چكيده به لاتين
This study presents an analytical solution for calculating sound transmission loss through a circular cylindrical shell made of polymeric foam. Also in another section, the acoustic analysis is carried out on two-walled cylindrical shells with a functionally graded viscoelastic core. The intended infinite cylinder is excited by an acoustic plane wave. The equations of motion for the cylindrical shells are derived by the first order shear deformation theory which based on Hamilton’s principle. Besides, modeling of the behavior of foams is performed using functionally graded Zener model which the mechanical properties vary concerning the frequency and in the thickness direction. Due to the lack of study on the vibro-acoustic of the viscoelastic graded materials, the results of this study are compared with those of some researchers in the literature of elastic materials, and excellent concurrences are observed. Also, the effects of different geometrical and material characteristics on the sound transmission loss factor are investigated. The investigation of the influences of various power-law index illustrates that by reducing this parameter, the sound transmission loss through the shell is increased. Also, the convergence problem is solved for two sections, and the effect of frequency on the needed number of modes for convergence is checked. It is shown that the needed number of modes for convergence is increased by increasing the excitation frequency. Finally, a comparison between four models of the cylinder such as functionally graded viscoelastic, functionally graded materials, viscoelastic and elastic in the same weight is performed. It is explored that the sound transmission loss factor in a functionally graded viscoelastic cylinder is more than the other models in the same weight.
