Maximum displacement measure
Maximum displacement measure
(OP)
Hello everybody,
As a beginner in vibrations I am looking for some help.
I am going to perform the vibration test where the displacement measurement of the system at first natural frequency is one of the main tasks.
Therefore as a first step I am going to run the sine sweep to determine this frequency.
As a test that allows me to determine the displacement I am going to dwell at the natural frequency.
The PSD profile obtained from field measurements is the only data I have related to vibrations that the system will be subjected in reality.
My questions: what is the appropriate acceleration for the dwell test? Should it be 3 times G (rms) from PSD? Is this approach right, in general?
Thank you very much for help
As a beginner in vibrations I am looking for some help.
I am going to perform the vibration test where the displacement measurement of the system at first natural frequency is one of the main tasks.
Therefore as a first step I am going to run the sine sweep to determine this frequency.
As a test that allows me to determine the displacement I am going to dwell at the natural frequency.
The PSD profile obtained from field measurements is the only data I have related to vibrations that the system will be subjected in reality.
My questions: what is the appropriate acceleration for the dwell test? Should it be 3 times G (rms) from PSD? Is this approach right, in general?
Thank you very much for help





RE: Maximum displacement measure
RE: Maximum displacement measure
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Dwell does not have a direct linkage to your random PSD, since the resonance coupling is not equal for all frequencies. Moreover, since there is amplification at resonance, there is usually little need to pump in additional energy.
TTFN
RE: Maximum displacement measure
I would probably describe my goals in a different way:
Our system is mounted within the enclosure. To determine the minimum size of this enclosure I need to know the maximum displacement of the unit due to vibrations (the unit is mounted on vibration isolators that allow some movement).
Is there way of measuring or calculating the maximum displacement during the random vibration test? I was told that the only option to measure it is during a sine test.
RE: Maximum displacement measure
Is the isolation purely passive?
Is the vibration purely random?
If you overlay the PSD response with diagonal lines the represent displacement, you can find the point of largest displacement, which may or may not be the resonance point.
TTFN
RE: Maximum displacement measure
Tobalcane
"If you avoid failure, you also avoid success."
RE: Maximum displacement measure
Modelling clay. And, no you can't calculate it, not if you have true random inputs. The chances are that you don't have true random excitation.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Maximum displacement measure
Having the random input profile and knowing natural frequency of my system, I can calculate the G(RMS) level of the narrow band around this frequency (lets say +/-5%).
Then multiplying it by 3 (3?) I can get the estimation of G at this frequency.
Thanks
RE: Maximum displacement measure
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Maximum displacement measure