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,'verynoisy')
md.enable_variable('p')
md.disable_variable('u')
md.disable_variable('lambda')
md.solve('max_res', 1E-6,'verynoisy')
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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--
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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