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Structural Engineering and Mechanics
  Volume 75, Number 1, July10 2020, pages 87-100

Combination resonances of imperfect SSFG cylindrical shells rested on viscoelastic foundations
Kamran Foroutan and Habib Ahmadi

    The present paper investigates the combination resonance behavior of imperfect spiral stiffened functionally graded (SSFG) cylindrical shells with internal and external functionally graded stiffeners under two-term large amplitude excitations. The structure is embedded within a generalized nonlinear viscoelastic foundation, which is composed of a two-parameter Winkler-Pasternak foundation augmented by a Kelvin-Voigt viscoelastic model with a nonlinear cubic stiffness, to account for the vibration hardening/softening phenomena and damping considerations. With regard to classical plate theory of shells, von-Kármán equation and Hook law, the relations of stress-strain are derived for shell and stiffeners. The spiral stiffeners of the cylindrical shell are modeled according to the smeared stiffener technique. According to the Galerkin method, the discretized motion equation is obtained. The combination resonance is obtained by using the multiple scales method. Finally, the influences of the stiffeners angles, foundation type, the nonlinear elastic foundation coefficients, material distribution, and excitation amplitude on the system resonances are investigated comprehensively.
Key Words
    nonlinear vibrations; combination resonance behaviors; spiral stiffened FG cylindrical shell; multiple scales method; geometric imperfections; nonlinear viscoelastic foundation; two-term excitation
Faculty of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, Iran

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