Forced Vibration: Amplitude Of Vibration Changes Periodically?

[roshan2004]

In forced vibration, amplitude of vibration changes periodically. Is it right ? I think it is a correct statement, since the amplitude of vibration is a periodic function.

 

[sophiecentaur]

Are you suggesting that you get a 'beat'?
You don't get a beat, just a reduced amplitude of response. The level will depend on the Q of the resonator and the frequency offset.

 

[Dale]

In forced vibration, amplitude of vibration changes periodically. Is it right ? I think it is a correct statement, since the amplitude of vibration is a periodic function.

I think there may be a bit of a terminology confusion here. The displacement is a periodic function in vibration. The amplitude is the maximum displacement, so it is not periodic.

 

[roshan2004]

So, does it decays exponentially then... ( I mean amplitude of the forced vibration)

 

[sophiecentaur]

The term 'forced vibration' means that a steady vibration frequency is applied. The result is a 1/exponential growth in amplitude takes place over time, until a max amplitude is reached. When the exitation is removed, there is an exponential decay in amplitude. There is no change in frequency at any time except for a small possible 'ringing' due to a discontinuity on switch on and switch off. But that is not usually considered.