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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)


Mechanical Engineering

First Advisor

Kamyar Nikpur


The dynamics of flexible rotors is investigated and the specific characteristics of rotors such as whirling, external and internal damping, gyroscopic effects and local flexibility due to cracks are discussed. It is found that the on-line, real-time vibrational testing of the operating systems can render valuable information as how to diagnose critical cracks before their unstable propagation engender catastrophic accidents. It is shown that when cracks are symmetrical, such as a fully opened penny-shape crack, the coupling of vibrational modes does not appear to exist. However, when compressive stresses partially close up the crack surfaces, the coupling phenomenon will be conspicuous. The characteristic equations of the cracked rotor demonstrate the shifting of natural frequencies of system, which can generally yield sufficient data for estimating the position and size of the crack in rotors.

Library of Congress Subject Headings

Rotors -- Vibration

Fracture mechanics

Damping (Mechanics)



Number of Pages



South Dakota State University