yade-users team mailing list archive

[chiara modenese <c.modenese@xxxxxxxxx>]

On 10 May 2010 17:43, Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx> wrote:

>
>
>> 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?
>>
>>  There is no trialFs in your figures, this is the key factor.
>
> us + (current-prev)/ks could make sense in some formulations if *=ratio was
> applied _before,_ but it is applied _after, _so that "current" is in fact
> the "trial" value (as you pointed out).
>
> OTOH, us is exactly (trialFs-prevFs)/ks, by definition of trialFs,
> (trialFs-currentFs)/ks is exactly the plastic part ,
> and (currentFs-prevFs)/ks is the elastic part.
>
> I don't see any difference between loading and unloading.


I agree that the plastic displacement is (trialFs-currentFs)/ks. However
your formulation is not incremental because you are using the trial value.
To me this would be the right procedure only in the case in which shearForce
is maintained constant. But shearForce is actually varying (right? Where do
you account for this variation in your formula?) and as I sketched in my
picture there is an elastic contribution that turns into plastic
dissipation. Can you see my point? I will find out the analytical
explanation.

Chiara

>
>
> Bruno
>
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