آناليز ارتعاشي تيرهاي كامپوزيتي باريك شونده چرخان

چكيده انگليسي :

Vibration Analysis of Rotating Tapered Composite Beams Rasoul Ghayour r ghayour@me iut ac ir 16th March 2010 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi S Ziaei Rad Prof Supervisor szrad@cc iut ac ir M Ghayour Assoc Prof Supervisor ghayour@cc iut ac ir Abstract The rotating tapered laminated composite beams are basic structural components when dealing with a variety of engineering structures such as airplane wings helicopter blades and turbine blades as well as many others in the aerospace mechanical industries The great possibilities provided by composite materials can be used to alter or change favorably the response characteristics of structures Due to the outstanding engineering properties such as high strength to weight and stiffness to weight ratios the composite beam structures are likely to play a significant role in the design of structures when the weight and strength are of primary consideration The behavior of composite beam structures can also be effectively and efficiently tailored by changing the lay up parameters The analysis of composite beams is of course significantly more difficult than that of metallic counterparts An important element in the dynamic analysis of composite beams is the computation of their natural frequencies and mode shapes This is important as the composite beam structures often operate in complex environmental conditions and are frequently exposed to a variety of dynamic excitations The characteristics of rotating flexible structures differ significantly from those of non rotating flexible structures Centrifugal inertia force due to rotational motion causes the variation of bending stiffness which naturally results in the variations of natural frequencies and mode shapes Moreover the stiffness property of composite structures can be easily modulated through changing their fiber orientation angles and number of layers The finite element method FEM is one of the most powerful numerical procedures for solving the mathematical problems of engineering and physics Nowadays some advanced formulation have been introduced among them is the hierarchical FEM HFEM In conventional FEM a beam element is modeled using two nodes at the end Therefore a large number of elements are needed to achieve an acceptable accuracy In HFEM some polynomial or trigonometric terms are added to the displacement and rotation function in order to obtain extra degrees of freedom Thus the same accuracy can be achieved by using much less number of elements This results in rapid convergence In this thesis a hierarchical finite element technique is applied to find the natural frequencies and mode shapes of composite beams in the bending mode of vibration by taking into account the taper and the rotation simultaneously The element mass and stiffness matrices are derived and the effects of offset rotation taper ratio and shear deformation on the beam natural frequencies are investigated Key words Vibration Tapered Composite Beam Hierarchical FEM Rotating

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آناليز ارتعاشي تيرهاي كامپوزيتي باريك شونده چرخان

روش اجزاء محدود مرتبه بالا ( HFEM ﴾