SfePy January 2012

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output nodal values to vtk
by freevryheid 10 Jan '12

10 Jan '12

I'm getting a 'not implemented' error here. What am I doing wrong? pb and mesh attached.

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Problems with PNG export
by Torsten Bronger 06 Jan '12

06 Jan '12

Hallöchen! I'd like to convert a VTK to a PNG without user interaction, i.e. no Mayavi window. I tried offscreen=True as a parameter for the viewer, but this leads to The program 'python' received an X Window System error. This probably reflects a bug in the program. The error was 'GLXBadContextTag'. (Details: serial 71 error_code 175 request_code 155 minor_code 5) (Note to programmers: normally, X errors are reported asynchronously; that is, you will receive the error a while after causing it. To debug your program, run it with the --sync command line option to change this behavior. You can then get a meaningful backtrace from your debugger if you break on the gdk_x_error() function.) You can test it with linear_elasticity.py of the release, and add the offscreen=True parameter. I don't want to create a bug report before I'm sure that I used this parameter properly, as I only derived it from the source code. Tschö, Torsten. -- Torsten Bronger Jabber ID: torsten...(a)jabber.rwth-aachen.de or http://bronger-jmp.appspot.com

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Re: Getting tension for each finite element
by Robert Cimrman 06 Jan '12

06 Jan '12

Hi Torsten! Look at the SfePy Primer [1], specifically the post-processing section. In short, you need to define a function ('post_process_hook' option in input file) that computes derived quantities from the computed variables (e.g. strain or stress from displacements). Let us know how it goes. Cheers, r. [1] http://docs.sfepy.org/doc-devel/primer.html ----- Reply message ----- From: "Torsten Bronger" <torsten...(a)gmail.com> To: <sfepy...(a)googlegroups.com> Subject: Getting tension for each finite element Date: Tue, Dec 20, 2011 22:22 Hallöchen! I used linear_elasticity.py as a starting point for simulating stress in thin silicon layers. My manual meshing worked, and the displacements seem to be calculated properly. However, how do I get the stress in each element? I need it for determining where the layer will break. The original node positions of the mesh are totally relaxated (no tension anywhere). Tschö, Torsten. -- Torsten Bronger Jabber ID: torsten...(a)jabber.rwth-aachen.de or http://bronger-jmp.appspot.com -- 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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Re: Digest for sfepy...@googlegroups.com - 2 Messages in 1 Topic
by Tom Aldcroft 05 Jan '12

05 Jan '12

On Thu, Jan 5, 2012 at 5:46 AM, <sfepy...(a)googlegroups.com> wrote: > Today's Topic Summary > > Group: http://groups.google.com/group/sfepy-devel/topics > > Modeling an adjustable X-ray optic [2 Updates] > > Modeling an adjustable X-ray optic > > Tom Aldcroft <tald...(a)gmail.com> Jan 04 08:31AM -0800 > > 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 > > > > Robert Cimrman <cimr...(a)ntc.zcu.cz> Jan 04 06:36PM +0100 > > Hi Tom! > > On 01/04/12 17:31, Tom Aldcroft wrote: >> 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. > > Looks like an interesting problem for SfePy. > >> 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... > > No problem, ask as you need, I will try to answer. But first I have some > questions as well :) > >> - Is SfePy appropriate for this problem? > > I guess so - could you be more specific what kind of equations you need to > solve? Something like [1]? Is the problem linear? Yes, the problem is linear. As for the specific equations to be solved, this should be standard linear elastic shell (2-d) formulation, but I don't have experience in actually solving the equations with real inputs and boundary conditions. To be more concrete, I want to solve for the bending of a thin plate due to an attached piezo: http://en.wikipedia.org/wiki/File:Piezo_bending_principle.jpg In our problem each piezo actuator is small compared to the mirror surface, about 10% of the size in each dimension. I'm not really interested in the details of the voltage potential (as in [1]), but instead just the effect of the piezo as a bending actuator to control the mirror surface. > >> 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? > > So the problem is in 2D, right? How many unknowns per grid node? This again > would depend on equations and hence the matrix. If there is a good linear > solver available (e.g. like for Poisson equation or elasticity), I would say > minutes or less. Yes, 2D. Well, technically it is 3D structure (the surface of a cylinder) but it satisfies the requirements for a thin plate structure and only requires a 2D mesh. A time of minutes is great. >> - 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. > > Like in [2], i.e., use dw_surface_ltr term on the appropriate boundary. > >> - Is there a way to specify the problem and solve in cylindrical >> coordinates? This is the natural coordinate system. > > Not per se, but it would IMHO be quite easy to add special terms for this. I guess if the problem can be specified and solved in Cartesian coordinates then it's easy enough to transform to cylindrical at the end. I'm not sure if a plate formulation is specified everywhere in terms of the in-plane and out-of-plane coordinates or if it is in fixed cartesian coords. >> - How do I specify 6-DOF constraints which correspond to the mirror >> mounts? > > Please clarify here a bit - what are exactly the DOFs you need to specify? > In > general, one specifies any DOFs using the ebcs keyword - look at any > example. I'm thinking of the case where the mount constrains all displacements and rotations at the mount point to a fixed value. Maybe I'm thinking about the problem incorrectly, but in our current model outputs there are 6 DOF (x,y,z, theta_x, theta_y, theta_z) at each point. > Thanks for your interest, I would like to see some nice SfePy applications > outside of my workplace. Excellent, I'm excited to use SfePy and would be happy to provide the code and some outputs as another documentation example when it's done. Thanks, Tom > Cheers, > r. > > [1] http://docs.sfepy.org/doc-devel/examples/piezo_elasticity/piezo.html > [2] > http://docs.sfepy.org/doc-devel/examples/linear_elasticity/linear_elastic_t… > > > > You received this message because you are subscribed to the Google Group > sfepy-devel. > You can post via email. > To unsubscribe from this group, send an empty message. > For more options, visit this group. > > -- > 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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EPD 7.2 full version (Academic use license)
by Md. Golam Rashed 05 Jan '12

05 Jan '12

Full EPD 7.2-1 can be downloaded from this link- http://download.enthought.com/epd_7.2/ License: "The academic version of EPD is a fully functional installation of the software that can be used indefinitely by students and employees at degree-granting institutions." so i guess we all can use it from the above link.

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primer update
by Robert Cimrman 03 Jan '12

03 Jan '12

Hi! I have implemented the concentrated point load term and updated primer accordingly - the analytical solution is really analytical now, and mesh refinement helps to converge to that solution as expected. Check it out, please, at [1], and report back any problems/errors/typos you find. r. [1] http://docs.sfepy.org/doc-devel/primer.html

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Progress Bar
by Md. Golam Rashed 02 Jan '12

02 Jan '12

As analysis takes quite some time, it'll be helpful if there is a progress bar or progressing % showing. example: progress 1% progress 2% progress 3% . . . . . . progress 15% . . etc. this feature will really help large problem. is it possible to integrate this feature into sfepy??? Thanks

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SfePy January 2012