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Opiela K.C., Zieliński T.G., Attenborough K.♦, Manufacturing, modeling, and experimental verification of slitted sound absorbers,
ISMA2020 / USD2020, International Conference on Noise and Vibration Engineering / International Conference on Uncertainty in Structural Dynamics, 2020-09-07/09-09, Leuven (BE), pp.409-420, 2020 Streszczenie: Designs with uniformly distributed slits normal or inclined to the incident surface exhibit a great potential because of their simplicity and good acoustical performance. However, production of materials of this sort is challenging as the required fabrication precision is very high. This paper deals with additive manufacturing, modeling, and impedance tube testing of a few slitted geometries and their variations, including cases where the dividing walls between slits are perforated. They were designed to be producible with current 3D printing technology and provide reliable measurements using standardized equipment. The normal incidence sound absorption curves predicted analytically and numerically were verified experimentally. It is observed that such simple configurations may lead to absorption properties comparable to porous acoustic treatments with more complex microstructure. The good agreement between the predictions and measurements supports the validity of the multi-scale modeling employed. Afiliacje autorów:
Opiela K.C. | - | IPPT PAN | Zieliński T.G. | - | IPPT PAN | Attenborough K. | - | The Open University (GB) |
|  | 20p. |
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Opiela K.C., Zieliński T.G., Dvorák T.♦, Kúdela Jr S.♦, Perforated closed-cell metal foam for acoustic applications,
e-FA2020, e-FORUM ACUSTICUM 2020, 2020-12-07/12-11, Lyon (FR), DOI: 10.48465/fa.2020.0925, pp.2879-2886, 2020 Streszczenie: Despite very good mechanical and physical properties such as lightness, rigidity and high thermal conductivity, closed-porosity metal foams alone are usually poor acoustic treatments. However, relatively low production cost weighs them in many applications in favour of their open-cell equivalents. In the present paper, this attractive and popular material is subject to consideration from the point of view of the improvement of its sound absorption characteristics. A classic method of perforation is proposed to open the porous interior of the medium to the penetration of acoustic waves and therefore enhance the dissipation of their energy. The interaction between the perforation diameter and closed-cell microstructure as well as its impact on the overall sound absorption of a similar foam were already studied in 2010 by Chevillotte, Perrot and Panneton, so these topics are not discussed much in this work. On the other hand, the objective here is to investigate if one can efficiently approximate the wave propagation phenomenon in real perforated heterogeneous materials with closed porosity of irregular shape by means of their simplified three-dimensional representation at the micro-level. The applied multi-scale modelling of sound absorption was confronted with measurements performed in an impedance tube. Moreover, as expected, numerical and experimental comparisons with relevant perforated solid samples show great benefit coming from the presence of a porous structure in the foam, although it was initially closed. Afiliacje autorów:
Opiela K.C. | - | IPPT PAN | Zieliński T.G. | - | IPPT PAN | Dvorák T. | - | Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK) | Kúdela Jr S. | - | Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK) |
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Zieliński T.G., Opiela K.C., Pawłowski P., Dauchez N.♦, Boutin T.♦, Kennedy J.♦, Trimble D.♦, Rice H.♦, Differences in sound absorption of samples with periodic porosity produced using various Additive Manufacturing Technologies,
ICA 2019, 23rd International Congress on Acoustics integrating 4th EAA Euroregio 2019, 2019-09-09/09-13, Aachen (DE), DOI: 10.18154/RWTH-CONV-239456, pp.4505-4512, 2019 Streszczenie: With a rapid development of modern Additive Manufacturing Technologies it seems inevitable that they will sooner or later serve for production of specific porous and meta-porous acoustic treatments. Moreover, these new technologies are already being used to manufacture original micro-geometric designs of sound absorbing media in order to test microstructure-based effects, models and hypothesis. In the view of these statements, this work reports differences in acoustic absorption measured for porous specimens which were produced from the same CAD-geometry model using several additive manufacturing technologies and 3D-printers. A specific periodic unit cell of open porosity was designed for the purpose. The samples were measured acoustically in the impedance tube and also subjected to a thorough microscopic survey in order to check their quality and look for the discrepancy reasons. Słowa kluczowe: Sound absorption, Additive Manufacturing Technologies Afiliacje autorów:
Zieliński T.G. | - | IPPT PAN | Opiela K.C. | - | IPPT PAN | Pawłowski P. | - | IPPT PAN | Dauchez N. | - | Sorbonne University Alliance (FR) | Boutin T. | - | Sorbonne University Alliance (FR) | Kennedy J. | - | Trinity College (IE) | Trimble D. | - | Trinity College (IE) | Rice H. | - | Trinity College (IE) |
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Opiela K.C., Zieliński T.G., Adaptation of the equivalent-fluid model to the additively manufactured acoustic porous materials,
ICA 2019, 23rd International Congress on Acoustics integrating 4th EAA Euroregio 2019, 2019-09-09/09-13, Aachen (DE), DOI: 10.18154/RWTH-CONV-239799, pp.1216-1223, 2019 Streszczenie: Recent investigations show that the normal incidence sound absorption in 3D-printed rigid porous materials is eminently underestimated by numerical calculations using standard models. In this paper a universal amendment to the existing mathematical description of thermal dispersion and fluid flow inside rigid foams is proposed which takes account of the impact of the additive manufacturing technology on the acoustic properties of produced samples. The porous material with a motionless skeleton is conceptually substituted by an equivalent fluid with effective properties evaluated from the Johnson-Champoux-Allard-Pride-Lafarge model. The required macroscopic transport parameters are computed from the microstructural solutions using the hybrid approach. A cross-functional examination of the quality (shape consistency, representative surface roughness, etc.) of two periodic specimens obtained from additive manufacturing processes is additionally performed in order to link it to the results of the multiscale acoustic modelling. Based on this study, some of the transport parameters are changed depending on certain quantities reflecting the actual quality of a fabricated material. The developed correction has a considerable influence on the predicted value of the sound absorption coefficient such that the original discrepancies between experimental and numerical curves are significantly diminished. Słowa kluczowe: Rigid porous material, Additive manufacturing, Sound absorption Afiliacje autorów:
Opiela K.C. | - | IPPT PAN | Zieliński T.G. | - | IPPT PAN |
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Opiela K.C., Rak M.♦, Zieliński T.G., A concept demonstrator of adaptive sound absorber/insulator involving microstructure-based modelling and 3D-printing,
ISMA 2018 / USD 2018, International Conference on Noise and Vibration Engineering / International Conference on Uncertainty in Structural Dynamics, 2018-09-17/09-19, Leuven (BE), pp.1091-1103, 2018 Streszczenie: The purpose of this work is to present and investigate the concept of adaptive sound absorbers, that is, periodic porous media with modifiable micro-geometry, so that their ability of sound absorption or insulation can be changed in various frequency ranges. To demonstrate this concept, a simple periodic porous micro-geometry with small bearing balls inside pores is proposed. By a simple positioning of the periodic porous sample the gravity force is used for the small balls to close some of the windows linking the pores, changing in that way the flow path inside pores, which entails significant modifications of the relevant parameters of permeability and tortuosity. Also the viscous characteristic length is changed, while the porosity as well as the thermal characteristic length remain unchanged. Nevertheless, such significant changes of some crucial transport parameters strongly affect the overall acoustic wave propagation in the porous medium. All this is studied using an advanced dual-scale modelling as well as experimental testing of 3D-printed specimens. Afiliacje autorów:
Opiela K.C. | - | IPPT PAN | Rak M. | - | inna afiliacja | Zieliński T.G. | - | IPPT PAN |
|  | 20p. |