Who is usung these contact laws?

Hi Bruno,

If I am not wrong:

Law2_SCG_MomentPhys_CohesionlessMomentRotation is a duplicate of Law2_ScGeom6D_CohFrictPhys_CohesionMoment (but with less features than the latter)
Law2_SCG_MomentPhys_CohesionlessMomentRotation is the only Law that implements the rolling resistance using quaternions (actually there is something similar about twist_creep in Law2_ScGeom6D_CohFrictPhys_CohesionMoment) which I would not recommend as I am not sure it always gives the expected result (has anybody tested it properly?)
In principle the rolling resistance implemented in Law2_SCG_MomentPhys_CohesionlessMomentRotation does not seem to be doing anything different than what is already implemented in Law2_ScGeom6D_CohFrictPhys_CohesionMoment which, however, uses an incremental fashion (a copy of what I introduced in the Law2_ScGeom_MindlinPhys_Mindlin Law) that seems to work fine from what I gathered
Why do you say it implements irreversible rolling friction?

Finally, I would remove it if nobody is using it.

Thanks!
Chiara

On 6 Jun 2012, at 09:01, Chareyre wrote:

> New question #199540 on Yade:
> https://answers.launchpad.net/yade/+question/199540
>
> Hi all,
>
> I'd like to remove some of the contact laws which are in Yade. Some of them are unmaintained and/or broken and/or duplicates, and too many contact laws is only making the choice uneasy.
> If you are using some of the contact laws listed below, please reply to this message, else it will be removed eventually.
>
> Law2_Dem3Dof_CSPhys_CundallStrack
> Law2_Dem3DofGeom_FrictPhys_CundallStrack
> Law2_SCG_MomentPhys_CohesionlessMomentRotation
> Law2_Dem3DofGeom_RockPMPhys_Rpm
> Law2_L3Geom_FrictPhys_ElPerfPl
> Law2_L6Geom_FrictPhys_Linear
>
> More details at https://blueprints.launchpad.net/yade/+spec/cleancontactlaws
>
> --
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Please, do not remove Law2_Dem3DofGeom_RockPMPhys_Rpm

Anton

Chiara: I was remembering the discussion on elastic unloading for rolling (what I called "irreversible") but I didn't know in which law it had been implemented. You confirm that it is in Law2_SCG_MomentPhys_CohesionlessMomentRotation. In that case the law has something specific and shouldn't be removed, I think.
Concerning twist_creep, it is relatively well tested (by us). It has similarities and served as an example for rolling IIRC, but it is very different, it's the normal component of torque and it defines a viscous creep.

Anton: Ok.

On 6 Jun 2012, at 10:40, Chareyre wrote:

> Question #199540 on Yade changed:
> https://answers.launchpad.net/yade/+question/199540
>
> Chareyre posted a new comment:
> Chiara: I was remembering the discussion on elastic unloading for rolling (what I called "irreversible") but I didn't know in which law it had been implemented. You confirm that it is in Law2_SCG_MomentPhys_CohesionlessMomentRotation. In that case the law has something specific and shouldn't be removed, I think.

OK. Yes, there was a discussion but I cannot find the link to it right now. This "irreversible" behaviour happens in all the Yade Laws where the rolling is implemented so it is not specific to Law2_SCG_MomentPhys_CohesionlessMomentRotation. The details of the implementation, however, are different (use of quaternions versus incremental implementation). Do you think that this could be a good reason for keeping it?

> Concerning twist_creep, it is relatively well tested (by us). It has similarities and served as an example for rolling IIRC, but it is very different, it's the normal component of torque and it defines a viscous creep.

Yes, I understood it is different but with a similar form.

Cheers,
Chiara

>
>
> Anton: Ok.
>
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>This "irreversible" behaviour happens in all the Yade Laws where the
rolling is implemented so it is not specific to
Law2_SCG_MomentPhys_CohesionlessMomentRotation.

I was not sure of that.

> The details of the implementation, however, are different (use of
quaternions versus incremental implementation). Do you think that this
could be a good reason for keeping it?

Maybe not, if the difference is only in implementation. Boon is not
using SMR?

Bruno

On 6 Jun 2012, at 11:41, Chareyre wrote:

> Question #199540 on Yade changed:
> https://answers.launchpad.net/yade/+question/199540
>
> Status: Answered => Open
>
> Chareyre is still having a problem:
>> This "irreversible" behaviour happens in all the Yade Laws where the
> rolling is implemented so it is not specific to
> Law2_SCG_MomentPhys_CohesionlessMomentRotation.
>
> I was not sure of that.
OK.

>
>> The details of the implementation, however, are different (use of
> quaternions versus incremental implementation). Do you think that this
> could be a good reason for keeping it?
>
> Maybe not, if the difference is only in implementation.

I believe that is the only difference but I have not tested much because I started to use the incremental formulation (which I did test but versus other implementations like Plassiard's formulation - still incremental). Maybe we could keep it for future reference in case that kind of use of quaternions became useful.

> Boon is not
> using SMR?
I think he has used it a long time ago for some background analyses but nothing more than that (not sure if he still reads the mailing list so I will have to ask him about it and then let you know).

Chiara

>
> Bruno
>
> --
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>Maybe we could keep it for future reference in case that kind of use of quaternions became useful.

It's in svn/bzr/git history anyway. Nothing will be lost.

On 6 Jun 2012, at 13:55, Chareyre wrote:

> Question #199540 on Yade changed:
> https://answers.launchpad.net/yade/+question/199540
>
> Chareyre posted a new comment:
>> Maybe we could keep it for future reference in case that kind of use of
> quaternions became useful.
>
> It's in svn/bzr/git history anyway. Nothing will be lost.
Great. In which case, I suggest to remove it so to avoid confusion and/or malfunctioning due to poor testing.
Chiara

>
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