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 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. _______________________________________________ Getfem-users mailing list address@hidden https://mail.gna.org/listinfo/getfem-users  -- Yves Renard (address@hidden) 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 ---------