ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06
5aSA9. Investigation of the vibroacoustical characteristics of cylindrical
shells.
Rostislav A. Dudnik
Andrei B. Kolpakov
Dept. of Phys., Inst. Arch. Civil Eng., 65 Il'inskaya St., 603600
N.-Novgorod, Russia
Experimental and theoretical investigations of the influence of
inhomogeneity upon the oscillations and radiation of thin cylindrical shells
are executed. The inhomogeneity is presented by either one additional mass
(m[sub 0]) fastened (at (Phi)=180(degrees)) on the shell surface, or two
identical inertia masses (m[sub 1]=m[sub 2]=m[sub 0]/2) which are fastened at
(Phi)=(plus or minus)(Phi)[sub 1]. The impact of such division of a unit
inhomogeneity on oscillating velocity distribution as well as on the pressure
radiated levels and directionality diagrams of the relevant shell models is
analyzed for different quantities of summary mass (m[sub 0]). The execution
analysis is limited by the investigation of azimuth lower-frequency modes. It
was shown that the considered distribution of inhomogeneity makes it possible
to control the radiation level of the shell in certain frequency ranges. The
investigation of a structure of near and far acoustical fields radiated by
these shells at various distances from the radiating surfaces was conducted
also. It was shown that as this distance increases, the number of the mode
providing the largest contribution to the complete field decreases.
Corresponding experimental results are presented.