Accelerometer readings -> Static Force for FEA
Accelerometer readings -> Static Force for FEA
(OP)
I am currently working an implement for a piece of (slow moving) off road equipment and I am trying to determine the best way to find the forces on the implement mount due to the equipment traveling on a rough road. We normally use a 3g static load for checking items that are on the off road equipment (this is based on a company design standard) but we are getting peak accelerometer readings of around 5-6g on a mock-up of the implement. I know that it is unreasonable to use these accelerometer readings for a static FEA since it happens over a very short time period, but I'm not sure how to get an equivalent static load based on the accelerometer readings. I think my best option would be to use the accelerometer as a trigger to take strain gage readings and use those to determine the force.
Can anyone provide a little guidance on this?
Can anyone provide a little guidance on this?





RE: Accelerometer readings -> Static Force for FEA
sounds like you want to smooth out the real accelerations ... use a fast accelerometer, then post process with a time constant (maybe something like a running RMS) to smooth the curve. then apply these accelerations to your model.
RE: Accelerometer readings -> Static Force for FEA
Cheers
Greg Locock
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RE: Accelerometer readings -> Static Force for FEA
I did a project on a 6 bottom roll-over plow. I don't remember the exact loading anymore, but I seriously doubt it was over 3g. I tested it but putting it behind a QuadTrak.
ISZ
RE: Accelerometer readings -> Static Force for FEA
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Accelerometer readings -> Static Force for FEA
If his loads are from off-road but slow speed impacts like a farm tractor or caterpillar tractor/grader/skip loader/non-road-qualified dump truck, then the speed is 4-5 mph and the impacts less jarring, right?
RE: Accelerometer readings -> Static Force for FEA
RE: Accelerometer readings -> Static Force for FEA
You have to be careful with RMS. What you found is maximum “RMS” acceleration load of 3.5g. Not maximum loads at 3 sigma. RMS is root mean square, in short mean or averaged loads. Thus the worst static load cases will be three times (3 sigma) RMS acceleration, which comes to 10.5g. In DoD, typical highway g loads are about 5g. So the 10.5g seems reasonable for slow off road equipment.
Tobalcane
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RE: Accelerometer readings -> Static Force for FEA
I agree and since the problem is random vibrations of multi-impacts, why not make a model of the worst case terrain and analytically model the response of the equipment.
This would yield fatigue life , which is the implicit requirement.
Another slightly more complicated method would be to get the analytical response (from the above model) to the input vibration spectra generated from a model of the terrain and the vehicle speed.
RE: Accelerometer readings -> Static Force for FEA
That is the gold standard for predictive CAE. For a passenger car we can do that up to about 5 Hz.
Cheers
Greg Locock
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