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[jduriez <jerome.duriez@xxxxxxxxxxxxxxx>]

Public bug reported:

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 ?

** Affects: yade
     Importance: Undecided
         Status: New

** Attachment added: "With UniaxialStrainer"
   https://bugs.launchpad.net/bugs/1300167/+attachment/4055419/+files/testUS.py

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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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