Date of Award

2009

Degree Type

Thesis

Department

Mechanical Engineering

First Advisor

Rashidi, Majid

Subject Headings

Rotors -- Dynamics, Rotors -- Bearings, Rotor bearing system, FEA, finite element analysis, permanent magnet alternator, PMA

Abstract

This thesis presents the results of the finite element analysis (FEA) approach for designing a Permanent Magnet Alternator (PMA). The PMA is configured as a cantilever hollow shaft supported by two identical rolling contact bearings. The performance requirements of the PMA are a maximum operating speed of 16,000 rpm, with a maximum shaft displacement of less than 0.010 in at its free end. The static and dynamic results of a cantilever beam was predicted by closed form solutions and verified to those results obtained from FEA for code validation. A mathematical model of a rotor-bearing system was proposed and analyzed for its dynamic unbalance response when subjected to a harmonic excitation force at the free end. The proposed design for a rotor-bearing geometry was modeled by SolidWorks, and then analyzed in COSMOSWorks using second order tetrahedral solid elements. Lastly, the FEA results of six parametric studies of a rotor-bearing system are presented. In these parametric studies, the rotor-bearing configuration from parametric study No.5 proved to satisfy the PMA first natural frequency and displacement requirements. The first natural frequency was determined to be 358,171 rpm, which is 22 times of the maximum operating speed of the PMA. Additionally, the maximum steady-state UX and UY displacements were obtained at 2.35E-06 in and 1.06E-05 in, respectively, which is less than the maximum allowable shaft displacement

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