yade-users team mailing list archive

[chiara modenese <c.modenese@xxxxxxxxx>]

2010/4/20 Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>

> On the same line : the energy dissipated by Cundall's damping in
> quasi-satic conditions is negligeable. You find that the work input from
> boundaries equals more or less plastic+elastic work at contacts (tests with
> pfc3D, damping~0.2, frictional contacts, ~50k iterations in a triaxial
> test). It corresponds with the fact that Cundall's damping looks useless in
> _some_ quasi-static conditions, after Yade simulations and discussions with
> Gaël, Vincent, and Vaclav.
>
> |Δε|*|σ| sounds straightforward, but with du and df, and non-linear
> elasticty on both normal and shear, and plasticity for fun, I have no
> initial guess... Computing the energy dissipated in
> Law2_ScGeom_FrictPhys_basic is straightforward, for sure.
> On the top of that, there is the case when plasticity==true at time "t",
> and plasticity==false at time "t+dt". You have to decompose |Δε| into
> plastic and elastic on one timestep. Straightforward again with the *_basic
> law, but with Hertz? I have no clue yet.
>
Let's take Law2_ScGeom_FrictPhys_basic law. As long as we adopt the
Mohr-Coulomb criterion to model friction, to me it is not so straightforward
to make distinction between plastic and elastic deformation. In fact, we do
not know that. In Mohr-Coulomb there is no concern about loading history.
Any thoughts?

Chiara

>
>
>
> Bruno
>
> Václav Šmilauer a écrit :
>
>  Put a "Real plasticWork" in the functor. Compute the energy dissipated at
>>> one contact on time increment dt, and include  a "plasticWork+= ..." in the
>>> if(plasticityCondition) bracket of the functor.
>>> Don't ask me how to define plastic work at contact with an elasto-plastic
>>> Hertz-based law... ;)
>>>
>>>
>>
>> I think since the formulation is incremental, you can use |Δε|*|σ| for
>> energy dissipated in plastic slip by Δε at plastic stress σ...?
>>
>> Generally, there is no unified function for dissipation. You could,
>> though, sum kinetic energy of particles, potential energy (if there is
>> some potential field), and subtract cummulative external work (boundary
>> conditions). That should give you pretty good image of system energy
>> evolution, including damping, plasticity and dissipation by numerical
>> entropy ;-)
>>
>> Cheers, v.
>>
>>
>>
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>
>
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