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Vibration and Stability Analysis of Cracked Rotor with Initial Bow

Mir Mohammadi, Ali | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58311 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Dehghani Firouzabadi, Rouhollah
  7. Abstract:
  8. In this study, the stability and vibrations of the rotor with initial bow and crack were investigated. Using a model developed to calculate the Euler-Bernoulli rotor motion equations with four degrees of freedom at each node, the occurrence of transverse cracks, their breathing, and initial bow, and the effect of these defects on the stability and response of the system were investigated. The occurrence of transverse cracks in rotating systems can threaten their performance and health and affect the stability and vibrations of the system. Initial bow caused by loading can lead to unwanted vibrations or serious failures. These defects are often caused by material, manufacturing, or assembly errors of the system. In this thesis, the effect of these defects on the response, stability, and vibrations of the system is investigated. In system modeling, the coefficients of the degrees of freedom depend on time and the equations of motion of the system are according to the differential equations of Matthew. The stability analysis of the system based on its equations is investigated with the help of Floquet theory diagrams. The results show that increasing the crack depth and initial shaft bow increases the response amplitude in the frequency and time domains, changes in the critical speeds, and the occurrence of additional harmonics in the system, especially when the crack breathing effect is considered in the modeling. Time response analysis using the Newmark-Beta method in linear and nonlinear models also indicates the effective role of cracks and curvature in the dynamic instability of the system. Also, stability analysis using the Floquet theory and comparison of the responses with the results obtained from ANSYS software is carried out to examine the accuracy of the developed model in finite element simulation
  9. Keywords:
  10. Rotor Dynamics ; Initial Bow ; Cracked Rotor ; Euler-Bernoulli Beam ; Floquet Theorem ; Stability ; Crack Breathing

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