Repositório RCAAP

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

It is presented a study for the development and resolution of the equations of the coupling flow - deformation in porous media saturated with compressible fluid. The cases in analyses are transients, two-dimensional or three-dimensional systems, and are studied with the objective of get displacements on the surface, the field of stresses and deformations in the geotechnical medium, submitted to a static or cyclic superficial load. The process allows simulation of the ground behavior, soil or rock, consisting of different elastic and hydraulic properties when submitted a static, cyclical or harmonic superficial load. A field of pressure in the pores is generated in all medium as consequence of this load in the surface of the ground. A computer program simulates the pressure in the pores and all process of balance, deformation and the initial condition: neutral pressure in all points, express porous pressure numerically. The developed mathematical model simulates the field of stresses and displacements in the interior of the porous media, connected to the draining fluid in the pores, to the deformation fluid and the constituent porous structure. It can be observed that the biggest deformation occurs, mainly, due to reduction of the emptiness s, as consequence of a rearrangement internal structure of the ground, soil or the rock in analysis. The study it is made considering that the constituent solid particles of the geotechnical medium are incompressible. The equations that conduct the phenomenon are solved numerically through the technique of the spectral method, using a mesh of points of collocation in the analyzed domain and following evolution of the pressure with the time. The dissipation of the pressure connects to the displacements in the porous media, inducing the variation of stress in the interior of the medium.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

The excessive vibrations are common during the chamfering of valve seats and induce operator to reduce cutting speed and feed rate, causing reduction of the productivity. The objective of this work was to study the chamfering of the intake valve seats of the cylinder head of an internal combustion engine. The valve seats are machined with PCBN blades from sintered steel rings with 370-410 HB hardness. This work was developed in a partnership with the companies Fiat Powertrain Technologies and Mapal Tools. The justification to do this work is that there was a need to know better the influence of cutting speed, feed rate and PCBN blade geometry in the vibrations and roundness deviations resulting from the machining of the valve seats. With this knowledge, modifications were proposed in order to obtain a stable cut, higher productivity, lower cost and a better sealing of the combustion chamber, resulting in smaller emission of gases from the engine. The analysis carried out showed that the vibrations and roundness deviations tend to reduce when applying cutting speed between 80 and 100 m/min, feed rate between 0.04 and 0.08 mm/rev, using PCBN blades with T-chamfer cutting edge honing around 60 μm.

The use of compacted graphite iron - CGI is growing in the automobile industry, replacing several components that usually are manufactured in grey cast iron. However, due to its poor machinability when compared to grey cast iron, the production cost sometimes is not competitive. Several research about machinability of CGI has already been developed, mainly in turning, milling and drilling operations. Little has been done with regards to tapping process, which is a more complex operation. The main objective of this work is the investigation of the performance of cemented carbide taps when cutting CGI 450 ASTM. It was is used M13x1,5 taps with four straight flutes, TiAlN coated. The tests were carried out in dry conditions and using cutting fluid applied by MQF (minimal quantity of fluid) and overhead flow. The work was split into two parts. In the first, the cutting tools were used in the production line of Tupy S.A., to produce different wear levels. The second part was developed at the laboratory, when tool wear was measured and experiments were carried out to obtain cutting forces and torque. The results showed that the cutting forces and torque depend on the cutting parameters. Analysis in the scanning electron microscope and optical microscope to determine the wear mechanisms suggested that the main wear mechanisms are adhesion and abrasion. Experiments were also carried out to study the effect of some important aspects of the process like concentricity, feed rate, thread length and tool defects.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Fundação de Amparo a Pesquisa do Estado de Minas Gerais