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Analytical and Experimental Study of Isolation of Sensitive Equipments from Ambient Vibrations

Mahvash Mohammadi, Akbar | 2008

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39146 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Bakhshi, Ali
  7. Abstract:
  8. In some activities, an almost free of any vibration environment is needed. Semi conductor production process and microelectronic microscopes are two examples in which a quiet environment is essential. The goal of this thesis is to attenuate ambient vibrations effectively and to prepare a suitable environment for two microelectronic microscopes. The designed system must be practical, economical and capable of being made in a short time interval. Considering mentioned properties a steel table with bolt connections supported on 4 air springs was built. To investigate dynamic properties, modal analysis was performed with the aid of finite element packages and experiments. To extract oscillations of the floor and the table, high sensitivity sensors were used. By the means of recorded accelerations or velocities on the floor, finite elements packages and random vibrations formulas oscillations on the table were extracted numerically. Finally experimental and analytical vibrations were compared. The effect of locations of air springs on the level of isolation is another part of this research which has been done with the aid of analytical solutions, numerical solutions by the means of finite elements packages and experiment. The level of efficiency of a table can be determined by using some graphs known as general purpose VC curves. At the end, velocities are transformed to the suitable form and compared with VC curves. VC curves asseses a limit to every centeral 1/3rd octave frequency. Recorded velocities showed that at frequencies of 6.35, 8, 10.08 and 12.7(Hz) “B” criteria, at frequency of 16(Hz) “C” criteria, and at higher frequencies “D” and “E” criteria were satisfied.
  9. Keywords:
  10. Random Vibration ; Modal Analysis ; Vibration Isolation ; Ambient Vibration ; Sensitive Equipments

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