yade-dev team mailing list archive

[chiara modenese <c.modenese@xxxxxxxxx>]

On 8 April 2010 09:46, Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx> wrote:

>
>  I need the incremental formulation for the normal force in the contact
>>> law. Could you tell me how to do that?
>>>
>> What is the problem exactly? You have the equation but you don't know how
> to implement it, or you have no equation?
> Why do you need the incremental formulation? Do you have irreversible
> non-linearities?

Hi Bruno,
I would need the incremental formulation because I need to make distinction
between loading and unloading stage. Do you see other ways to do that?
Anyway not sure that the incremental formulation is the solution of my
problem..

>
>
>   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?
>>>
>>>
>> Yes and yes.
>
>
>  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...
>>
> Mmmmh... It is not so complicated but wouldn't it be exactly the same?
> Un(t+dt)=Un(t) + dt[(Un(t+dt)-Un(t))/dt]?
> Or the rotation of the normal makes the difference? In that case I'd store
> the previous Un and use the increment dUn=U(t+dt)-U(t) as you suggest.
>
> Perhaps this would be actually the easiest method, not the most
complicated. Thanks for suggestions.

>
> Bruno
>
>
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