Prestrain in arteries

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  • bracamontej
    Junior Member
    • Mar 2019
    • 14

    Prestrain in arteries

    Greetings!

    I'm working on simulation of arteries from in vivo imaging. For this I plan to use the prestrain module.

    I'm trying to work in two steps, first imposing an approximate prestrain field from theory and adapt it to be compatible with the actual geometry. For this I'm using the prestrain elastic material and the prestrain constrain using first a simple uncoupled Mooney-Rivlin model.

    Latter I want to use that prestrain as initial condition for the artery inflation process. For this I included an inflation time step and the prestrain initial condition with init and reset parameters set to 1.

    Nevertheless I'm not getting my files to run. I'm using FEBio 2.9 version. I'm attaching the prestrain constraint file (febpre_strain.feb) and the prestrain initial condition files (febpre_strain_ic.feb).

    I'm out of ideas and I checked the syntax along the files. Could anyone please give them a look and tell what could be the problem? I'm clueless at this stage.

    Best regards,

    Johane Bracamonte
    Attached Files
  • maas
    Lead Code Developer
    • Nov 2007
    • 3400

    #2
    Hi Johane,

    I know we communicated via email, but for the record just wanted to add a comment here. I suspect that the main issue is the definition of the prestrain gradients which contain zeroes on the diagonals. Let us know if you require further assistance.

    Cheers,

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

    Comment

    • bracamontej
      Junior Member
      • Mar 2019
      • 14

      #3
      Thank you Dr. Maas,

      I fixed my Deformation Gradient components (F0) and got the problem to converge. Attached is a file that successfully assign an Deformation Gradient field approximation (theoretical solution from Chuong and Fung, 1986) and updated to eliminate any geometry distortion (febprefine.feb). a Fung orthotropic material model is used and material axes are defined per element so that they are aligned with radial and circumferential directions.

      Nevertheless, for the problem to converge stretches must be small. In case of arteries, that is small opening angles and small radius changes from stress-free to unloaded/loaded configurations. Regrettably, that is not the case for most arteries. Is there a way to enforce larger (and more realistic) residual stretches?

      Thanks and regards,

      Johane Bracamonte
      Attached Files

      Comment

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