> Hi V., if I correctly understood, the shear force (the incremental > one) behaves as you describe, but the TOTAL shear force (the one that > we store in the simulation) is really expressed in the global system > (right?).
(let's suppose that https://bugs.launchpad.net/yade/+bug/493102 is solved for the rest of this discussion) shearForce (the total, current one) is defined for interaction (not for particle), in global coordinates. Now, let's say shearForce is (-1,-1,-1), and that we have 2 bodies, A and B, which are assigned to id1 and id2. It means that you apply (-1,-1,-1) to A (id1) and -(-1,-1,-1)=(1,1,1) to B (id2). If you swap the particles (A=id2, B=id1), then shearForce will be computed in the inverse sense: See e.g. ScGeom::updateShear (or updateShearForce), where it is clear: normal is already inverse (always from id1 to id2), then everything is symmetric for id1 and id2 (therefore the same if you swap id1/id2); relativeVelocity will be inverted, so will be shearVelocity, shearDisplacement and shearIncrement / shearForce increment. (This will happen similarly in Dem3DofGeom, but it is less obvious to follow in the code) With swapped particled (A=id2, B=id1), therefore, shearForce will be (1,1,1). But we apply now (1,1,1) to B (which is now id1) and (-1,-1,-1) to A (which is now id2). So you see real forces on bodies are the same. > Moreover if my external force on the particle is in one direction, I > would always expect an opposite sign for the total shear force (we > oscillates around the same value but the sign should always be > opposite to it). Sorry, I am not clear as to what you mean here. HTH, Vaclav _______________________________________________ Mailing list: https://launchpad.net/~yade-dev Post to : [email protected] Unsubscribe : https://launchpad.net/~yade-dev More help : https://help.launchpad.net/ListHelp
