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Vibration Analysis of Rotor-Disk Systems

Toomaj, Arman | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42882 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Behzad, Mehdi; Mehdigholi, Hamid
  7. Abstract:
  8. Utilization of the rod fastened rotors in gas turbines as well as induction motors increased recently due to several advantages. Rods in rod fastened rotors are connected to shafts in both sides of the rotors and pre-tightened using bolts in each ends. Predictions of dynamic characteristics of these rotors have specific complications as a result of effects of contact interfaces raised due to applied pre-tightening load. Studies carried out in the field of vibration analysis of rotors consist of investigation of vibration of shafts, bearings and other connected components to the rotors. One of the best methods for modeling and analyzing complicated structures such as rod fastened rotors is finite element method. In this project, structure of rotor-disk system of rod fastened rotors is modeled using suitable elements for each component of them. Also, effects of contact stiffness in the contact interfaces are modeled using theories of contact between rough surfaces. Effects of surface roughness and axial pre-tightening force are investigated using Greenwood-Williamson and Onions-Archard models. Effects of these parameters on bending contact stiffness are studied. Furthermore, natural frequencies, bending mode shapes and critical speeds of the rotor are studies and effects of aforementioned parameters on natural frequencies are investigated too. In addition, unbalance response of the rotor is studied. Finally, a simplified test rig of rod fastened rotor built. Then, natural frequencies and mode shapes of the rotors obtained through modal testing. These results compared with calculated amounts of the developed finite element program. According to the results, developed code can predict modal properties of the rotor satisfactorily.

  9. Keywords:
  10. Finite Element Analysis ; Dynamic Modeling ; Rotor Dynamics ; Rod Fastening Rotors ; Contact Stiffness

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