Dear David,
When a variable is disabled, this just means that it is in fact
considerered as a data. So you can of course use set_variable on it to
change its value. Or may be I misunderstood you question.
You an also enable or disable a brick, so that you can have two versions
of your brick and switch from one version to another.
Best regards,
Yves.
Le 20/01/2016 13:45, David Danan a écrit :
> I see, thank you for your answer. In that case, i have another
> question in the continuation of this one.
>
> In order to reproduce these convexification iterations, i have to
> solve a sequence of problems where the coefficient of friction is
> fixed at each iteration.
> The following small piece of code is used for the friction
>
> md.add_filtered_fem_variable('p', mflambda_C, CONTACT_BOUNDARY);
> md.add_linear_generic_assembly_brick(mim_c,
> '(u-(u.N1)*N1-p).(Test_p)', CONTACT_BOUNDARY);
> md.add_nonlinear_generic_assembly_brick(mim_c,
> '(1/r)*Coulomb_friction_coupled_projection(lambda, N1, u, gap-u.N1,
> (fric_max-fric_min)*exp(-alpha_fric*Norm(p))+fric_min,
> r).Test_lambda', CONTACT_BOUNDARY);
>
> where u and lambda are the other variables of the problem. This
> problem is solved by the partial solve mechanism, as you suggested
>
> md.disable_variable('p')
> md.solve('max_res', 1E-6,'very noisy')
> md.enable_variable('p')
> md.disable_variable('u')
> md.disable_variable('lambda')
> md.solve('max_res', 1E-6,'very noisy')
> P=md.variable('p')
>
> For the next problem, i would like to delete the first brick and add a
> new one where the "p" is replaced (in the function
> Coulomb_friction_coupled_projection) by the tangential displacement
> obtained in the previous iteration. Is such a thing possible? In other
> world, is it possible to replace a variable by a data vector defined
> by the user (something halfway between set_variable and disable)?
>
> If it is not, is there another effective way to "update" the
> coefficient of friction?
>
> Thank you in advance.
> David.
>
> -----E-mail d'origine-----
> De : Yves Renard <[email protected]>
> A: David Danan <[email protected]>; getfem-users <[email protected]>
> Envoyé le : Je, 14 Jan 2016 13:28
> Sujet : Re: [Getfem-users] Non convex problems and Getfem solver
>
>
> Dear David,
>
> There is no specific treatment for non-convex problems in GetFEM. The
> default solver is a pure Newton-Raphson algorithm (with a line-search
> of course) on the whole coupled problem. Of course, it is possible
> to adapt some other particular strategy for specific situations. This
> can be done adapting the default solver or using the existing
> mechanism of partial solve for instance (or by the use of several
> model objects).
>
> Best regards,
>
> Yves.
>
>
> Le 13/01/2016 09:38, David Danan a écrit :
>
> Dear users,
>
> i would like to know whether the Getfem solver can handle
> non-convex problems, let's say for instance a Signorini problem
> with a non monotone friction law where the coefficient of friction
> is described by
> \mu(\|\dot{\bu}_\tau\|)=(a-b)\cdot e^{-\alpha\|\dot{\bu}_\tau\|}
> +b, where a,b, \alpha >0 et a\geq b.
>
> If it is, what kind of procedure is used with the Newton
> iteration? Convexification iteration ( fix the value of the
> coefficient of friction, in that case, at each "Convexification "
> iteration to a given value depending on the tangential slip rate
> found in the previous iteration) ? Something else?
> Thank you in advance.
> David.
>
>
> _______________________________________________
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> [email protected]
> https://mail.gna.org/listinfo/getfem-users
>
>
>
> --
>
> Yves Renard ([email protected]) tel : (33) 04.72.43.87.08
> Pole de Mathematiques, INSA-Lyon fax : (33) 04.72.43.85.29
> 20, rue Albert Einstein
> 69621 Villeurbanne Cedex, FRANCE
> http://math.univ-lyon1.fr/~renard
>
> ---------
--
Yves Renard ([email protected]) tel : (33) 04.72.43.87.08
Pole de Mathematiques, INSA-Lyon fax : (33) 04.72.43.85.29
20, rue Albert Einstein
69621 Villeurbanne Cedex, FRANCE
http://math.univ-lyon1.fr/~renard
---------
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