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.