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From: Rafael Vazquez <vazquez@im...>  20111117 08:17:14

Dear Fei Duan, thank you very much for your suggestion. I agree with you that it would be nice to have the functions to compute the stress components and to export them in VTK format. I will try to add those for the next release, but since I don't have so much time to develop the code these days, it may take some time. But if you want (or any other user wants) to implement those two functions, and to share them with the other users, I would be happy to give you some support. Regards, Rafael Vazquez Il 16/11/2011 19:05, fei duan ha scritto: > Dear GeoPDEs users, > As we all know, it is essential for us to compare the analysis results > obtained from GeoPDEs and another commercial FEA software, for example, > ABAQUS, to see how do IGA and GeoPDEs give a better analysis result than > classical FEA. > The displacement of a specific point is usually too small to compare and > what we often do is to compare the stresses of the same point in the two > results obtained from GeoPDEs and ABAQUS respectively to see which one is > more close to the experimental result or theoretical result. > Unfortunately, the current release of GeoPDEs does not have a function to > figure out the stress components of the nodes in the domain. > I recommend that two functions should be added into GeoPDEs in the next > release and we can download from SVN as soon as possible. One is the > function that figure out the stress components of the nodes in the domain > and the other is the function to export the stress components to VTK format > for plotting. > Thanks a lot. > Best regards. >  > All the data continuously generated in your IT infrastructure > contains a definitive record of customers, application performance, > security threats, fraudulent activity, and more. Splunk takes this > data and makes sense of it. IT sense. And common sense. > http://p.sf.net/sfu/splunknovd2d > _______________________________________________ > Geopdesusers mailing list > Geopdesusers@... > https://lists.sourceforge.net/lists/listinfo/geopdesusers > 
From: fei duan <fei.upc@gm...>  20111116 18:06:01

Dear GeoPDEs users, As we all know, it is essential for us to compare the analysis results obtained from GeoPDEs and another commercial FEA software, for example, ABAQUS, to see how do IGA and GeoPDEs give a better analysis result than classical FEA. The displacement of a specific point is usually too small to compare and what we often do is to compare the stresses of the same point in the two results obtained from GeoPDEs and ABAQUS respectively to see which one is more close to the experimental result or theoretical result. Unfortunately, the current release of GeoPDEs does not have a function to figure out the stress components of the nodes in the domain. I recommend that two functions should be added into GeoPDEs in the next release and we can download from SVN as soon as possible. One is the function that figure out the stress components of the nodes in the domain and the other is the function to export the stress components to VTK format for plotting. Thanks a lot. Best regards. 
From: Rafael Vazquez <vazquez@im...>  20111103 18:25:39

Hi Xinkang, your mail couldn't be read in the list, I think because of the attached files. I reproduce it below, with the answers to your questions. Regards, Rafa >> Dear GeoPDEs Users, >> I have two questions to ask. >> The first question >> >> I am trying to solve a 3D elasticity problem 'NAFEMS Benchmark >> LE1' by using GeoPDEs. > >> The geometry structure is created by the file 'NAFEMS_LE1.txt' as >> follows: >> # NURBS representation of quarter of a elliptical ring of thickness 0.1, >> # (x/3.25)^2+(y/2.75)^2=1;(x/2)^2+(y/1)^2=1 >> # dimention_of_the_geometry numbers_of_patches >> 3 1 >> # the degree in each Cartesian direction >> 1 2 1 >> # the number of control points in each direction >> 2 3 2 >> # knots >> 0.00000 0.00000 1.00000 1.00000 >> 0.00000 0.00000 0.00000 1.00000 1.00000 1.00000 >> 0.00000 0.00000 1.00000 1.00000 >> # X=x*w >> # y=y*w >> # Z=z*w >> 2.00000 3.25000 1.414213562 2.298097039 0.00000 0.00000 >> 2.00000 3.25000 1.414213562 2.298097039 0.00000 0.00000 >> 0.00000 0.00000 0.707106781 1.944543648 1.00000 2.75000 >> 0.00000 0.00000 0.707106781 1.944543648 1.00000 2.75000 >> 0.00000 0.00000 0.000000000 0.000000000 0.00000 0.00000 0.10000 >> 0.10000 0.0707106781 0.0707106781 0.10000 0.10000 >> # weights >> 1.00000 1.00000 0.707106781 0.707106781 1.00000 1.00000 >> 1.00000 1.00000 0.707106781 0.707106781 1.00000 1.00000 >> Acoording to the structure I built and the model 'NAFEMS Benchmark >> LE1' , we can see that 'problem_data.press_sides=[2]' and >> 'problem_data.symm_sides=[3 4]'; so I use the following code to solve >> this problem: >> % NAFEMS_LE1_3D: solve the linear elasticity problem NAFEMSLE1. >> % 1) PHYSICAL DATA OF THE PROBLEM >> clear problem_data >> % Physical domain, defined as NURBS map given in a text file >> problem_data.geo_name = 'NAFEMS_LE1_3D.txt'; >> % Type of boundary conditions for each side of the domain >> problem_data.nmnn_sides = []; >> problem_data.drchlt_sides = []; >> problem_data.press_sides = [2]; >> problem_data.symm_sides = [3 4]; >> % Physical parameters >> E = 2.1e11; nu = 0.3; >> problem_data.lam = @(x, y, z) ((nu*E)/((1+nu)*(12*nu)) * ones (size >> (x))); >> problem_data.mu = @(x, y, z) (E/(2*(1+nu)) * ones (size (x))); >> % Source and boundary terms >> P = 1.0e7; >> problem_data.f = @(x, y, z) zeros (3, size (x, 1), size (x, 2)); >> problem_data.g = @(x, y, z, ind) zeros (3, size (x, 1), size (x, 2)); >> problem_data.h = @(x, y, z, ind) zeros (3, size (x, 1), size (x, 2)); >> problem_data.p = @(x, y, z, ind) P * ones (size (x)); >> % 2) CHOICE OF THE DISCRETIZATION PARAMETERS >> clear method_data >> method_data.degree = [3 3 3]; % Degree of the bsplines >> method_data.regularity = [2 2 2]; % Regularity of the splines >> method_data.nsub = [10 1 50]; % Number of subdivisions >> method_data.nquad = [4 4 4]; % Points for the Gaussian >> quadrature rule >> % 3) CALL TO THE SOLVER >> [geometry, msh, space, u] = solve_linear_elasticity_3d (problem_data, >> method_data); >> Unfortunately, all the numbers in {u}, which represents the >> displacements of all nodes, are all zero. > >> I can't figure out what's wrong with my code, however, I guess >> someting must be wrong with 'the Source and boundary terms' or >> 'boundary conditions for each side of the domain'. Could you give me >> an advise of how to correct the mistakes? I had not noticed. We implemented the pressure condition for the 2D case, but not for the 3D case. Well, you only have to copy the pressure condition part from "solve_plane_strain_2d" to "solve_linear_elasticity_3d", and adapt it to the 3D case (compute the coordinate z, and make the pressure also a function of z). This should be easy, but if you need any help just ask me. I will add this in the next release. >> The second question >> I have run the example of 'ex_plane_strain_ring' and obtain the >> displacement of all the nodes. How can I find a function to compute >> all the components of stress of all the nodes, and export them to VTK >> format for plotting? The code as it is doesn't have a function to export the components of the stress, but it shouldn't be difficult to implement one by yourself. You will need two functions, similar to sp_eval and sp_eval_msh (or sp_eval_div and sp_eval_div_msh). The main differences should be in the second function (the one with _msh), because instead of using the field shape_functions you will have to use shape_function_gradients to compute the components of the stress. Once you have these two functions, exporting to VTK format should be easy, with functions similar (maybe the same?) to sp_to_vtk and msh_to_vtk. >> Thanks a lot. >> Best regards. >>  >> Xinkang Li >> Zhejiang University >> Hangzhou Zhejiang >> China >> TEL：13456979712 >> Email: lixinkang1987@... <mailto:lixinkang1987@...> >> >> > 
From: 李新康 <lixinkang1987@16...>  20111103 12:49:41

# NURBS representation of quarter of a elliptical ring of thickness 0.1, # (x/3.25)^2+(y/2.75)^2=1;(x/2)^2+(y/1)^2=1 # dimention_of_the_geometry numbers_of_patches 3 1 # the degree in each Cartesian direction 1 2 1 # the number of control points in each direction 2 3 2 # knots 0.00000 0.00000 1.00000 1.00000 0.00000 0.00000 0.00000 1.00000 1.00000 1.00000 0.00000 0.00000 1.00000 1.00000 # X=x*w # y=y*w # Z=z*w 2.00000 3.25000 1.414213562 2.298097039 0.00000 0.00000 2.00000 3.25000 1.414213562 2.298097039 0.00000 0.00000 0.00000 0.00000 0.707106781 1.944543648 1.00000 2.75000 0.00000 0.00000 0.707106781 1.944543648 1.00000 2.75000 0.00000 0.00000 0.000000000 0.000000000 0.00000 0.00000 0.10000 0.10000 0.0707106781 0.0707106781 0.10000 0.10000 # weights 1.00000 1.00000 0.707106781 0.707106781 1.00000 1.00000 1.00000 1.00000 0.707106781 0.707106781 1.00000 1.00000 