yade-users team mailing list archive

[chiara modenese <c.modenese@xxxxxxxxx>]

On 10 May 2010 10:33, Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx> wrote:

>
>
>>    > plasticDissipation +=
>>
>>  (shearDisp+(1/currentContactPhysics->ks)*(shearForce-prevForce)).dot(shearForce)
>>
>>
>> If the increment is fully plastic, prevForce is the max_previous but
>> shearForce is not yet equal to the max_current value since you set
>>
>> shearForce *= ratio
>>
>> only after having determined the plasticDissipation. Is this correct?
>>
>>  You are right, there is some nonsense, I've been mixing two different
> formulations (also : the dot product is using the "trial" shearForce, and
> shear disp. is counted twice...).
>
> Would it be better that way (same as Vaclav's formula for stress/strain in
> the same thread)? :
>
>
> 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           }


Hi Bruno, please see attached file. I am not completely sure but I think it
would be correct to distinguish between loading and unloading phase. I am
trying to prove it analytically, I am not yet totally confident.. What do
you think?

Chiara

>
>
> Bruno
>
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Attachment: plastic.pdf
Description: Adobe PDF document