Eng. & Tech. Journal, Vol.29, No.11, 2011 * Engineering College, University of Baghdad/ Baghdad 2156 Geometrically Nonlinear Free Vibration Analysis of Cylindrical Shells Using high Order Shear Deformation Theory-A Finite Element Approach Dr. Nabil Hassan Hadi *& Kayser Aziz Ameen * Received on :5/4/2011 Accepted on: 20/6/2011 Abstract A nonlinear finite element model for geometrically large amplitude free vibration analysis of laminated composite shallow cylindrical shell panel is presented using high order shear deformation theory (HSDT). The nonlinearity is introduced in the Green – Lagrange sense. The effects of different orthotropic ratios, thickness ratio, curvature ratio and boundary condition are study also frequency ratio (nonlinear frequency to linear frequency) of cylindrical shell are determined as function of shell amplitude ratio. Keywords: High order shear deformation, Shell, Free vibration, Nonlinear Finite element Method. ل وا ا ال ا ة"ازات اھ ا$% &% ا’ ()ت ا*+ – دة ا- ا)* ط-/ ا دة ا ا ا طة ا اازھت ا ذات ا!"ل ا$% ا ا&’ ا(ا)!* ا+, &- ا. ا ا/( 0 ل!1 "- 2- دة ا . 2- 3(ا’ 4$ه ا6- ا78 د ا9 ا. اد) ة:اص ا)< ا&( 0- =- ! درا2- دد ا&( ! درا2- ?@’ ووط اBس وا) ا&( ،(ا)!? ا! &( ،&’ ا) دد ا< ا7دد ا اE ا7 ( ت ا&( E ا&( F1G 2- و(ا)!* ا+,ـ ر .