Resumo em Inglês:
Abstract: A comparison of five different spatial discretization schemes is performed considering a typical high speed flow application. Flowfields are simulated using the 2-D Euler equations, discretized in a cell-centered finite volume procedure on unstructured triangular meshes. The algorithms studied include a central difference-type scheme, and 1st- and 2nd-order van Leer and Liou flux-vector splitting schemes. These methods are implemented in an efficient, edge-based, unstructured grid procedure which allows for adaptive mesh refinement based on flow property gradients. Details of the unstructured grid implementation of the methods are presented together with a discussion of the data structure and of the adaptive refinement strategy. The application of interest is the cold gas flow through a typical hypersonic inlet. Results for different entrance Mach numbers and mesh topologies are discussed in order to assess the comparative performance of the various spatial discretization schemes.Resumo em Inglês:
Abstract: The search for a smokeless propellant has encouraged scientists and engineers to look for a chlorine-free oxidizer as a substitute for AP (ammonium perchlorate). Endeavors seemed to come to an end when ADN (ammonium dinitramide) appeared in the West in the early 1990s. Although some drawbacks soon became apparent by that time, the foremost obstacle for its use in rocket-motors came from the patent originally applied for in the United States in 1990. Furthermore, environmental concerns have also increased during these two decades. Ammonium perchlorate is believed to cause thyroid cancer by contaminating soil and water. In addition, AP produces hydrogen chloride during burning which can cause acid rain and ozone layer depletion. Unlike AP, ADN stands for both smokeless and green propellant. Since then, much progress has been made in its development in synthesis, re-shaping, microencapsulation and solid propellant. The high solubility of ADN in water has also allowed its application as liquid monopropellant. Tests have revealed Isp (specific impulse) superior to that normally observed with hydrazine, one of the most harmful and hazardous liquid propellants. With constraints of use, along with the patent near to expiry, scientists and engineers are rushing to complete developments and patents until then.Resumo em Inglês:
Abstract: In the last twenty years military explosives and energetic materials in general have changed significantly. This has been due to several factors which include new operational requirements such as Insensitive Munitions (IM), but is also due to the availability of new materials and to new assessment and modelling techniques. These permit more effective use of materials and a more detailed understanding of the processes involved in applying the technology. This article will outline some of the effects in addition to taking a glance at what the future might hold.Resumo em Inglês:
Abstract: A new methodology was developed to characterize and to quantify the polymer content in PBX (HMX/Viton) by Fourier Transform Infrared Spectroscopy (FT-IR), using the Termogravimetric analysis (TG) as reference techniques for the quantitative method. The quantification methodology, proposed by us, using the Fourier transform infrared-attenuated total reflectance (FT-IR/ATR) showed excellent results, being faster than the usual methodologies and can eliminate the generation of chemical residues.Resumo em Português:
Resumo: Reações para obtenção de derivados de hidantoína foram conduzidas a partir de aldeídos de cadeia curta e da 5,5-dimetilhidantoína. O acompanhamento das reações foi realizado por espectroscopia na região do infravermelho médio (MIR) por meio da formação de novas bandas características da estrutura do composto desejado. A análise MIR revelou que estas alterações espectrométricas ocorrem somente na reação com o formaldeído, indicando a formação do produto 1,3-bis(hidroximetil)-5,5-dimetilhidantoína, em presença de água. As bandas de absorção que confirmam a reação foram observadas em 3334 cm-1 (υ OH), 1770 e 1710 cm-1 (υ C=O) e em 1056 cm-1 (υ C-O), sendo esta última, atribuída ao grupo contendo hidroxila primária. A reação da 5,5-dimetil hidantoína com acetaldeído e com propanaldeído não ocorreu sob as condições adotadas neste trabalho.Resumo em Inglês:
Abstract: Reactions to obtain hydantoin derivatives were carried out with 5,5-dimethylhydantoin and short-chain aldehydes. Monitoring of the reactions was performed using qualitative mid-infrared spectroscopy (MIR) through the formation of new bands characteristic of the desired product. MIR analysis showed that these spectrometric alterations occur only in the reaction with the formaldehyde, indicating the formation of the desired product, 1,3-bis (hydroxymethyl) 5,5-dimethylhydantoin, in the presence of water. The absorption bands that confirmed the reaction were observed at 3334 cm-1 (υ OH), 1770 and 1710 cm-1 (υ C=O) and 1056 cm-1 (υ C-O), the last of which is assigned to the group containing primary hydroxyl.Resumo em Português:
Resumo: O principal objetivo deste trabalho foi realizar a simulação computacional no software CadWind® de uma bobinagem filamentar para um vaso de pressão aplicado a motor foguete A simulação realizada foi de uma bobinagem helicoidal não-geodésica, variando o ângulo de bobinagem na parte cilíndrica do vaso de pressão, devido às aberturas polares serem diferentes e vaso comprido. Também foram realizadas simulações variando o padrão de bobinagem. Os resultados indicam que um padrão de bobinagem mais elevado proporciona um maior ancoramento e distribuição das fibras nos domos.Resumo em Inglês:
Abstract: The main objective of this work was to accomplish the computational simulation in the software CadWind® of a filament winding for an applied pressure vase to motor rocket. The adopted simulation was of a non-geodesic helical winding, varying the winding angle in the cylindrical part of the pressure vessel, due the polar holes be different and the vessel long. Also simulations were accomplished varying the winding pattern. The results indicate that a more substantial winding pattern provides increased fiber deposition and distribution on the outer region of the domes.Resumo em Inglês:
Abstract: Equatorial scintillation is a phenomenon that occurs daily in the equatorial region after the sunset and affects radio signals that propagate through the ionosphere. Depending on the temporal and spatial situation, equatorial scintillation can represent a problem in the availability and precision of the Global Positioning System (GPS). This work is concerned with evaluating the impact of equatorial scintillation on the performance of GPS receivers. First, the morphology and statistical model of equatorial scintillation is briefly presented. A numerical model that generates synthetic scintillation data to simulate the effects of equatorial scintillation is presented. An overview of the main theoretical principles on GPS receivers is presented. The analytical models that describe the effects of scintillation at receiver level are presented and compared with numerical simulations using a radio software receiver and synthetic data. The results achieved by simulation agreed quite well with those predicted by the analytical models. The only exception is for links with extreme levels of scintillation and when weak signals are received.Resumo em Inglês:
Abstract: This work presents a methodology for determining the reliability of fracture control plans for structures subjected to cyclic loads. It considers the variability of the parameters involved in the problem, such as initial flaw and crack growth curve. The probability of detection (POD) curve of the field non-destructive inspection method and the condition/environment are used as important factors for structural confidence. According to classical damage tolerance analysis (DTA), inspection intervals are based on detectable crack size and crack growth rate. However, all variables have uncertainties, which makes the final result totally stochastic. The material properties, flight loads, engineering tools and even the reliability of inspection methods are subject to uncertainties which can affect significantly the final maintenance schedule. The present methodology incorporates all the uncertainties in a simulation process, such as Monte Carlo, and establishes a relationship between the reliability of the overall maintenance program and the proposed inspection interval, forming a "cascade" chart. Due to the scatter, it also defines the confidence level of the "acceptable" risk. As an example, the damage tolerance analysis (DTA) results are presented for the upper cockpit longeron splice bolt of the BAF upgraded F-5EM. In this case, two possibilities of inspection intervals were found: one that can be characterized as remote risk, with a probability of failure (integrity nonsuccess) of 1 in 10 million, per flight hour; and other as extremely improbable, with a probability of nonsuccess of 1 in 1 billion, per flight hour, according to aviation standards. These two results are compared with the classical military airplane damage tolerance requirements.Resumo em Inglês:
Abstract: Climatological features of convective parameters (K index, IK; 950 hPa K index, IK950; Showalter index, IS; lifted index, ILEV; total totals index, ITT; and convective available potential energy, CAPE) derived from 12 UTC radiosounding data collected at the Alcântara Launch Center (CLA; 2°18'S, 44º22'W) from 1989 to 2008 were computed. The parameters IK, IK950, IS and ITT (ILEV and CAPE) showed a seasonal variation coherent (not coherent) to the annual cycle of precipitation. Interdaily variability was high all year round and was comparable to the monthly average seasonal variation. For IK and IK950, the monthly fraction of days with favorable conditions for precipitation occurrence (FRAC) showed good agreement with the monthly fraction of days with precipitation greater than 0.1 mm (PRP). For ITT and IS, the seasonal variation of FRAC was lower than the seasonal variation of PRP; for ILEV and CAPE, there were marked differences between FRAC and PRP. IK seasonal variation was primarily due to the presence of a deeper (shallower) low-level moist layer in the wet (dry) season. Among the studied convective parameters, the use of IK or IK950 for assessing precipitation occurrence was recommended.Resumo em Inglês:
Abstract: Aramid fiber reinforced polymer composites have been used in a wide variety of applications, such as aerospace, marine, sporting equipment and in the defense sector, due to their outstanding properties at low density. The most widely adopted procedure to investigate the repair of composites has been by repairing damages simulated in composite specimens. This work presents the structural repair influence on tensile and fatigue properties of a typical aramid fiber/epoxy composite used in the aerospace industry. According to this work, the aramid/epoxy composites with and without repair present tensile strength values of 618 and 680MPa, respectively, and tensile modulus of 26.5 and 30.1 GPa, respectively. Therefore, the fatigue results show that in loads higher than 170 MPa, both composites present a low life cycle (lower than 200,000 cycles) and the repaired aramid/epoxy composite presented low fatigue resistance in low and high cycle when compared with non-repaired composite. With these results, it is possible to observe a decrease of the measured mechanical properties of the repaired composites.Resumo em Inglês:
Abstract: This work aims to determine the diffusion coefficient of the plasticizers dibutyl phthalate (DBP), dioctyl phthalate (DOP) and dioctyl azelate (DOZ) on the internal insulating layer of solid rocket motors. These plasticizers are originally present in the layers of rubber, liner and propellant, respectively. This species are not chemically bonded and tend to diffuse from propellant to insulating and vice versa. A computer program based on the mathematical model of Fick's second Law of diffusion was developed to perform the calculus from the concentration data obtained by gas chromatographic (GC) analyses. The samples were prepared with two different adhesive liners; one conventional (LHNA) and the other with barrier properties (LHNT). A common feature of both liners was that they were synthesized by the reaction of hydroxyl-terminated polybutadiene (HTPB) and diisocyanates. However, a bond promoter was used to increase the crosslink density of the LHNT liner and to improve its performance as barrier against the diffusion. The effects of the diffusion of the plasticizers were also investigated by hardness analyses, which were executed on samples aged at room temperature and at 80ºC. The results showed an increase trend for the samples aged at room temperature and an opposite behavior for the tests carried out at 80ºC.Resumo em Português:
Resumo: O presente trabalho descreve os processos de obtenção de compósitos termoestruturais de carbono reforçado com fibras de carbono. O processamento desses materiais tem início pela definição de uma arquitetura do reforço de fibras de carbono, seja na forma de empilhamento simples do reforço, de tecidos ou na forma de reforço multidirecional. A incorporação de matriz carbonosa no reforço de fibras, pelo preenchimento de vazios e interstícios, promove a densificação do material, e o incremento de massa específica. Duas rotas de processamento são predominantes na obtenção desses materiais, o processo via impregnação líquida e o processo via impregnação em fase gasosa. Em ambos os casos, processos térmicos levam à formação de matriz de carbono com propriedades específicas, que derivam de seus materiais precursores. Os processos diferem entre si, também, pelo rendimento, enquanto os processos executados por impregnação líquida apresentam rendimento de, aproximadamente, 45%, os processos por impregnação em fase gasosa apresentam rendimento em torno 15%.Resumo em Inglês:
Abstract: The present work describes the processes used to obtain thermostructural Carbon/Carbon composites. The processing of these materials begins with the definition of the architecture of the carbon fiber reinforcement, in the form of stacked plies or in the form of fabrics or multidirectional reinforcement. Incorporating fiber reinforcement into the carbon matrix, by filling the voids and interstices, leads to the densification of the material and a continuous increase in density. There are two principal processing routes for obtaining these materials: liquid phase processing and gas phase processing. In both cases, thermal processes lead to the formation of a carbon matrix with specific properties related to their precursor. These processes also differ in terms of yield. With liquid phase impregnation the yield is around 45 per cent, while gas phase processing yields around 15 per cent.Resumo em Português:
Resumo: Um detector de nêutrons do tipo "Long-Counter" está sendo utilizado dentro do contexto do projeto DREAB (Dosimetria da Radiação no Espaço Aéreo Brasileiro) para monitorar o fluxo integral de nêutrons oriundos de interação atmosférica da radiação cósmica, o qual tem importância na dose de radiação recebida por seres humanos ao nível do solo e é o principal responsável pela dose recebida por tripulações e instrumentação sensível de aeronaves. Neste trabalho são apresentados os testes preliminares efetuados com o detector de nêutrons do tipo "Long-Counter", utilizando uma fonte de nêutrons de 241Am/Be onde foi avaliada a dependência direcional da resposta do equipamento nos sentidos radial e transversal e também foi verificada a resposta após um acréscimo de retro-blindagem no equipamento, de forma a minimizar o nódulo traseiro de resposta em relação ao nódulo frontal, condição esta de interesse para o trabalho em andamento.Resumo em Inglês:
Abstract: A "Long-Counter" neutron detector is being used in the context of the DREAB (Dosimetry of the Radiation in the Brazilian Airspace) project to monitor the integral flow of neutrons deriving from the interaction of cosmic radiation with the atmosphere, which is important for measuring radiation doses received by humans at ground level and is mainly responsible for doses received by aircraft crews and sensitive instrumentation. In this work the preliminary tests performed with the Long-Counter neutron detector are presented using a 241Am/Be neutron source where the radial and transversal directional dependence of the equipment was evaluated and also an additional backward-shield in the equipment was verified, as a way of minimizing the back nodule response in relation to the frontal nodule, which is a condition of interest for the current work in progress.Resumo em Inglês:
Abstract: The Satellite Launch Vehicle developed in Brazil employs a specialized unit at the launch center known as the Movable Integration Tower. On that tower, fixed and movable work floors are installed for use by specialists, at predefined periods of time, to carry out tests mainly related to the pre-launch phase of that vehicle. Outside of those periods it is necessary to detect unexpected movements of platforms and unauthorized people on the site. Within that context, this work presents an evaluation of different resolutions of convolution mask and tolerances in the efficiency of a proposed algorithm to supervise scenery changes on these work floors. The results obtained from this evaluation are satisfactory and show that the proposed algorithm is suitable for the purpose for which it is intended.Resumo em Português:
Resumo: Materiais Absorvedores de Radiação Eletromagnética (MARE) são compostos que absorvem a radiação eletromagnética incidente em determinadas faixas de frequências e a dissipam sob a forma de calor. Esses materiais são obtidos a partir do processamento adequado de matrizes poliméricas incorporadas com compostos que atuam como centros absorvedores da radiação incidente, na faixa de micro-ondas. Este trabalho mostra a avaliação eletromagnética de MARE processados pelo uso de uma hexaferrita de cálcio modificada pela incorporação dos íons CoTi e La. A substituição realizada pelos íons mencionados mostra, via análises de MAV, que a ferrita apresenta baixos valores de magnetização de saturação (123,65 Am2/kg) e de campo coercitivo (0,07 T), indicando o seu amolecimento. Amostras de MARE preparadas com diferentes concentrações desta hexaferrita (40 - 80% em massa) apresentam mudanças nos parâmetros complexos de permeabilidade e permissividade e no desempenho da atenuação da radiação incidente. Valores de atenuação da radiação incidente entre 40 e 98% são obtidos.Resumo em Inglês:
Abstract: Radar Absorbing Materials (RAM) are compounds that absorb incidental electromagnetic radiation in tuned frequencies and dissipate it as heat. Its preparation involves the adequate processing of polymeric matrices filled with compounds that act as radar absorbing centers in the microwave range. This work shows the electromagnetic evaluation of RAM based on CoTi and La doped Ca hexaferrite. Vibrating Sample Magnetization analyses show that ion substitution promoted low values for the parameters of saturation magnetization (123.65 Am2/kg) and coercive field (0.07 T) indicating ferrite softening. RAM samples obtained using different hexaferrite concentrations (40-80 per cent, w/w) show variations in complex permeability and permittivity parameters and also in the performance of incidental radiation attenuation. Microwave attenuation values between 40 and 98 per cent were obtained.Resumo em Inglês:
Abstract: This paper presents an ongoing work at the Institute of Aeronautics and Space (IAE) to provide a process and a system to support the management of knowledge and new technologies applied to the conception and development of the Brazilian Satellite Launcher Program. This management is not only necessary to organize the actual research efforts but also to identify communalities and necessities for the strategic planning of future research projects and development activities. The results of the research projects are usually new technologies that ought to be employed in the development of the Launcher Program. The proposed knowledge management system will not only enable assessing these new technologies but also help in defining and planning the research topics in each important area of this multidisciplinary program, according to the Institute's strategic goals and space mission.