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Free Vibration Alanysis of Rotating Cylindrical-Conical Shells with Elastic Boundary Conditions

Sarkheil, Saeed | 2017

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 49491 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Saadat Foumani, Mahmoud
  7. Abstract:
  8. In this research the vibration of rotating and non-rotating shells was investigated. In the non-rotating shells field, the vibration of joined cylindrical shells and joined conical shells that each sections of them has independent material, thickness, length and angle were investigated. By analyzing the free vibration of joined conical shells, we can perform the free vibration analysis on every complex thin-walled geometry.In the rotating shells field, first the governing equations of the rotating conical shells are derived and then, the vibration of rotating cylindrical-conical shells and joined conical shells were investigated. The governing equations of rotating conical shells and rotating cylindrical-conical shells were solved using power series method. But the rotating joined conical shells problem was solved using matrix transform method to decrease the solution time. At the end, the effects of elastic boundary conditions on free vibration of joined conical shells was investigated. In all the considered problems, after the derivation of equations and solving them, the comparative studies were done with the results in the papers and finite element analysis. In addition, in the non-rotating field a modal test is performed on the shell composed of three conical sections. After validation, the effect of parameters such as circumferential wave number, cone angle, ratio of length to diameter and thickness on the natural frequencies of the shell is investigated. Results show that in the rotating cylindrical-conical shell, if the angle of the conical section is about 5-10 degree, the natural frequency of this geometry takes minimum. In addition, in the elastic boundary condition problems, the stiffness of the circumferential spring has the maximum effect on natural frequencies of the shell. After that the axial spring stiffness has more effect and compare to these boundaries, radial spring and rotational spring has negligible effect on the natural frequency
  9. Keywords:
  10. State Space ; Power Series Solution ; Transfer Matrix ; Rotating Cylindrical Shell ; Cylindrical-Conical Shell ; Joined Conical Shells ; Forward Freqencies ; Backward Frequencies

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