بررسي كمانش ورق هاي با خواص ناهمسان در ضخامت نسبتا" تحت بارگذاري مكانيكي و حرارتي

چكيده انگليسي :

Buckling of Thick Functionally Graded Plates under Mechanical and Thermal Loading Vajiheh Fadaki V fadaki@yahoo com Date of Submision March 12 2011 Department of Civil Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Prof Mojtaba Azhari azhari@cc iut ac ir Advisor Prof Bijan Boroomand boromand@cc iut ac ir Abstract Mechanical and thermal buckling analysis of moderately thick functionally graded material plates are presented in this study Functionally graded materials FGMs are advanced composites that are designed to tolerate high temperatures in low thicknesses and they have a suitable application in temperature gradients FGMs are made from a mixture of two different materials mostly ceramic and metal FGM plates FGPs have two fully ceramic and metallic surfaces and the material properties vary continuously and smoothly through the thickness Ceramic supplies high thermal resistance while metal provides high stiffness and ductility These kinds of plates contribute a particular role in structures such as thermal barrier structures for the space shuttle combustion chamber nuclear plants and etc the material properties of functionally graded materials vary continuously and smoothly through the thickness according to power law distribution while the poison s ratio is supposed to be constant In this paper the buckling of squared functionally graded material plates by employing the higher order shear deformation theory are studied A finite strip approach is developed to analyze the plates with two longitudinal simply supported edges and arbitrary boundary conditions for lateral edges The finite strip method relies on the energy approach The strain displacement and stress strain relations will be extended then by use of energy approach the stiffness matrix and the geometric stiffness matrix of a strip will be establish After composing the stiffness matrixes of the plate and exerting the boundary conditions by minimizing the total energy of the plate an eigenvalue problem yields The critical buckling load of plate will be obtained by solving this eigenvalue problem Thermal buckling analysis of FGM plates is performed in two stages prebuckling stage in which the plate remains flat and the in plane stresses develop while the temperature increases and the buckling stage which is similar to mechanical buckling of the plate The numerical results under mechanical loading uniform and linear thermal loadings through the thickness are compared with the critical buckling values obtained by implementing classical higher order and 2D higher order deformation plate theories The convergency of the method is investigated in this paper In comparison with finite element method and closed form solution finite strip method converges faster So FSM is economical for solving the buckling problem of rectangular functionally graded material plates The effect of boundary conditions power law index side to thickness ratio and the aspect ratio on the critical buckling load and critical buckling temperature of FGM plates is presented in this study The results show that the critical buckling temperature increases by increasing the side to thickness ratio and the aspect ratio while decreases by growth of the power of volume fraction The critical buckling of plate under linear temperature is about twice of plate under uniform temperature The study concludes that higher order shear deformation theory accurately predicts the behavior of functionally graded plates whereas the classical plate theory overestimates buckling load and temperature Key Words Plates buckling Higher order shear deformation theory Finite strip approach

فدكي، وجيهه السادات

بررسي كمانش ورق هاي با خواص ناهمسان در ضخامت نسبتا" تحت بارگذاري مكانيكي و حرارتي

كمانش حرارتي , روش نوار محدود , تئوري برشي مرتبه سوم ,