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Frequency range for measuring shock load on frame.

Frequency range for measuring shock load on frame.

Frequency range for measuring shock load on frame.

(OP)
I am measuring the peak accelerations on a small tractor frame when running through a bumpy field.  Someone has suggested that the frequency range be limited to 50 or 100 hz because the destructive forces are more prevalent in the lower frequencies.  When I measure over a wider frequency range (0-1600 hz), the peak acceleration is 200 m/s².  When I measure with a frequency range limited to 50 hz the peak acceleration is around 20 m/s². Which frequency range should I use to accurately discribe the load on the frame.

Thanks for your replies.

vechman

RE: Frequency range for measuring shock load on frame.

The low frequencies contain a lot of energy, and would be the ones to cause bending, etc.  The higher frequencies wiggle loose all the fasteners.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: Frequency range for measuring shock load on frame.

Strain causes fatigue, so it is more useful think about displacement than acceleration, but also number of cycles is imprtant so people look at velocity in the frequency domain.

I doubt you'll get much fatigue related to wheel inputs above 100 hz.



 

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: Frequency range for measuring shock load on frame.

I would also look at strain.  The strains throughout the frequency spectrum contribute to fatigue.  Low amplitude/high frequency can be as bad as high amplitude/low frequency.

Have analyzed failures where the low amplitude/high frequency range had more effect on the failure (wind vibration on transmission structure)

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