Engenharia Mecânica

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Programa de Pós-Graduação em Engenharia Mecânica

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Agora exibindo 1 - 20 de 301

Formulação do método dos elementos de contorno com dupla reciprocidade usando elementos de ordem superior aplicada a problemas de campo escalar generalizado
(Universidade Federal do Espírito Santo, 1999-03-12) Bulcão, André; Loeffler Neto, Carlos Friedrich; Oliveira, Paulo César
The formulation and application of the Boundary Element Method to problems embodied by the so called Scalar Field Theory are presented. In the formulation, it is used the Dual Reciprocity Technique to treat domain integrals for which traditional procedures can not transform the integral equation into an algebraic equation linear system, only involving variables along the boundary. The Scalar Field Theory is widely applied to several Engineering areas, such as: Thermosciences, Fluid mechanics, Solid Mechanics, Electromagnetism, Corrosion, among others. In the presented applications, the problems are physically interpreted mainly though Heat Transfer and Solid Mechanics. Besides, several analysis of problems ruled by Laplaceís, Poissonís and Diffusion Equations are presented. Basically, aiming to estimate the Boundary Element Method performance, certain parameters - which influence its results, such as the refinement level used in the discretizations - are varied and different boundary element types are considered. For such, the obtained numerical solutions are compared with the analytical ones, or even with those originated by the application of other numerical methods. In some cases, it is drawn a parallel between the performance of the Boundary Element method with the Finite Element Method, or either with the Finite Volume Method.
Influência do cobre na ductilidade a quente dos aços
(Universidade Federal do Espírito Santo, 2001-02-16) Pauli, Evandro Armini de; Cominelli, Oswaldo Guilherme; Macedo, Marcelo Camargo Severo de; Alé, Ricardo Miranda; Furtado, Henrique
The influence of different additions of Cu and cooling rate on the hot ductility of steels have been examined, in the temperature range 750 a 950°C, at low strain rate of 2x10-3 s -1 . The effect of increasing Cu level has been found negligible to samples tested at high cooling rate. Samples tested to low cooling rate were more sensible to the Cu level variation, those having high Cu showing impairment in the hot ductility. Cu rich phases have been found in all testing conditions apart from a single one of low Cu and fast cooling rate where no Cu rich phases have been found. Those Cu rich phases apparently have little or no effect on the hot ductility of steels investigated.
Análise dos estágios iniciais da corrosão de aço-carbono e aço patinável expostos em ambiente marinho-industrial e rural
(Universidade Federal do Espírito Santo, 2002-09-02) Oliveira, Luciano Sacramento de; Queiroz, Rogério Silveira de; Macêdo, Marcelo Camargo Severo de; Larica, Carlos; Bastos, Ivan Napoleão
ASTM A36 and ASTM A242 steel samples were exposed for 4 months in marineindustrial and rural sites. The meteorological conditions and the SO2, SO4 -2, Cl- and TSP concentrations were evaluated during all the research period. The corrosion products were characterized by x-ray difractometry and Mössbauer spectroscopy. The samples exposed in rural environment showed g-FeOOH and g-Fe2O3, while samples exposed in marine-industrial environment showed a-FeOOH and g-FeOOH. Corrosion rates and thickness losses were determined through mass loss essay. ASTM A36 mass loss was larger than ASTM A242 mass loss. Simple linear regressions were performed for mass loss in function of time and multiple linear regressions were performed in order to produce equations for corrosion rates in function of environmental parameters for ASTM A36 and ASTM A242 steels. It was verified that Cl- and SO4 -2 ions were the more influent factors in corrosion of samples exposed in marine- industrial environment. There must be a competitive adsortion process between Cl- and SO4 -2 ions for marineindustrial environment. For samples exposed in rural environment, it was verified that pollutants probably don t influence linearly their corrosion rates. Therefore, meteorological factors as humidity must be more important to corrosion of steel exposed in this environment.
Um novo perfil interpolante aplicado ao método de volumes finitos em situações une e bidimensionais
(Universidade Federal do Espírito Santo, 2002-12-17) Santório, Carlos Alexandre; Oliveira, Paulo César; Loeffler Neto, Carlos Friedrich; Mansur, Webe
In this report, a new scheme of discretization for the method of finite bulks, called FLEX which was proposed for a simulation of problems ruled by differential equations as type of elliptic and hyperbolic. Its performance was appraised through tests from the literature of numeric methods and through tests developed for all the report. The new scheme showed features of convergence and compatible and comparable stabilities to the traditional schemes of Central Difference, Power Law and Flux-Spline . Its accuracy appeared to depend on the type de physical problem. Physical problems ruled by differential partial elliptic equations implied convectiondiffusion which owns a distribution of the variable flux like one purpose by the FLEX scheme which showed a solution with the level of the error minor, in comparison with the remaining schemes. In the traditional problems case of this class, where there isn t the presence with this specific featuring the results proved to be intermediaries. To hyperbolic problems even with a poor discretization within limits of finite difference to the transient term the new scheme appeared interesting features for a simulation of this kind of phenomena in the same sense to non-refined mails to converge to the solution of reference in the rate greater than the others two schemes which were mentioned here and used in the comparison.
Estudo de corrosão em tubulações de Gás de Coqueria
(Universidade Federal do Espírito Santo, 2004-12-17) Vieira, Wander Pacheco; Macêdo, Marcelo Camargo Severo de; Scandian, Chérlio; Miranda, Luiz Roberto Martins de
Within an integrated steelworks process, several types of gases are produced. From an energy volume standpoint, the most important among them are those resulting from the production of coke and hot metal, namely, Coke Oven Gas (COG) and Blast Furnace Gas (BFG), respectively. If they are not properly treated, these gases may display intense corrosive features due to the presence of humidity and corrosive agents. As a result, the steel piping used for carrying these gases can fail because of clogging and perforation, as it happens in the case of COG. As part of an experiment, six test specimens were immersed in a condensate for up to six months. They were made of ASTM 283-C steel and were inside sealing pots within the COG piping. The corrosion rate and the loss of thickness were determined by bulk loss chemical tests. The characterization of the corrosion product’s composition was undertaken through tests such as X-ray diffractometry, infrared spectrophotometry, fluorescence spectrometry, Mössbauer spectroscopy as well as optical and scanning electronic microscopy.
Análise da dinâmica acoplada de uma máquina elétrica rotativa e sua estrutura de suporte
(Universidade Federal do Espírito Santo, 2004-12-22) Rocha Junior, Edmilson Bermudes; Mattos, Márcio Coelho de; Simonetti, Domingos Sávio Lyrio; Balthazar, José Manoel
It’s performed in this work the dynamics of the analyzes of a system made of a directcurrent electrical unbalanced engine, supported by an elastic structure. This kind ofsystem is seen as an non-ideal system, that is, an interaction between the engineand the electrical system. The importance of the study of problems involving thedocking of dynamics of various systems has increased through the constructivecharacteristics of the machines and its structures. It is believed that the constructivemachines tend to be more flexible and may work in higher rotations as well. Then,some phenomena that were not noticed in other generation machines can beobserved now and the use of a more complete models are necessary to explain it.On the operational side a bigger demand of the control system is made even morenecessary. The set of equations that lead the system studied in this work engine-structure is composed by the mechanical equations resulted from the Lagrangeequations and the ones from the Kirchhoff law tension. Moreover, the Runge-Kuttafivth order is used , with a variable pitch aiming at the simulation system. Finally, theanalyzes of the electrical motor arousal independence and series performance isrealized, taking into account the influence of the structure over the rotation.
Análise dinâmica de problemas escalares não-homogêneos através do método dos elementos de contorno
(Universidade Federal do Espírito Santo, 2006-03-30) Santolin, Wagner Dalvi; Markcilei Lima, Dan; Loeffler Neto, Carlos Friedrich; Mansur, Webe João; Barra, Luiz Paulo da Silva
One of the biggest limitations of the Boundary Element Method (BEM) consists in modeling non-homogeneous problems. To minimize the onerous task to make models using the subregions technique, the Quasi-Dual Reciprocity formulation was adapted to simulate these cases. Such formulation is able to deal with heterogeneities by a special way ceding to lead the integral formulation of the mathematical model and its consequent discretization exclusively in terms of boundary values, without necessity of sub-regions. One of the most promising applications of the non-homogeneous models in the present time is the seismic analysis for prospection of oil. In these cases if it also makes necessary to represent the wave propagation phenomena, cases these, very cumbersome and complex. It is very common the numerical simulation of dynamic problems implies in badly accuracy to represent high vibration modes. This fact can distort the numerical reply sufficiently and the use of an incremental time step scheme with fictitious damping is usually requested, to avoid the tax of waste of the numerical response. Thus, this work has the objective to analyze the performance of the formularization cited in non-homogeneous problems, in which admits dynamic processes. While the Quasi-Dual formulation is used to model the material properties, the traditional Dual Reciprocity technique also is here employed, with the purpose of modeling the dynamic action.
Desenvolvimento de metodologia de levantamento de características de conjugado de motores elétricos sem retirada de operação
(Universidade Federal do Espírito Santo, 2006-05-22) Muniz, Pablo Rodrigues; Sousa, Gilberto Costa Drumond; Dynnikov, Vladimir Ivanovitch; Cunha, Fransérgio Leite da; Fardin, Jussara Farias
As an alternative to the procedures used in the industry and described in technical standards, available oscillografic recorder is proposed to be used, with relative high sampling rate, to record electrical voltage and current of a motor, with posterior calculations and estimates of power supplied form the motor to the load, obtaining methodology of survey of torque characteristics of electric motors without withdrawal of the machine from the operational plant, without the needing for laboratories and workshops. As a result, good precision methodology is achieved, of low cost, not destructive, that does not interfere in the production obtained by the motor and it is fitter for industries that do not have available the motor technical documentation, or that need to validate the available documentation.
Análise comparativa de aços ARBL usados na fabricação de tubos flexíveis para produção de petróleo no mar, em formações com baixo teor de H2S : um estudo de FPH utilizando solução de tiossulfato de sódio
(Universidade Federal do Espírito Santo, 2006-06-02) Girelli, Rosental Alves; Scandian, Cherlio; Macêdo, Marcelo Camargo Severo de; 1º membro da banca
This document is an experimental study of the Stress Corrosion Cracking (SCC) and Hydrogen Embrittlement (HE) behavior of a Brazilian high-strength low-alloy steel, in media with low content of H2S. It is intended to begin a qualification process of the material, which is already used in flexible pipes for petroleum production operations at the sea in situations where there is no H2S presence, to also act in cases where low concentration of this gas exists. A heat treatment is proposed for the resistance improvement of the material in these environments. The base for experimental results comparison was another material, a French one, which is already qualified and used in flexible pipes for sour oil (with H2S) production. Hence, three materials were tested: the original Brazilian one, without heat treatment (it is used in flexible pipes, in situations without H2S), the same material with the heat treatment suggested for the property improvement and possible use in low H2S environments and the French one (qualified material used in flexible pipes for oil production operations, in situations where the presence of H2S is a reality). The SCC Slow Strain Rate and Constant Strain techniques were used as the experimental tests and the media was an aqueous solution of NaCl with micro addictions of sodium thiosulfate (Na2S2O3), indicated to simulate corrosive environments with low concentration of H2S. Damage parameters (energy), embrittlement measurements, tensile properties and also fracture features of the specimens were evaluated at the comparative analysis of the materials.
Tensores fundamentais da formulação dos problemas elásticos axissimétricos pelo método dos elementos de contorno
(Universidade Federal do Espírito Santo, 2006-06-29) Stikan, Rafael Pacheco; Loeffler Neto, Carlos Friedrich; Menandro, Fernando César Mera; Schneider, Edgar
This work presents the Boundary Element formulation to axysimmetric elastic problems. The Kelvin solution, which uses a unitary concentrated load in an infinite elastic domain to generate the fundamental solution, is taken into account. Initially, the three-dimensional problem expressed in cartesian coordinates is transformed to cylindrical ones. In a second step the mathematical expressions are integrated in the “ ” variable, changing into a two-dimensional model. In this mathematical strategy occur elliptic integrals and their derivatives, which are manipulated to achieve the fundamental stresses. Cumbersome singular integrals would need to be solved using traditional collocation of source points on the boundary. Here the positions of source points are external to physical domain, avoiding singularities.
Estratégias para melhoria da completidade da sequência de funções de interpolação empregadas na formulação quase-dual do método dos elementos de contorno
(Universidade Federal do Espírito Santo, 2006-06-30) Jardim, Allan Costa; Loeffler Neto, Carlos Friedrich; Mansur, Webe João; Silva, Joccitiel Dias da
The Quase-Dual formulation is a new technique to allow the applications of Boundary Element approach to solve efficiently mathematical models associated to physical problemas in wich it is difficult to obtains the inverse integral form. The advective-diffusive problemas and non-homogeneous problems are some of the important problems in this last class. The current model uses a set of auxiliary independent functions and has difficulties to simulate two dimensional problems with constant fluxes. The reason of this defficient behavior is probably due to absence of completeness. The present text presents a strategy to try to eliminate this problem, based on the introduction of new terms in the set of auxiliary functions. The aim is to improve completeness condition. As a result of proposed procedures, reciprocal matrices are generated at the final discreized equation system, in a similar way to Dual Reciprocity technique. Examples of constant fluxes are simulated with the new procedures and their results are discussed and analysed with details.
Estudo da resistência ao desgaste abrasivo de ferros fundidos brancos alto cromo e molibdênio
(Universidade Federal do Espírito Santo, 2006-07-07) Regattieri, Cíntia Nunes Braga; Mello, José Daniel Biasoli de; Scandian, Cherlio; Costa, Henara Lillian; Macêdo, Marcelo Camargo Severo de
The performance of high chromium white cast iron (HCWCI) reggarding abrasive wear is a function of both the materials microstructure and properties and the tribosystem parameters. Thus, this work intends to evaluate the effects of chemical composition and tribological conditions on the wear resistance of HCWCI with different molybdenum contents (0, 3, 6 and 9 wt%). Twenty different alloys were estudied with a fixed Cr/C ratio of 10. The chromium contents were 16, 20 and 24 wt% for the hypoeutectic, 28 wt% for the eutectic and 32 wt% for the hypereutectic alloys. The abrasive wear resistance were evaluated by pin-on-disk (two-body configuration) and three-body abrasive wear tests. For the two-body configuration, the alloys with ferritic and perlitic matrix showed the highest wear rates. The wear rates of Mo free alloys tested with a in three-body configuration test increased with the chromium content. For the compositions with Mo alloying, the behavior abrasive was almost the same, except for the hypereutectic alloys with higher wear rates. The micro mechanisms involved were analyzed. For the two body tests (pin-on-disc), the worn samples surfaces showed micro cutting as prevailing micro mechanism. Differences between the alloys were detected by differences in both the intensity and depth of grooves and the inter groove region morphology. Multiple ductile indentations covered almost the totality of the worn surfaces in the threebody tests, except for the hypereutectic alloys (6 and 9 % Mo), which presented a brittle micromechanism detected by detachment and cracking of carbides.
Desenvolvimento de medidor de vazão de gás por ultra-som: modelagem, protótipo e testes
(Universidade Federal do Espírito Santo, 2006-12-14) Ramos, Rodrigo; Mattos, Márcio Coelho de; Loureiro, Bruno Venturini; Donatelli, João Luiz Marcon; Trevisan, Osvair Vidal; Silva Filho, Jose Alberto Pinheiro da
The use of transit time ultrasonic flow measurement technique has increased very quickly in the last years, so that it is urgently necessary to develop Brazilian technology in this instrumentation field. This work presents the development of a transit time flow meter prototype, called MEVUS, devoted to measurement of gas flows. It presents the mathematical modeling of the governing physical process of the interaction between the ultrasonic wave and the flow that one wants to measure, which is supposed completely developed in a circular pipe. It also presents a systematization of the uncertainty analysis related to the measurement process. The process of conception, analysis and design of the prototype is equally described, so that the reader can easily understand the problems found during the development, highlighting the proposed solutions and the feedback of the creation process of MEVUS Medidor de Vazão por Ultra-Som (Ultrasonic Flowmeter). Performance tests were conducted in the Flow Machines Laboratory of the Mechanical Engineering Department UFES. They are clearly described. The conclusions are presented, as well as the suggestions for future works
Análise dinâmica com recuperação de tensões para materiais com gradação funcional: simulação numérica e validação experimental
(Universidade Federal do Espírito Santo, 2007-10-18) Fraga Filho, Carlos Alberto Dutra; Romero, Rivânia Hermógenes Paulino de; Menandro, Fernando César Meira; Sisquini, Geraldo Rossoni; Nunes, Luiz Carlos da Silva
The objective of this work was to design and the manufacture samples of materials withbehaviors, under mechanical loads, similar to functionally graded materials (with continuousvariation of the structural properties); to perform dynamic mechanical experiments, with theproduced samples; and to obtain results of simulation for dynamic loads, in order to validatea numerical model proposed by researchers of this university for the characterization of thefunctionally graded materials.The study it was divided in the following phases: confection of the specimens, adoptionof the composed beam model for the produced specimens, preparation and realization ofdynamic mechanical experiments, obtention of analytical results for the vibration problem,definition of the numerical model applied to the problem and numerical simulation ofmechanical loads.The experimental, analytical and numerical results show similar behavior for all testedspecimens. The natural vibration frequency, despite the method of obtention (experimentalmeasurement, analytical development, numerical simulation), difers at most by 15,4313%.The proposed numerical technique is found, thus, to be adequate to the modeling of layeredmaterials
Estudo da corrosão de aços-carbono e patinável durante 39 meses de exposição em ambiente marinho-industrial
(Universidade Federal do Espírito Santo, 2007-12-15) Leite, Leandro Alberto Silva; Queiroz, Rogério Silveira de; Macêdo, Marcelo Camargo Severo de; Bozzi, Antônio César
Following the results presented by OLIVEIRA (2002), in which the corrosive process analysis was carried out after 4 months exposition, the corrosion pattern for longer periods of exposition under similar geo-environmental conditions is investigated by this present work. ASTM A36 and ASTM A242 steel samples were exposed during 39 months in two industrial marine sites located in the southern shore of Espírito Santo State. Meteorological conditions were monitored and SO2 concentration was tested during the exposition period. Mössbauer s spectroscopy was used to characterize the corrosion outcomes. The samples from both sites presented similar composition, with emphasis to α-FeOOH. Smaller fractions of γ- FeOOH, Fe3O4, γ-Fe2O3 and α-Fe2O3 were also observed, being the latter originated from the particulates precipitated from the surrounding environment. Corrosion rates and thickness losses were determined through mass loss essays. The ASTM A36 steel sample showed steeper curves as function of time and always superior to those found for the weathering steel in both sites, especially for the area with higher SO2 concentration. ASTM A242 steel presented specific results for each site. In the less aggressive site, it showed a more stable corrosion process with good formation of protective rust layer and mass loss of around 2% in mass, whilst at the other site it presented similar pattern as the ASTM A36 steel, although less intense. Finally it was determined the industrial applicability of the ASTM A242 steel at regions with lower concentration of sulfates
Análise experimental dos processos de transferência de calor aplicados à concentração solar
(Universidade Federal do Espírito Santo, 2008-07-28) Anjos, Vitor Luiz Rigoti dos; Ramos, Rogério; Donatelli, João Luiz Marcon; Pimentel, Luiz Cláudio Gomes
Having in mind the necessity to pump heavy crude oil from notoriously sunny regions of Brazil (northern Brazil regions general speaking or northern Espirito Santo state specifically), the utilization of solar radiation appears as an alternative thermal source to heat on-shore pipelines and storage tanks. The present work exhibits the basic steps to project, design, construction and test of a parabolic solar concentrator prototype, as well as shows experimental results gotten from the activities developed by the whole project and points out some possibilities to enhance the system for future operations. Here, the main objective is to increase heat transfer to a tube installed on parabolic focus (absorber tube). Using distinct configurations for the absorbers tubes, the work fluid is heated and analysis are prosecuted over collected data aiming to reach the main goal, which is to study the pressure drop reduction by viscosity decreasing of heavy oils flow using solar energy collected by a parabolic concentrator.
Microabrasão de compósitos de matriz metálica a base de tungstênio empregados em coroas de perfuração utilizadas em sondagem mineral
(Universidade Federal do Espírito Santo, 2008-08-09) Lozzer, André Menegaz; Mello, José Daniel Biasoli de; Scandian, Cherlio; Macêdo, Marcelo Camargo Severo de; Souza, Roberto Martins de
It is important in rock core drilling for the diamond bit crown to be meticulously worn such that the cut is performed on the lithology. The objective of this work is to evaluate wear on composite matrix alloys used in perforation drill bits, produced from a tungsten powder skeleton held by an infiltrating metal alloy. Wear is evaluated through free ball micro-abrasion testing (Calowear), using abrasive slurry of Fe2O3, SiC, and SiO2. This work presents the relation between material hardness, tungsten mean size and composition of the metal powder, besides confronting acting micromechanisms in order to construct a specific wear map. Were also performed Vickers hardness, laser interferometry, and scanning electronic microscopic analysis of the wear mechanisms. It was found that composites hardness is not a determinant factor for wear resistance, as well as became evident the systemic character of the wear processes. Were found mechanisms of sliding, multiple indentation, besides the simultaneous, though dissociate, occurrence of both.
Influência do tipo de abrasivo de jateamento no desempenho de esquemas de pintura sobre aço carbono
(Universidade Federal do Espírito Santo, 2008-08-22) Caser, Giovani do Carmo; Macêdo, Marcelo Camargo Severo de; Lima Neto, Pedro de; Scandian, Cherlio
The object of this study is to analyze the use of steel converter slag, a steel plant byproduct, as an abrasive for blasting and its influence in paint systems performance. Steel coupons were blasted with such abrasive particles and coated with epoxy and alkyd products. For comparison, other samples were blasted using copper slag, a well-known abrasive used by the industry. Besides the abrasive particles own characteristics like morphology, hardness, specific mass, etc., it was analyzed the abrasive effect on the blasted surfaces like topography, surface chemical composition, general appearance and adherence of coatings. Coated coupons were also exposed to accelerated tests in salt spray cabinet, immersion in distilled water and in cathodic disbondment cell, to understand the surface preparation behaviour with such different abrasives. Converter slag blasted against steel samples were able removing a layer of hard and smooth oxide layer, formed in the plate hot mill (mill scale), creating a topography with surface parameters (Ra, Rz, Rt e Rq), similar to the ones normally obtained by use of others abrasives. Characteristics like particle hardness, specific mass, morphology and grain size distribution certainly influenced the results. Converter slag analyzed showed high contents of soluble ions, mainly calcium, which were transferred to the blasted surfaces. The performance of alkyd and epoxy coatings applied over such substrates and tested for adherence, corrosion and blistering formation in salt spray and immersion in distilled water, was clearly inferior to the ones blasted with black copper slag. This trend was not seen in the epoxy coated samples, which showed similar performance between abrasives, indicating a real possibility for use with such coatings.
Estudo dos efeitos do tratamento de mercerização nas propriedades mecânicas das fibras de sisal
(Universidade Federal do Espírito Santo, 2008-08-30) Santos, Eduardo Felix Cordeiro dos; Scandian, Cherlio; Tavares, Sérgio Souto Maior; Macêdo, Marcelo Camargo Severo de
abstract
Análise estatística de correlações PVT de petróleos
(Universidade Federal do Espírito Santo, 2008-10-08) Gomes, Garben Bravim; Mattos, Márcio Coelho de; Donatelli, João Luiz Marcon; Schiozer, Denis José
A precise estimation of a reservoirbehavioris veryimportant for the correct evaluation of hydrocarbons amount, prediction of the performance, development of production facilities and planning of efficient recuperation methods. But direct evaluation of all petroleum properties is not viableduring operation of an exploratory well bore. This problem is solved by estimating some properties from others whose evaluation in laboratory is easier. Several correlations were proposed and commented in the literature forcorrelating oil formation volume factor, solubility ratio, bubble point pressure, reservoir temperature, oil gravity,gas gravity, and so on. These models have been nominated PVT correlations, although sometimes the include some non PVT properties as oil and gas viscosity. The most famous correlationsis thatproposed by Standing, Glaso and Vazquez-Beggs, which have been modified by other researchers as, for example, De Gheto, Al Marroun and Petrosky. In this work,we present statistical analysis of some correlations (for bubble point pressure estimation) for Standing, Glaso and Vazquez-Beggs correlations. The experimental data are that presented by De Gheto in 1995

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