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Re: Energy dissipation

 

On 21 April 2010 15:25, Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx> wrote:

>
>
>> Doesn't the problem with different plasticity condition come into play
>> only if you store shear force instead of strain? That would break for
>> non-linear elasticity...?
>>
>>
>>
> Not sure it makes a difference. How do you define the plastic strain in
> your case? I guess it uses plastic = total - elastic, with elastic = some
> sort of  ftmax/ks (remember... ;)).
> Now, what if you cannot write elastic=ftmax/ks due to non linearity?
>
> Worth than that : unload the normal component with null shear velocity. It
> will meet the plasticity criterion at some point (assuming purely frictional
> law). Some elastic energy will be transfered to plasticity with total dUs=0.
> I see this special case only now... I'll have to tackle this even for
> FrictPhys_basic.
>

In FrictPhys we do not compute strains/stresses, so let's put everything in
terms of energy. It should not be too difficult to get the plastic work
(alias the energy dissipated). All we need, I think, is to know the shear
displacement at current and previous time step, the shear force and the
maximum shear displacement after that we slip. In formula the plastic work
would read

W_plastic = Fs*(us_t - us,max_t)

Then we can sum up the above one among all the contacts and over the
simulation time.  To compute _us,max_ should I just read

us,max_t = Fs_max/ks

per each time step (as Fn could increase, decrease.. )?

Chiara



> Bruno
>
>
>
>
>
>  v
>>
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>>
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>
> --
> _______________
> Bruno Chareyre
> Associate Professor
> Grenoble INP
> Lab. 3SR
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