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[jduriez <jerome.duriez@xxxxxxxxxxxxxxx>]

> The real problem I see is that UniaxialStrainer is modifying positions.
So, we agree on most important part.


> It seems UniaxialStrainer should be simply removed (or someone will fix?).
I do not have precise ideas on what should be a "strainer" and, if it 
can be used in discrete mechanics, but maybe other people have, and 
anyway I have the feeling that this engine is used (at least by 2 
people). So, after other points of view, I could fix it, even if I will 
maybe not use it.

It is probably only a matter of setting the velocity corresponding to 
the change in position.


-- 
Jérôme Duriez
Post-Doctorant UJF
Laboratoire 3SR
Bureau E139 - 04.56.52.86.30

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https://bugs.launchpad.net/bugs/1300167

Title:
  (Not) Defining velocities in UniaxialStrainer ?

Status in Yet Another Dynamic Engine:
  New

Bug description:
  Hi,

  I have the feeling that there is something "wrong" with
  UniaxialStrainer where the velocities of the "posIds" and "negIds"
  bodies are not defined, and I illustrate it with following examples
  (attached)

  It deals with 2 contacting spheres, with an oblic contact. One sphere is moved towards the 2d sphere, and here both normal and tangential relative displacements occur. 
  - In testUS.py the moving sphere is moved through UniaxialStrainer
  - Whereas in testUSb.py the movement comes from an initial value of velocity (and NewtonIntegrator)

  And, obviously, the two simulations are different (see e.g. the plot
  of fZ sustained by moving sphere). While I would tend to consider
  these two simulations as identical.

  What do you think ?

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