On Monday, February 24, 2020 at 12:42:17 AM UTC+1, Wolfgang Bangerth wrote:
>
>
> > In my question I meant whether is it possible to evaluated plastic
> strain
> > component from currently implemented plasticity algorithm as a further
> > development of this code?
>
> I am pretty sure that it is, by just computing the difference between the
> elastic stress (C eps(u)) and the actual stress computed. In fact, for the
> current situation, the actual stress computed equal to the elastic stress
> where it is less than the yield stress (and so the plastic strain is
> zero),
> and it is simply a fraction of the elastic stress where it exceeds the
> yield
> stress. Once you have the plastic stress, you can compute the plastic
> strain
> by multiplying it by C^{-1}.
> Thank you very much Prof. Wolfgang for your suggestion and I hope you are
> doing all well. As far as I understood now from your suggestion is that on
> the base of additive decomposition, I can subtract elastic stress (C
> eps(u)) from the actual stress computed to have the plastic stress part.
> But here I just noticed in the program that we also need (eps(u)) or the
> elastic strain part to have elastic stress part's value when the domain is
> in the plastic region.
In one dimension problem there is I think no problem because from
stress strain curve one knows already the elastic stress value (which is
yield stress) but here we have multidimensional problem i.e. stress and
strain as a 2nd order tensor. Therefore I am thinking now that how this
elastic strain tensor can be evaluated to have elastic stress part to be
subtracted from total calculated stress.
One of the idea I have so far is to use the calculated "strain_tensor" to
find the elastic stress as "elastic_stress_tensor =
(stress_strain_tensor_kappa + stress_strain_tensor_mu) * strain_tensor".
But again the point is that the "strain_tensor" here is the total strain
rather than elastic strain component.
Kindly correct me if I misunderstood your suggestion at any point or if
there is an alternate approach possible. Thank you again in advance.
Stay healthy stay safe!
>
>
> > Then as a step further I would be trying to store this plastic strain in
> cells
> > or Gauss points along with the modified yield strength (due to isotropic
> > hardening) so that history of loading is stored too in the domain.
>
> I imagine that that, too, can be done. I'm not an expert in plasticity,
> but I
> see no fundamental reasons why what you want to do should not be possible.
> There are also classes CellDataStorage and TransferableQuadraturePointData
> and
> parallel::distributed::ContinuousQuadratureDataTransfer that can help you
> with
> storing information at quadrature points.
>
> Best
> W.
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: bang...@colostate.edu
> <javascript:>
> www: http://www.math.colostate.edu/~bangerth/
>
>
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