Maximum load from vibration data
Maximum load from vibration data
(OP)
Hi,
I have vibration data from an automotive product which plots accleration in G's vs time. I am attempting to estimate a force value from this data to use in pull testing and linear FEA calculations (which will be done before a final vibration test). For example, there are impulse values as high as 10 G's, but only last a few miliseconds. The values are generally close to 3 G's. I know 10 G's of sustained acceleration would induce failure, based on basic calculations, yet no failure was seen. How do I determine what the highest force value I should use for my calculations, and eliminate the values that don't induce a sustained force?
Thanks,
Frank
I have vibration data from an automotive product which plots accleration in G's vs time. I am attempting to estimate a force value from this data to use in pull testing and linear FEA calculations (which will be done before a final vibration test). For example, there are impulse values as high as 10 G's, but only last a few miliseconds. The values are generally close to 3 G's. I know 10 G's of sustained acceleration would induce failure, based on basic calculations, yet no failure was seen. How do I determine what the highest force value I should use for my calculations, and eliminate the values that don't induce a sustained force?
Thanks,
Frank





RE: Maximum load from vibration data
How was it obtained?
What is the highest frequency of interest?
What anti-aliasing filter was used?
Is there a possibility that noise is present in the data?
What is the sampling frequency (should be at least 10 times the highest frequency of interest,preferably more)?
Were the accelerometers calibrated in G peak or G rms?
What accelerometers were used and what is their resonant frequency?
Regards
Dave
RE: Maximum load from vibration data
RE: Maximum load from vibration data
RE: Maximum load from vibration data
Anyway, do not be dismayed by the test data, it is perfectly normal to get very high g values in short term peaks that would destroy the part if they were applied at low frequency. For instance on an engine you'll see spikes to 30-100g, eg if the block weighs 200 kg then applying a 20 ton force to the block would hurt it. In reality it will withstand millions of cycles.
Turning vibration data into load data is a black art... could you consider applying a load spectrum to the model and adjusting it until you get the same acceleration response? This is actually remarkably difficult.
Cheers
Greg Locock
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RE: Maximum load from vibration data
TTFN
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RE: Maximum load from vibration data
Fore example: If you get a shock event and the info come in G vs time say 50g at .050 sec. The frequency this would happen would be at 1/(2*.050)= 10Hz. Thru FEM you find out that the part you are conserned with has a first mode at 10Hz then the 50g is the load on that part.
Tobalcane
"If you avoid failure, you also avoid success."