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The vibration isolation for a forced vibration system is possible, when:

The vibration isolation for a forced vibration system is possible, when: Correct Answer ω/ω<sub>n</sub> &gt; 2<sup>0.5</sup>  

Concept:

Vibration isolation is the way to reduce the effect of vibration, generating from the machine, and transmitting to foundation. 

The isolators are used to reduce transmissibility (TR).

 

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  • When ω/ωn = 0 ⇒ TR = 1, (independent of ζ)
  • When ω/ωn = 1 and ξ = 0 ⇒ TR = ∞, (independent of ζ)
  • When frequency ratio ω/ωn = √2, then all the curves pass through the point TR = 1 for all values of damping factor ξ.
  • When frequency ratio ω/ωn < √2, then TR > 1 for all values of damping factor ξ. This means that the force transmitted to the foundation through elastic support is greater than the force applied.
  • When frequency ratio ω/ωn > √2, then TR < 1 for all values of damping factor ξ. This shows that the force transmitted through elastic support is less than the applied force. Thus vibration isolation is possible only in the range of ω/ωn > √2. Here the force transmitted to the foundation increases as the damping is increased.

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