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 (address@hidden) 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
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