Recurring Meeting of Cleveland Clinic - University of Utah

Date: January 22, 2014

Time: 3:00 PM EST

Means: Conference call

Attendees:

1. Ahmet Erdemir (Cleveland Clinic)
2. Jason Halloran (Cleveland Clinic)
3. Jeff Weiss (University of Utah)
4. Steve Maas (University of Utah)
5. Ben Ellis (University of Utah)

Agenda:

1. Progress on in situ strain test problem.

   • http://wiki.simtk.org/openknee/Febio/InSituStrain

2. Discuss test problem for set definitions.

   • http://wiki.simtk.org/openknee/Febio/SetDefinitions

3. Update on local coordinate systems and connector elements.

   • http://wiki.simtk.org/openknee/Febio/RigidBodyMotions

4. Decide action items for next meeting.
5. Other.

Immediate Action Items:

• Cleveland Clinic (Ahmet)
  • Provide links to University of Utah team for wiki help pages.
  • Provide links to University of Utah team on activities related to cloud computing prototype.
  • Prepare a simple multi-directional in situ strain test problem.
• University of Utah (Steve)
  • Run in situ strain test problem with actual ligament properties (low ground substance modulus) to evaluate tension-compression nonlinearity.
  • Provide the FEBio file for the test problem along with the statement of required FEBio version.
  • Test the in situ strain feature in an anatomically realistic three-dimensional ligament model.
  • Incorporate the use of sets in FEBio output (xplt) file.
• University of Utah (Steve and Ben)
  • Learn more about coordinate systems and connectors to identify strategies for implementation of these features.

Notes:

1. Progress on in situ strain test problem.
   • Steve noted an issue in the original solution of the test problem. Specifically, the in situ strains were enforced during loading step as well. Steve fixed this issue and updated the force-displacement figure. It seems like the loads cross the 0 N axis at expected displacement values. Steve will confirm this analytically as well.
   • The compression-tension nonlinearity is still not apparent. For physiological ligament properties, force-displacement slope during compression should be small. Ideally, the forces generated in compression should be zero. Yet this depends on the ground substance (matrix) material used along with the fiber representation. Steve will use actual ligament parameters as advised by Jeff. He will also evaluate this feature in a three-dimensional ligament model.
   • Steve will upload the FEBio input file for the test problem and note the required version of FEBio needed to solve these problem types.
   • Ahmet noted that the specification of in situ strain in multiple directions may be beneficial, e.g. for artery modeling (longitudinal and circumferential strains). The goal of the FEBio team is to provide this feature in a generalizable way. Ahmet will prepare an illustrative test problem.
2. Discuss test problem for set definitions.
   • Steve already implemented the capability to define element, node, and face sets in FEBio input file. These sets can be used to apply boundary conditions and describe interactions. The following steps will include incorporation of these set definitions for output requests and in FEBio output (xplt) file.
   • This feature may also allow splitting of input files, which may ease model development.
   • Both teams note that this is a great usability feature for model development, post-processing, and related scripting. It should be promoted accordingly.
3. Update on local coordinate systems and connector elements.
   • The University of Utah team did not have a chance to read documentation related to coordinate systems and connectors. They will catch up with this background information and come up with a plan to implement this feature.
4. Decide action items for next meeting.
   • See Immediate Action Items above.
5. Other.
   • University of Utah team asked for tips in regard to utilizing the wiki. Ahmet will send the appropriate links to wiki help pages.
   • Ahmet informed the University of Utah team on the development of a cloud computing prototype and XSEDE. He will send them the appropriate links for reference.