Comando Geral de Tecnologia Aeroespacial

São José dos Campos, Brazil

Comando Geral de Tecnologia Aeroespacial

São José dos Campos, Brazil
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Sugahara T.,Comando Geral de Tecnologia Aeroespacial | Reis D.A.P.,Comando Geral de Tecnologia Aeroespacial | Moura Neto C.,Comando Geral de Tecnologia Aeroespacial | Barboza M.J.R.,University of Sao Paulo | And 3 more authors.
Materials Science Forum | Year: 2010

Ti-6Al-4V is currently used in aeronautic and aerospace industry mainly for applications that require resistance at high temperature such as, blades for aircraft turbines and steam turbine blades. The titanium affinity by oxygen is one of main factors that limit the application of their alloys as structural materials at high temperatures. Notable advances have been observed in the development of titanium alloys with the objective of improving the creep properties. Increased oxygen levels are associated with increased microhardness and decreased ductility in titanium. In spite of this, Ti-6Al-4V containing an (α+β) structure continues to be the workhorse of the titanium industry due to their high specific strength, corrosion resistance, excellent high temperature properties and metallurgical stability. The objective of this work was to study the influence of equiaxed and Widmanstätten microstructures on oxidation rates and creep behavior of the Ti-6Al-4V alloy. The samples were exposed to different conditions of time and temperature to evaluate the oxidation rates. This influence on the oxidation rates was evaluated in terms of weight gain, α-case depth and microhardness profile at 500 and 600 °C. Preliminary results indicated that the equiaxed microstructure with average grain size of 10 μm exhibits faster oxygen diffusion. Short-term creep tests were performed under constant load in a stress range from 291 to 472 MPa at 500 °C and in a stress range from 97 to 291 MPa at 600 °C. The stress exponents obtained lie in the range from 4.0 to 11.3. The apparent activation energies for steady-state creep determined in the present work were estimated to be 316 and 415 kJ/mol at 291 MPa for the equiaxed and Widmanstätten microstructures, respectively. On the basis, the creep of Ti-6Al-4V is consistent with the lattice diffusion-controlled dislocation climb process in α-Ti, for both microstructures. The creep rates of Widmanstätten microstructure were two orders of magnitude lower than of equiaxed microstructure in both temperatures. Apparently, the higher creep resistance with a Widmanstätten microstructure can be attributed to α/β interfaces acting as obstacles to dislocation motion and to the average grain size of 395 μm, which reduces the grain boundary sliding, dislocations sources and the rate of oxygen diffusion along grain boundaries. © (2010) Trans Tech Publications.

Rangel R.K.,Brazilian Technological Institute of Aeronautics | Kienitz K.H.,Brazilian Technological Institute of Aeronautics | Brandao M.P.,Comando Geral de Tecnologia Aeroespacial
IEEE Aerospace Conference Proceedings | Year: 2011

This paper describes the development of a multipurpose portable electrical Unmanned Aerial Vehicle (UAV) system, consisting of aircraft, ground station and field support equipment. This UAV can be employed in different applications, such as tactical surveillance, and power line inspection. The system allows the operator to remotely fly and control the aircraft from a one-man portable ground station. We also describe the development of the UAV electrically propelled airborne platform system, including two aircraft types (rotative and fixed wing type), the assembling of the onboard hardware, the one-man portable ground station components, and subsystem integration. An overview of on-ground and in-flight tests required for the system qualification is also presented. This system proves that employing low-cost and off-the-shelf equipment to develop flexible UAV models is possible. © 2011 IEEE.

Braga N.A.,National Institute for Space Research | Cairo C.A.A.,Comando Geral de Tecnologia Aeroespacial | Matsushima J.T.,National Institute for Space Research | Baldan M.R.,National Institute for Space Research | Ferreira N.G.,National Institute for Space Research
Journal of Solid State Electrochemistry | Year: 2010

Hybrid three-dimensional electrodes produced from microcrystalline boron-doped diamond (BDD) and/or nanocrystalline diamond films were grown on porous titanium (Ti) substrate by hot filament chemical vapor deposition (HFCVD) technique. Powder metallurgy technique was used to obtain the Ti substrates provided by interconnected and open pores among its volume. Diamond growth parameters were optimized in order to provide the entire substrate surface covering including the deeper surfaces, pore bottoms, and walls. The morphology and structure of these electrodes were studied by scanning electron microscopy (SEM) and visible Raman spectroscopy techniques, respectively. Electrochemical response was characterized by cyclic voltammetry measurements. Results showed a wide working potential window and low background current characteristic of the diamond electrodes. The kinetic parameters also pointed out to a quasi-reversible behavior for these hybrid three-dimensional diamond/Ti electrodes. © 2009 Springer-Verlag.

Braga N.A.,National Institute for Space Research | Cairo C.A.A.,Comando Geral de Tecnologia Aeroespacial | Ferreira N.G.,National Institute for Space Research | Baldan M.R.,National Institute for Space Research | Trava-Airoldi V.J.,National Institute for Space Research
Diamond and Related Materials | Year: 2010

Nanocrystalline diamond (NCD), formed on three-dimensional (3D) titanium (Ti) substrates, through the etching of reticulated vitreous carbon (RVC) was investigated. Porous Ti was prepared by powder metallurgy and the RVC was produced at 1300 and 2000 °C graphitization index. In this chemical vapor infiltration/deposition process, the RVC sample was used as the only carbon source that ensured the production of pertinent growth species directly on the Ti surfaces including its inner and bottom (the opposite side of the sample). The films were deposited at 630 °C substrate temperature. NCD scanning electron microscopy images showed agglomerates of nanometer crystallites with a uniform surface texture covering all sample. Raman measurements showed the typical two shoulders at 1150 and 1490 cm- 1 attributed to NCD formation. Electrochemical response by cyclic voltammetry measurements confirmed a wide potential window for such electrodes in addition to its exceptional reversibility response. © 2010 Elsevier B.V. All rights reserved.

Rocha R.M.d.,Comando Geral de Tecnologia Aeroespacial | Moura E.A.B.,Brazilian Nuclear Energy Research Institute (IPEN) | Bressiani J.C.,Brazilian Nuclear Energy Research Institute (IPEN) | Bressiani A.H.A.,Brazilian Nuclear Energy Research Institute (IPEN)
Radiation Physics and Chemistry | Year: 2010

Methylsilicone resin as a polymer precursor for a SiOC ceramic material was cured and foamed by electron beam (EB) irradiation in air prior to the pyrolysis under an inert atmosphere. Methylsilicone foams were obtained without additional foaming agent when exposed to accelerated electrons with radiation doses up to 9 MGy and dose rate of 2.8 kGy/s. During irradiation the polymer was melted and simultaneously gaseous products were formed by the methyl group oxidation and by the poly-condensation crosslinking reactions. The formed gases could not escape from the molten polymer and began to aggregate into bubbles. The effect of the radiation dose on the polymer foam molecular structure, the gel fraction and the ceramic yield was analyzed. The results indicate that the maximum amount of crosslinking in methylsilicone, when EB radiation is used, occurred between 1.0 and 2.0 MGy radiation dose. Methylsilicone foams were pyrolysed in N2 atmosphere at temperatures of 1200 and 1500 °C, resulting in amorphous SiOC and partially crystalline ceramic foams, respectively. A porosity of ~84% was achieved in the pyrolyzed foams, with cell size ranging from 30 to 300 μm and density of about 0.31 g cm-3. © 2009 Elsevier Ltd. All rights reserved.

Braga N.A.,National Institute for Space Research | Cairo C.A.A.,Comando Geral de Tecnologia Aeroespacial | Baldan M.R.,National Institute for Space Research | Trava-Airoldi V.J.,National Institute for Space Research | Ferreira N.G.,National Institute for Space Research
Diamond and Related Materials | Year: 2011

Diamond films grown on three-dimensional (3D) porous titanium substrate were obtained by hot filament chemical vapor deposition (HFCVD) technique. The growth parameters strongly influenced the film properties during this complex film formation process. The pressure inside the reactor as well as the methane concentration showed their influence on the film morphology, quality, and growth rate. The substrates were totally covered by a diamond coating including deeper planes leading to a 3D porous diamond/Ti composite material formation. The sp 2/sp 3 ratio as "purity index" (PI) and the "growth tendency index" (GTI), evaluated from Raman and X-ray spectra respectively, were obtained for these composite materials as a function of their growth parameters. © 2010 Elsevier B.V. All rights reserved.

Luz S.M.,Comando Geral de Tecnologia Aeroespacial | Minari G.M.,University of Taubaté | dos Santos I.C.,University of Taubaté
Journal of Aerospace Technology and Management | Year: 2010

This paper presents a comparison of the relevant characteristics of São Paulo State's Vale do Paraíba automotive and aerospace clusters observed and analyzes the technological and productive chains strengthening. In order to accomplish it, the adopted methodological procedures are of qualitative nature, by means of documentary research. The results pointed out that the government established, in the mid-1945, the currently named Departamento de Ciência e Tecnologia Aeroespacial (DCTA), as a research and development (R&D) center and, by 1979, Embraer, a state-owned aeronautical construction industry. It was also sought to generate conditions so that domestic companies could emerge around and replace the dependency on aerospace systems and subsystems international suppliers by developing indigenous technological capacities. The automotive cluster under study started in the São Paulo State's Vale do Paraíba (PPV) by means of the regionalization of multinational automotive construction firms migrated from ABC Paulista region looking for physical space for their growth, also relying on tax benefits. The survey results indicate that, in spite of fundamental differences with regard to their productive chains strenghtening processes, they showed similar adverse results.

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