Institute of Fundamental Technological Research
Polish Academy of Sciences

Staff

Michał Rak, MSc

Department of Intelligent Technologies (ZTI)
position: doctoral student
e-mail:


Recent publications
1.  Rak M., Ichchou M., Holnicki-Szulc J., Identification of structural loss factor from spatially distributed measurements on beams with viscoelastic layer, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2007.11.026, Vol.310, pp.801-811, 2008

Abstract:
The problem of estimation of a structural loss factor for a beam covered with a viscoelastic layer is addressed in the paper. Two estimation methods based on analytical models for wave propagation in viscoelastic homogenous beams are tested. The methods use different theoretical solutions for spatial distribution of a wave field in the beam. The solutions depend on a complex wave number and frequency. At each frequency within an investigated range the wave number, for which model predictions best approximate experimental response, is found. Structural loss factor is calculated based on the identified value of wave number. Experimental data are measured in a cantilever beam test. For verification purposes the obtained values of loss factor are compared with the results of Oberst test. The presented methods enable determination of loss factor for arbitrary discrete frequencies. They provide an alternative to modal techniques which estimate only values of the parameter corresponding to resonant frequencies.

Affiliations:
Rak M. - other affiliation
Ichchou M. - École Centrale de Lyon (FR)
Holnicki-Szulc J. - IPPT PAN

Conference papers
1.  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

Abstract:
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.

Affiliations:
Opiela K.C. - IPPT PAN
Rak M. - other affiliation
Zieliński T.G. - IPPT PAN

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