Nodal Load

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  • Joanne Kwon
    Junior Member
    • Jan 2008
    • 13

    Nodal Load

    To mimic spherical nanoindentation on hydrogel a spherical rigid body has been created followed by a poro-elastic box to represent hydrogel.

    I would like to study the effect on the hydrogel as the indenter pushes it in.
    Hence, I grouped all the nodes on the top surface of a hemisphere and then gave them a nodal force along z-axis to push into the box. However, no matter how great force I gave, nothing happened. I gave -1,000,000 on the load curve to push in but no result.

    Could you be kind to tell me what I have done wrong?
    I have attached the file.

    Thanks.

    Regards
    Joanne
  • maas
    Lead Code Developer
    • Nov 2007
    • 3400

    #2
    Hi Joanne,

    You have the z-displacement degree of freedom of the rigid body fixed. You have to set the type to "free" to open up that degree of freedom.

    Cheers,

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

    Comment

    • Joanne Kwon
      Junior Member
      • Jan 2008
      • 13

      #3
      I have problems with diverging.

      I tried re-running the program changing the variables over and over but only managed to run it up to 1.5 secs for the whole duration of 2 secs.
      Would you mind looking into the code and giving me some tips to solve this problem? ('t47.zip')
      I wonder whether the zero pressure I set on the boundary conditions is the cause of this.

      Furthermore, I tried running the program chaning the load curve condition from using 'rigid body z-displcement' to 'nodal z-force'. However, I come across the same diverging problem, which is worse because I only managed to run it up to 0.665 sec this time. ('t54.zip')

      I tried re-running the program with different parameter values but no success.
      It would be really appreciated if you can suggest a way to solve this problem.

      With many thanks
      Joanne

      Comment

      • maas
        Lead Code Developer
        • Nov 2007
        • 3400

        #4
        Hi Joanne,

        I'm afraid that the problem is suffering from a bug in the FEBio version you have. Your version has trouble with nodes that are contacting the edge of the mesh. The good news is that this issue is fixed in the next version and your problem runs fine with the new version (which will be coming out in the next two weeks). I've ran your model with our new version and attached the results.

        Cheers,

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

        Comment

        • Joanne Kwon
          Junior Member
          • Jan 2008
          • 13

          #5
          Dear Steve

          Always thanks for your kind help.

          I guess I just have to wait for the next version.
          Would it be compatible with Window Vista though?

          Regards
          Joanne

          Comment

          • maas
            Lead Code Developer
            • Nov 2007
            • 3400

            #6
            Hi Joanne,

            The next version will be as compatible as the current version, so if you can run your current version on Vista, you should be able to run the next version on it as well.

            Cheers,

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

            Comment

            • Joanne Kwon
              Junior Member
              • Jan 2008
              • 13

              #7
              Dear Steve

              It would be really appreciated if you can possibly tell me when the next version of FEBio will be out.

              It has not been out yet, right?

              Regards
              Joanne

              Comment

              • maas
                Lead Code Developer
                • Nov 2007
                • 3400

                #8
                Hi Joanne,

                Actually, we released version 1.1 on tuesday. If you chose to receive emails from us, you should have received a notification. There was also an announcement on this forum.

                You can download the software from http://mrl.sci.utah.edu/software.php. Let us know if you have any questions.

                Cheers,

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

                Comment

                • jsoons
                  Junior Member
                  • Jan 2008
                  • 10

                  #9
                  Hi Steve,

                  I've chose to receive mail-notifications about FEBio, but I didn't get any anoucement...?

                  greets Joris

                  Comment

                  • maas
                    Lead Code Developer
                    • Nov 2007
                    • 3400

                    #10
                    Hi Joris,

                    You are not listed in our email contact list. To receive emails, you can go to the "edit profile" page (http://mrl.sci.utah.edu/register/edit_profile.php) on the mrl website and uncheck the checkbox relating opting out of update notifications.

                    Also, please only post replies that are relevant to the thread. If you have a question and believe it might be useful for other people, please start a new thread. Otherwise, you can also reach us (or any other users) by sending a private message. You can do this, for instance, by finding a particular user in the member list and selecting the "send a private message" option in the member profile.

                    Thanks,

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

                    Comment

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