Abstract
This study presents results of an experimental investigations of the materials used in passive damping vibrations. The main purpose of this paper was to examine the damping properties of selected viscoelastic materials (VEM), using the modal analysis. In presented analysis three configurations of specimens were considered. At first, the separated steel beam was analyzed. As results of this analysis, the frequencies and amplitudes of the beam during resonance were obtained. In next part of the work the modified specimen was investigated. In this modification the bitumen-based material (as a damper) was fixed to the surface of the beam. This method is known as free layer damping (FLD) treatment. In last configuration, the butyl rubber layer was connected to the steel beam. Using the Unholtz-Dickie UDCO-TA250 electrodynamic vibration system, the natural frequencies and amplitudes of free vibrations for all examined specimens were obtained. The vibration amplitude of the beam was measured using piezoelectric acceleration sensors. In order to define the damping capabilities of both the bitumen based material and the butyl rubber, the relative amplitude of specimens and the loss factor using half-power bandwidth method were calculated.
Highlights
There is many sources of sounds and vibrations in the aircraft structures and the cars
The results of performed modal analysis are presented as Frequency Response Function (FRF)
Obtained results of experimental modal analysis showed that the best damping of beam is observed for frequencies above 1000 Hz
Summary
There is many sources of sounds and vibrations in the aircraft structures and the cars. The first way to decrease the vibration of aircraft structures and cars is minimization of vibrations of engine. Viscoelastic polymers are commonly used in automotive and aviation industry as passive damping [1, 18]. Such materials have both viscous and elastic properties. Because viscoelastic polymers have such features, after removing the load from them, some of the energy is recovered and some is dissipated in the form of thermal energy Their damping capabilities strongly vary with the temperature and frequency (Figs 1, 2). The storage modulus E’ has the highest value in the glassy region
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