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The evaluation of the tribological conditions, among which the friction by means of simple models are questionable because the influence of superficial roughness and strength of materials, among other factors, is not considered. This paper presents a detailed analysis on the influence of surface roughness on friction at the specimen/die interface. The studies are based on experimental data obtained by the ring compression test, which they were compared with results of simulations and the calibration curves of friction modeled in finite element software. A series of ring compression tests was performed to obtain the friction coefficient for various ranges of surface roughness of the specimen. Key words: ring compression test, surface roughness, friction coefficient, numerical simulation.

This work has the purpose of studying loudspeakers in which the cores usually constructed from cast iron or rolled metal are replaced with parts of alloy obtained from the Powder Metallurgy process. The study comprises the obtaining of hysteresis curves of pure iron and some sintered alloys such as FeP, FeNi and FeSi and simulation by the finite element considering a conventional topology of a commercial loudspeaker. The simulations include the evaluation of flow in the air gap and a theoretical study of the powers developed compared to loudspeakers with conventional cores. Keywords: powder metallurgy, simulation by the finite element, loudspeakers.

The aim of this work is the study of sintered titanium parts for medical applications components, via process of Powder Metallurgy (M/P). This study will be a basis for the manufacture of an orthodontic interpenetrating screw. A study of constituent powders was accomplished and samples were prepared. In sequence, its physical properties were analyzed. For all alloy composition studied, the parameters of production process were respected as: compactation pressure, sintering atmosphere, and sintering time. The porosity determined by Archimedes principle was approximately 11.5%. This result is comparable to that found in the literature. The average density obtained by M/P was 4.03 g/cm3 for sintered titanium, with a density close to theoretical density of titanium, 4.5 g/cm3. Key words: powder metallurgy, sintering, orthodontic screw.

No presente trabalho, foi feito um estudo sobre caracterização parcial de uma liga Nitinol atuador tipo M fabricada pela Memory-Metalle. Através dos resultados obtidos em Calorimetria Diferencial de Varredura mostraram-se as temperaturas de transformação de fases onde ocorrem as propriedades notáveis, efeito memória de forma e superelasticidade. Estas temperaturas irão determinar a aplicação da liga no produto. As temperaturas transformação de fases são definidas como As (austenite start), Af (austenite finished), Ms (martensite start) e Mf (martensite finished), ou seja, início e fim da transformação austenítica e início e fim da transformação martensítica. In this work, it was studied a partial characterization of a Nitinol actuator M-type alloy, manufactured by Memory- Metalle. From the results obtained in differential scanning calorimetry, it was shown the temperatures of phase transformation where occur the remarkable properties, shape memory effect and super-elasticity. These temperatures will determine the alloy application in the product. The phase transformation temperatures are defined as As (austenite start), Af (austenite finished), Ms (martensite start) and Mf (martensite finished), which means beginning and end of austenite transformation and the beginning and end of the martensitic transformation.

O objetivo deste trabalho é realizar um estudo comparativo sobre a influência de lubrificantes no coeficiente de atrito da liga de alumínio AA6351. O atrito tem um efeito significativo na deformação do material, alterando a força de compressão e o desgaste da matriz e da peça. A escolha de um lubrificante com eficiência na redução do atrito da interface peça/matriz aumenta à vida útil da ferramenta e, consequentemente, melhora a margem de lucro quando em produção industrial. Para o forjamento de ligas de alumínio, recomendam-se lubrificantes à base de grafite e água ou grafite e óleo. Neste estudo, três lubrificantes comerciais foram testados: grafitado (Aerodag G), sintético (Synd Forg 100-A) e um a base de óleo (Dechelub 5562). A metodologia adotada: obtenção de corpos de prova, ensaio do anel em prensa hidráulica variando-se os lubrificantes, simulação em programa computacional para aquisição das curvas de calibração e comparação dos resultados. Comparando os dados experimentais com as curvas obtidas por simulação foi verificado que, entre os três lubrificantes testados, o sintético obteve o melhor desempenho, seguido do lubrificante à base de óleo. O lubrificante à base de grafite obteve um desempenho inferior para essa aplicação. The aim of this paper is a comparative study about the influence of lubricants on the friction coefficient of aluminum alloy AA6351. The friction has a significant effect on the deformation of the material, changing the compression strength and wear of the matrix and the piece. Choosing a lubricant able to reduce friction interface piece/matrix provides tool life gain and consequently improves the manufacturing profit margin. For the forging of aluminum alloys are recommended lubricants based on graphite and water or graphite and oil. On this study, three commercial lubricants were tested: a graphited (Aerodag G), a synthetic (Synd Forg 100-A) and an oil-based (Dechelub 5562). The methodology consists on obtaining specimens ring shaped, ring test in hydraulic press changing the lubricants, computer program simulation for the acquisition of the calibration curves and comparison of results. Comparing the experimental data with the curves obtained by simulation, we found that, among the three lubricants tested, the best performer was the synthetic, followed by oil-based lubricant. The graphite based lubricant had the worst performance.

Este trabalho tem por objetivo a investigação do efeito da moagem de alta energia sobre a morfologia, tamanho de partícula e compressibilidade do compósito Mo-Cu. O compósito Mo-Cu combina a alta resistência mecânica do Mo com a alta condutividade térmica e elétrica do Cu. Estas características são importantes para dissipadores de calor e condutores elétricos. A moagem de alta energia produz pós compósitos com alto nível de homogeneização e refina o tamanho de grão. A síntese do compósito Mo-30Cu, partindo dos pós de Mo e Cu, foi realizada para tempos de moagem de 1, 4, 8, 16 e 32 horas. A fim de observar a influência do tempo de moagem sobre a microestrutura, empregaram-se as técnicas de microscopia eletrônica de varredura e granulometria a laser. Esta avaliação permitiu observar o comportamento morfológico e a interação entre os elementos do material produzido. Os resultados mostram que com o decorrer do tempo de moagem ocorreu a diminuição do tamanho de partículas, que demonstra a viabilidade de obtenção deste compósito. The purpose of this work is to analyze the effects of high energy milling on the granulometry, powder morphology and compressibility of Mo-Cu composite. The Mo-Cu composite combines high mechanical strength of Mo with the high thermal and electrical conductivity of Cu. These characteristics are important to heat sink and electrical conductors. The high energy milling produces composite powders with high homogeneity and refines the grain size. The synthesis of Mo-30Cu composite, starting from powders of Mo and Cu, was realized for milling times of 1, 4, 8, 16 and 32 hours. Scanning electron microscopy and laser granulometry were used to follow the influence of milling time on the microstructure. This allowed to observe the morphological evaluation and interaction between the elements of the material produced. The results show that the particle size and compressibility decreased with the milling time, which shows the viability to obtain this composite by the proposed process.

The aim of this work was the development of magnets in a ring form, four poles, for speed sensor of motorcycles, from barium and strontium ferrites. The model of the magnets developed was based on magnets already manufactured for this purpose. Thus, several raw materials were tested with additive variation. The samples were prepared and measured, and the data were compared to commercially produced magnets. Finally, the magnets were mounted in the speed sensors and field tests were carried out. The magnets developed showed excellent results as having the highest remanent magnetism of 500 Gauss for the PFL barium ferrite alloy with 4% of stearic acid and 1 or 2% of silica, resulting 20% above the required magnetism. Keywords: ferrite magnets, powder metallurgy, speed sensor.