Rotordynamics is a branch of dynamics that deals with investigation of dynamic behavior of rotating systems. Dynamic analysis of turbomachinery motors is vital and important because of the high speeds of the turbomachinery rotors and vibration problems that can be occured in these high speeds. Turbojet rotor can produce strong vibration due to its high speed in the operational conditions and this vibration may cause damage to the rotating parts of the turbojet motor or even failure of the motor completely.Thus, to avoid resonant situations, modal analysis of rotor is very important in the design and development stages Full rotordynamic analysis is aslo mandatory in design and preventive maintenance of rotor, to avoid strong vibrations before and after manufacturing. For this purpose, effective approaches such as finite element method which is used in this thesis are used to analyze the system. In this thesis, investigation of dynamic behavior and modal analysis of two turbojet rotors are done. Investigation of the small rotor consists of modal analysis of the non-rotating rotor and analysis of the dynamic behavior of the rotor in the rotating conditions. Modal analysis of rotor is done in the free-free and clamped boundary conditions (by considering the bearings) using one-dimensional Timoshenko beam finite element model, 3D finite element model by Ansys software, justify; MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: none" Modal and full rotordynamic analysis of the bigger rotor are done using beam FEM. Natural frequencies and mode shapes in the rotating and non-rotating conditions, Campbell diagram, critical speeds, unbalance response and operational deflection shapes in the critical speeds are the results obtained for the bigger rotor using beam elements. The results of the analyses of the bigger rotor can be used to optimize the design of the rotor in order to consider the design characteristics related to vibrations and prevent vibration problems before manufacturing of the rotor. Keywords : Turbojet rotor, Modal analysis, Modal Testing, Dynamic behavior, Finite element method, Campbell diagram
