[michael.jeunehomme@gmail.]

Hello :-) .
I'm currently trying to model a fibre drawing process(axisymetric problem) and i want to observe the stress distribution along the fibre. So, along my fiber i have a decreasing temperature profile. The viscosity of my fibre is given by the Vogel-Fulcher-Tamman (VFT) law.
The stress in the fibre is computed (i guess) with tau_axial=-pI+2*visco*D, where D is the apropriate component of the strain rate tensor.

The problem is that i observe oscillations of tau at the end of my fibre, where the lowest temperatures are reached. And after some investigation it seems that the problem does not come from the viscosity (that has values about 1e13/1e14 at this location) but rather comes from D. I noticed that D begins oscillating in these region...

Anyone has an idea of how to solve this? Are the limits of the model reached or is there a possibility to avoid the strain rate oscilations?