a question about ellipsoidal fiber distributed material?

[andromeda]

Hi everybody
I have a question about ellipsoidal fiber distributed material which is describe in FEBio user manual p.125. In the manual the Cauchy stress tensor is described as follows:

Capture.JPG

apparently, n shows the unit vector along fiber direction in current configuration, but in the reference (Ateshian et al. 2009) the same formulation was represented but n denotes the unit vector along fiber direction in reference configuration. I want to know which one is correct?

Thanks,
Faezeh

[maas]

Hi Faezeh,

The user's manual is incorrect. The n vector is defined in the reference configuration.

Cheers,

Steve

[andromeda]

Hi Steve

Thanks, and what about (teta, phi). Are they in global coordinate or local?

Thanks,
Faezeh

[maas]

I believe they are in the local coordinates defined by the mat_axis tag. So, if you have not defined a mat_axis tag in the material definition, they should be global coordinates.

Cheers,

Steve