Vibro-acoustic behavior of a hollow FGM cylinder excited by on-surface mechanical drives

The linear three-dimensional elasticity theory in conjunction with the powerful transfer matrix solution technique is employed to investigate the steady-state nonaxisymmetric sound radiation characteristics of an arbitrarily thick functionally graded hollow cylinder of infinite length subjected to arbitrary time-harmonic on-surface concentrated mechanical drives. A formal integral expression for the radiated pressure field in the frequency domain is obtained by utilizing the spatial Fourier transform along the shell axis and Fourier series expansion in the circumferential direction. The method of stationary phase is subsequently employed to evaluate the integral for an observation point in the far-field. The analytical results are illustrated with numerical examples in which water-submerged metal-ceramic FGM cylinders are driven by harmonic concentrated radial/transverse surface forces and circumferential moment. The far-field radiated pressure amplitudes and directivities are calculated and compared with those of equivalent bi-laminate hollow cylinders with comparable volume fractions of constituent materials. The effects of FGM material profile, cylinder thickness, excitation frequency and type on the radiated far-field are examined. Limiting cases are considered and the validity of results is established by comparison with the data in the existing literature as well as with the aid of a commercial finite element package.