2134/11851
Victor V. Krylov
Victor V.
Krylov
New type of vibration dampers utilising the effect of acoustic 'black holes'
Loughborough University
2013
untagged
Mechanical Engineering
Engineering not elsewhere classified
2013-03-05 09:14:07
Journal contribution
https://repository.lboro.ac.uk/articles/journal_contribution/New_type_of_vibration_dampers_utilising_the_effect_of_acoustic_black_holes_/9225539
One of the well-known ways of damping resonant flexural vibrations of different engineering
structures or their elements, e.g. finite plates or bars, is to reduce reflections of flexural waves
from their free edges. In the present paper, a new efficient method of reducing edge
reflections is described that utilises gradual change in thickness of a plate or a bar from the
value corresponding to the thickness of the basic plate to almost zero. It is proposed to use
specific power-law shapes of plates of variable thickness (wedges) that ideally provide zero
reflection even for negligibly small material attenuation – the so-called ‘acoustic black hole
effect’. In particular, for powers m ≥ 2 - in free wedges, and m ≥ 5/3 – in immersed wedges,
incident flexural waves become trapped near the edge and do not reflect back. Since, because
of ever-present edge truncations in real manufactured wedges, the corresponding reflection
coefficients are always far from zero, to make up for real wedges and make the systems more
efficient it is proposed to deposit absorbing thin layers on wedge surfaces. It is shown that the
deposition of thin damping layers on the wedge surfaces can dramatically reduce the
reflection coefficients. Thus, the combination of a wedge with power-law profile and of thin
damping layers can utilise the acoustic ‘black hole’ effect resulting in very effective damping
systems for flexural vibrations.