Error when running OpenKnee 1.0 (tf_joint.feb) with Febio 2.5

[Neelima Sharma]

Hello,

I am using Febio 2.5 on Mac OSX and trying to run the file tf_joint.feb from OpenKnee 1.0 on the same. I get the following error when I attempt to run the file:
FATAL ERROR: Missing attribute "mat" of tag "Elements" (line 97012)
When I open the file, I can see the attribute "mat" defined for all the Elements. I believe this is a syntax error, perhaps Febio 2.5 and OpenKnee version 1.0 are not compatible anymore. I also tried Febio 2.1, which is the oldest version available, but the problem persists. Is there an easy way out of it? Any help is much appreciated! Thanks a lot!

[Ahmet Erdemir]

If you have not done so, try the updated file (tf_joint_FEBio_v2.feb) released as part of Open Knee(s) - Generation 1 (Version g1-s1-v1.1.0.391). Direct link is

https://simtk.org/frs/download_confirm. ... oup_id=485

Let me know if you have the same issues.
ahm.

[Neelima Sharma]

I did run the updated file as well, and the error I was running into was:

FATAL ERROR: Rigid body rotations cannot mix prescribed and free components.
Rigid body: 0, Material: 0

Any hints on what may be wrong?

Thank you, really appreciate your help!

[Ahmet Erdemir]

The simulations in that file prescribe femur flexion while setting all other degrees of freedom for the femur free. Tibia is fixed by the way. Did you try using FEBio 2.1? That model was running in that version. I suspect that an update on rotation formulations in FEBio v2.5 may have broken this. I am also following up with FEBio folks.
ahm.

[Neelima Sharma]

I get the following error, a part of which is new and another part is the same old problem, when I try running v2 on febio 2.1

Failed loading plugin libFENeoHookeanPI.dylib
Reason: Failed to load the file.

FATAL ERROR: Rigid body rotations cannot mix prescribed and free components.
Rigid body: 0, Material: 0

Thanks,
Neelima

[Ahmet Erdemir]

In the file find (at the bottom):

Code: Select all

			<rigid_body mat="1">
				<prescribed bc="Rx" lc="2">0.785</prescribed>
			</rigid_body>
			<rigid_body mat="1">
 				<force bc="x" lc="3">0.0</force>
 				<force bc="y" lc="3">0.0</force>
 				<force bc="z" lc="3">0.0</force>
 				<force bc="Ry" lc="3">0.0</force>
 				<force bc="Rz" lc="3">0.0</force>			
			</rigid_body>

and change it as:

Code: Select all

			<rigid_body mat="1">
				<prescribed bc="Rx" lc="2">0.785</prescribed>
				<prescribed bc="Ry" lc="2">0.0</prescribed>
				<prescribed bc="Rz" lc="2">0.0</prescribed>
			</rigid_body>
			<rigid_body mat="1">
 				<force bc="x" lc="3">0.0</force>
 				<force bc="y" lc="3">0.0</force>
 				<force bc="z" lc="3">0.0</force>
			</rigid_body>

This will prescribe all the rotational degrees of freedom for femur and keep translations free. This should resolve the problem "FATAL ERROR: Rigid body rotations cannot mix prescribed and free components." Of course, this may limit what kind of boundary conditions that you can run. Let me know if this will work with FEBio 2.5

ahm.

[Neelima Sharma]

This seems to be working with Febio 2.5 but not with Febio 2.1. The error that I get in the latter case is -

Code: Select all

Failed loading plugin libFENeoHookeanPI.dylib
 Reason: Failed to load the file.

===== reforming stiffness matrix:
	Nr of equations ........................... : 184062
	Nr of nonzeroes in stiffness matrix ....... : 7148229

Assertion failed: (false), function MassMatrix, file /Users/KingsleyZ/Documents/MRL/software_compiling/FEBio2/FEBio2_intel_32:64bits/FEBioMech/FEElasticShellDomain.h, line 46.
Abort trap: 6

The code is running, I hope it converges.
Thank you so much for all your help!

[Ahmet Erdemir]

The errors you get with FEBio v2.1 may be related to its compilation for Mac. I advise you to contact FEBio team in this regard. Their forums may be helpful as well.
ahm.