Re: Torque
by Robert Cimrman
In examples/large_deformation/hyperelastic.py a rotation by displacements is applied. By using a similar function the vectors defining the force couples could be defined for dw_surface_ltr (IMHO). Does it make sense?
r.
----- Reply message -----
From: "Andre Smit" <freev...(a)gmail.com>
To: <sfepy...(a)googlegroups.com>
Subject: Torque
Date: Sat, Dec 18, 2010 05:10
What is the best way to apply a torque load to a model?
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Andre
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1 year, 1 month
1D line elements in SfePy
by Nimish
I am currrently looking for FEM packages to help me solve a system of
beams and columns, basically a collection of 1D bernoulli/timoshenko
line elements.
I started reading SfePy docs and i am getting the idea that doing the
above is not really possible here, am i right?
Are only 2D area elements permitted in SfePy?
Or is there any direct support for solving 1D line elements too..
Cheers
Nimish
3 years, 3 months
Evaluate a solution in the arbitrary point in the domain
by Alec Kalinin
Dear SfePy users,
Is it possible to evaluate a solution not only in the FEM mesh node, but in
any arbitrary point in the domain with the given (x, y, z) coordinates?
For example, consider Dirichlet problem for Poisson equation. We apply
essential boundary conditions on the surface nodes and after the problem
has been solved we have the solution vector, i.e. vector of values in the
FEM mesh nodes. But I want to know the solution in point v(x, y, z) that is
not FEM mesh node. What is the best way to obtain solution in this point v?
Sincerely,
Alec Kalinin
5 years
elliptical hole under isotropic stress
by David N. Mashburn
Hello sfepy developers and users!
I am modelling a simple linear elastic sheet under isotropic stress with
an elliptical hole in the center (and I have it working under sfepy,
great little platform!).
It is obvious the model should initially yield more easily in the
direction of the short axis of the ellipse. What is not so obvious to me
is what should happen in the limit as stress goes to infinity. Part of
me wants to believe that the hole should eventually become a circular,
but the results of the simulation show that the ellipse eventually
switches its aspect ratio with what was the the short axis becoming the
long axis and vice-versa.
My question is whether:
A: The finite element result is the product of a
small-displacement/non-moving mesh artifact (and if so, if there is a
way to get the correct behavior using sfepy...)
OR
B: My intuition about the physical behavior of this ideal system is
incorrect and the ellipse really wouldn't round out into a circle under
increasingly large stress (aka, the FE model is still physical/correct
with large displacements).
This might be obvious to people who have done more finite element
modeling than I have, but thanks anyway! I'm attaching a picture to make
it easier to see at a glance (quarter-ellipse with x and y symmetry
boundary conditions and equal tractions applied at the top and right
boundaries).
Thanks!
-David Mashburn
5 years, 3 months
post process energy calculation
by Anastasia Konovalova
Hello, sfepy group,
I have a question about post-process calculations. For my problem I used
the modified examples linear_elastic.py and hyperelastic.py. After the
calculation of strain and stress tensors I need to get energy of
deformation
\int_{V} S : C,
where C = 2*E+I.
I think I need to calculate the multiplication of tensors first, as some
material variable, and then integrate it.
So I have 2 questions:
1. How can I calculate the double scalar multiplication of two arrays
strain and stress that have shape (number of elements, 1, 6, 1)? (Double
scalar multiplication of A and B is a scalar that can be got as
A_{ij}B_{ji}). Because of the shape of arrays I can't use
numpy.inner(stress,strain). I made some function for these calculation, but
perhaps, the simplier way exsists.
2. Then I get the multiplication - the scalar function of energy I should
integrate it. For this I get the dw_volume_integrate term. I'm trying to
integrate material parameter, where energy has been saved.
solid.update({
'E' : get_W(stress,strain),#energy in elements
})
U = problem.evaluate('dw_volume_integrate.i1.Omega(solid.E, v)',)
Or may be I should use some new variable and initialize it in post-proc.
I'm asking for help in correct formulation of this integral. Should I
define energy as material parameter or some new variable? And how I can do
it.
Thanks in advance,
5 years, 5 months
