SfePy October 2018

sfepy@python.org

6 participants
8 discussions

Calculate total force from cauchy stress

by Patricia Garcia Cañadilla

Dear Robert, I have a 2D body of hyperelastic material which contracts and I would like to compute the total force developed by the body from the cauchy stress. I am trying to follow some of your indications I found in this group, but I still couldn't make it works. Could you please help me to fix the problem? I am getting the following error: key = (region.name, integral.order, integration) AttributeError: 'dict' object has no attribute 'name' I am trying to do the following, inside stress_strain post-processing function: def stress_strain(out, problem, state, extend = False ): from sfepy.base.base import Struct from sfepy.mechanics.tensors import StressTransform from sfepy.mechanics.tensors import transform_data from sfepy.discrete.common.mappings import get_normals ev = problem.evaluate field = problem.fields['displacement'] region = problem.domain.regions['Gamma'] integral = problem.integrals['i2'] n = get_normals(field,integral,regions) stress = ev('dw_tl_fib_a.1.Omega(f1.fmax, f1.eps_opt, f1.s, f1.fdir, f1.act, v, u )',mode='qp', term_mode= 'stress'); F = ev('ev_def_grad.1.Omega(u)',mode='el_avg'); transform = StressTransform(F) Cstress = transform.get_cauchy_from_2pk(stress) T = Cstress*n; Force = ev('ev_surface_integrate.2.Gamma(T)') And here it is part of the problem configuration file. fields = { 'displacement': ('real', 'vector', 'Omega', 1), } materials = { 'solid' : (None, 'get_elastic_pars'), 'load' : (None, 'linear_tension'), 'f1' : 'get_pars_fibres1', } variables = { 'u': ('unknown field', 'displacement', 0), 'v': ('test field', 'displacement', 'u'), } regions = { 'Omega' : 'all', 'Fix1' : ('vertices in x < %.10f' % (fix_point + eps2), 'facet'), 'Fix2' : ('vertices in x > %.10f' % (fix_point - eps2), 'facet'), 'Fix' : ('r.Fix1 *v r.Fix2', 'facet'), 'Gamma' : ('vertices of surface','edge'), } ebcs = { 'fixb' : ('Fix', {'u.all' : 0.0}), } integrals = { 'i1' : ('v', 1), 'i2' : ('s', 2), }

1 year, 5 months

Navier - Stokes at high viscosity

by Ben Melosh

I am trying to model Stokes flow at very high viscosities (~10^20), from my results it looks like I cannot achieve this and am better suited using viscosities of ~10^5 or so. I know there is this older post [1] which states: "A word of warning though: SfePy does not have a dedicated Navier-Stokes solver (the Newton (+ and direct) solver use that is in the navier_stokes.py example is rather naive, and works for small problems with only, with viscosity "high enough")" Has there been a different solver implemented since this was posted? If not, what do you recommend to work with such large viscosities? Thank you [1] "Problem with the mesh while trying to solve the Navier Stokes equations with sfepy"

1 year, 8 months

Contributing to sfepy development

by Amine Aboufirass

Dear All, I am a python developer interested in contributing to the sfepy project. There is quite a bit of material in the "How to contribute" page ( http://sfepy.org/doc-devel/developer_guide.html#how-to-contribute). So far I have been able to : - fork repository to my github account - clone forked repository into my local computer - look through issues in sfepy github page for opportunities to help resolve salient issues. I am thinking about this one in particular https://github.com/sfepy/sfepy/issues/367 - Look into forking workflow in Atlassian website ( https://www.atlassian.com/git/tutorials/comparing-workflows/forking-workflow ) - Pursue basic git tutorials. so far I have only experience working with svn vcs. I am confused abut how to properly set up a standalone sfepy development environment in conda. Of course installing a regular environment is easy *conda install -c conda-forge sfepy* The above command seems to take care of all dependencies, including the python installation itself. However I don't understand how this can be combined with *git clone *such that I can install the cloned fork within conda environment. How are the dependencies handled? What of the python version dependency? I do not see these anywhere in the repository, it seems to only contain sfepy scripts and modules. Thanks for your consideration and look forward to hearing from you. Best Regards, Amine

1 year, 8 months

Mailman

by Phung Huynh Ngoc

PhungGroup

1 year, 8 months

Set and Group based regions( was Re: Re: Back after 6.5 years. ;-) )

by Steve Spicklemire

OK! Thanks so much Robert. I’ve got things back to more or less where they were. One issue I think I never sorted out before was handling boundary conditions in a clean way. I’d like to be able to specify regions symbolically. I see in the docs there’s a concept of vertices in a “group” or “set” but I’m not sure how to create a .geo file that has either “groups” or “sets” defined by lines or points. Can anyone point me to the docs describing how to do this? thanks! -steve Robert Cimrman wrote: > Hi Steve, > > Welcome back :) >

1 year, 8 months

Coupled phase field and linear elasticity

by Daniel Wheeler

Hi, I'd like to try and solve the problem outlined here, https://pages.nist.gov/pfhub/benchmarks/benchmark4.ipynb/ Is this a problem that Sfepy could handle? I'm assuming the elasticity part of the problem would be straightforward, but what about a fourth order phase field equation? Given that it's tractable are there examples that match the form of the elasticity equation and/or any Cahn-Hilliard type examples for Sfepy? Cheers, Daniel -- Daniel Wheeler

1 year, 9 months

Beginning sfepy through conda installation

by Anil Kunwar

Dear All, I installed sfepy in Ubuntu computer using : conda install -c conda-forge sfepy command, after that I downloaded sfepy by cloning from github. I am trying to run the examples. If I am within the sfepy environment in conda, then how can I execute an input file completely? For example, I run the cube.py using : (mysfepyenv).../path/to/cube.py/directory$ sfepy-run simple cube.py How can I postprocess it? Is it something like this: (mysfepyenv).../path/to/cube.py/directory$ sfepy-run postproc cube.py When I do this, it yields the following message: ModuleNotFoundError: No module named énthought' ... ModuleNotFoundError: No module named 'traits' ... How do I install them? Yours Sincerely, Anil Kunwar

1 year, 9 months

Back after 6.5 years. ;-)

by steve＠spvi.com

Hi SfePy folks, I worked on a couple problems using sfepy 6.5 years ago, and then drifted away. Today I tried to run my old code using the latest SfePy and it's mostly broken. ;-( What is the best way to see what's changed since 2012 and how one should go about updating code from that time? thanks! -steve

1 year, 9 months

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SfePy October 2018