Programa de Pós-Graduação em Engenharia Mecânica - PPGEM /ITEC

URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/2341

O Programa de Pós-Graduação em Engenharia Mecânica (PPGEM) do Instituto de Tecnologia (ITEC) da Universidade Federal do Pará(UFPA). Tem por objetivo formar recursos humanos qualificados, e incentivar a pesquisa e o aprofundamento dos estudos técnicos e científicos relacionados ao campo de atuação da Engenharia Mecânica com aplicação na realidade e necessidades da região amazônica.

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Agora exibindo 1 - 9 de 9

Acesso aberto (Open Access)
Análise de sistemas de controle de vibração em máquinas rotativas utilizando atuadores formados por ligas com memória de forma
(Universidade Federal do Pará, 2009-12-04) SILVA, José Adriano Brito da; MESQUITA, Alexandre Luiz Amarante; http://lattes.cnpq.br/3605920981600245
The application of shape memory alloys (SMA) has been showed as a promising alternative in the vibration control area mainly due to the shape memory and pseudoelastic phenomena which this alloys present. In addition, they show large recovery forces and damping capacity when compared to traditional materials. Despite a great number of papers dealing with SMA abilities applied to vibration control in structures, there are only a few reports about applications of SMA in rotordynamics. Hence, this work focuses basic aspects in the numerical application of SMA actuators for vibration control in rotating machines. In the first analysis of this work it is used a Jeffcott rotor with SMA sleeves placed into one of the bearings. It has been employed different sleeve thickness in the martensite and austenite states and the changes in terms of amplitude and frequency are compared. Furthermore, in the second analysis, two different rotating systems with two discs and SMA springs applied at one and both bearings are analyzed under different set-ups. The springs have been placed externally to bearings and the work temperature is set according to the requirement of vibration control. Moreover, it was used a computational code to represent the thermomechanical behavior of SMA springs as well as a numerical code based on Finite Element Method (FEM) to simulate the dynamic behavior of rotors. The results of the numerical analyses demonstrated the SMA are efficient in the vibration control of rotating systems due to accomplish great reductions in the displacement amplitudes, changes in the critical speeds, suppression of unwanted movements and control of precession orbit shape.
Acesso aberto (Open Access)
Controle de vibração em reatores elétricos através de absorvedores dinâmicos viscoelásticos
(Universidade Federal do Pará, 2006-04-18) VALE, Alan Rafael Menezes do; SOEIRO, Newton Sure; http://lattes.cnpq.br/7303174583088137
Equipments used in electric substations have specific functions in the functioning and maintenance of the functionality of such installations, being equipment applied to control reactive currents, short circuit currents and maneuver poles in transmission systems of electric energy. It was detected that some reactors in functioning had presented high levels of structural vibration. Two of these reactors operate in the substation of Rurópolis city, situated the west of Pará state. Another decurrent problem of the raised level of vibration of these structures is the generation of hot spots in the electromagnetic nucleus of the reactor, being able to generate bubbles of highly inflammable gases. The existence of these operational problems can cause to the North of Brazil Transmission System functional interruptions in the transmission of electric energy. That would cause in the North region and other linked ones (Northeast, Southeastern and Center-West) raised social and financial damages. The application of tools for reducing the vibrate-acoustic trouble (reduction of the levels vibration and, therefore, noise) can prevent structural and operational damages that result in its operative non-availability reducing, consequently, losses and the necessity of the development of equipment of cost raised with low indices of vibration. In the intention of if reducing such levels, it is considered the application of dynamic absorbers in the external structure of the reactors. With the calculated absorbers in amount, position and parameters (mass, stiffness and damping) expects to create a system syntonized with the frequency of the excitement of electromagnetic nature, that will absorb part of the vibratory energy of the reactor, having minimized raised detected levels and, therefore, all the subsequent problems. Viscoelastic materials will be used in the dynamic absorbers (with temperature and frequency dependent dynamic properties), because these materials to increase the field of activity of the dynamic absorbers, adjusting themselves it the raised verified modal density in the metallic shells of the reactor.
Acesso aberto (Open Access)
Desenvolvimento de painéis confeccionados a partir de fibras de coco para controle acústico de recintos
(Universidade Federal do Pará, 2008-10-31) VIEIRA, Rodrigo José de Andrade; SOEIRO, Newton Sure; http://lattes.cnpq.br/7303174583088137
A reasonable alternative for noise control in enclosures is based on the use of sound absorption materials (porous and fibrous), which convert acoustic energy into heat, due to air viscosity. The material acoustic absorption characteristic is determined by its sound absorption coefficient, which depends mainly on frequency, sound incidence angle, density, thickness and internal structure of the material. From the Amazon, due to its enormous biodiversity, thousands of natural products and sub products are retrieved, some of which are not completely used. Thus, many residues reach other industrial sectors, such is the case of the coconut fiber, which can be used in many ways. Therefore, the present work defines and describes an acoustic panel manufacturing process, based on coconut fiber, including the experimental determination of important parameters for noise control in enclosures. Also, a numerical model is implemented to investigate cost and quality control parameters, in order to assist the development and manufacturing of new panels. First, the necessary information is collected to start the development process of coconut fiber panels, following an “informational project” methodology. Next, all the steps related to the panel manufacturing process are described, looking forward to obtaining its acoustical, mechanical and physical-chemical main properties. From the numerical simulations, one tries to analyze and predict the coconut fiber panel behavior (apart from a commercially available acoustical panel), and investigate its influence over the acoustical parameters of an auditorium (reverberation time, sound pressure decay, and intelligibility). With the development of the coconut fiber panels, one expects to contribute for the creation of new sectors on the local economy, mainly considering the elevated costs of the actual acoustical panels available in the market. Finally, another outstanding advantage of the coconut fiber panels proposed here is the possibility of its usage in the context of regional architecture, where emphasis is given on local materials.
Acesso aberto (Open Access)
Estudo de técnicas de análise modal operacional em sistemas sujeitos a excitações aleatórias com a presença de componente harmônico
(Universidade Federal do Pará, 2006-02-17) CRUZ, Sérgio Luiz Matos da; MESQUITA, Alexandre Luiz Amarante; http://lattes.cnpq.br/3605920981600245
Traditional modal parameter identification usually require measurements of both the input force and the resulting response in laboratory conditions. However, when modal properties are to be identified from large structures in operation, usually the possibilities to control and measure the loading on the structure is rather limited. In this case, the modal testing is usually performed using response data only. Operational Modal Analysis (OMA) or Operational Modal Testing is a method where no artificial excitation needs to be applied to the structure or force signals to be measured. In this case, the modal parameters estimation is based upon the response signals, thereby minimizing the work of preparation for the test. However, standard OMA techniques, such as NExT, are limited to the case when excitation to the system is a white stationary noise. The NexT assumes that the correlation functions are similar to the impulse response functions, and then, traditional time domain identification methods can be applied. However, if harmonic components are present in addition to the white noise, these components can be misunderstood as natural modes in the plot of response spectrum. In this work, it is shown that it is possible identify if a peak in the response spectrum correspond to a natural mode or an operational mode. It is achieved through the application of the probability density function. It is also presented a modification in the LSCE algorithm in such manner that it can support harmonics in the operational excitation. In order to validate the methods presented in this work, it is shown numerical and experimental cases. In the former, results for a mass-spring-damper of five degree of freedom are presented, and in the latter a beam supporting an unbalanced motor is analyzed.
Acesso aberto (Open Access)
Estudo de vibrações eólicas em linhas de transmissão de energia elétrica de alta tensão
(Universidade Federal do Pará, 2008-10-30) SANTOS, Alexandre Sá dos; SOEIRO, Newton Sure; http://lattes.cnpq.br/7303174583088137
The increasing demand for electrical energy has stimulated the technological advance of the equipment associated to its transport, generating a situation in which one has to operate under ever increasing nominal voltages, mainly due to economical reasons. This fact has a direct implication on the diameter of the conductors, elevating their cost, as well as that of the supporting structures. In order to overcome this problem, without cost elevation of the electrical transmission line project, the idea is to use more than one conductor per phase, in a parallel assembly with small distances between cables, which can be achieved through the insertion of spacers at regular intervals between the supporting towers. However, operational mechanical problems may arise such as, for example, total or partial rupture of cables and/or spacers due to dynamical wind excitations. Thus, this work investigates the dynamical behavior of a bundle of cables of electrical transmission lines, using a finite element model, which reproduces the coupling between cables and the transmission lines’ spacers-dampers and the fixing structures, considering non-linear geometrical effects due to huge cable displacements, and line continuity, i.e., the adjacent vain, which is taken into account by the model as an equivalent stiffness. Wind load is modeled through a non-deterministic process, from its statistical properties, such that two parts are considered: an average load, statistically analyzed, and a variable load, analyzed as a transient. Results show that the variable load part conduces to a dynamic response of the model, which could represent a dominant behavior. Therefore, the traditional methodology of assuming wind load as a static excitation could lead, in some cases, to disastrous consequences.
Acesso aberto (Open Access)
Influência do ruído de tráfego em edifícios e proposta de solução desenvolvida com auxílio de modelos numéricos
(Universidade Federal do Pará, 2011-05-27) GUIMARAES, Erick Van Casseb; MELO, Gustavo da Silva Vieira de; http://lattes.cnpq.br/8850986817571748
In Brazil, the number of houses and apartments that suffer the influence of noise pollution is quite large. Currently, this question gained important local attention when Belém-PA was elected the “National Capital of Noise” for several years in a row, according to data obtained by the IBGE. Among the most common types of noise pollution, the biggest complaint of society is regarding traffic noise, which is inherent to the daily life of any great city. While the traffic noise concerns increase, so does the preoccupation with a degree of discomfort from the population, justifying the development of means to quantify and reduce such discomfort beyond the means of regulations for this situation by Brazilian standards. Therefore, the condition of traffic noise, while a principal agent of annoyance for the population in which it refers to the noise pollution, it comes to justify the necessity to realize a study that aims at the development of elements of construction by means of new geometrics and composition of existing materials that minimize the penetration of traffic noise to the internal environments of these constructions. So, this work presents the results of studies of the acoustic behavior in situated constructions next to roads of great flow of vehicles which suffer interferences caused by the generation of traffic noise. So far, there were measures carried out in the field of a 25 story building in advanced stages of construction and was chosen as the subject for this study, which represents a numerical modeling of this building with the help of the software ODEON.
Acesso aberto (Open Access)
Projeto e construção de câmaras reverberantes em escala reduzida para o estudo das características de perda de transmissão de divisórias confeccionadas a partir de materiais regionais
(Universidade Federal do Pará, 2006-09-05) TOUTONGE, José de Aviz; SOEIRO, Newton Sure; http://lattes.cnpq.br/7303174583088137
To project and build reverberant chambers, in scaled model, for the determination of materials transmission loss used for noise control purposes was the objective of this research. Besides, the research seeks to establish a methodology of analysis and interpretation of the acoustic parameters starting from the theory of scaled models, in such way that one can infer the transmission loss of the studied materials. The necessity of this construction occurs due to the non availability of real scale reverberant chambers (only available in some regions of Brazil), making it difficult and raising the costs of material performance tests in other Brazilian regions. Therefore, reverberant chambers were constructed in a reduced scale of 1:6, in order to allow the transmission loss study of party walls, developed with regional materials, confronting their performances and, simultaneously, their use in academic activities. Despite the fact of the chambers have been constructed in reduced scale, the scale factor (1:6) was not considered, meaning that measurements had been carried through in the real octave bands between 125 Hz and 8 kHz. Party walls had been assayed for the determination of the acoustic parameters, based on ISO 140 and 354. Finally, from experimental results, it was possible to prove the efficiency of materials used in the construction of partitions, which could be used for noise isolation purposes in buildings and industrial enclosures. Apart from the experimental assays, analytical calculations had been fulfilled according to the formulation of Analysis Energy Statistics (SEA) in order to provide evidence and validation of the results.
Acesso aberto (Open Access)
Projeto e construção de uma câmara reverberante em escala reduzida para a caracterização acústica de materiais absorventes
(Universidade Federal do Pará, 2007-05-31) GUEDES, Reginaldo Cascaes; SOEIRO, Newton Sure; http://lattes.cnpq.br/7303174583088137
In the area of Acoustics, concerning the last decades, a significant growth has been observed in the demand for data regarding not only the absorbing characteristics of acoustical materials, but also the usage of numerical methods which are able to represent the acoustical behavior of real systems. These real systems demand a significant infrastructure, which means a great deal of investments. Thus, in order to attend such demands for new data, to allow the development of research regarding the sound absorbing characteristics of regional materials and to develop practical classes on acoustics, both for graduate and post-graduate students, this work presents all the information regarding the project and construction of a scaled reverberant chamber (1:6 of a 200 m3 real chamber). Besides, a methodology is presented regarding the qualification and adequacy of the internal acoustic field, based on the guidance of ISO-354. On the other hand, experimental results for the miniaturized chamber are presented and discussed, which characterize and validate the usage of the coconut fiber panels, developed by the Acoustics and Vibration Group of the Federal University of Pará. Finally, numerical results, based on Ray Tracing Methods, are presented and compared to those measured for the scaled chamber, seeking the validation of the developed numerical model.
Acesso aberto (Open Access)
Variáveis térmicas de solidificação, espaçamento dentríticos secundários e resistência à corrosão de ligas hipoeutéticas Al-Ni
(Universidade Federal do Pará, 2008-08-14) COSTA, Giselle Barata; SÁ, Fernando Antonio de; http://lattes.cnpq.br/8275621144223544
In this research is carried out a sequence of experiments with Al-Ni hypoeutectic alloys to analyze the upward vertical directional solidification on transient conditions of heat flow. Experimental approaches were developed to quantitative the thermal variables of solidification, as follow: local time solidification; dislocation rate of liquidus isotherms, tip cooling rates and thermal gradients. This study analyzes the dendrite secondary arms spacing in relation to solidification thermal variables and to alloy composition, beyond link these parameters with corrosion resistance of these alloys. These experimental dendrite parameters, concerning to alloys solidification as Al - 1, 1,4 and 1,8%Ni, couldn’t be compared with the main theoretical model of dendrite growth by others researches, because, to alloy studied there shortage of thermophysic properties, impossible this comparison. The corrosive behavior is analyzed by potentiodynamic polarization technique and cyclic polarization technique lead into 3,5%NaCl solution on room temperature, coarse structure dendritics tend to increase the corrosion rates of Al-Ni hypoeutectic alloys. The experimental results obtained by the corrosion tests were correlated with dendrite microstructure. This way, experimental tendencies of growth dendrite were determined to upward vertical directional solidification.

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