SfePy March 2013

sfepy@python.org

6 participants
12 discussions

Re: Torque
by Robert Cimrman 09 Mar '18

09 Mar '18

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? -- Andre -- You received this message because you are subscribed to the Google Groups "sfepy-devel" group. To post to this group, send email to sfepy...(a)googlegroups.com. To unsubscribe from this group, send email to sfepy-devel...(a)googlegroups.com. For more options, visit this group at http://groups.google.com/group/sfepy-devel?hl=en.

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1D line elements in SfePy
by Nimish 22 Jan '16

22 Jan '16

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

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Evaluate a solution in the arbitrary point in the domain
by Alec Kalinin 03 Apr '14

03 Apr '14

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

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elliptical hole under isotropic stress
by David N. Mashburn 13 Jan '14

13 Jan '14

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

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possible GSoC project ideas
by Robert Cimrman 07 Jun '13

07 Jun '13

Hi, we are trying to sign up under the PSF umbrella for this year's Google Summer of Code because of an e-mail from Ankit Mahato, who expressed interest to help developing SfePy as his GSoC project this summer. So let us discuss possible project ideas here. I will post results of the discussion to [1]. Ankit's ideas are (my summary): #1 parallelization - cluster support using mpi4py #2 pre- and post-processing GUI frontend #3 incorporating phase changing materials (his research area) Ankit, could you post full text your ideas into this thread? The pdf you sent me does not allow selecting text. My comments: For me, #1 is something that I was planning to do "soon" anyway as I am going to need it for my research work - a help would come really handy, but we will have to think carefully about the implementation. I think I prefer having a parallel layer above the current serial FEM, so that the current code can stay as it is, unaware that it runs in parallel. I am not sure yet how difficult it is going to be, but it won't be trivial. #2 would be nice, but IMHO it is not so important as having a solid and reasonably fast FEM core. #3 would IMHO be the most useful for Ankit, and a nice addition to modelling capabilities of SfePy. Other possible topics can be found in our issues list ("enhancement" label). IMHO it would be good to prospective student(s) to try tackling some of the issues listed below to get acquainted with SfePy code before the GSoC starts: #196 Document properly term evaluation modes and postprocessing/probing. #195 describe how to add Neumann BC in a diffusion example and tutorial (tutorial part done by Alec) #167 improve gallery page #164 Python 3 compatibility #154 automatic testing of terms #140 test schroedinger.py #133 Provide examples for SfePy Terms Implementing the other enhancements would be, of course, also very useful, but those IMHO too difficult for someone trying to learn the code. They are certainly quite difficult for me, as they are not done yet =:) (shell elements!) Cheers, r. [1] http://sfepy.org/doc-devel/development.html

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Modeling an adjustable X-ray optic
by Tom Aldcroft 21 May '13

21 May '13

I'm working on modeling a next-generation X-ray mirror for which the shape can be actively controlled by use of many thin piezo-electric actuators mounted on the mirror surface. The mirror is basically a glass conical paraboloid with a 1 meter radius and 200 micron thickness (e.g. http://en.wikipedia.org/wiki/X-ray_optics). Our project is currently using a proprietary FEA package, but the model setup and turnaround time is slow, in part because there is only one part-time engineer who can run it. SfePy looks like a great package and we're hoping that it could be used to automate running a large number of different cases. I've spent some time reading the documentation but I have a few questions that I hope can be answered before going too much further. I want to apologize in advance if some of my wording is imprecise, I have a physics background but this topic is a bit outside my realm... - Is SfePy appropriate for this problem? - If a specify a grid with about 800 x 400 points (azimuthal, axial) and about 10 boundary conditions (corresponding to mount points), what is the rough order of magnitude of time to compute the solution? Is it seconds, minutes, hours, or days? - The linear elastic examples show a problem with a specified displacement. How do I specify an input force? The piezo essentially provides a tensile force along the surface. - Is there a way to specify the problem and solve in cylindrical coordinates? This is the natural coordinate system. - How do I specify 6-DOF constraints which correspond to the mirror mounts? Thanks in advance for any help! Tom Aldcroft

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Finding the right surface term for a diffusion problem
by Ben Derrett 02 Apr '13

02 Apr '13

Hello, In the weak formulation of my problem (a 2D diffusion problem), I have the term \int_{\Gamma^N} p\nabla V\cdot M n where \Gamma^N is region where Neumann BC is applied, p is a test function, V is the unknown function, M is a 2x2 matrix and n is the normal vector. Has an SfePy term been written corresponding to this? Alternatively, is there a SfePy term corresponding to the integral \int_{\Gamma^N} p\nabla V\cdot q, where q is a vector? I saw the term dw_surface_lcouple, but it doesn't seem to support the weak evaluation mode. Thanks, Ben

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Using postproc.py with the --watch option
by Ben Derrett 26 Mar '13

26 Mar '13

Hello, As I understand it, using postproc.py with the --watch option should update the view when the results file changes. I ran the command ./postproc.py -w rectangle_fine_quad.vtk > and then changed rectangle_fine_quad.vtk, but the view did not update itself. What do I need to do to get it to work? (I'm using SfePy 2012.4-git-59ad3cfd5a2f66f9ce56aa15656906920c4ccdfe and Mayavi 4.2.0.) (This option seems useful since you could watch how the visualization changes as you change your PDE. Perhaps it should be enabled by default.) Regards, Ben

2 3

setup.py install missing something?
by steve 24 Mar '13

24 Mar '13

Hi Folks, I'm trying to update to 2013.1 (thanks BTW for the update!). OSX 10.8. Strangely, if I try to install globally I'm getting: sfepy: WARNING: module /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sfepy/terms/termsMass.py cannot be imported! sfepy: reason: 'module' object has no attribute 'dw_mass' Traceback (most recent call last): File "simple.py", line 19, in <module> from sfepy.applications import PDESolverApp File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sfepy/applications/__init__.py", line 2, in <module> from pde_solver_app import PDESolverApp, solve_pde, assign_standard_hooks File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sfepy/applications/pde_solver_app.py", line 6, in <module> from sfepy.fem import ProblemDefinition File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sfepy/fem/__init__.py", line 20, in <module> from problemDef import ProblemDefinition File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sfepy/fem/problemDef.py", line 25, in <module> from sfepy.solvers.ts import TimeStepper File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sfepy/solvers/__init__.py", line 14, in <module> OptimizationSolver], package_name='sfepy.solvers') File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sfepy/base/base.py", line 1061, in load_classes mod = import_file(filename, package_name=package_name) File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sfepy/base/base.py", line 149, in import_file mod = __import__('.'.join((package_name, name)), fromlist=[name]) File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sfepy/solvers/__init__.py", line 14, in <module> OptimizationSolver], package_name='sfepy.solvers') File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sfepy/base/base.py", line 1061, in load_classes mod = import_file(filename, package_name=package_name) File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sfepy/base/base.py", line 149, in import_file mod = __import__('.'.join((package_name, name)), fromlist=[name]) File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sfepy/solvers/generic.py", line 5, in <module> from sfepy.fem import ProblemDefinition ImportError: cannot import name ProblemDefinition But if I "build_ext --inplace" and run from the source directory... it works. ?? Any idea what I've done wrong? thanks, -steve

3 3

ERROR: Traits
by Angel Goñi Moreno 21 Mar '13

21 Mar '13

Hi, I am new to SfePy, After installing everything, I run $ ./simple.py examples/diffusion/poisson.py as the tutorial says. The file cylinder.vtk is created. Then I run ./postproc.py cylinder.vtk but when I do so I get the next error: *traits.trait_errors.TraitError: The 'current_scene' trait of an Engine instance must be a Scene or None, but a value of <enthought.mayavi.core.scene.Scene object at 0xc6ff6b0> <class 'enthought.mayavi.core.scene.Scene'> was specified.* I can run mayavi first and then load the file cylinder.vtk but it shows the cylinder all blue and not as in the tutorial online. Any help will be much appreciated!! Cheers! Angel.

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SfePy March 2013