frictional model
 

Hi all. I'm trying to modify the Schaeffer's frictional viscosity model. But I cannot find the expression of "the second invariant of the deviatoric stress tensor". I have to make a UDF. Dose anyone know the expression of "the second invariant of the deviatoric stress tensor" by using C language?

Thanks.

Hi oka, Could you learn to make a UDF for Schaeffer's frictional viscosity. If yes, please guide me too.