Werner,
I only get peripherally involved with vibe testing around here, so i know a
lot of people who can give you more definitive answers, but here goes...
Don and Doug have already told you about the Mil-Std's that i know about.
In addition, we often test to DO-160D (i think D is the latest rev),
Section 8 for vibe.
Our vibe guru tells me that Mil-Std-202 does give some levels for
component vibe testing, but no guidance as to what is an appropriate level.
He also mentioned that the qualification levels for SEM-E cards might be
useful.
Vibration is specified in terms of in input spectrum (Power Spectral
Density for random vibration as a function of frequency, double amplitude
for sinusoidal vibration as a function of frequency). These tests are all
for box level, not circuit card level. I am not aware of any Mil-Std test
for circuit cards by themselves. Understanding and predicting the input to
the circuit cards is the big trick, because the chassis will attenuate some
frequencies and amplify others (that kinda nailed me about this time last
year when i ran into a somewhat lower-than-expected resonance frequency on
a test fixture that caused the 5 g sinusoidal acceleration input to be a
125 g response on the board i was testing). For simplicity, random
vibration is often reported in terms of Grms, which is basically a function
of the area under the frequency vs. PSD curve, but it can be very
misleading if you aren't paying attention: you can really pad your Grms
number by taking your test out to a higher frequency without causing a
significant amount of extra damage to most electronics.
I've always been told that box level mounting is to be done 'similarly to
what is used in the application' or if that is not known, as rigidly as
possible. We tend to take advantage of the 'or' as much as possible and
bolt the box being tested to as big of a hunk of metal as we can. That way
we can somewhat limit those 25x multipliers like i ran into last year.
I hope this is somewhat along the lines of what you were asking about..
ross
===================================
Ross Wilcoxon
Senior Mechanical Engineer
Advanced Technology Center
Rockwell Collins, Inc.
400 Collins Road NE, M/S 108-101
Cedar Rapids, IA 52498
319-295-7139, fax: 319-295-3751
Werner Engelmaier
<[log in to unmask] To: [log in to unmask]
OM> cc:
Sent by: TechNet Subject: [TN] Vibration testing
<[log in to unmask]>
08/28/2003 06:57
PM
Please respond to
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Forum."; Please
respond to
Engelmaier
Hi T'Netters,
Can anybody point me to the MIL-spec that specifies the vibration testingof
electronic assemblies.
What do the specify interms of vibration, and in terms of mounting.
Thanks,
Werner Engelmaier
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