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
