A four-variable refined plate theory for dynamic stability analysis of S-FGM plates based on physical neutral surface

Dynamic instability analysis of S-FGM on elastic medium is investigated using a four-variable refined plate theory. The material is graded in the thickness direction and two power law based on the rule of mixture is used to estimate the effective material properties. The neutral surface position for such S-FGM plates is determined and the third-order shear deformation theory based on exact neutral surface position is employed. If the neutral surface is used, the FGM plates can easily be treated, because the coupling between stretching and bending deformations is not occurred. Even though present theory uses only four unknown variables, have strong similarities with CPT in many aspects such as boundary conditions, equation of motion and stress resultant expressions. Hamilton's principle is utilized to derive the equations of motion. It is assumed that the elastic medium is modeled as Pasternak elastic medium. The governing equations are written in the form of Mathieu-Hill equations and then Bolotin's method is employed to determine the instability regions. Various numerical results are presented to reveal the influences of static and dynamic load factors, power law index, elastic medium parameter, and side-to-thickness ratio on the dynamic stability characteristics of S-FGM plates. Also, the formulation should provide engineers with the capability for the design of S-FGM plates for special technical applications including aircraft, rocket, wing surfaces and missile skins. (C) 2015 Elsevier Ltd. All rights reserved.