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Medientyp:
E-Artikel
Titel:
Local vibration of an elastic plate and zero-group velocity Lamb modes
Beteiligte:
Prada, Claire;
Clorennec, Dominique;
Royer, Daniel
Erschienen:
Acoustical Society of America (ASA), 2008
Erschienen in:The Journal of the Acoustical Society of America
Sprache:
Englisch
DOI:
10.1121/1.2918543
ISSN:
0001-4966;
1520-8524
Entstehung:
Anmerkungen:
Beschreibung:
<jats:p>Elastic plates or cylinders can support guided modes with zero group velocity (ZGV) at a nonzero value of the wave number. Using laser-based ultrasonic techniques, we experimentally investigate some fascinating properties of these ZGV modes: resonance and ringing effects, backward wave propagation, interference between backward and forward modes. Then, the conditions required for the existence of ZGV Lamb modes in isotropic plates are discussed. It is shown that these modes appear in a range of Poisson’s ratio about the value for which the cutoff frequency curves of modes belonging to the same family intercept, i.e., for a bulk wave velocity ratio equal to a rational number. An interpretation of this phenomenon in terms of a strong repulsion between a pair of modes having a different parity in the vicinity of the cutoff frequencies is given. Experiments performed with materials of various Poisson’s ratio demonstrate that the resonance spectrum of an unloaded elastic plate, locally excited by a laser pulse, is dominated by the ZGV Lamb modes.</jats:p>