@article {Magand:1996:1610-1928:707,
title = "Time frequency analysis of energy distribution for circumferential waves on cylindrical elastic shells",
journal = "Acta Acustica united with Acustica",
parent_itemid = "infobike://dav/aaua",
publishercode ="dav",
year = "1996",
volume = "82",
number = "5",
publication date ="1996-09-01T00:00:00",
pages = "707-716",
itemtype = "ARTICLE",
issn = "1610-1928",
url = "https://www.ingentaconnect.com/content/dav/aaua/1996/00000082/00000005/art00005",
author = "Magand, Fran{\c{c}}ois and Chevret, Patrick",
abstract = "In order to set up an automatic target recognition system for low frequency sonar, it is required to understand the mechanisms involved in acoustic scattering by simple elastic shapes. Within this scope, this paper investigates the energy distribution of cylindrical shell echoes in
the time-frequency plane, when both the geometry (shell thickness) and thc mechanical characteristics (shear wave velocity, density) of the elastic material are varying. A large number of impulse responses are calculated using the classical modal decomposition formalism, and a systematic time-frequency
analysis of shell echoes is performed via the Smoothed Pseudo Wigner-Ville Distribution. Symmetric (S
0) and antisymmetric (A
0) Lamb waves are first identified on some time-frequency images by comparing the group velocity dispersions estimated from both the
time-frequency distribution and the Resonance Scattering Theory. It is then shown that, in the case of thin shells, the main energy contribution in the time-frequency plane is concentrated in a broad frequency range around the coincidence frequency that corresponds to the bifurcation of a
0
+
and a
0
waves. The midfrequency enhancement of the energy is then confirmed by a simple wave propagation model for circumferential waves.",
}