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[Jérôme Duriez <question249830@xxxxxxxxxxxxxxxxxxxxx>]

Question #249830 on Yade changed:
https://answers.launchpad.net/yade/+question/249830

    Status: Open => Answered

Jérôme Duriez proposed the following answer:
Hi Cyndie,

Let me try to answer your questions:
§ "In order to avoid that, I have applied the same engine twice ..."
   -> I'm sorry, I do not get your point. This engine is intended to deform (hence, to be applied to) a whole box, not a corner.


"I am using kinemCNDEngine with rigid frictionless walls- does it still working under such conditions or should I have periodic boundaries or add friction to my rigid walls?" and following § "The same problem..."
   -> As soon as you deal with a box defined as in Fig. 1 of [Duriez2011], the engine "is working". On the other hand, you can not use it in periodic boundaries (where there is no box..). About friction, I used walls friction for reasons stated in § 2.2 of [Duriez2011]. The frictionless feature that you're currently using may explain that one of your "tho" is ~ 0. The non-symmetry may maybe arise from a non quasistatic situation ? I'm sorry to not be more precise here, I never measured stress inside the samples when I used this engine, only normal and tangential stresses acting on upper plate (that by the way appears reasonnably equal to the ones of lower plate, see Fig 2.17 and 2.18 of [Duriez2009])


"- Can the upper and bottom plate move vertically?"
   -> No. Quoting the doc, this engine "perform(s) a constant normal displacement shear, by translating *horizontally* the upper plate". The constant normal displacement (CND) condition means that the vertical distance between these two plates is constant. So vertical movements of the upper and bottom plates are not imposed by this engine. They might be allowed by the three other "Kinem.." engines designed to impose other classical - for interface media - loading conditions.


"Is the point (2D)/the line (3D) joining the vertical and the upper plate still the same during the test?"
   -> This point
* evolves in global coordinates frame
* correspond to different material points of the rotating vertical plates during loading
* is the same material point of the upper plate (its extremity)

Note that examples/simple-shear/simpleShear.py illustrates (in a
mechanical meaningless case, because of a nonadequate spheres sample)
how the box is deformed with this engine, and that § 2.2 and 2.3 of
[Duriez2011] (sorry to quote it again..) should be quite explanatory.

Jérôme


[Duriez2011] : https://www.yade-dem.org/doc/publications.html#duriez2011 (tell me if you can not access to fulltext)
[Duriez2009] : see corresponding entry in https://www.yade-dem.org/doc/publications.html#master-and-phd-theses

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