Design of Vibration fixture

[dipakpunde]

hi,
I am designing vibration fixture for an actuator , I want to find Natural frequency of fixture by theoretical calculations? vibration fixture should match 3000 HZ frequency.
Vibration fixture consist of below parts
• Base plate
• Steel female spline to connect output shaft
• 6 screws to mount Steel female spline with base plate
• 3 mounting bolt to mount actuator on the base plate
Thank you
Dipak

 

[IRstuff]

"vibration fixture should match 3000 HZ frequency."

Not sure what you mean by that. the fixture should have a natural frequency WAY above the maximum test frequency. Test fixtures are supposed to transmit vibration energy from the tester without modifying it.

TTFN
faq731-376

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[MikeHalloran]

Just as a point of reference, building floors that deflect L/360 under design load, have a natural frequency around 4 Hz.

If you're going to test at 3000Hz, you need a very stiff fixture.



Mike Halloran
Pembroke Pines, FL, USA

 

[dipakpunde]

thanks for your quick replay.

my basic requirement is "vibration fixture should match 3000 HZ frequency."

so how can we theoretically calculate natural frequency?

i have done the FEA analysis with few iterations however is there any formula to get natural frequency easily?

thank you
Dipak

 

[IRstuff]

Your requirement makes no sense to me, though. Why must it have a 3 kHz natural frequency?

In any case, I think the answer to your question is no; there is no simple way to calculate natural frequency of a complex structure.

https://www.wpi.edu/Pubs/E-project/...stricted/Final_Presentation-BuckleyChiang.pdf

TTFN
faq731-376

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[dgallup]

Very simple structures (springs, simple beams, tuning forks) can be calculated relatively easily. Beyond that, you need FEA modal analysis.

As noted, the test fixture natural frequency should be well above the test frequency. Running the test at the fixture natural frequency will quickly destroy the fixture.

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[dipakpunde]

Thank for all replays.

I have done FEA analysis to verify design.