How to set human head model with multiple material

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  • KaravaevAS
    Junior Member
    • Jan 2016
    • 21

    How to set human head model with multiple material

    Hello dear forum's users!

    So can anybody help with the following:

    We need to simulate dynamic impact of a solid brick with a human head. The human head consist 3 materials (bones, brain, soft tissue), we already have computational mesh of the head.

    So how can i set multiple material model in Febio? Can i assign material directly to the cells of computational mesh or only for domains?

    with best regards, Alexander
  • KaravaevAS
    Junior Member
    • Jan 2016
    • 21

    #2
    Hm, i a little bit saw into the .feb file structure and assumed that in the old versions of Febio material is assigned directly to the cell:

    <hex8 id="1745" mat="1"> 2390, 2391, 2395, 2394, 2454, 2455, 2459, 2458</hex8>

    but my Febio solver (v. 2.4.2.7885) doesn't take such files.

    So my "PreView" program splits all element to the 2 "Parts" and each of the "Part" contains hexas with one material:

    <Elements type="hex8" mat="1" elset="Part1">
    <elem id="1"> 1, 2, 6, 5, 65, 66, 70, 69</elem>
    ...
    <Elements type="hex8" mat="2" elset="Part2">
    <elem id="1450"> 13, 14, 18, 17, 77, 78, 82, 81</elem>

    Then such .feb file compiles on Febio solver.

    Do i understand correct that in new versions material are assigned via "Parts" of elements and not to each element directly?

    Comment

    • maas
      Lead Code Developer
      • Nov 2007
      • 3400

      #3
      Hi,

      Indeed, materials are assigned to parts and not to individual elements. This was done (many years ago at this point) because it allowed several optimizations to be made in the code. There is still a way to assign different material parameters to different elements and it would require the implementation of a custom plugin. Since you only have three materials, I suggest partitioning the mesh into three parts and then assigning the materials to the partitions. Let us know if you need any instructions on how to do this in PreView.

      Cheers,

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

      Comment

      • maas
        Lead Code Developer
        • Nov 2007
        • 3400

        #4
        Hi,

        Indeed, materials are assigned to parts and not to individual elements. This was done (many years ago at this point) because it allowed several optimizations to be made in the code. There is still a way to assign different material parameters to different elements and it would require the implementation of a custom plugin. Since you only have three materials, I suggest partitioning the mesh into three parts and then assigning the materials to the partitions. Let us know if you need any instructions on how to do this in PreView.

        Cheers,

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

        Comment

        • KaravaevAS
          Junior Member
          • Jan 2016
          • 21

          #5
          Thank's a lot for response Steve!

          I've already made procedure from me mesher program to save model directly to .feb file without PreView because i have complex structure of head and it's difficult to define contact area and part by hands. Now i'm in the testing process of our experiment.

          By the way, your program interface seems to be well designed and friendly (i mean PreView and PostView), also you have very simple and clear xml structure of .feb executable file, so it's very easy to understand and work with it. i'hope we will try solver itself.

          So i have to more not related questions

          1) When i load my febio file to PreView, it automatically defines surfaces in the project tree (i mean Model->Geometry->"File_Name"->Surfaces). So what rule PreView uses to define such surfaces and could i disable this function?

          2) Should i somehow close answered thread?

          Comment

          • KaravaevAS
            Junior Member
            • Jan 2016
            • 21

            #6
            Thank's a lot for response Steve!

            I've already made procedure from my mesher C++ program to save model directly to .feb file without PreView. i have complex structure of head and it's difficult to define contact area and parts manually. Now i'm in the testing process of our experiment.

            By the way, your program interface seems to be well designed and friendly (i mean PreView and PostView), also you have very simple and clear xml structure of .feb executable file, so it's very easy to understand and work with it. i hope sooner we will test the solver.

            So i have to more not related questions

            1) When i load my febio file to PreView, it automatically defines surfaces in the project tree (i mean Model->Geometry->"File_Name"->Surfaces). So what rule PreView uses to define such surfaces and could i disable this function?

            2) Should i somehow close answered thread?

            with best regards, Alexander

            Comment

            • maas
              Lead Code Developer
              • Nov 2007
              • 3400

              #7
              Hi Alexander,

              I'm happy to hear you like our pre- and post-processor. Do let us know if there is anything we can improve.

              Regarding your questions.

              1) PreView partitions the surface based on a "sharp-angle" criterion. Basically, if angle defined by the normal of two neighboring facets is larger than some threshold, PreView places a hard edge there. You can repartition the surface from the Mesh panel. Find the Autosmooth option and change the angle. You can also create new partitions by selecting the surface facets and select the Partition button in the Mesh Panel (under facet selection options).

              2) No, that's okay, don't worry about that. I don't think we have ever closed a thread .

              Cheers,

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

              Comment

              • dara_9200
                Junior Member
                • Aug 2016
                • 4

                #8
                Hi,

                I have my Human Aorta geometry segmented and meshed in Hypermesh software. When exporting it to PreView I see it as a whole. I need to apply different material properties to different parts of a solid. How can I do that in PreView? Although, when I have different element types (Hex & Tet) for each part PreView differentiates parts of a body. Now I have one element type applied to different segments, that are not recognized in PreView nor .feb script.

                Thank you so much for your time,
                Dara

                Comment

                • maas
                  Lead Code Developer
                  • Nov 2007
                  • 3400

                  #9
                  Hi Dara,

                  Currently, PreView only reads the mesh from the hypermesh format. It does not read any partitioning info. I can probably add this easily if you can send me your aorta model (or any model really) that has some partitioning data in it.

                  Thanks,

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

                  Comment

                  • dara_9200
                    Junior Member
                    • Aug 2016
                    • 4

                    #10
                    Thanks a lot for your time and kind offer,

                    I tried uploading the file here, but I couldn't. Can you please send me your email so I can send you the file? I want to apply different constitutive parameters to middle section which is assumed to be a diseased part of the tissue, but PreView doesn't recognize the exported model from HyperMesh as a body with multiple domains. Thanks again,

                    Best,
                    Dara

                    Comment

                    • maas
                      Lead Code Developer
                      • Nov 2007
                      • 3400

                      #11
                      Hi Dara,

                      You can email the file to me at this address steve dot maas at Utah dot edu. If the file is really big (> 15 Mb), please zip the file before emailing it to me.

                      Cheers,

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

                      Comment

                      • dara_9200
                        Junior Member
                        • Aug 2016
                        • 4

                        #12
                        Great. Thanks Steve,
                        I Just sent the file.

                        Comment

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