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[Jan Stránský <question271097@xxxxxxxxxxxxxxxxxxxxx>]

Question #271097 on Yade changed:
https://answers.launchpad.net/yade/+question/271097

    Status: Open => Answered

Jan Stránský proposed the following answer:
Hi Alexander,

1) There are 2 types of contacts in Yade: cohesive and non-cohesive
> (frictional).


this is a bit subjective (see Bruno's answer), but one classification could
be like that. I.e.:
- cohesive contacts exist even for negative penetrationDepth ("tension")
- non-cohesive contacts are deleted in "tension" case

Non-cohesive contacts appears every time when 2 spheres overlap each
other.


Not necessarily. If you do not define Ig2_Sphere_Sphere or if the 2 spheres
have incompatible groupMask, they would not interact. But **usually** it is
like you described

3) By default Yade creates cohesive contacts only at the beginning (first
> step) of the simulation


I know only CPM well enough, in that case by default it does not create any
cohesive contact. I **guess** it is the same for other materials/laws (or
at least I would expect and implement it in that way)..

4) At each step InsertionSortCollider and Ig2_Sphere_Sphere_ScGeom
> classes defines only new contacts (interactions), previous contacts
> update themselves (for example non-cohesive interaction brokes when they
> became apart, cohesive interaction in CohFricMat  brokes when maximum
> tensile or maximum shear force is reached etc.).


Basically yes, two points:
- Ig2 is called also for existing interactions (updating ScGeom parameters)
- "contacts update themselves". Contacts does not update themselves, but
they are updated by Ig2 and Law2 functors

cheers
Jan

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