Search found 77 matches

by Ahmet Erdemir
Thu Feb 17, 2022 9:37 am
Forum: Open Knee: A Three-Dimensional Finite Element Representation of the Knee Joint
Topic: Generation 1 Cut Planes
Replies: 2
Views: 705

Re: Generation 1 Cut Planes

They are aligned with MRI axis and field of view.
by Ahmet Erdemir
Sun Feb 14, 2021 7:02 am
Forum: Open Knee: A Three-Dimensional Finite Element Representation of the Knee Joint
Topic: Kinematics data channel name conventions
Replies: 4
Views: 855

Re: Kinematics data channel name conventions

Dear Kostas, First of all, each kinematics-kinetics data folder should have a state file (within the zipped vproj file as I recall) that has all the coordinate system transformations, e.g. between anatomical, optimized, tibia, femur, robot, optotrak, etc. That state file corresponds to that motion, ...
by Ahmet Erdemir
Fri Jan 22, 2021 5:44 am
Forum: Open Knee: A Three-Dimensional Finite Element Representation of the Knee Joint
Topic: Kinematics data channel name conventions
Replies: 4
Views: 855

Re: Kinematics data channel name conventions

Dear Kostas, During experimentation of the tibiofemoral joint, the tibia was indeed fixed. Yet, the reporting of joint kinematics is for posterior translation of tibia. See https://simtk.org/plugins/moinmoin/openknee/Infrastructure/ExperimentationMechanics?action=AttachFile&do=get&target=Knee+Coordi...
by Ahmet Erdemir
Tue Dec 15, 2020 6:49 am
Forum: Open Knee: A Three-Dimensional Finite Element Representation of the Knee Joint
Topic: The Question about Pre-strain
Replies: 24
Views: 4264

Re: The Question about Pre-strain

I did try that, however, in 2.5 files 'fiber' is seen as a synonym for 'mat_axis'. In 3.0 files this is no longer the case. When loading it into FEBio Studio (3.0 files) it shifts into the MRTI part. We are currently using FEBio version 2.9. We also create our models in a scripted fashion, without ...
by Ahmet Erdemir
Mon Dec 14, 2020 6:26 am
Forum: Open Knee: A Three-Dimensional Finite Element Representation of the Knee Joint
Topic: The Question about Pre-strain
Replies: 24
Views: 4264

Re: The Question about Pre-strain

Dear Marloes, Did you try by defining fiber direction outside the elastic material definition? As <material id="11" name="acl" type="uncoupled prestrain elastic"> <density>1.5e-09</density> <k>73.2</k> <elastic type="trans iso Mooney-Rivlin"> <c1>1.95</c1> <c2>0</c2> <c3>0.0139</c3> <c4>116.22</c4> ...
by Ahmet Erdemir
Thu Aug 13, 2020 9:41 am
Forum: Open Knee: A Three-Dimensional Finite Element Representation of the Knee Joint
Topic: Can user submit their model on 'simulations' platform?
Replies: 1
Views: 658

Re: Can user submit their model on 'simulations' platform?

Simulation feature was a test implementation to be able to run a simple femur-ACL-tibia model at user-desired kinematics boundary conditions. The feature does not permit users to submit their own models. I recommend you to download FEBio (https://febio.org/) on your computer to run simulations with ...
by Ahmet Erdemir
Tue Dec 17, 2019 8:15 am
Forum: Open Knee: A Three-Dimensional Finite Element Representation of the Knee Joint
Topic: Ligament bending
Replies: 3
Views: 902

Re: Ligament bending

The bending that you see is expected as the ligaments have a ground substance with a small but stabilizing modulus (providing compression and bending stiffness). You can set that ground substance to zero to represent a purely tension only ligament material. Yet, the simulation will likely have conve...
by Ahmet Erdemir
Tue Oct 22, 2019 7:54 am
Forum: Open Knee: A Three-Dimensional Finite Element Representation of the Knee Joint
Topic: File not opening.
Replies: 1
Views: 787

Re: File not opening.

Dear Prasanna, .NII format is for storing images, e.g. MRIs of the knee. They are NOT model files. Open Knee(s) - Generation 1 has meshes as .inp files that can be imported to Abaqus. Nonetheless, all our model files for Generation 1 and Generation 2 (see wiki page "Roadmap") are in FEBio format (.f...
by Ahmet Erdemir
Tue Oct 22, 2019 7:50 am
Forum: Open Knee: A Three-Dimensional Finite Element Representation of the Knee Joint
Topic: Ligament bending
Replies: 3
Views: 902

Re: Ligament bending

Hi Sebastian,

Can you clarify what you mean by unphysiological bending of LCL and MCL? Are they penetrating the bone surface? If so, this can be resolved by activating contact between these ligaments and bones.

Ahmet
by Ahmet Erdemir
Mon Oct 22, 2018 5:24 am
Forum: Open Knee: A Three-Dimensional Finite Element Representation of the Knee Joint
Topic: Knee extension of the model including patella
Replies: 2
Views: 1053

Re: Knee extension of the model including patella

Dear Lefteris, oks001 is NOT the specimen modeled in Open Knee(s) - Generation 1, which is in tf_joint_FEBio_v2.feb. You can get the geometries for Open Knee(s) - Generation 1 in the source code repository, specifically at https://simtk.org/svn/openknee/_gen1/dat/geo/version2geo/ Please note that wh...