Hello,
I would like to reproduce a test configuration in which an acceleration is set at the base of the specimen. There are 4 fasteners with contacts (Coulomb) and I need a time analysis, not frequency.
The problem is the real behavior is governed by the dynamic amplification in the model, especially the acceleration at the top of the specimen. But by only setting the base acceleration, the top acceleration is always too small in my simulation, so the behavior is not ok.
I have tested a lot of ways to take damping into account (structural, rayleigh, contacts) but the acceleration is always too small at the top of the specimen...Even when zero damping, the acceleration at the top is not very high,..
Does anyone has any idea how to deal with this kind of problem in Abaqus ?
Thanks ;).
Rémi
Hi, create boundary condition by acceleration. The another solution - use gravity. Show us the pictures with boundary condition and loads.
The dynamic amplification is dependent on both the input load frequency and the system frequency. Dynamic excitation doesn't always mean there will be amplification. Consider two extreme in a spring mass system where one end is being subjected to excitation and the response is being measured at the end where mass is attached.
In between these two extremes there is a range where amplification happens, and it goes to infinity at resonance frequency.
Now in your case, have you compared your system frequency and input acceleration frequency with experiment? If they do not match, you won't get the same response.
Hello Abhimanyu,
thanks for your answer.
Regarding your question, the acceleration imposed at the base of the model is the one from the tests. Besides, the natural frequencies from the model match very well the ones from the tests (less than 1% on the first mode).
I think my problem comes from the presence of contacts, which modify the way Abaqus treats damping...because when my contacts are tied, I can find an equivalent material damping that gives the good acceleration at the top of the masse. But I cannot do it when i put the contacts on (with a penalty Coulomb friction model).
I would be glad if you had any clue about that.
Thanks ;)
Rémi
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