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clarification on damping broadening peak

clarification on damping broadening peak

clarification on damping broadening peak

(OP)
I came accross an old thread and wanted to make a small comment, but thread is closed:

Here is the thread
http://www.eng-tips.com/viewthread.cfm?qid=160351

It was stated:

Quote:

Bear in mind that damping will broaden the peak as well as reducing its height, so increasing the damping can actually increase the response at a particular speed.

This seems incorrect to me, at least by study of a SDOF system:   Here is an example (which I'm sure is nothing new to anyone here).   
http://home.comcast.net/~electricpete/eng-tips/SDOF_VaryDamping.pdf

Increasing the damping does broaden the shape of the peak, but the amplification at any given frequency is lower as we increase damping, correct?
 

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

RE: clarification on damping broadening peak

You are right of course, for an SDOF system.

"so increasing the damping can actually increase the response at a particular speed."

was wrong, for your simple SDOF system.

BUT, there are many more complex systems where adding damping does increase the off-resonant response, eg increasing the damping levels in a shock absorber. You see the same in engine mounts, diff mounts and suspension bushes.

Nice catch.

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: clarification on damping broadening peak

(OP)
Thanks. That makes sense.

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

RE: clarification on damping broadening peak

In fcat thinking baout it it seems to depend on whether you have a base excitation system, or are looking at the transmissibility through a system.

So, in the case of a driveshaft, it might well be closer to yuor SDOF example.



 

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

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