Eraldo Jannone da Silva

Development of new standard procedures for the evaluation of dental composite abrasive wear

This article discusses the development of a test bench and a methodology for the study of composite resin abrasive wear. To evaluate the operation of the test bench and to compare the proposed methodology with other existing ones, a study was made of the five composites most commonly used by dentists. The one-way ANOVA method and the Tukey test were used to statistically analyze the results by multiple comparisons of the groups of resins tested. Using the proposed methodology, these resins were classified in an increasing order of abrasive wear strength, as follows: Charisma (the lowest abrasive wear strength), Tetric, TPH, Herculite and Z-100 (the highest abrasive wear strength) ( P< 0.05). In comparison to other methodologies, the results of the proposed methodology presented the lowest coefficient of variation.

Application of the Minimum Quantity Lubrication (MQL) technique in the plunge cylindrical grinding operation

Precision cylindrical grinding is used extensively in the manufacture of precision components in the metal-mechanical industry in general. Modern CNC grinding machines have improved this process with respect to the positioning and rigidity of the machine-workpiece-tool system, allowing the production of high precision parts with low dimensional tolerances. Besides the difficulties inherent to the process, awareness has grown in recent years regarding the environmental issues of cutting fluids. As a response, the industry has begun to seek alternative lubrication and cooling methods. Among the various existing techniques, Minimum Quantity Lubrication (MQL) has been considered as an alternative. This technique can be understood as a combination of conventional lubrication and cooling methods and dry machining, in which a small quantity of lubricating oil mixed with compressed air flow is delivered in the wheel-workpiece interface. The MQL technique is already widely employed in machining processes with tools of defined geometry (e.g. turning), in which produces very satisfactory results. However, the MQL technique has been little explored in grinding processes (non-defined tool geometry), in which the really effective heat removal methods are required due to the frictional heat generation in the grinding zone. Consequently, the aim of this study was to evaluate the plunge cylindrical internal grinding operation when using the MQL technique and the conventional cooling method. Roughness and roundness were the outputparameters. As a result, it was found that the best values of roughness Ra were obtained with the conventional lubrication method. The MQL technique applied as proposed was not able to flush the chips away from the grinding zone, leading to the highest Ra values. No significant differences were detected among the cooling methods when analyzing the roundness results. The workpiece fixture method selected was responsible for the overall unsatisfactory results.

Aspectos microscópicos da influência dos processos de esterilização em pontas diamantadas

Received: April 15, 2002; Revised: January 20, 2003This paper shows a study about the influence of type and number of sterilizations in the cuttingability of diamond points used in dentistry. As a result, the sterilization using the oven was theprocess, which didn’t result in a decreasing in the cutting ability of the diamond points and, untilthe second sterilization, it resulted in a increasing of the cutting ability.

Green manufacturing: uma análise da produção científica e de tendências para o futuro

This paper presents an analysis of the international scientific publications in the green manufacturing area. We used the Web of Science database to identify 239 articles published between 1991 and 2013. The articles involved 589 authors from 36 countries, 246 institutions, and 142 journals/conferences. We found that 51.4% of the articles were published within the last five years. Among the countries involved, the most prolific were the United States and China. The most prolific journal was the Journal of Cleaner Production with 19 articles. Most of the authors, 85.7%, were one-time authors in the field. The highest yield was 11 articles by one author, and the most cited author received 368 citations. We concluded that the green manufacturing area has increased its relevance in recent years by focusing on theoretical and empirical-theoretical studies.

The Grinding Wheel Performance in the Transverse Cylindrical Grinding of an Eutetic Alloy

This paper presents a research in which the performance of two different grinding wheels (a conventional and a CBN wheel) was evaluated in a transverse cylindrical grinding of a eutectic alloy. Three cutting conditions were tested: rough, semi-finishing and finishing. As evaluating parameters, the cutting force, the roughness and the wheel wear were measured. As a result, the best values of the cutting force and the roughness were obtained when grinding with the conventional wheel, due to the best dressing operation performed, for all the cutting conditions. The CBN presented the best G ratio values. Although, the G ratio values observed for the CBN wheel were lower than the expected one due to the non-effective dressing operation applied. In the conditions tested, in terms of cutting force and roughness, the conventional wheel is the best choice. In terms of G ratio, a cost analysis is crucial to determine if the differences observed among the wheels can justify the use of the CBN wheel. In a positive case, the dressing operation must be improved.

Advanced Ceramics: Evaluation of the Mechanism of Stock Removal and Ground Surface Quality

The aim of this work is to evaluate the mechanism of stock removal and the ground surface quality of advanced ceramics machined by a surface grinding process using diamond grinding wheels. The analysis of the grinding performance was done regarding the cutting surface wear behavior of the grinding wheel for ceramic workpieces. The ground surface was evaluated using Scanning Electron Microscopy (SEM). As a result it can be said that the mechanism of material removal in the grinding of ceramic is largely one of brittle fracture. The increase of the hmax can reduce the tangential force required by the process. Although, it results in an increase in the surface damage, reducing the mechanical properties of the ground component.

The Inlet Engine Valves Grinding Using Different Types of Cutting Fluids and Grinding Wheels

In this paper an experimental research is presented in which different types of cutting fluids (a cutting oil and three different types of soluble oils) and grinding wheels (alumina and vitrified CBN) were tested in the inlet engine valves grinding. As evaluation parameters the workpiece residual stress and the grinding wheel wear were analyzed. The cutting fluid and the grinding wheel types adopted resulted in changes in all the parameters, due to the different lubricant abilities among the fluids and due to the differences in the mechanical and thermal properties among the abrasives tested. For grinding this steel, the CBN wheel is the best choice, mainly due to compressive residual stress results obtained for all cutting fluids tested. The cutting oil is the most adequate cutting fluid to be used, due to its higher lubricity and ability in keeping the wheel sharp for longer periods of time, reducing the overall grinding energy and the thermal damage.

Prototypical Implementation of a Remanufacturing Oriented Grinding Machine

Considering the current scenario of limited resources and increased environmental regulations, frameworks to support the development of more sustainable production equipment are sought. Remanufacturing can bring benefits in terms of extending product lifetime by allowing multiple usage phases. Due to the diversity of mechanical, electrical and electronic components with different degree of replacement criteria of grinding machines, remanufacturing emerges as a relevant approach. The aim is to present a prototypical implementation of a remanufacturing oriented grinding machine, based on a storyboard which describes the main activities carried out during the machine lifecycle, including a comparative LCA of end of life scenarios.

Influência da Dureza dos Discos Abrasivos no Corte de Materiais Dúcteis

O corte de materiais por disco abrasivo e um dos processos que apresentam as melhores caracteristicas de economia, eficiencia e rapidez sendo muito utilizado no meio industrial. Fatores como porcentagens e homogeneidade da mistura dos componentes, tamanho, forma (abrasividade), tenacidade e dureza dos graos abrasivos, tipos de ligantes e de abrasivos, velocidade de corte e velocidade de mergulho influenciam na seguranca, no desempenho e comportamento da operacao. Este trabalho apresenta um estudo sobre a influencia da dureza dos discos abrasivos no desempenho do processo de corte em operacoes do tipo remocao a seco. O aumento da dureza dos discos propiciou um aumento da forca tangencial de corte e da relacao G, devido a mais forte ligacao entre o grao e o ligante no composito. Os resultados mostram que a dureza dos discos abrasivos afeta a economia, pois influencia na vida util dos discos abrasivos em termos de numeros de cortes proporcionados; a produtividade, pois esta relacionada com o numero de trocas de discos desgastados; os esforcos necessarios para a operacao, pois estao relacionados com as forcas tangenciais de corte.