yade-dev team mailing list archive

[boon chiaweng <booncw@xxxxxxxxxxx>]

Thank Bruno, for keeping me up to date with the current development.  

Just a note for others: my post didn't appear in my email inbox (hotmail), but appeared in yade-dev's mailing archive.  If u can't read it, u can read it in the archive.

Merry Christmas!


Cheers,

CWBoon   

 

> Date: Fri, 25 Dec 2009 12:22:18 +0100
> From: bruno.chareyre@xxxxxxxxxxx
> To: yade-dev@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Yade-dev] periodic cell
> 
> Thank you Boon for this summary!
> 
> It sounds perfectly in line with what we have in mind.
> 
> >                             deltaUi = deltaUi + eij xi dt
> >           where eij is the strain rate of the space, and xi is the 
> > particle coordinate
> >
> This is done in NewtonsIntegrator if proportionalStrain=1.
> >
> >     * The relative approach of velocity of two particles (used to
> >       compute force increments) is found by summing their relative
> >       real velocities and a velocity related to the strain rate of the
> >       periodic space:             
> >                         Vi (rel) = Vi (real) + eij(S)zi(diff)
> >
> This velocity is defined if proportionalStrain=2. However, there is 
> still a small problem in this case (see the comment in NewtonIntegrator).
> > The equations for servo-control to keep stress constant is :
> >        volumetricstrainrate = volumetricstrainrate + 
> > G(desiredMeanStress - measuredMeanStress)
> > where G is the 'gain' of the servo control.  No expressions are given 
> > to G.  I don't really understand.
> >
> In previous discussions, we said that G could be dt/mass_of_the_cell. 
> Cundall perhaps just used numerical experiments to find a suitable value 
> in his case.
> 
> > **
> > e1 (rate)= (2/3)shearStrainRate + volumetricStrainRate/3
> > e2 (rate) = -(1/3)shearStrainRate + volumetricStrainRate/3
> > e3 (rate) = -(1/3)shearStrainRate + volumetricStrainRate/3
> >
> As I see it, Cundall didn't tackle the case of arbitrary deformations, 
> which is the point of the current discussions, especially those related 
> to vectors and matrices representations.
> 
> Best wishes.
> 
> Bruno
> 
> 
> 
> 
> 
> 
> >
> >
> >               
> >
> >
> > > Date: Wed, 23 Dec 2009 13:48:51 +0100
> > > From: bruno.chareyre@xxxxxxxxxxx
> > > To: yade-dev@xxxxxxxxxxxxxxxxxxx
> > > Subject: Re: [Yade-dev] periodic cell
> > >
> > > Hi,
> > >
> > > I'm still not sure how to make everything consistent with all the
> > > vectors and matrices representing strain, shear, refSize, _size, Hsize,
> > > etc. It is more a question of maths than implementation, in some 
> > cases I
> > > don't know how to define the vector representation properly.
> > >
> > > I'll focus on periodic compressors for now (strain control using mass),
> > > I see most of the integration is/can be done here. We can decide later
> > > what needs to be kept in Cell or not.
> > >
> > > Bruno
> > >
> > >
> > >
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> 
> -- 
>  
> _______________
> Chareyre Bruno
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> 
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