EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
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5 resultados
Resultados da Pesquisa
Item Dynamic behavior of tapping axial force.(2021) Pereira, Igor Cezar; Mapa, Lidianne de Paula Pinto; Barros, Thamiris Nogueira de; Fortes, Reinaldo Clemente; Silva, Marcio Bacci da; Guimarães, Gustavo PaulinelliBackground Tapping is one of the processes that most requires attention in the industry, due to the stage in which it occurs and its characteristics. In the case of tapping, it is common to use components and equipment with less rigidity, which com promises the dynamic behavior in several situations and can lead to process distortion or failure. Purpose The objective of this paper is to study the dynamic behavior of tapping in relation to several characteristics of the process. Methods The dynamic behavior of the force signal was used to evaluate the process, varying the cutting parameters and the clamping system of the workpiece. Results The experimental results indicate that the foating system did not present a good dynamic behavior at high cutting speeds, this greater application of vibration is due to the resonance due to the combination of oscillations under forced and natural vibration. Conclusions The natural frequency of the foating fxture system infuenced the behavior of the axial forces. The increase in cutting speed resulted in a direct increase in the axial force vibrations as its frequency came close to the natural frequency of the system. Through dynamic analysis of the axial force signal observed the dynamic characteristics of the process and the machine tool. This allowed the dynamic evaluation of the system through the measurement of force signals generated in the threading process.Item Investigations on complex acoustic modes of rocket engines combustion chambers for damping allocation.(2021) Guimarães, Gustavo Paulinelli; Pirk, Rogério; Souto, Carlos D'Andrade; Góes, Luiz Carlos SandovalCombustion instability can severely impair the operation of many kinds of combustion engines. Acoustic resonators are widely used to suppress the pressure oscillations caused by the coupling between the combustion process and the combustion chamber acoustic modes. Combustion chambers with subsonic flow in its inlets and outlets, like gas turbine combustors, exhibit some acoustical damping due to the presence of openings. In such chambers, the acoustic modes are complex. In a complex mode, the antinode regions can be shifted from its position in the corresponding real mode. In this work an experimental acoustic modal analysis of a cavity with an opening was performed. Acoustic frequency response functions were obtained by using a volume acceleration source, a microphone and a data acquisition system. The PolyMAX algorithm was used to estimate longitudinal modes in its real and complex versions. A comparison was performed and the results show that, for some modes, the antinode region placement could change reasonably. This suggests that the use of complex modes for location of antinode regions provides more accurate results and consequently could be a better way to identify positions, where resonators provide maximum damping in order to minimize combustion instability in subsonic combustion chambers.Item Dynamic substructuring by the craig–bampton method applied to frames.(2020) Mapa, Lidianne de Paula Pinto; Neves, Francisco de Assis das; Guimarães, Gustavo PaulinelliPurpose The Craig–Bampton method is a substructuring technique that reduces the number of internal degrees of freedom of substructures by approximations, using a set of truncated vibration modes. It is useful for structural designs with many degrees of freedom. This work aims to develop substructuring through the Craig–Bampton method for free vibration analysis on planar frames according to the frequency range of interest. Methods The fnite-element models of diferent substructures were assembled. Thus, the degrees of physical freedom were reduced according to the frequency range of interest. The reduced-order models were coupled. Thus, the physical response was obtained. Detailed calculation and the algorithm fowchart are provided. Conclusions The study of frame dynamics using the present method in diferent frequency ranges of interest was presented and validated with the results of a commercial software. It was possible to clarify the coupling formulations of the component mode synthesis, as well as the amount of reduction of the number of equations provided by the method, reaching less than 4% of the complete model, for the considered cases.Item Acoustical performance of Helmholtz resonators used as vehicular silencers.(2018) Martins, Lucas Rodrigues; Guimarães, Gustavo Paulinelli; Fragassa, CristianoThis study proposes to evaluate the acoustical performance of a reactive vehicular silencer made entirely of Helmholtz resonator. Four or seven resonators are idealized to be in a series configuration, all the dimensions except cavity length and resonators are fixed. An algorithm processes inputted characteristic engine noise signal obtained from literature, identify peaks, and calculates ideal cavity length for attenuation. The transmission loss of the system is analytically calculated. Attenuation levels obtained are satisfactory. The required volume of the resonator to achieve the same resonance frequency as low frequency noise peak demands impractical cavity length, proving it to be flawed. It is suggested to use resonators of two or three different diameter for different frequency range in order to overcome this problem.Item Analysis of the acoustical behavior of cavities using impedance functions.(2016) Guimarães, Gustavo Paulinelli; Pirk, Rogério; Souto, Carlos D'Andrade; Góes, Luiz Carlos SandovalThe acoustic design of cavities is an important task in a variety of engineering applications, from automotive or aerospace industries to equipment coating designs. In this work, the acoustic impedance functions (a frequency domain model) were calculated using analytical, numerical, and experimental methods. Those different approaches were presented in a unified manner in order to allow comparisons among them. The relationship of the impedance function and a classical frequency response function (FRF) was also established. A circular duct of rigid walls was assumed with different boundary conditions as closed end, as well as opened and absorbed extremities. Three duct configurations were implemented in order to compare analytical, numerical, and experimental results. Finally, it could be possible to evaluate some aspects that are characteristic of a large range of acoustic systems applications as the existence of complex modes and frequency-dependent behavior of absorption material. This study aims the usage of the impedance functions to analyze the acoustic behavior of cavities, as well as to compose the background in order to develop, in the future, an acoustic modeling process using impedance functions.