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

  1. #1

    Default 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?

  2. #2
    Join Date
    Nov 2007
    Location
    Salt Lake City, UTAH
    Posts
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    Default

    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

  3. #3

    Default

    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 at 11:47 AM.

  4. #4

    Default

    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

  5. #5
    Join Date
    Jun 2019
    Location
    Colombia
    Posts
    10

    Default

    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

    Quote 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

  6. #6
    Join Date
    Nov 2007
    Location
    Salt Lake City, UTAH
    Posts
    2,329

    Default

    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

  7. #7
    Join Date
    Jun 2019
    Location
    Colombia
    Posts
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    Default

    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

  8. #8
    Join Date
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    Location
    Salt Lake City, UTAH
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    Default

    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

  9. #9
    Join Date
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    Location
    Colombia
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    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

  10. #10
    Join Date
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    Location
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    Default

    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

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