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Vibration and Aeroelastic Stability Analysis of Sandwich Turbomachinery Blade with Magnetorheological Elastomer Core

Bornassi, Saeed | 2018

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 51200 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Haddadpour, Hassan; Mohammad Navazi, Hossein
  7. Abstract:
  8. This dissertaion deals with the vibration and aeroelasticity analysis of a turbomachinery cascade with Magnetorheological Elastomer (MRE) based sandwich blades. At first, bending vibration of the rotary blades equipped with an MRE core based on the three-layered sandwich beam theory have been studied in the flexural and edgewise directions. Further, the torsional vibration is investigated and the effects of different parameters such as the intensity of the magnetic field, rotating speed and the MRE layer thickness on the natural frequencies and loss factors of the system are studied. On the basis of the modeling obtained for the structural dynamics and based on the Whitehead's unsteady aerodynamic theroy, the governing equations of motion of a blade cascade were derived and the effects of different parameters on the instability of the system; including torsional flutter and bending-torsional flutter, have been investigated taking into account the tuned and mistuned charactrsitics of the blades. The governing equations were derived by obtaining the kineric energy, potential energy and the work done by the external forces and using the assumed modes method along with the Lagrange’s equations. By the eigenvalue analysis of the equations governing on the structure dynamics and the coupled system, the natural frequency and the corresponding loss factor of the struture were obtained and the aeroelastic flutter instability was investigated, respectively. The results show that the concept of sandwich structure with an MRE core improves the vibration characteristic and stability of the turbomachinery blades. It was shown that the magnetic field intensity and MRE layer thickness have significant influences on the loss factor of the system. Adding an MRE layer to the blade structure increases the flutter speed and consequently improves the aeroelastic stability. With increasing magnetic field, the flutter speed increases and increasing MRE layer thickness generally increases the flutter stability margin. The results also demonstrate the beneficial influence of the magnetic field mistuning based on the random and alternate distributions on the flutter stability
  9. Keywords:
  10. Sandwich Structure ; Aeroelastic Instability ; Magnetorheological Elastomer(MRE) ; Field Strength ; Vibrational Analysis ; Turbomachinery Blade ; Whitehead Aerodynamic Theory

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