Yves, thank you very much for your help. My problem is indeed a 2d problem. The initial configuration is a plate, and we assume the displacements function of 2 variables only, the 3th dimension of the plate is negligible versus the other dim. (I think it could be considered as a plane stress problem)
I would greatly appreciate if you could send me the written info you are mentioning regards jean-yves heddebaut Le Apr 29, 2008 à 4:56 PM, Yves Renard a écrit : > On Monday 28 April 2008 18:39, you wrote: >> Dear getfem users, >> >> I would like to reuse the non linear elasticity brick to make a >> brick representing the behavior of non linear membranes. >> The idea is to apply the Cosserat hypothesis, which gives a >> simplified Green-Lagrange strain tensor. >> >> The dimension of the vgrad term in the >> asm_nonlinear_elasticity_tangent_matrix function would be (:,2,3) iso >> (:,3,3) in the 3 dim brick, and I think I could reuse the function >> without modification. > > You mean that you have a 2D problem but with a 3D displacement ? > >> The elasticity_nonlinear_term, on the contrary, has to be adapted, >> but I do not see how to do it. >> Could anybody help me understand the logic behind the compute >> function ? >> >> here is how I understand it, please tell me where I am wrong (I am >> considering the Saint venant kirchoff hyperelastic law) >> >> 1.gradU is the gradient of the displacements, based on the preceding >> iteration displacements > > The goal is to compute the tangent matrix and the residue, so gradU > is the > gradient of the displacement of the current state (ok for preceding > iteration). > >> >> 2.E is the Green-Lagrange strain tensor, also based on the preceding >> iteration displacements > ok > >> >> 3.gradU becomes gradU+I ( deformation gradient iso displacement >> gradient ?) > yes, it is computed because the term (Id+grad U) intervene in the > expression > of weak form. this is the gradient of the deformation. > >> >> 4.tt is a tensor containing the rigidity coefficients > Yes, for version = 0 this is the tangent terms (rigidity terms) and > for > version = 1 just the term (Id+grad U) multiplied by the stress tensor. > >> >> Could somebody tell me what is done in the "version==0" loops ? > > This is the (ugly) computation of the whole tangent term. In > particular the > multiplication of a fourth order tangent tensor given by > AHL.grad_sigma(E, > tt, params). I agree that this could be simplified in practical > situations > but the goal was to make a generic computation in a first time. > >> >> I would greatly appreciate any help >> >> jean-yves heddebaut >> > > If you need more explanations, I think I have something writen > somewhere on > that particular expression. > > > Yves. > > > -- > > Yves Renard ([EMAIL PROTECTED]) tel : (33) > 04.72.43.87.08 > Pole de Mathematiques, INSA de Lyon fax : (33) > 04.72.43.85.29 > 20, rue Albert Einstein > 69621 Villeurbanne Cedex, FRANCE > http://math.univ-lyon1.fr/~renard > > --------- _______________________________________________ Getfem-users mailing list [email protected] https://mail.gna.org/listinfo/getfem-users
