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[Jan Stránský <question660540@xxxxxxxxxxxxxxxxxxxxx>]

Question #660540 on Yade changed:
https://answers.launchpad.net/yade/+question/660540

    Status: Open => Answered

Jan Stránský proposed the following answer:
Hello,
in general, Yade does not put any limitations for the parameters values. But is assumes you choose them "reasonably". Reasonable means e.g. positive stiffness. However, in certain cases it may treat "non-reasonable" values in a special way, like for etaRoll<0, "If negative, rolling moment will be elastic" (from the docs).

The specific use always depend on your problem and level of simplification. E.g. you can simulate non-spherical particles with spheres and "non-realistic" higher friction angle.
E.g. in your case, young=1e6 (assuming Pa units) seems too low to me, but it may be the best value at the same time :-)

Some notes about a few parameters:
- elastic parameters (E, Ks/Kn and alphaKr in your case) should be identified first, as their response is independent on the inelastic parameters.
- phi, friction angle, has reasonable values in the range [0,pi/2]
- I would first try the model without rolling stiffness and resistance. If it gives good results, I would choose the more simple model.

You can also try some dimensional analysis to reduce parameters for
calibration. E.g. you will find that Poisson's ratio depends on Ks/Kn
and etaRoll, but not on E etc.

cheers
Jan

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