How to define more three sets of mat_axis on each element?

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  • danielcpnkimo
    Junior Member
    • Dec 2017
    • 9

    How to define more three sets of mat_axis on each element?

    Hi, I'm trying to simulate biaxial extension of Fung orthotropic compressible material matrix with exponential-power law fiber oriented following user-defined vector.
    How can I define more than one set of mat_axis on each element?
    I need two user-definedmaterial axis for two different fibers and one material axis for the Fung orthotropic material at each element.
    How can I do that?
    I know I can use the following to define the hetrogeneous distribution of fibers.

    Code:
    <MeshData>
         <ElementData var="mat_axis" elem_set="part3">
              <elem lid="1">
                   <a>1,0,0</a>
                   <d>0,1,0</d>
              </elem>
              <elem lid="2">
                   <a>1,1,0</a>
                   <d>0,1,1</d>
              </elem>
         </ElementData>
    </MeshData>
    But what I need is to assign each element in the same elem_set="part3" with three mat_axis, 2 for fibers and 1 for orthotropic material. How can I achieve that?
  • maas
    Lead Code Developer
    • Nov 2007
    • 3400

    #2
    Hi,

    I assume you are using a solid mixture to create your material. If so, you can use the following syntax to set the mat axis of a solid component of a mixture:

    Code:
    <ElementData var="solid[0].mat_axis" elem_set="part3">
      ...
    </ElementData>
    So, basically, you prepend mat_axis with solid[n], where n is the (zero-based) index of the solid in the mixture. In your input file you will then have three of these sections, one for each of the components of your mixture. Please give that a try and let us know if that worked for you.

    Cheers,

    Steve
    Department of Bioengineering, University of Utah
    Scientific Computing and Imaging institute, University of Utah

    Comment

    • danielcpnkimo
      Junior Member
      • Dec 2017
      • 9

      #3
      Thanks! It works now after I changed the code to the following patterns!

      Code:
          <Material>
              <material Name="Plant CMT" id="1" type="solid mixture">
                  <solid type="Fung-ortho-compressible">
                      <mat_axis type="user"/>
                      <E1>100000000</E1>
                      <E2>400000000</E2>
                      <E3>400000000</E3>
                      <G12>1.5384615e+08</G12>
                      <G23>1.5384615e+08</G23>
                      <G31>1.5384615e+08</G31>
                      <v12>3.0000000e-01</v12>
                      <v23>1.0000000e-02</v23>
                      <v31>1.0000000e-02</v31>
                      <c>1</c>
                      <k>400000000</k>
                      <density>1100</density>
                  </solid>
                  <solid type="fiber-exp-pow">
                      <mat_axis type="user"/>
                      <ksi>40000000000</ksi>
                      <alpha>1</alpha>
                      <beta>2</beta>
                      <theta>0</theta>
                      <phi>0</phi>
                  </solid>
              </material>
          </Material>
      	
      	:
      	:
      	
         <MeshData>
              <ElementData elem_set="CellWall" var="solid[0].mat_axis">
                  <elem lid="1">
                      <a>1, 0, 0</a>
                      <d>0, 1, 0</d>
                  </elem>
      		:
      	    <elem lid="1024">
                      <a>1, 0, 0</a>
                      <d>0, 1, 0</d>
                  </elem>
      		</ElementData>
              <ElementData elem_set="CellWall" var="solid[1].mat_axis">
                  <elem lid="1">
                      <a>1, 0, 0</a>
                      <d>0, 0, -1</d>
                  </elem>
      		:
      	    <elem lid="1024">
                      <a>9.9518473e-01, -9.8017140e-02, -0.0000000e+00</a>
                      <d>0, 0, -1</d>
                  </elem>
      		</ElementData>
          </MeshData>
      Last edited by danielcpnkimo; 11-20-2018, 11:47 AM.

      Comment

      • danielcpnkimo
        Junior Member
        • Dec 2017
        • 9

        #4
        Hi, after changing the material axes of orthogonal material, I found that actually it doesn't work because the results look like the one without changing the material axis.
        I just impose a pressure inside the cylinder so the result of displacement should be closed to axisymmetric. and I've make sure my material axes and fibers have been set correctly as follow,
        mat_axis (1).png BC and fibers (1).png
        The results of isotropic case looks fine
        tot_disp_isotropic.png
        However, the results of orthotropic case looks like the one without changing axes of the material matrix of each element, that is, the total displacement is not axisymmetric.
        tot_disp_orthotropic.png
        Maybe the setting of material axes for many solids in a solid mixture doesn't work!? Or I made some mistake.
        I've attach my file in this reply. Please help and let me know what may be the wrong parts, thanks!
        CylindricalCellWall.feb

        Comment

        • apaz
          Member
          • Jun 2019
          • 44

          #5
          Hi,

          I am facing the same problem with depth-dependent orientations of fibers, I am using a biphasic material with a solid mixture as the solid phase. But this approach is not working for me so far. Is there any update on this problem?

          Kind regards,
          Alex

          Originally posted by maas View Post
          Hi,

          I assume you are using a solid mixture to create your material. If so, you can use the following syntax to set the mat axis of a solid component of a mixture:

          Code:
          <ElementData var="solid[0].mat_axis" elem_set="part3">
            ...
          </ElementData>
          So, basically, you prepend mat_axis with solid[n], where n is the (zero-based) index of the solid in the mixture. In your input file you will then have three of these sections, one for each of the components of your mixture. Please give that a try and let us know if that worked for you.

          Cheers,

          Steve

          Comment

          • maas
            Lead Code Developer
            • Nov 2007
            • 3400

            #6
            Hi Alex,

            It looks like there are indeed some issues with assigning mat_axis to the solid component of a biphasic material. I will look into that, but you should be able to assign the mat_axis to the biphasic material directly. Since material axes concatenate, the solid's mat axes will also see its parents mat axis. Please give that a try and let me know if that worked.

            Cheers,

            Steve
            Department of Bioengineering, University of Utah
            Scientific Computing and Imaging institute, University of Utah

            Comment

            • apaz
              Member
              • Jun 2019
              • 44

              #7
              Hi,

              Thank you for your fast reply. So, Is there not a way to define independent orientation of fibers when they are solid constituents in a biphasic material? Because I am importing these specific orientations for each family of fibers.
              An option would be only using phi and theta angles referenced to the local coordinate system?

              Regards,
              Alex

              Comment

              • maas
                Lead Code Developer
                • Nov 2007
                • 3400

                #8
                Hi Alex,

                Can you please send me your input file, or at least the material definition and which parameters you want to define via the ElementData section? I'll take a closer look and see if I can offer a solution or address any issues in FEBio.

                Thanks,

                Steve
                Department of Bioengineering, University of Utah
                Scientific Computing and Imaging institute, University of Utah

                Comment

                • apaz
                  Member
                  • Jun 2019
                  • 44

                  #9
                  Independent_Fibers_Orientation.feb

                  Dr Maas,

                  This is an example. I want to orientate the fibers along two different independent directions into the same element in a biphasic material.

                  Thank you,
                  Alex

                  Comment

                  • maas
                    Lead Code Developer
                    • Nov 2007
                    • 3400

                    #10
                    Hi Alex,

                    I sent you a link with a new version of FEBio3 that (I think) addresses this issue. Let me know what you find.

                    Cheers,

                    Steve
                    Department of Bioengineering, University of Utah
                    Scientific Computing and Imaging institute, University of Utah

                    Comment

                    • apaz
                      Member
                      • Jun 2019
                      • 44

                      #11
                      Hi Steve,

                      Thank you. The version you sent me is working well.

                      Kind regards,
                      Alex

                      Comment

                      • sfang17
                        Junior Member
                        • May 2018
                        • 6

                        #12
                        Hi Steve,

                        I followed the instructions given in this thread to assign individual fiber direction of a von-Mises distribution to each element.
                        I used mat_axis type "angles" to define the direction.
                        However, the executable keeps telling me:
                        [QUOTE] tag "theta" (line 5481) : missing attribute "lid" [QUOTE]
                        Other details:
                        1. I also defined b parameter individually to each element using your "map" method posted in another thread. That worked well.
                        2. I am currenly using febio 3.0.1 on mac as executable.

                        I am wondering if you have insights on this?
                        Thanks.
                        Shu
                        Attached Files

                        Comment

                        • maas
                          Lead Code Developer
                          • Nov 2007
                          • 3400

                          #13
                          Hi Shu,

                          In the ElementData section you can only define the local element coordinates by specifying two vectors. I can look into adding support for using angles, if you'd like, but in the meantime, you will have to convert the angles to vectors.

                          Cheers,

                          Steve
                          Department of Bioengineering, University of Utah
                          Scientific Computing and Imaging institute, University of Utah

                          Comment

                          • sfang17
                            Junior Member
                            • May 2018
                            • 6

                            #14
                            Thank you, Steve!
                            I will proceed with the vector method. I think it can work just as fine.
                            Thank you again for your help.

                            Best,
                            Shu

                            Comment

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