سعید صرامی

Sandwich plates as structural members, have received a lot of attention in industrial structures and large construction projects due to their low specific weight, resistance to fatigue and high bending strength. Since Industrial structures are commonly reposed to dynamic loads, plate vibration can result in injury to structures, especially when the excitation frequency is close to the natural frequency of the structure. Therefore, nonlinear vibration analysis of plates is one of the most attended topics in the dynamics of structures. In this article, the nonlinear free vibration of sandwich plates with a viscoelastic core is studied based on von Karman's assumptions and using the First-order shear deformation theory. The viscoelastic properties of the plate core follow Boltzmann's integral law. Also, the Laplace transform is used to convert equations from the time domain to the Laplace domain. For the discretization of the equations, the finite strip numerical method is used. Finally, by numerically solving an eigenvalue problem in the Laplace-Carson domain, the nonlinear frequencies of sandwich plates with a viscoelastic core with different vibration amplitudes are calculated. The results show that, with the increase of the vibration amplitude and the coefficients of the relaxation function of the viscoelastic core, the ratio of the nonlinear frequencies decreases in this type of plates.