (street width). The etching process can also be chosen. But it is time consuming and the cleaning afterward is prone to cause environmental pollution. Nanosecond laser is another option. Yet its high energy density will cause large heat affect zone which is detrimental to the cutting edge. On the contrary picosecond laser uses photochemical ablation for material removal.Not much heat is generated while machining. The effect of changing its frequencies, cutting speeds, energy density, and focus points on the quality of machining processes, which include making blind holes, grooving, and planning, is studied. Surface roughness is the chosen index for machining quality. After extensive test, the following parameters are found to be best suited for machining silicon wafer: focus 1.66mm, frequency 100KHz, feed 50mm/s, energy density 1000 pulse/mm. The resulting surface roughness is Ra=0.09μm.
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Jian, Gang-You, and 簡綱佑. "Study of ultrasonic vibration-assisted WEDM and electrolytic machining on poly-silicon." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/78405576290718502216.
Full textAbstract:
碩士國立中央大學
機械工程研究所
98
This research investigates the effect of operation parameters on poly-silicon. This paper is mainly divided into two major parts： The first part is studying of ultrasonic vibration-assisted wire electrical discharge machining, ultrasonic vibration was mounted on wire electrode of WEDM. Produce high-frequency and small periodic amplitude characteristic, can be working debris easy flushed and avoid secondary discharge, in hopes of improving the machining efficiency and accuracy in the technology. The second part is the surface carries on etching and leveling after WEDM by the electrolytic machining. According to the result, when machining voltage of 20V、electrolyte concentrate of 6M、machining gap of 0.9mm、electrode rotational speed of 0rpm and machining time of 5min can be improved from 4.83μm(Ra) to 3.67μm(Ra)and surface roughness improvement rate up to 24.02%(Ra).
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Yeh, Chin-chang, and 葉金璋. "Processing Characteristics of Polycrystalline Silicon by Wire Electrical Discharge Machining and Electrochemical Grinding." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/13731829407360907827.
Full textAbstract:
博士國立中央大學
機械工程學系
102
Nowadays, the researches and developments of renewable energy have become the universal consensus. Among them, the developments of solar cell attract the greatest attention. In the process of making solar cell, the cutting process of silicon ingot is the key to determine the cost. Multi-wire saw has been used in the traditional cutting to conduct machining process. Its advantage is to multi-wire-type processing, which heighten the processing efficiency. However, multi wire requires great tension and produces stress that could easily damage the silicon ingot. In addition, during the process, abrasive could not be used completely. The complicated recycle processes of abrasive contaminate the environment. Thus, in recent years, related research proposed in the literature, by using wire electrical discharge machining (WEDM) cutting silicon ingot, this method can effectively improve the shortcomings multi-wire saw. WEDM has been applied onto the single-crystal silicon cutting. Most researches adopted single-crystal silicon as the process material. However, it is hard to find a literature review on the machining characteristics of a polycrystalline silicon surface and the quality improvements after processing. The main reasons of polycrystalline silicon are changing boundaries, high electrical resistance and other characteristics, which lead WEDM can not be process smoothly. Polycrystalline silicon manufacturing process is simple, lower cost, stable photoelectric efficiency and other advantages. Therefore, a new method to improve the polycrystalline silicon processing problems needs to be developed. This thesis adopts machining characteristics of polycrystalline silicon research by WEDM and electrochemical grinding (ECG) these two methods. This paper divided into two research directions. The first part discusses when the polycrystalline silicon by using WEDM processing, the impact of discharge parameters on the polycrystalline silicon and the adjustments of phosphorous dielectric improve its processing efficiency and processing characteristics. The second part is the application of ECG surface defects after WEDM be grinded, it improves the removal of surface roughness and affected layer by using Taguchi-method experiment planning, the main factor affects the analysis process to get through. Follow added graphene in dielectric. By using the high hardness and high lubricity of graphene to improve processing characteristics of the original surface and explore the impact of process parameters for the processing. After the experiments by this thesis, it is sure that in the WEDM processing, phosphorous dielectric improves the discharge process effectively and makes the discharge energy booster to enhance conductivity. Under the no-changing existed processing parameters condition, it improves the cutting speed and reduces kerf loss. In the ECG processing, by adding graphene, the surface problems effectively improved after WEDM machining residues and reduce friction force during processing and it enhances the grinding tool life. It is expected the results of this thesis could be referenced for the future research in both industrials and academic field.
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Qiang, Bian Guang, and 卞廣強. "The study of using assistant electrode in wire electrical discharge machining of polycrystalline silicon." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/n5856j.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
104
This study presentsa state-of-the-artconcept using assistant source electrodes assembled with target polycrystalline silicon workpiece to enhance machining performances on the observations of material removal rate, surface alloying and surface roughness in wire electrical discharge machining. The designed experiment elaborated key parameters such as three levels of the thickness of the source electrodes (0/15/25 mm), two levels of the servo voltage (80/100V), pulse-on time (50/100 µs) and determined electrical resistivity (1.4/1.7 Ω) in the predetermined discharging circuit for seeking the best parametric combinations. These entailed total 24 tests in a full factorial experiment. The observations are analyzed using statistical methods (Main effect plots and ANOVA) for the examinations of the significance of the operated parameters. The results reflected that the material removal rates were up to 9.43 mg/min when assistant electrodes of 25mm were facilitated whereas the same was only 8.74 mg/min without using assistant electrodes. In addition, the use of assistant electrodes produced surface alloying by up to 18.28% of aluminum content in the scanned matrix. Similarly, the measurements of the surface roughness suggested the greater value (Sa 9.44 µm) were produced with assistant electrodes of 25 mm, compared to the null value recorded without assistant electrode involved.
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Chiang, An-Chun, and 江銨畯. "Multi-objective optimization of wire electrode discharge machining using assisting electrode on polycrystalline silicon." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/g4k6ek.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
106
This study presents a state-of-the-art wire electrical discharge machining technology using assisting electrodes shaping polycrystalline silicon workpiece to improve the material removal rate, and surface roughness with surface modification. The experimental work was carried out with the consideration of the Joule heat effect under the operating parameters of open voltage (50-100 V), pulse on-time (30-60 μs), assisting electrode thickness (0-25 mm), and frequency control (120-180 unit) of servo voltage in 10-18 V. Statistical methods such as the main effect plots and ANOVA were used for determining the preferable combinations and the significance of the operating parameters, respectively. For the result showed that high material removal rate (7.62 mg/min) and low surface roughness (Sa 5.36 μm), with the aluminum content of ~3.48% were obtained on the machined surface when assisting electrodes of 15 mm were facilitated in the tests. When the single objective equations were superimposed with the predetermined weightings, the multi-objective function can be established. The preferable combination suggested open voltage of 50 V, pulse on-time of 30 μs, and frequency control of 180 unit without assisting electrode, which resulted in the least error for reduced material removal rate (63%), increasing surface roughness (7%) and reduced surface modification (73%), compared to those in the single objective optimization.
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Yu-Feng, Chang, and 張裕峰. "Study on the Technical Process of Fabricating Nano-Porous Silicon Structure Using Electro-Chemical Machining." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/20181561999114883634.
Full textAbstract:
碩士崑山科技大學
機械工程研究所
95
Recently the nano-technology was rapidly developed. The demanding needs of nano-scale materials were required more and more in the industrial. Therefore, it is important to investigate the fabrication process and method of nano-structure materials. Owing to the nano-porous structure material has some unique physical characteristic, likes larger ratio of surface area and volume, adjustable energy gap and high sensitivity properties, thus the porous material is very suited to become the raw material of the optical-electric components and micro-sensors. In another hand, the porous diameter and depth of nano-porous structure material can be improved more effectively by way of adapting non-traditional machining in fabrication. After researching and reviewing the references, we conclude that the generous research used for fabrication of porous structure are all adapt either in horizontal or vertical electro-chemical reaction tanks, both have shown some discrepancy were not able to precisely control the corrosion area, density of electrical current and the distance between silicon and electrode. In order to control more precisely the parameters of experiment and refer mentioned above about the advantage and discrepancy of both chemical reaction tanks, the “modified electro-chemical reaction tank”, made of PTFE material, is developed to be experienced and verified the effect of tightness, corrosion, and operation. The modified vertical chemical reaction tank not only can prevent the leakage of HF solution but also is capable of controlling the parameters of nano-porous structure experiment more precisely. Then, Taguchi Method L9 orthogonal array were employed to layout experiment arrangement, and placed the silica wafer in the HF solution with electric current flowed into the solution in order to observe the results of its chemical action. The silica wafer was developed to porous structure due to corrosive action in the anode pole and all relative results could be acquired by utilizing the micro-balance and SEM. After calculating the S╱N ratios under various factors and levels, response tables and diagrams were generated as well as the main influencing and the optimal combination of parameters in fabricating of porous structure by electro-chemical. Based on the results of ANOVA analysis, the variation, deviation, and degree of contribution of parameters were found. Finally the optimal combination of parameters must be confirmed by confirmation experiment. Based on the results of experiment, the porous silicon was influenced by the machining parameters of electro-chemical machining. The different type porous silicon will be obtained under different machining parameters. The machining parameters of electro-chemical machining included of the concentration of HF solution, the density of current, the distance between electrode and silicon wafer and the resistance of work piece. The poor machining parameters of electro-chemical machining will be produced failure porous structure or induced electro-polishing. The porous silicon, made by electro-chemical machining, with high optical performance could use as the electrical-optical components. In this study, we use the modified electro-chemical reaction equipment to obtain the main influencing parameter with Taguchi method, and it is effect to save experimental time and cost.
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Kuo-LunKao and 高國倫. "Metal Contact Printing and Silicon Bulk Machining for Fabrication of Sub-Micrometer Three Dimensional Structures." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/11726266061104783490.
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Lan, Kuen-chih, and 藍坤志. "The effect on Polycrystalline Silicon Surface Roughness by Electrical Chemical Machining Grinding Using Graphene Oxide Suspension." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/56961985890911503960.
Full textAbstract:
碩士國立中央大學
機械工程學系在職專班
102
There are some conclusions gotten from the experiment. The surface roughness and average friction coefficient are 0.092μm and 0.33μ by traditional mechanical grinding process; the surface roughness and average friction coefficient are 0.051μm and 0.10μ by adding 0.5% graphene into solution. The latter surface roughness and friction coefficient is 1.8 times and 3.3 times compared to the former. The research shows that the tribological properties of graphene reduce the friction coefficient of solution and improve the surface roughness on workpiece. The research can be applied to grinding process of silicon wafer. The method can not only simplify the experiment steps but also enhance the process efficiency. The research is expected to be an application reference for industry and academic area.
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CHEN, JHIH-CING, and 陳志清. "Study on Surface Properties of Aluminum - based Silicon Carbide Composites by Wire Cutting and Discharge Machining." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/69q52g.
Full textAbstract:
碩士中州科技大學
機械與自動化工程系
106
The purpose of this study is to build machining data base of aluminum-metal matrix complex (AMMC), in order to replace traditional machining with non-traditional machining of EDWC. Three types of aluminum-metal matrix complexes were used to develop complex materials of the hardness via different contents of SiC percentage. Results showed that not only defects of materials casting plausibly was disadvantageous to mechanical properties of aluminum-metal matrix complexes but also led to wire-breakage as machining of EDWC. The effects of aluminum-metal matrix complexes on the characteristics of machinability of EDW as below: (1) With increasing on time of cutting conditions, the surface roughness of aluminum-metal matrix complexes increases. The EDW surface of aluminum-metal matrix complexes was rougher than that of as-cast A356.2 due to microstructure of SiC; (2) The factor's order of cutting feedrate for AMMC measured by simulated regression as followed: thickness of the workpiece, on time, feedrate override of the table, SiC contents; (3) In order to acquire the precision of workpieces by setting higher water flow rate, resistivity of dielectric fluid and wire tension prior to wire-breakage. The thickness and hardness distributions of remelted layer in cross-sectional area of EDW surface differed from that of EDM. The dimension of remelted layer of AMMC in cross-sectional area of EDW surface was not as the same as in terms of measuring instruments such as OM, Hv and SEM. Although there was the thinner distributions of AMMC than that of A356.2 due to microstructure of SiC changed the microstructure of remelted layer and mechanical properties.
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Chou, Irene A. "Mechanical properties of silicon carbide reinforced alumina nanocomposites : machining-induced surface residual stress and crack healing behavior /." Diss., 1998. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9914241.
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Yang, Sheng-Shiu, and 楊勝旭. "Effects of the Machining Conditions on Polishing Mechanism of Silicon Wafer for the Continuous Composite Electroplated Polisher." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/11473166656359700273.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
92
In the study, the effects of the machining conditions, ex, machining positions, loads and rotating speed ratio on machining mechanism of wafer are investigated by using the continuous composite electroplated polisher and find the best machining conditions of the polisher. Experimental results show that when the wafer and polisher are full contact, the operating of machinery is most smooth and the flatness is better. When the load is increased, the reducing rate of average roughness（Ra）and maximum roughness（Rmax）, removal rate, and the speed of mirror degree are increased. The machining mechanism and the stability of machinery is depended on the value of rotating speed ratio. In the different rotating speed ratio, the flatness of wafer is difference. For example, the rotating speed ratio is 1, the flatness is 1.5 μm/38 mm. The rotating speed ratio is 2, the flatness is 2.3 μm/38 mm. Finally, choose the rotating speed ratio, which the values of rotating speed are close and complex on the range of rotating speed which machinery can be operating most stable in machining process. Because of the machining mechanism are similar and the grinding locus are finer. Hence, the flatness of wafer becomes better. When the rotating speed ratio is 1.1, the flatness is 1.46μm/38 mm. The rotating speed ratio is 1.11, the flatness is 1.45μm/38 mm. The effect of the rotating speed ratio of the wafer and polisher on the grinding locus type of grinding surface is theoretically analyzed. Results show that when the rotating speed ratio is irregular, the distribution of grinding locus becomes finer. The analyzable results of locus and provable results of experiment are the same.
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Li, Chia-Hung, and 李嘉鴻. "A Study on Surface Characteristic by Using Dielectric with Phosphorous on Wire Electrical Discharge Machining Cutting Polycrystalline Silicon." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/84710166027762337744.
Full textAbstract:
碩士國立中央大學
機械工程研究所
97
During solar cell processing, wafer cutting is an import procedure for yield, nowadays wire saw is the main cutting process, it has multi-wire with high efficiency, but has produced stress while cutting, it may let wafer break, and the particle can not be used fully, the particle will contaminate environment. Therefore, wire electrical discharge machining was investigated to improve wire saw processing, but most of research of material is single-crystal silicon, the poly-crystal investigate is few, because poly-crystal silicon with higher resistance, it is hard to machine for wire electrical discharge machining. This research is mainly divided into two major parts, the first part adopts pure water as dielectric in order to know the possibly of machinine, and investigate the influence of characteristic of each processing parameter The second part is according to the previous part results to improve the machining efficiency, we add sodium pyrophosphate powder in pure water, we want use phosphorous’ high electric conductivity to improve the efficiency, and use high temperature let phosphorous doping into wafer’s surface by wire electrical discharge machining to achieve p-n junction. Comparing with conventional solar cell processing, can save ion implantation, let the processing simply. Form the experiment results, using sodium pyrophosphate as dielectric can get fast feed ratio is 0.528 mm per second while pulse on time is 6.5μs, ampere is 10A, and comparing in the same parameter, the feed ratio increase 2.4 magnification, and improve surface roughness by electrolysis at high temperature, as previous results corroborating that dielectric with phosphorous can improve machining efficiency and dopping phosphorous into surface simultaneously.
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Chen, Hua-lin, and 陳華琳. "Effects on Quality Characteristic by Using Mixed Dielectric with Phosphorous on Wire Electrical Discharge Machining Cutting Polycrystalline Silicon." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/56969603219778095382.
Full textAbstract:
碩士國立中央大學
機械工程研究所
98
During solar cell processing, wafer cutting is an import procedure for yield, nowadays wire saw is the main cutting process, it has multi-wire with high efficiency, but has produced stress while cutting, it may let wafer break, and the particle can not be used fully, the particle will contaminate environment. Therefore, wire electrical discharge machining was investigated to improve wire saw processing, but most of research of material is single-crystal silicon, the poly-crystal investigate is few, because poly-crystal silicon with higher resistance, it is hard to machine for wire electrical discharge machining. This study is divided into two major parts, the first part of the pre-test to sodium pyrophosphate solution as dielectric, the Mole concentration 0.05M, adding different amounts of phosphoric acid to explore the feasibility of processing, the experiment with the different parameters and to understand the effect of processing characteristics of the trend. The second part o use the Taguchi method for processing the surface of phosphorus content on the processing with different parameters. The experimental results indicate that the best combination of process parameters, the Mole concentration of sodium pyrophosphate 0.025M, phosphoric acid than 1000:15, processing current 1.2A, pulse time 6μs and resting time 9μs. Detected by EDS, you can get the best surface phosphorus content 0.67wt%. By Mapping and Line scanning analysis confirm the processing of phosphoric acid added to sodium pyrophosphate solution can improve the processing of phosphorus content in the surface and inhibits the infiltration of impurities, while the effect of doping the surface can be obtained.
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Fang, Xin-Ren, and 方信人. "Establishment and experimental verification of simulation model of single-crystal silicon nanochannel curve machining to the preset width and depth." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/43t72z.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
106
The paper proposes a simulation model for nanochannel curve machining to the preset width and depth. First of all, the paper uses a Cubic Spline curve equation acquired from the self-set control points .This study uses the obtained cubic spline curve equation to further calculate the multiple integers’ tiny line segments of a near-curve, and conducts AFM for machining a nanochannel which is a straight-line segment and a curve segment machining experiments. The paper firstly uses the method of machining a straight-line trapezium groove to the preset depth and width, and then calculates the offset amount and the number of cutting passes required for machining the straight-line trapezium groove up to the preset depth and width. The paper also uses the self-set control points to obtain the curve equation of the path for machining. Besides, the paper innovatively proposes using the control point set by the first curve, and then uses offset equation and the offset amount obtained above to find a method for calculating the control point of curve equation of other passes on the same cutting layer. Furthermore, the paper calculates the curve equation of other passes on the same cutting layer. Since the AFM machine is unable to carry out curve machining, the paper proposess applying the calculation equation of the chord error between curves and tiny line segments, and further using straight-lined near-curve method to calculate the near-curve straight line formed by connection of many tiny line segments. But the accuracy of AFM machine is 1nm only, so the various intersecting points of the tiny line segments are taken as integers to carry out machining. In order to reduce the error, we take, when carrying out measurement, the cross-section at a nearly ideal curve position for measurement. Finally, the paper carries out comparison between simulation results and experimental results of the simulation model of the self-established curve machining up to the preset width and depth. It is proved that the simulation model established by the paper is reasonable and acceptable. When carrying out, in general, cutting of an nanochannel straight-line segment trapezium groove, by AFM machine it is usually found that as it is getting close to the target depth, down force has to be changed for one more time so as to make the depth of the last cutting layer approach to the target depth. Nonetheless, since the time required for the AFM machine to actually carry out change of down force is around 7 minutes, this method needs to spend more time for change of down force for one more time. In order to achieve the least preparation time for machining during application to experiments, the paper uses the machining of nanochannel straight-line segment trapezium groove up to the preset depth and width, which is a machining method requiring less cutting passes and less times of change of down force, as well as its target function and constraints. At the beginning, the paper firstly sets the safety coefficient of the greatest down force for probe cutting, and starts simulated cutting of the depth of trapezium groove at the down force under safety coefficient. After that, the paper step by step adjusts the down force and simulates cutting of the cutting depth of trapezium groove, making it step by step approach to the target depth of trapezium groove. After the paper confirms that it is close to the target depth of trapezium groove, the paper sets the down force value for the first cutting pass on each cutting layer. For the second cutting pass, down force is to be changed to acquire the same cutting depth as that of the first cutting pass. Finally, specific down force energy (SDFE) theoretical model is applied to further estimate the number of cutting layer and the down force of the first cutting pass of the achievable preset depth of the nanochannel straight-line segment trapezium groove. Furthermore, the least number of times of change of down force can be achieved. Here, in order to prevent occurrence of broken probe due to probe fatigue after cutting for multiple times, safety coefficient is set to achieve the greatest down force under the safety coefficient. The paper also uses this down force to step by step adjust the down force size slowly, and makes cutting by the down force approach to the preset depth. Nevertheless, for the preset cutting depth on the first cutting layer, SDFE method can be used to directly obtain the preset cutting depth. Thus, the procedures of stepwise approach can be neglected. As to cut to the preset depth after cutting on the second cutting layer and the third cutting layer, SDFE equation cannot be directly used to estimate this depth. Hence, optimal stepwise approach method has to be used to repeatedly simulate and adjust the down force for carrying out cutting on the second cutting layer or cutting on the third cutting layer in order to make the depth of straight-line segment trapezium groove of the nanochannel cutted by the set down force, exactly approach to the preset depth. After cutting to the preset depth is confirmed, the above method is used to adjust the offset amount to achieve the preset width of the cutted straight-line segment trapezium groove. The paper proposes integration of straight-line segment machining and curve machining of nanochannel trapezium groove to different preset depths and widths. In accordance with the above method, the paper firstly simulates the better down force that satisfies less cutting passes and less times of change of down force for various cutting passes on different cutting layers of straight-line segments. The acquired better down force is further applied to the integrated straight-line segment machining and curve machining of nanochannel trapezium groove.
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Lin, Hong-Heng, and 林鴻亨. "Study of Two-step Machining Process by Creep Feed Grinding and Mirror Finish Grinding with Ultralow Feed Rates for Silicon Nitride." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/wy9g22.
Full textAbstract:
碩士逢甲大學
材料科學所
90
ABSTRACT Post-sintering grinding and polishing processes are a common practice to eliminate the occurrence of dimensional non-uniformity of ceramic materials due to the shrinkage during sintering, however such a process also needs to meet the requirements of good machined surface quality with least machining damages introduced in the ceramic bodies. Silicon nitride, as our interest in this study, is well known for its remarkable mechanical properties such as high strength, high elastic modulus, high specific grinding energy, low toughness, and its fracture behavior associated with the brittle mode, which would heighten the difficulty of machining process and the machining cost as well. The machining process would directly affect the mechanical properties of surface and sub-surface regions of silicon nitride ceramics. Thus, this research is aimed to investigate how to achieve better ceramic performance and higher grinding efficiency via the two-step combined grinding process through the creep-feed grinding and the mirror-finish grinding for enhanced machining performance of silicon nitride based ceramic products. There are various machining parameters involved in the two-step combined grinding process such as the abrasive type and bond type of grinding wheels, depth of cut, and wheel speed, and the application of alumina free abrasive slurry. These factors would substantially affect the ceramic workpiece quality, wear of grinding wheel and machining efficiency in such a grinding process. This work was meant to systematically investigate how these machining parameters would influence surface fracture mechanism of silicon nitride, surface integrity, and grinding efficiency as a result of the two-step combined grinding process. Both machined surface quality and effectiveness of two-step grinding process are evaluated by the analysis of SEM, AFM, XRD, ESCA and profilometer. The results indicated that the greatly improved machining efficiency can be achieved through the creep-feed grinding in conjunction with mirror-finish grinding for fine-grained Si3N4 doped with 2 wt% Al2O3 and 6 wt% Y2O3 (avg. grain size 0.306 □m) with either diamond or white alumina (WA) wheels. The minimum average surface roughness (Ra) of Si3N4 samples,34 nm and 24 nm, was resulted from using #1200 WA wheel and #3000 diamond wheel at the second step mirror-finish grinding, respectively. The residual stress at surface and sub-surface zones of Si3N4 responding to grinding process, which was qualitatively examined by lowering and broadening of major XRD peaks, was similar for both diamond and WA wheels as the same machining parameters in mirror-finish grinding were employed. The injection of alumina free abrasive slurry into the grinding contact zone between the wheel and workpiece was demonstrated as an effective means to illuminate the fine machining damage and microcracks at sample surface by exerting the addition wear of silicon nitride sample by free abrasives during the grinding process. In this study, we found that the first-step creep feed grinding process by using coarse-grit #270 diamond wheel (avg. grit size 53 □m) would reach maximum material removal rate, which can be followed by the second-step mirror-finish grinding process as using fine-grit #1200WA, #3000 diamond or #5000 diamond wheel in conjunction with the alumina free abrasive (3 □m). The optimal surface quality for silicon nitride under the two-step grinding process was achieved with 1□m/pass depth of cut, 3000 rpm wheel speed, and slow table feed rate of 1 m/min. Keywords: Silicon nitride, grinding efficiency, two-step combined grinding process, creep-feed grinding, mirror-finish grinding, alumina free abrasive slurry, ESCA, AFM, slow table feed, machining damage
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Lu, Chang-Hung, and 呂昶宏. "Analysis of machining force and temperature field for fabricating single-crystal silicon trapezium groove by offset cutting method and analysis of downward depth at the junction of T-shaped nanochannel." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/4zc7wu.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
104
The paper applies offset cutting method to fabricate single-crystal silicon trapezium groove at a fixed cutting depth. Cutting of 1st cutting path is carried out on each cutting layer at a fixed cutting depth, then cutting of the 2nd cutting path is carried out by making rightward offset the cutting tool, thus competing a offset cutting cycle. If it is required to broaden the width of trapezium groove, rightward offset the cutting tool can be made for cutting to complete cutting of the 3rd cutting path. Using the above method, the number of cutting layers can be increased, and their cutting width and cutting depth can thus be increased as well. The paper also applies the equations for estimating cutting force and down force, both established by specific down force energy (SDFE) concept, and simulates the down force and cutting force for the 1st cutting path during offset cutting of trapezium groove on the 1st cutting layer, as well as those for rightward offset cutting of the 2nd cutting path. First of all, considering a smaller size probe, SDFE equation is used to calculate the cutting force and down force for such offset cutting method at a fixed cutting depth in this paper. After that, three-dimensional quasi-steady molecular statics nanocuting simulation model is used to simulate acquisition of down forces and cutting forces in the 1st and 2nd cutting paths using offset cutting method for cutting on the 1st cutting layer by the same smaller sized probe and cutting depth. Comparison is made between the cutting forces and down forces obtained from the above mentioned two methods, in order to prove the rationality of using SDFE equation to acquire cutting force and down force of offset cutting method. The three-dimensional quasi-steady molecular statics nanocuting simulation model not only calculates the down force and cutting force of each cutting path at a fixed cutting depth, but also calculates equivalent stress and equivalent strain, as well as the increased temperature of the cutted single-crystal silicon workpiece. The paper further analyzes the temperature distribution of the cutted single-crystal silicon workpiece. Besides, the paper explores the T-shaped nanochannel at a cutting depth of around 20nm at a fixed down force. This paper proposes employing SDFE concept at the junction between horizontal cutting path and vertical cutting path, using the same fixed down force in the middle of horizontal cutting path, and downpressing and cutting the workpiece material in the direction of vertical cutting path. SDFE method and CAD software are used to simulate the removing volume, thus forming a depressed shape with a depressed depth. SDFE equation and CAD software are used to simulate the cutting and cutting depth of each horizontal cutting layer and the depressed depths at the junction of T-shaped nanochannels on different horizontal cutting layers. As observed from the simulation results, the cutting depth at the junction between horizontal cutting layer and vertical cutting layer of T-shaped nanochannel is almost equivalent to an increased cutting depth on an additional horizontal cutting layer. The paper also compares the experimental results and simulation results of the depressed depths measured at the junction of T-shaped nanochannel being cutted up to the 5th cutting layer. Hence, the paper’s proposal of using SDFE method to simulate and estimate the depressed depth produced at the junction between horizontal and vertical cutting paths on each cutting layer of T-shaped nanochannel, is proved to be feasible.