In this study the unique Magotteaux Mill® system was used to control the grinding chemical conditions, which may be adjusted by varying grinding media, purging gas and pH, during grinding. An electrochemical apparatus was used to investigate oxidation-reduction behaviour of grinding media and sulphide mineral electrodes, as well as their galvanic interaction in-situ of the Magotteaux Mill®. Galvanic interaction between the grinding media (mild steel, 15% chromium, 21% chromium and 30% chromium media) and the sulphide minerals (bornite, arsenopyrite and pyrite) was initially quantified in-situ of the mill by electrochemical techniques under different grinding atmospheres (nitrogen, air and oxygen). An innovative mathematical theoretical model was developed to describe the effect of galvanic interaction on oxidation rates of the grinding media during grinding, which was verified by the experimental data. Galvanic interaction enhanced the oxidation of the grinding media and produced more oxidized iron species in the mill discharge. It was observed that oxidized iron species (EDTA extractable iron) was linear with galvanic current between the grinding media and the sulphide minerals, in agreement with the prediction of the theoretical model. The effect of grinding conditions on pulp chemistry, surface properties and floatability was investigated by the measurement of dissolved oxygen (DO), pH, pulp potential (Eh), ethylene diamine-tetra acetic acid (EDTA) extraction, X-ray photoelectron spectroscopy (XPS) and floatation recovery. / PhD Doctorate

Thesis (M.S.)--University of Michigan, 1983.

Thesis (M.S.)--University of Michigan, 1970.

Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2005. / Steven Danyluk, Committee Chair ; Richard Salant, Committee Member ; Jeffrey Streator, Committee Member ; Michael Sacks, Committee Member ; Dennis Hess, Committee Member ; Leonard Borucki, Committee Member. Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 1983.

Thesis (M.S.)--University of Michigan, 1970. / eContent provider-neutral record in process. Description based on print version record.

Thesis (Ph.D.)(Metallurgical Engineering)--University of Pretoria, 2005. / Includes summary. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2006. / Full text release at OhioLINK's ETD Center delayed at author's request

Made available in DSpace on 2014-06-11T19:23:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-05-04Bitstream added on 2014-06-13T18:50:40Z : No. of bitstreams: 1 fujita_h_me_bauru.pdf: 3757663 bytes, checksum: 66acc24c6f3d11d42e726d1b452899b3 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O sucesso da cerâmica estrutural na maioria das aplicações depende não somente das propriedades do material e do projeto da peça, mas também da qualidade do produto usinado. Um dos fatores citados como obstáculo à ampla utilização das cerâmicas é a falta de confiabilidade dos componentes de cerâmica, em função da grande dispersão dos valores de resistência mecânica provocada por defeitos que podem ter origem no processo de retificação. A retificação de cerâmica, assim como na indústria de processamento metal-mecânica, é realizada normalmente com abundância de fluidos de corte. A utilização destes fluidos refrigerantes resulta em problemas ecológicos, fisiológicos e econômicos. Desde a última década, a opinião pública, o mercado, as leis e regulamentos têm pressionado as indústrias para considerar os riscos ambientais na manufatura. Com o propósito de avaliar alternativas ao método convencional de lubri-refrigeração, foi estudada a viabilidade da técnica de refrigeração otimizada, onde o fluido de corte é aplicado à mesma velocidade periférica do rebolo, penetrando na região de corte com menos turbulência. Também foi analisada a técnica da Mínima Quantidade de Lubrificação (MQL), na qual o grande volume de fluido de corte é substituído por um jato de ar contendo uma quantidade ínfima de lubrificante. Os métodos foram comparados através da análise de desempenho durante o processo de retificação (forças de corte, emissão acústica, energia de retificação) e pela caracterização dos corpos de prova (rugosidade, danos subsuperficiais) e do rebolo (relação G). A profundidade de corte e o efeito do spark-out também formaram parte do escopo deste trabalho. Os resultados obtidos mostraram que a profundidade de corte exerce grande influência durante o processo... / The success of structural ceramics in most applications depends not only on the materials properties and component design, but also the quality of machined products. One factor usually mentioned as a barrier to the wide use of ceramics is the lack of reliability of ceramic components, because the variability on the mechanical strength caused by defects that can be impaired in the grinding process. The grinding of ceramics, as much as with steel grinding is performed generally with excess of cutting fluids (coolants). The use of coolants results in serious ecological, physiological and economic issues. Since last decade the public opinion, the market, the laws and regulations have pushed the industries to consider the environmental risks in the manufacturing process. Then, in order to evaluate alternatives to the conventional method of cooling and lubrication, it was studied the viability of the optimized technique, where the cutting fluid is applied to the same peripherical speed of the wheel, penetrating in the cutting zone with less turbulence. Also, it was verified the technique of Minimum Quantity of Fluid (MQF), where a large amount of cutting fluid is replaced by an air compressed flow containing a small quantity of lubricant. The methods were compared through performance analysis during the grinding process (cutting forces, acoustic emission and specific grinding energy) and by characterization of specimens (roughness, subsurface damage) and wheel (G ratio). The depth of cut and the effect of spark-out were part of the scope of this work too. The results obtained showed that the depth of cut has great influence during the process and in the characterization of ceramics, while spark-out does not seem to be so significant. Another conclusion is that MQF is not viable in ceramics grinding with the working conditions proposed. The results obtained... (Complete abstract, click electronic access below)

Orientador: Eduardo Carlos Bianchi / Banca: Luiz Eduardo de Angelo Sanchez / Banca: Leonardo Roberto da Silva / Resumo: O processo de retificação é um processo de acabamento, e, portanto, possui características como bom acabamento superficial e alta precisão dimensional e geométrica. As peças usinadas por este processo possuem um alto valor agregado, pois as mesmas já passaram por outros processos de usinagem e/ou tratamentos térmicos e revenimento. Um fator limitador do processo de retificação é a quantidade de calor gerada durante o mesmo, energia esta que é minimizada pela aplicação de fluidos de corte durante a retificação. Porém os fluidos utilizados, na maior parte dos casos são poluentes e contém substâncias prejudiciais à saúde, além de possuir um alto custo de compra, manutenção e descarte. Visando reduzir a quantidade de fluido utilizada durante o processo de retificação o presente trabalho foi proposto, com o objetivo de melhorar a técnica da mínima quantidade de lubrificação através da aplicação combinada com ar comprimido à baixa temperatura a fim de melhorar o efeito de refrigeração e assim minimizar a geração de calor na região de corte. Para avaliar a eficácia da técnica foram escolhidas as variáveis de acabamento como a rugosidade e a circularidade, e de eficiência do processo como o desgaste do rebolo e potência consumida durante a usinagem. Estes valores foram medidos para três métodos distintos de aplicação de fluidos de corte durante o processo de retificação, a fim de compará-los, o método proposto para o presente trabalho, CAMQL (técnica de mínima quantidade de fluido co... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Grinding is a finishing process, and therefore has characteristics such as good surface finish, high dimensional and geometric precision. Because it is this kind of manufacture process, the parts machined by this have a high added value, since they have already undergone other machining processes and/or heat treatments and tempering. A limiting factor of grinding process is the amount of heat generated during it; which energy is minimized by application of cutting fluids. But these fluids, in most cases are pollutants and could contain substances that are harmful to health, in addition to having a high cost of purchase, maintenance and disposal. In order to reduce the amount of fluid used during the grinding process, the present research has been proposed with the aim of improving the technique of minimum quantity of lubrication by the combined application with compressed air at low temperature in order to improve the cooling effect ant thus minimize the heat in cutting zone. To evaluate the effectiveness of this technique, the finishing variables such as roughness and roundness, and process efficiency, such as grinding wheel wear and power consumed during machining, were chosen. These values were measured for three different methods of cutting fluids application during the grinding process, in order to compare them, the proposed method, CAMQL (cold air minimum quantity of lubrication) as compared to conventional fluid application (flood) and the minimum quantity lubrication with air in room temperature. For all parameters, the proposed cutting fluid reduction reached, in general, positives results, proving its... (Complete abstract electronica acess below) / Mestre