yade-dev team mailing list archive

[luc scholtes <lscholtes63@xxxxxxxxx>]

Hi Bruno :)

>From my few tests, it seems that the problem is in the computation for the
moment law (everything goes fine when the moment is desactivated), and, from
this part, CFpm is exactly the same as CohesivefrictionalContactLaw. Have
you tested your law with the moment?

I'm going to test it with and without Eigen in order to try to find out.

  Luc

ps: was the bug you fixed related to the moment computation?

2010/5/26 Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>

> Hi Luc,
>
> I've took care of TTWater recently (well, the problems were not due to
> eigen anyway).
> For CohesivefrictionalPM, could you compare with and without eigen? Is it
> really similar to CF law?
> We fixed a crash in CF law a few days ago. CohesiveTriaxialTest looked
> correct after a quick look at results but I didn't check details.
> How do you see there is a problem (sorry but I don't know what I should
> read in the code you pasted)?
>
> Bruno
>
> luc scholtes a écrit :
>
>> Hi Anton,
>>
>> Thank you for the link.
>>
>> After few tests, it seems that CohesivefrictionalPM does not work in its
>> actual version (is it related to Eigen?...). More particularly, it seems
>> that the problem comes from the part related to the moment rotation law (see
>> the concerned code below). I know that it is a pity to have copy/paste this
>> code from Bruno's work on CohesivefrictionalContactLaw, but I cannot see
>> where is the problem (I tried to follow all the wm3->Eigen conversions, and
>> it seems ok).
>>
>> Does anibody have any suggestion? I am stucked...
>>
>>  Luc
>>
>>
>>    /* Moment Rotation Law */
>>    // NOTE this part could probably be computed in ScGeom to avoid
>> copy/paste multiplication !!!
>>    Quaternionr delta( b1->state->ori *
>> phys->initialOrientation1.conjugate() *phys->initialOrientation2 *
>> b2->state->ori.conjugate()); //relative orientation
>>    AngleAxisr aa(angleAxisFromQuat(delta)); // axis of rotation - this is
>> the Moment direction UNIT vector; angle represents the power of resistant
>> ELASTIC moment
>>    if(aa.angle() > Mathr::PI) aa.angle() -= Mathr::TWO_PI; // angle is
>> between 0 and 2*pi, but should be between -pi and pi
>>         phys->cumulativeRotation = aa.angle();
>>         //Find angle*axis. That's all.  But first find angle about contact
>> normal. Result is scalar. Axis is contact normal.
>>    Real angle_twist(aa.angle() * aa.axis().dot(geom->normal) ); //rotation
>> about normal
>>    Vector3r axis_twist(angle_twist * geom->normal);
>>    Vector3r moment_twist(axis_twist * phys->kr);
>>         Vector3r axis_bending(aa.angle()*aa.axis() - axis_twist); //total
>> rotation minus rotation about normal
>>    Vector3r moment_bending(axis_bending * phys->kr);
>>    Vector3r moment = moment_twist + moment_bending;
>>
>>    Real MomentMax = phys->maxBend*std::fabs(phys->normalForce.norm());
>>    Real scalarMoment = moment.norm();
>>
>>    /*Plastic moment */
>>    if(scalarMoment > MomentMax)
>>    {
>>      Real ratio = 0;
>>      ratio *= MomentMax/scalarMoment; // to fix the moment to its yielding
>> value
>>      moment *= ratio;             moment_twist *=  ratio;
>>      moment_bending *= ratio;
>>    }
>>
>>    phys->moment_twist = moment_twist;
>>    phys->moment_bending = moment_bending;
>>         rootBody->forces.addTorque(id1,-moment);
>>    rootBody->forces.addTorque(id2, moment);
>>
>> or maybe from the
>>
>>
>> 2010/5/26 Anton Gladky <gladky.anton@xxxxxxxxx <mailto:
>> gladky.anton@xxxxxxxxx>>
>>
>>
>>    Hi, Luc!
>>
>>    Have a look here:
>>    https://yade-dem.org/wiki/Wm3%E2%86%92Eigen
>>
>>    Eigen is a actively developed mathematical library. Wm3 is, as I
>>    know, does not develops now. Eigen gives a great functionality
>>    through API and well-supported.
>>    ______________________________
>>
>>
>> ------------------------------------------------------------------------
>>
>>
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>
>
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> Bruno Chareyre
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> Grenoble INP
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