A retificação, processo final de usinagem de uma peça, utiliza fluidos de corte com a finalidade de lubrificação, refrigeração e remoção de cavacos. No entanto, esses fluidos são extremamente agressivos com o meio. Com o avanço tecnológico a tendência mundial é produzir peças cada vez mais sofisticadas, com elevado grau de tolerância geométrica, dimensional, com bom acabamento superficial, com baixo custo e, principalmente, sem causar danos ao meio. Para tanto, ao processo de retificação está intrínseca a reciclagem do fluido de corte, que se destaca pelo seu custo. Através da variação da velocidade de avanço no processo de retificação cilíndrica externa do aço ABNT D6, racionalizando a aplicação de dois fluidos de corte e usando um rebolo superabrasivo de CBN (nitreto de boro cúbico) com ligante vitrificado, avaliaram-se os parâmetros de saída da força tangencial de corte, emissão acústica, rugosidade, circularidade, desgaste da ferramenta, tensão residual e a integridade superficial através da microscopia eletrônica de varredura (MEV) dos corpos-de-prova. Com a análise do desempenho do fluido, do rebolo e da velocidade de mergulho, encontraram-se as melhores condições de usinagem propiciando a diminuição do volume de fluido de corte e a diminuição do tempo de usinagem, sem prejudicar os parâmetros geométricos e dimensionais, o acabamento superficial e a integridade superficial dos componentes.

Grinding, the final stage of the machining process, employs a significant amount of cutting fluids for lubrication, cooling and swarf removal. However, these cutting fluids are extremely aggressive to the environment. With technological progress, the world tendency is to produce more and more sophisticated pieces,having a high degree of geometrical and dimensional tolerance, good surface finish, hlow cost and, mainly, insignificant impact on the environment. Therefore, recycling cutting fluids is intrinsic and cost-cutting for the grinding process and This work aimed to assess several output parameters in external cylindrical grinding: tangential force, acoustic emission, surface roughness, roundness, tool wear, and residual stress. Also, analysis of microstructural features through Scanning Electron Microscopy (SEM) was carried out. Tests was developed for ABNT D6 steel, using a CBN grinding wheel with vitrified bond and two types of cutting fluids Analyzing cutting fluid performance, grinding wheel time and feed rate, the best grinding conditions were found, leading to a decrease in cutting fluid volume and grinding time without impairing the geometrical and dimensional parameters, surface finish and surface integrity of the parts.

Over the years, grinding has been considered one of the most important manufacturing processes. Grinding is a high precision process, and the loss of a single workpiece in this stage of the production is unacceptable, for the value added to the material is very high due to many processes it has already undergone prior to grinding. This study aims to contribute toward the development of an experimental methodology whereby the pressure and speed of the air layer produced by the high rotation of the grinding wheel is evaluated with and without baffles, i.e., in an optimized grinding operation and in a traditional one. Tests were also carried out with steel samples to check the difference in grinding wheel wear with and without the use of baffles.

The purpose of this work is to explain the concept of cutting fluids reasonable usage through the fluid minimum quantity in grinding processes. On that purpose, the development of a new nozzle and an own and adequate methodology should be required in order to obtain good results and compare them to the conventional methods. The analysis of the grinding wheel/cutting fluid performance was accomplished from the following input parameters: flow rate variation by nozzle diameter changes (three diameters values: 3mm, 4mm and 5mm), besides the conventional round nozzle already within the machine. Integral oil and a synthetic emulsion were used as cutting fluids and a conventional grinding wheel was employed. The workpieces were made of steel VC 131, tempered and quenched with 60HRc. Thus, as the flow rate and the nozzle diameter changes, keeping steady fluid jet velocity (equal to cutting velocity), attempted to find the best machining conditions, with the purpose to obtain a decrease on the cutting fluid volume, taking into consideration the analysis of the process output variables such as cutting strength, cutting specific energy, grinding wheel wear and surface roughness. It was verified that the 3mm diameter optimized nozzle and the integral oil, in general, was the best combination among all proposed.

The application of cutting fluid in a deep grinding process is becoming more and more important, mainly where the cutting fluids are used as an "external" agent to the grinding conditions. The role of the fluid in grinding operations is in refrigeration of the workpiece, removal of the shavings, lubrication of the grinding zone, and refrigeration and cleaning of the wheel. The efficiency of a cutting fluid will depend mainly of the type of fluid that will be used. In this work, the influences of the type of cutting fluid used in a deep grinding process of the steel VC131 using CBN grinding wheel are analyzed. Three different types of cutting fluids were used: a vegetable emulsion, a synthetic solution and a integral oil. The variables analyzed during and after the grinding process were the grinding force, the superficial roughness, the acoustic emission (EA), the temperature of the piece and the G ratio (relationship between the volume of material removed from the piece and the volume worn off the grinding wheel). The integral oil showed the best performance relative to the following output variables: EA, cutting force and G ratio. The vegetal emulsion was the fluid that best dissipated heat from the cutting region.

New worldwide trends such as globalization have rendered grinding processes increasingly important for industry, making it essential to perform in-depth studies of variations in grinding process parameters in the pursuit of greater cost effectiveness. This paper presents a comparative analysis of three different infeed rates, using a conventional grinding wheel on quenched and tempered D2 steel workpieces. Higher infeed rates are known to be correlated with shorter grinding times, rendering the process more economically attractive. Two different coolant fluids, 5% emulsion and pure oil, were used. The tests were carried out using the smallest possible amount of coolant and an optimized 5 mm diameter nozzle. The parameters analyzed were tangential force, specific energy, acoustic emission, roundness error and surface roughness. The surfaces of the workpieces were also examined by scanning electron microscopy (SEM). The results revealed that increased infeed rates could reduce processing times without compromising the quality of the workpiece profile, thereby reducing the cost of the process. The best cutting fluid, albeit more harmful to human health and less environmentally friendly, was found to be pure oil.

Nesse trabalho, procurou-se estudar os mecanismos de desgaste de diversas geometrias de ferramentas cerâmicas (Al2O3 + SiCw e Al2O3 + TiC) e ferramentas de PCBN. Para isto foram realizados ensaios de torneamento com alta velocidade de corte em uma superliga à base de níquel (Waspaloy) com dureza de aproximadamente 40 HRC sob condição de corte a seco. As superligas são conhecidas como materiais de difícil usinabilidade devido à alta dureza, alta resistência mecânica em alta temperatura, afinidade para reagir com materiais da ferramenta e baixa condutividade térmica. Os resultados mostraram que o material da ferramenta e a geometria influenciaram o comportamento dos mecanismos de desgaste. De uma maneira geral, o tipo de desgaste dominante foi o de entalhe e os mecanismos foram abrasão, attrition (aderência com arrastamento) e provável difusão na maioria das ferramentas utilizadas.

The purpose of this work is to study the wear mechanisms in several geometries of ceramic tools (Al2O3 + SiCw and Al2O3 + TiC) and PCBN tools. Several high speed turning experiments were accomplished in nickel-base superalloy (Waspaloy) with hardness of approximately 40 HRC under dry cutting condition. The nickel based superalloys are known as difficult to cut materials due to their high hardness, high mechanical straight at high temperature, chemical affinity to tool materials and lower thermal conductivity. The results showed that the material of the tool and geometry influence the behavior of wear mechanisms. In general, the dominant type of wear was notching and the mechanisms were abrasion, attrition and probable diffusion in most of the used tools.

Nesse artigo é apresentada uma pesquisa experimental sobre os danos térmicos que aparecem nas válvulas de admissão dos motores após passarem pelo processo de retificação. Foram utilizados, nessa experimentação, quatro tipos de fluidos de corte e dois rebolos (CBN e Al2O3), sendo analisadas a tensão residual, a microdureza e a microestrutrura das peças fabricadas com esses materiais. Esses fluidos e rebolos resultaram em diferentes tipos de tensões residuais. O óleo de corte, por exemplo, induziu nas peças tensões residuais de compressão. Em relação ao rebolo de CBN, devido às melhores propriedades de seus grãos abrasivos, estes proporcionaram tensões de compressão para todos os fluidos testados. Em relação às alterações microestruturais, notou-se que nenhuma alteração térmica foi detectada nas peças, embora a inexistência de alterações microestruturais nem sempre sugerem que tensões residuais favoráveis foram obtidas.

This paper presents an experimental research in which the thermal damage in inlet engine valves grinding was evaluated. Four different cutting fluids and two grinding wheel were tested and were analyzed the workpiece residual stress, the micro hardness and the optical observation of the workpiece microstructure. The cutting fluid and the grinding wheel types adopted resulted in different types of residual stress. The cutting oil resulted in compressive residual stresses, even using the conventional wheel. The CBN wheel, due to the best proprieties of its grains resulted in compressive residual stresses for all fluids tested by the reducing of the grinding energy and its easier dissipation from the grinding zone. The microstructure investigations showed that the source of the tensile residual stresses observed was the thermal cycles imposed. No microstructure alterations were detected. Although, the absence of microstructure alterations not always suggests that favorable residual stresses can be obtained.

Esse artigo tem como objetivo apresentar o projeto, a construção e os resultados obtidos no estudo da osseointegração com um torquímetro de alta precisão. Esse torquímetro, especialmente desenvolvido para este tipo de pesquisa, pode ser usado para desenvolver pesquisas odontológicas da osseointegração de implantes dentários. Os implantes foram feitos em sete coelhos que foram avaliados após 21 e 42 dias. Alguns coelhos sofreram estimulações ultra-sônicas em seus implantes, enquanto outros foram analisados sem se submeterem a estas estimulações. Os resultados mostraram o bom funcionamento do torquímetro e que o torque para remover o implante do coelho é diretamente proporcional ao tempo de osseintegração e que as estimulações ultra-sônicas podem influenciar o torque necessário para remover o implante em alguns casos.

This paper has as objective, to present the project, the construction and the results obtained in the study of the osseointegration with a torque gauge of high precision. The torque gage, especially developed for this research type, was used to improvement of odontological research on osseointegration of dental implant. The implants were done in seven rabbits that were available after 21 and 42 days. In some rabbits were made ultra-sonic stimulations at rabbits' implants. The results showed that the torque to remove the implant of the rabbits is directly proportional at the time of osseointegration and that the ultra-sonic stimulations can also influence the torque in some cases.