yade-dev team mailing list archive

[chiara modenese <c.modenese@xxxxxxxxx>]

On 6 May 2010 23:11, chiara modenese <c.modenese@xxxxxxxxx> wrote:

> Hi Bruno,
>
> could you explain me in formula how did you get the plastic dissipation for
> the friction component? I see
>
> plasticDissipation +=
> (shearDisp+(1/currentContactPhysics->ks)*(shearForce-prevForce)).dot(shearForce)
>
> Is shearDisp the total shear displacement, right? I would compute the
> dissipation incrementally, something like
>
> plasticDissipation += [delta_us + (Fs_max_current - Fs_max_prev)/ks] *
> Fs_max_current
>
> Is this the same as you did? If not where I am eventually wrong? Sorry if I
> ask..
>
> Thanks a lot,
> Chiara
>


Hi Bruno,
I am checking the formulation for the energy friction dissipation. Here it
is what you proposed (possible option, not committed yet I think):

if( shearForce.squaredNorm() > maxFs ){
          Real ratio = Mathr::Sqrt(maxFs) / shearForce.norm();
          Vector3r trialForce=shearForce;//store prev force for definition
of plastic slip
          shearForce *= ratio;
          plasticDissipation +=
          ((1/currentContactPhysics->ks)
*(trialForce-shearForce))//plastic disp.
          .dot(shearForce);//active force           }

I have one big guess. How can this formulation being incremental using
trialForce? Let's take a simple case: normal force is set to a constant
value. Then say that trialForce will increase. In this case shearForce is
the same since normal force is as well (like maintaining constant the
maximum elastic shear displacement). If any time you get the work done as
above, I would say that
1/ks*(trialForce-shearForce)
is the total plastic displacement, is it? Why do you think it is
incremental? In which way it is?

thanks, Chiara