yade-dev team mailing list archive

[chiara modenese <c.modenese@xxxxxxxxx>]

On 28 April 2010 16:19, chiara modenese <c.modenese@xxxxxxxxx> wrote:

>
>
> 2010/4/8 Václav Šmilauer <eudoxos@xxxxxxxx>
>
> > I need the incremental formulation for the normal force in the contact
>> > law. Could you tell me how to do that? Should I simply used the
>> > normalVelocity component computed at contact as we do for the shear
>> > force? What about the sign convention? Should it remain the same,
>> > right?
>> Using relative velocity (it will be much easier than for shear, since it
>> is 1D) would be the simplest, it seems.
>>
>> Or if you want to go more precise, you could store previous normal
>> deformation, then compute the current one (total formulation), divide by
>> Δt to get increment and add it to previous incremental normal
>> deformation... Perhaps too complicated...
>>
>
> Hi,
> if I get the incremental displacement in the normal direction as
>
> dU(t+dt) = U(t+dt)-U(t)
>
> where U(t+dt) and U(t) are total formulation, it is fine or should I take
> into account the rotation of the normal?
> (btw, it is the incremental formulation that will permit me to calculate
> the potential elastic energy for the non linear elastic Hertz formulation in
> the normal direction..)
>
> thanks, Chiara
>

Suggestion (x Bruno). Why do not we add the incremental formulation for the
normal direction (say as optional) in the FrictPhys_Basic law so that the
potential energy can be computed directly inside the go functor instead of
having an external loop as you did? Moreover as elastic energy is computed
now, it would be fine for the normal direction but you are also adding the
component due to the shear force without considering that sliding could
occur (so in that case you cannot more compute E simply as Fs*us, you need
the difference between the total energy and the plastic one). One more
reason to compute the incremental formulation in the normal direction.
Energy computations are not superfluos since they can help to understand how
the system evolves..

Chiara



>
>>
>> Cheers, v.
>>
>>
>>
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