中文摘要：

The free vibration of a functionally graded material hollow sphere submerged in a compress-ible fluid medium is exactly analyzed.The sphere is assumed to be spherically isotropic with material consta-nts being inhomogeneous along the radial direction.By employing a separation technique as well as thespherical harmonics expansion method,the governing equations are simplified to an uncoupled second-orderordinary differential equation,and a coupled system of two such equations.Solutions to these equations aregiven when the elastic constants and the mass density are power functions of the radial coordinate.Numericalexamples are finaUy given to show the effect of the material gradient on the natural frequencies.

英文摘要：

The free vibration of a functionally graded material hollow spheresubmerged in a compress- ible fluid medium is exactly analyzed. Thesphere is assumed to be spherically isotropic with material consta-nts being inhomogeneous along the radial direction. By employing aseparation technique as well as the spherical harmonics expansionmethod, the governing equations are simplified to an uncoupledsecond-order ordinary differential equation, and a coupled system oftwo such equations. Solutions to these equations are given when theelastic constants and the mass density are power functions of theradial coordinate. Numerical examples are finally given to show theeffect of the material gradient on the natural frequencies.