No description available.

No description available.

This dissertation presents a series of studies relating to optimization of kinematics and consumables during chemical mechanical planarization processes. These are also evaluated with the purpose of minimizing environmental and cost of ownership impacts.In order to study diamond micro-wear and substrate wear during planarization processes, a series of static etch tests and wear tests were performed using different types of diamond discs and subjected to various treatments. Scanning Electron Microscopy (SEM) and Inductively Coupled Plasma Membrane Spectroscopy (ICPMS) were used to estimate the extent of diamond micro-wear and substrate wear.Next, the impact of various factors (type of slurry abrasive, pH, abrasive content and abrasive concentration) on pad wear rate during planarization process was studied. Another study in this dissertation focuses on the development of a novel technique of using coefficient of friction (COF) data to distinguish between good and bad diamond discs. This study made use of the innovative tool diamond disc dragging device (DDD-100) designed and developed for the purpose of this study.It is known that the performance of chemical mechanical planarization depends significantly on the polishing pad grooving type and the kinematics involved in the process. Variations in pad grooving type as well as pressure and sliding velocity can affect polishing performance. One study in this dissertation investigates the effect of pressure and sliding velocity on the polishing performance. The study is conducted on multiple pressure and sliding velocity variations to understand the characteristic of each condition. A subsequent study focuses on the impact of pad grooving type on polishing performance.The greatest contribution of this dissertation involves development of the novel slurry injector to optimize the utilization of slurry during planarization processes. Slurry is a critical component in chemical mechanical planarization processes and accounts for approximately 50 percent of the cost of ownership (CoO). The novel injector apart from reducing the consumption of slurry, also contributed in addressing problems associated with foaming, reduced the number of defects and achieved better within wafer non-uniformity (WIWNU).

Automotive companies are actively pursuing to increase the use of high-strength-lightweight alloys such as aluminum, magnesium, and advanced/ultra high-strength steels (A/UHSS) in body panel and structural part applications to achieve fuel efficiency while satisfying several environmental and safety concerns. A/UHSS sheet materials with higher strength and crashworthiness capabilities, in comparison to mild steel alloys, are considered as a near-term (i.e., ~5 years) choice of material for body and structural components due to their relatively low cost when compared with other lightweight materials such as aluminum and magnesium. However, A/UHSS materials present an increased level of die wear and springback in stamping operations when compared to the currently used mild steel alloys due to their higher surface hardness and high yield strength levels. In order to prevent the excessive wear effect in stamping dies, various countermeasures have been proposed such as alternative coatings, modified surface enhancements in addition to the use of newer die materials including cast, cold work tool, and powder metallurgical tool steels. In this study, a new die wear test method was developed and tested to provide a cost-effective solution for evaluating various combinations of newly developed die materials, coatings and surfaces accurately and rapidly. A new slider type of test system was developed to replicate the actual stamping conditions including the contact pressure state, sliding velocity level and continuous and fresh contact pairs (blank-die surfaces). Several alternative die materials in coated or uncoated conditions were tested against different AHSS sheet blanks under varying load, sliding velocity circumstances. Prior to and after wear tests, several measurements and tribological examinations were performed to obtain a quantified performance evaluation using commonly adapted wear models. Analyses showed that (1) the rapid wear method is feasible and results in reasonable wear assessments, (2) uncoated die materials are prone to expose severe form wear (galling, scoring, etc.) problems; (3) coated samples are unlikely to experience such excessive wear problems, as expected; (4) almost all of the the recently developed die materials (DC 53, Vancron 40, Vanadis 4) performed better when compared to conventional tool steel material AISI D2, and (5) in terms of coating type, die materials coated with thermal diffusion (TD) and chemical vapor deposition (CVD) coatings performed relatively better compared to other tested coating types; (6) It was seen that wear resistance correlated with substrate hardness.

To survive in today's manufacturing environments companies must push the standards of accuracy and speed to the highest levels possible. Electro Discharge Machining (EDM) has been used for over 50 years and recent developments have seen the use of EDM become much more viable. The goal of this research is to produce and evaluate electrodes produced by different manufacturing methods. The use of electroforming and spray-metal deposition has only recently become viable methods of producing usable rapid tooling components. The speed and accuracy as well as the cost of manufacture play a vital role in the tool and mould manufacturing process. Electroforming and spray-metal deposition offer an alternate option to traditional machining of electrodes. Electroforming is one method of producing electrodes for EDM. The fact that electroforming can be used to produce multiple electrodes simultaneously gives it the advantage of saving on costs when multiple electrodes are needed. Spray-metal deposition offers another alternative that is much cheaper and relatively faster to manufacture. The used of these non-traditional manufacturing methods in this research are compared to the performance of traditional solid electrodes in terms of machining time, material removal rate, tool wear rates and surface roughness at several standard machining settings. The results of this research are presented in this thesis along with conclusions and comments on the performance of the different methods of electrode manufacture. The major findings of the research include the solid electrodes performed better than the electroformed electrodes in Material Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (Ra) at all machine settings. However it was found that the production cost of the solid electrodes was six times that of the electroformed electrodes. The production of spray metal electrodes was unsuccessful. The electrode shell walls were not an even thickness and the backing material broke through the shell making them unusable. It is concluded that with further refinements and research, electroforming and spray metal processes will become an extremely competitive method in electrode manufacture and other rapid tooling processes.

No description available.

Additive Manufacturing (AM) has revolutionized manufacturing processes by enabling the realization of custom products with intricate geometric features that were either too complex or even intractable for subtractive manufacturing processes. Yet, functional surfaces generated in AM have to be often finish machined because of their relatively inferior roughness. The first phase of this research worked around this limitation by tailoring the topography of an AM surface in-process to entail textures that further enhance certain functionalities in a process called Additive Texturing (AT). In this context, the Selective Laser Melting (SLM) process ability to realize intricate surface microfeatures was explored experimentally, evaluating its geometrical limitations. Utilizing such limitations, various patterns comprising pillars, channels, and re-entrant structures were printed to control the wetting behaviour of SLM stainless steel. AT's efficacy is demonstrated in its capability to generate hydrophobic AM surfaces with water contact angles exceeding 140°. Similarly, other texturing patterns comprising dimples, linear, V-shaped, and X-shaped grooves were investigated to tailor the tribological response of textured surfaces under dry sliding conditions. Evidently, a specific wear rate and coefficient of friction reduction of 80% and 60%, respectively, demonstrated another potential for AT. The undesirable tensile Residual Stresses (RS) that inevitably accumulate during the SLM process's rapid heating and cooling cycles were investigated in the second phase of this research. Laser Peening (LP) was utilized to post-process the printed samples to eliminate the initial tensile RS and induce near 500 Mpa compressive RS. Moreover, the LP parameters were explored and optimized to enhance RS, surface roughness, hardness, and wear resistance. / Thesis / Doctor of Philosophy (PhD)

Le procédé de projection à froid a démontré ses avantages uniques dans la préparation de revêtements métalliques, composites et céramiques. Parmi ces revêtements, ceux constitués de magnésium pur ou de composites à matrice métallique à base de magnésium font partie des matériaux les plus prometteurs en raison de leur excellente résistance spécifique. Pourtant, les mécanismes de fabrication, par ce procédé de projection, des revêtements magnésium et composites à base de magnésium n'ont pas été étudiés. C’est le sujet de cette thèse. Les recherches menées dans cette étude s’articulent autour de plusieurs domaines, à savoir: La science des matériaux avec des études sur l’effet de la granulométrie des particules de magnésium, l’effet de la taille et de la teneur (15% vol. - 60 % vol.) des particules de renforcement (SiC) ; La mécanique des fluides avec des modélisations de géométrie de buse, d’écoulement de gaz et des vitesses des particules de magnésium et alliage de magnésium (AZ91D) ; Les caractérisations des dépôts avec des analyses de microstructure et des mesures de microdureté, d’adhérence et de comportement au frottement des revêtements;Les résultats montrent que la projection à froid peut être utilisée pour fabriquer des revêtements de magnésium purs ou composites sans aucune oxydation ou transformation de phase. La taille de ces particules doit rester dans une fourchette acceptable pour égaler la vitesse critique (entre 653 m•s-1 et 677 m•s-1) permettant la déposition. Concernant plus spécifiquement les résultats sur les revêtements de magnésium pur, le maximum de rendement de dépôt est obtenu par projection d’une poudre de granulométrie comprise entre 22 μm et 64 μm. L’adhérence atteint 11.6 ± 0.5 MPa lorsque le substrat est préchauffé à 200 oC. Pour le cas des revêtements AZ91D, la construction du dépôt s’effectue par effet de verrouillage mécanique. Le type de frottement observé sur ces revêtements est une usure adhésive. Dans les revêtements composites d’AZ91D – SiC, la teneur en particules de renforcement SiC présentes dans le dépôt diminue avec leur taille dû à l'effet «onde de choc». Le rendement de dépôt augmente avec la teneur en SiC de 15 vol.% à 30 vol.%, puis diminue au-delà de 30 vol%. Le type de frottement correspond à une usure par abrasion. / Cold spraying has shown unique advantages in preparing coatings of metal, composite and ceramic. However, the deposition mechanism of magnesium and magnesium-based composite coatings fabricated using cold spraying was not researched although magnesium and metallic matrix composites based magnesium have drawn more and more attention due to their excellent specific strength. Therefore, the deposition mechanism of magnesium and magnesium-based composite coating has been studied in this study. The research carried out in this study involves several fields:Effect of the particle velocity of magnesium particles on the deposition efficiency, microstructure, microhardness and bonding strength of coatings; Effect of the particle size of magnesium particles on the deposition efficiency and microstructure of coatings;Effect of the substrate preheating on the microstructure, microhardness and bonding strength of coatings;Effect of the particle velocity of magnesium alloy (AZ91D) particles on the deposition efficiency, microstructure, and frictional behavior of coatings;Effect of the particle size of strengthening phrase (SiC) on the microstructure, bonding strength and frictional behavior of coatings;Effect of the particle content (15 vol.% - 60 vol.%) of strengthening phrase (SiC) on the microstructure, bonding strength and frictional behavior of coatings.The results show that cold spraying can be used to fabricate magnesium and magnesium-based coatings without any oxidation or phase transformation. The critical velocity of magnesium particles is 653 m•s-1- 677 m•s-1. Magnesium particles with a size too large or too small are not suitable to the deposition. The maximum of deposition efficiency of magnesium particles are obtained using the powder with a size range of 22-64 μm. The maximum of bonding strength between magnesium coatings and substrates is 11.6 ± 0.5 MPa as the substrate is preheated at 200oC. The deposition of AZ91D coatings is due to the effect of mechanical interlocking. And the friction type of AZ91D coatings is adhesive wear. The friction type of AZ91D – SiC composite coatings turn to be abrasive wear. The SiC content in composite coatings decreases as the SiC particle size decreases due to the effect of bow shock. The deposition efficiency of AZ91D and SiC mixed powder increases as the SiC content increases from 15 vol.% to 30 vol.%, and then decreases as the SiC content increases from 30 vol% to 60 vol.%.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / In this work, methodologies to evaluate the wear of flexible riser pipe and bend stiffener samples were developed. In order to achieve this goal, a three coordinate measuring machine (3CMM) was used to evaluate the wear rates of samples tested in in a large-scale tribometer. Additionally, the events that occur during the sliding wear of these samples were correlated with vibration signals from the tribometer structure. The first methodology was applied to estimate the linear wear of riser samples of the polyamide outer coating that was based on the thickness reduction during the test. The second methodology was designed to estimate the volumetric wear loss of the bendstiffener samples. To evaluate the thickness loss of the riser samples, the Calypso® software was used to define the alignment and to determine and execute the measurement strategy. In order to assess the bend-stiffener volume, the same software was used to define the system alignment. The Dimension Volume® software was used to define and to perform the measurement strategy. The sample volume was calculated using a specially designed program that was developed in Matlab®. In order to analyze the vibrations during the wear test, a routine of data acquisition, monitoring and storage of vibration signals in Labview® software was developed and implemented. The results showed that the developed methodology to quantify the riser thickness loss using a 3CMM is viable and efficient in measuring the wear process of this tribosystem. It was also found that the developed program using Matlab® was an effective tool to evaluate the volumetric losses of bend-stiffeners samples. The measurement strategy using a mesh spacing of 1 mm x 1 mm was considered the most adequate to estimate the volume of a bend-stiffener sample accurately and with the least possible amount of points. Furthermore, it was observed a vibration peak located at 16.71 Hz, that should be related to the wear process. / Neste trabalho foram desenvolvidas e aplicadas duas metodologias para quantificar o desgaste em amostras de risers e enrijecedores utilizando uma máquina de medir a três coordenadas (MM3C). Tais amostras foram testadas em um tribômetro capaz de realizar ensaios de desgaste por deslizamento em escala real. Adicionalmente, foram correlacionados os eventos que ocorrem durante o processo de desgaste destas amostras com as vibrações na estrutura do tribômetro. A primeira metodologia foi aplicada na estimativa do desgaste linear em amostras de risers, com base na variação de espessura, enquanto que a segunda foi destinada à estimativa do desgaste volumétrico em amostras de enrijecedores, tendo por base a perda de volume das mesmas. Para avaliar a perda de espessura nas amostras de riser foi utilizado o software Calypso® na definição do alinhamento e na determinação e execução da estratégia de medição. Já na avaliação do volume das amostras de enrijecedores, foi utilizado o mesmo software na definição do alinhamento. O software Dimension Volume® foi empregado na definição e execução da estratégia de medição, e, para calcular o volume destas amostras, foi elaborado e utilizado um programa em Matlab®. Com o intuito de analisar as vibrações durante o ensaio de desgaste, foi desenvolvida e implementada uma rotina de aquisição, monitoramento e salvamento dos sinais de vibrações no software Labview®. Os resultados obtidos permitiram concluir que a metodologia desenvolvida para quantificação da perda de espessura de risers usando uma MM3C é uma técnica viável e eficiente. Constatou-se, também, que o programa desenvolvido em Matlab® foi uma ferramenta eficaz na avaliação volumétrica das amostras de enrijecedores. A estratégia de medição com malha 1 mm x 1 mm foi considerada a mais adequada para estimar o volume de uma amostra de enrijecedor, com precisão e com a menor quantidade de pontos possível. Além disso, verificou-se que o pico da amplitude vibratória esteve localizado em 16,71 Hz, que deve estar relacionado ao processo de desgaste. / Mestre em Engenharia Mecânica

<p>Predmet istraživanja ove disertacije predstavlja unapređenje, modelovanje i optimizacija procesa elektroerozivne obrade (EDM) savremenih inženjerskih materijala. Prvo su predstavljene dve inovativne metode: EDM u dielektrikumu sa pome&scaron;anim prahom i EDM sa pomoćnom elektrodom, a zatim i njihova kombinacija. Za generisanje matematičkih modela primenjene su metodologija odzivne povr&scaron;ine i alati ve&scaron;tačke inteligencije. U nastavku su postavljeni optimizacioni procesi određivanja ulaznih parametara sa jednom i vi&scaron;e funkcija cilja koji su re&scaron;eni primenom klasičnih metoda optimizacije. U zavr&scaron;nom osvrtu sprovedena je verifikacija dobijenih modela i optimalnih ulaznih parametara elektroerozivne obrade.</p> / <p>The subject of the research of this dissertation is the improvement, modeling and optimization of the electrical discharge machining (EDM) of advanced engineering materials. First, two innovation methods are presented: EDM in powder mixed dielectric fluid and EDM with assisted electrode and that their combination. The method of response surface and artificial intelligence tools were applied to generate mathematical models. The optimization problems of determining the input parameters with single and multiple target functions are solved by the application of classical optimization methods. Finally, verification of the obtained models and optimal input parameters of electrical discharge machining was carried out.</p>