yade-dev team mailing list archive

[Václav Šmilauer <eudoxos@xxxxxxxx>]

OK, my list of weird people has 2 items now:

* gomechanicians
* contact law freaks

Seriously, though (and with all due respect), for me the reference is
continuum mechanics; in structural engineering (presumably in mechanical
engineering as well), in FEM etc etc, outer normal is used, leading to
tension having positive sign. I am happy I already persuaded Bruno.

For ht work to be done on this: since the ScGeom-based laws use
shearForce in the incremental formulation, all the increments must have
signs changed. I think it doesn't need more than a few hours of
attentive code walkthrough (by someone who is familiar with the code)
and some testing.

-- 
NormalShearInteraction::{normalForce,shearForce} has undefined orientation
https://bugs.launchpad.net/bugs/493102
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Status in Yet Another Dynamic Engine: Confirmed

Bug description:
NormalShearInteraction::{normalForce,shearForce} should contain forces on the interaction, which can be used for various purposes by other functions. However, different functors use them with different sign

ef2_Spheres_Elastic_ElasticLaw (a.k.a. ElasticContactLaw):

   applyForceAtContactPoint(-currentContactPhysics->normalForce-shearForce, ... )

Law2_Dem3DofGeom_CpmPhys_Cpm:

   applyForceAtContactPoint(BC->normalForce+BC->shearForce, ...)

This is a convention issue, but must be fixed. Should normalForce and shearForce be oriented as it applies on id1 (first case) or id2 (second case)? 2nd case is nicer WRT applyForceAtContactPoint syntax, but that one is arbitrary as well.