Mailman 3 January 2018 - SfePy

Material Parameters of Individual Nodes
by derj...＠web.de April 11, 2022

April 11, 2022

Hello! It's a great tool you built there! I'd like to use it for some kind of topology optimisation. Is there an "idiomatic" way to set the material parameters of individual nodes? Thank you very much! JonnyB

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Calculate total force from cauchy stress
by Patricia Garcia Cañadilla Jan. 17, 2019

Jan. 17, 2019

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), }

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Re: Torque
by Robert Cimrman March 9, 2018

March 9, 2018

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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Convergence issue with hyperelastic material
by Jan Heczko Jan. 23, 2018

Jan. 23, 2018

Hi, everyone! I have this script (attached) where a block of a hyperelastic, "almost incompressible", material is deformed uniformly. The results seem acceptable with coarse meshes (e.g. N_NODES=3, lo_mesh.png), but weird things show up with finer ones (N_NODES=10, hi_mesh.png). I've tried tweaking some solvers settings (e.g. changing `i_max` or `eps_r` etc. or switching to `ScipyIterative` linear solver), which led to some minor changes, but did not actually solve the problem. Can this be due to the solvers setting? Or is it a property of the displacement-based formulation? (i.e. would mixed formulation work better?) I also noted that the example `large_deformation/compare_elastic_materials.py` seems to converge reliably, but loading is imposed by surface tractions instead of prescribed displacements in it. Thanks, Jan

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Re: Newby question - Pb to fix BCs on a mesh from Tetgen
by Marc Saudreau Jan. 23, 2018

Jan. 23, 2018

Hi Robert, Thanks for your quick reply, your help and for the issue in Github on that specific point. All the very best Marc

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Re: Newby question - Pb to fix BCs on a mesh from Tetgen
by Marc Saudreau Jan. 23, 2018

Jan. 23, 2018

Hi Robert, I succeeded in applying my Bcs with Tetgen. Following one example you provided in the Sfepy distribution (acoustic_wg.vtk) I added to my VTK file a section: POINT_DATA number of nodes SCALARS node_groups int 1 LOOKUP_TABLE default Where I set "number of nodes" according to my mesh Then I copy all node attributes provided by the *.node file generated by Tetgen Then I use the following syntax in Sfepy: regions = { 'Omega' : 'all', # or 'cells of group 6' 'Gamma_Left' : ('vertices of group 4', 'edge'), 'Gamma_Right' : ('vertices of group 5', 'edge'), } '4' and '5' are the number I currently use to identify my BCs. And surprisingly it works ! Regions definition did not work when I use 'facet' instead or 'edge'. I wonder why, when I read the *.node file from Sfepy, the node attributes can not be used to set BCs ? All the very best Marc

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Re: Newby question - Pb to fix BCs on a mesh from Tetgen
by Marc Saudreau Jan. 23, 2018

Jan. 23, 2018

Thanks Robert for your reply. You're right: the -k option generates a VTK file. However this file do not contain any information about face colour/number. The only information about faces/facets is store in the *.face file generated by Tetgen. Can you tell me how to manage the face/facets information in VTK to be able to use them in sfepy to define my Bcs ? I will see if I can write a little program to add the face/facets information from the *.face file into the VTK file. Thanks again for your help. All the very best Marc *************************************** Marc Saudreau U.M.R. 547 PIAF (INRA-Univ. Blaise-Pascal) Centre INRA de Clermont-Fd-Theix Site de Crouël 5 chemin de Beaulieu 63039 Clermont-Ferrand Cedex 2 mob : 07.81.80.58.92 tel : 04.43.76.14.27 fax : 04.73.62.44.54 email : marc.saudreau(a)inra.fr http://www6.ara.inra.fr/piaf_eng/ http://www.uca.fr/recherche/structures-de-recherche/laboratoires/laboratoir…

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New SfePy user - materials, regions, equations - interactive vs. script modes
by Ben Melosh Jan. 12, 2018

Jan. 12, 2018

Hi I am a new SfePy user and have several questions. I have looked through the documentation and this mailing list extensively as well as many of the examples. Firstly, there seems to be differences in the code between interactive iPython mode and writing .py files. For example, the documentation of the equation block [1] is different than entering equations interactively [2]. Is there any documentation describing these differences? I would like to use both methods. I am still trying to understand how to define specific regions in the mesh and assign them specific material values. For example take the circle_in_square.mesh provided in the install, I would like to assign different material values (such as viscosity) for the circle and the square and then calculate stress and strain rate variations by applying shear stress boundary conditions. Any help and advice is appreciated, once I work through this I would be happy to contribute a beginners-beginner guide to SfePy from my experience. Ben [1] http://sfepy.org/doc-devel/users_guide.html#syntax-of-terms-in-equations [2] http://sfepy.org/doc-devel/tutorial.html#sec-interactive-example-linear-ela…

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Newby question - Pb to fix BCs on a mesh from Tetgen
by marc.saudreau＠sfr.fr Jan. 12, 2018

Jan. 12, 2018

‌Hi,  I'm trying to run a Sfepy example : poisson_short_syntax.py with a mesh coming from tetgen (see bar.node and bar.ele files). I have two groups of vertices: 4 and 5 on which I want to impose the temperature. When I use the following instruction: regions = {     'Omega' : 'all', # or 'cells of group 6'     'Gamma_Left' : ('vertices of group 4', 'facet'),     'Gamma_Right' : ('vertices of group 5', 'facet'), } The command failed because, I think,  groups are defined on nodes in my mesh and not on facets. So I change the previous instruction to: regions = {     'Omega' : 'all', # or 'cells of group 6'     'Gamma_Left' : ('vertices of group 4', 'vertex'),     'Gamma_Right' : ('vertices of group 5', 'vertex'), } In that case Sfepy runs but the solution is a T = 0 in all the domain: sfepy: left over: ['absolute_import', '__builtins__', '__spec__', 'verbose', '__doc__', '__cached__', '__file__', '__name__', 'data_dir', '_ _loader__', '__package__', '_filename'] sfepy: reading mesh [tetra4] (C:\Users\msaudreau\AnacondaProjects\bar.node)... sfepy: ...done in 0.01 s sfepy: creating regions... sfepy:     Omega sfepy:     Gamma_Left sfepy:     Gamma_Right sfepy: ...done in 0.01 s sfepy: equation "Temperature": sfepy: dw_laplace.i.Omega( coef.val, s, t ) = 0 sfepy: using solvers:                 ts: no ts                nls: newton                 ls: ls sfepy: updating variables... sfepy: ...done sfepy: setting up dof connectivities... sfepy: ...done in 0.00 s sfepy: matrix shape: (232, 232) sfepy: assembling matrix graph... sfepy: ...done in 0.00 s sfepy: matrix structural nonzeros: 2596 (4.82e-02% fill) sfepy: updating materials... sfepy:     coef sfepy: ...done in 0.00 s sfepy: nls: iter: 0, residual: 0.000000e+00 (rel: 0.000000e+00) Does someone understand what's going on ?? Thanks a lot for any help. All the very best    Marc

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Example for an explicit solver?
by Yuxiang Wang Jan. 4, 2018

Jan. 4, 2018

Dear SfePy, Greetings! I read on the arXiv paper that there is (or will be) an explicit solver (e.g. for collisions, in contrast to the iterative implicit solver) in SfePy. I wonder what is the status of that solver, or if possible, do you have a working example using the explicit time stepping method? Thank you! Shawn -- Yuxiang "Shawn" Wang, PhD yw5aj(a)virginia.edu +1 (434) 284-0836

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