Affiliations: DEM, Instituto Superior Técnico, Tech. Univ. of
Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal | IDMEC-IST, Instituto Superior Técnico, Tech. Univ.
of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
Abstract: This article presents a study on the use of the dynamical response
of multi-laminated periodic bars to create resonance band gaps within useful
frequency ranges. The objective is to control, in a passive form, the
longitudinal vibration transmissibility in specific and wide enough frequency
ranges of interest. This is achieved by the separation of two adjacent
eigenfrequencies. A relation between the modal analysis, the harmonic analysis
and the Bloch wave theory is proposed, for which no reference was found
in the searched literature. As shown, the selection of appropriate material
pairs is essential to obtain useful frequency ranges. The use of pairs of steel
and cork agglomerate is proposed, since it allows the design of attenuators at
lower frequencies through a prediction based on finite element analysis (FEA).
This approach requires the storage modulus of cork for which analytical and
numerical FEA models were verified and validated. A methodology to obtain
experimentally the storage modulus of cork is presented. Regarding the
structural improvement problem, we discuss a methodology to design periodic
bars for a specific location of the first attenuation's frequency range and
illustrate the main results through several examples.
Keywords: Passive isolation, vibration, multi-laminated bar, cork agglomerates, structural modification
