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چكيده انگليسي :

Vibration Analysis of Rotating Beams with Functionally Graded Properties Peyman Hajheidari p hajheidari@me iut ac ir Date of Submission 2011 09 19 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisors Mostafa Ghayour ghayour@cc iut ac ir Hamid Reza Mirdamadi hrmirdamadi@cc iut ac irAbstract Rotating beams have found extensive practical applications in mechanical engineering and aerospace the beams play an important role in the modeling of engineering applications such as turbine blades airplane propellers and robot manipulators among others Due to the extensive applications for rotatingbeams the vibration analysis of beams is important The constant needs of the industry impel the engineering community in seeking of new concepts and newstrategies in order to improve the structural response of structures as well as to enhance the endurance ofmaterials This is particularly true in the case of rotating blades that are subjected to severe environmentalconditions such as high temperatures as well as mechanical conditions such as high rotating accelerations centrifugal forces geometric stiffening among others Creation and discovery of advanced compositematerials containing functionally graded materials is a solution for this problem Utilizing functionallygraded materials is effective because of high mechanical and thermal resistance and also is not difficult todelimitate An important characteristic in the dynamic analysis of functionally graded beams is computational of theirnatural frequencies and mode shapes This is important as the functionally graded beams structures oftenoperate in complex environment conditions with high temperature and are frequently exposed to a varietyof dynamic excitations The characteristics of rotating flexible structures differ significantly from those ofnon rotating flexible structures Centrifugal inertia force due to rotational motion causes the variation ofbending stiffness which naturally results in the variations of natural frequencies and mode shapes Moreover the stiffness property of functionally graded structures can be easily modulated through changingpower law exponent of functionally graded materials Power law exponent dictates the material variationprofile through the predetermined direction of the beam The finite element method is one of the most powerful numerical procedures for solving complex problemsin various branches of engineering and physics Nowadays some advanced elements have been introduced among them is element with 8 degrees of freedom In normal element i e element with 4 degrees offreedom a beam element is modeled using two nodes at the end and every node has two degrees offreedom Therefore a large number of elements are needed for modeling of the beam and to achieve anacceptable accuracy By using element with 8 degrees of freedom some derivational terms are added to thenodes of element and displacement function obtains extra degrees of freedom Thus the same accuracy canbe achieved by using much less number of elements This results in rapid convergence In this thesis the free vibration analysis of rotating and non rotating beams made of functionally gradedmaterials for purely out of plane motion flap and purely in plane motion lag is investigated Numericalfinite element method with two type element 4 and 8 degrees of freedom is applied to find the naturalfrequencies and mode shapes of functionally graded beams in the bending mode of vibration by taking intoaccount the taper ratio and the rotation simultaneously In this study as well as a nonlinear model isdeveloped appealing to a nonlinear strain displacement relation Numerical Newark s method is employed

حاج حيدري، پيمان

آناليز ارتعاشات تيرهاي چرخان با ويژگي هاي عملكرد درجه بندي شده

مواد FGM , تير باريك شونده , روش المان محدود , روش عددي نيومارك , فركانس هاي طبيعي