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transmissivity

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A really quiet weekend this time, I spent most of it working on my engineering course. This time it’s all about Vibrations. If this formula means something to you, then welcome to my world:

transmissivity

Let me see if I can decode this a little:

  • T stands for Transmissibility – i.e. how much does a system respond to an externally applied vibration?
  • Ω (Omega) is the frequency of the applied vibration;
  • ω (omega) is the natural resonant frequency of the system, calculated from its mass and the stiffness of its mountings;
  • ζ (zeta) is the damping ratio from shock absorbers etc.

The point of all this is: if T is high and ζ is low, the system will resonate, with consequences ranging from the annoying (e.g. a rattling car door) to potentially disastrous. Remember the Tacoma Narrows Bridge? Not the one there now, but “Galloping Gertie”, the one that shook itself to bits in 1940 when subjected to high winds, just four months after its completion. There are also limits on human exposure to vibration, with the 4-8 Hz range deemed the worst for us, because our internal organs start resonating, apparently. Urgle.

Well, I’ve finished the assignment, in time, and there’s a month to go before the exam. Then I’ll have the winter to myself. I’m considering a night class, maybe a language?

Written by brian t

September 22, 2002 at 9:00 pm

Posted in study

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