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[Jérôme Duriez <question269063@xxxxxxxxxxxxxxxxxxxxx>]

Question #269063 on Yade changed:
https://answers.launchpad.net/yade/+question/269063

    Status: Open => Answered

Jérôme Duriez proposed the following answer:
Yet Another Detailled Explanation (attempt, at least) about your "main
question":


The mechanics behind the Ansys and Yade computations have *NOTHING* in common:

- discrete mechanics with (almost) spring constitutive laws (interaction
forces <-> relative displacements) for Yade on one hand

- continuum mechanics with elastic or elasto-plastic constitutive
relations (stress <-> strain) for Ansys on the other hand.


Obviously, since both methods are used sometimes to describe the same physical reality, it should be possible to let match the results of these two methods....
However, this requires a non-trivial calibration procedure, so that the parameters of the two models (Yade and Ansys) lead to similar results. 
As a matter of fact, this is non-trivial at all, since Ansys parameters have nothing in common with Yade parameters: they do not enter in the same equations !


As for the outputs of Yade and Ansys models, you may again first consider that they have nothing in common ! Yade describes a particulate system (=> displacement, forces...), Ansys describes a continuum (=>stress and strain tensors).
Again, it is however possible to link to some extent these different quantities. But, after some reasoning ! 

For instance, stress tensor definitions -- from forces within a discrete
system -- makes really sense only for high number of particles (=>
Representative Elementary Volume notion). Which is not the case with
getBodyStress(). You still might be obtain some insights from such
function, but, in the general case, you will never obtain an uniform
stress field simulating uniaxial tension as you may get with Ansys !

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