constituve law

Hello all,
 I wish that i have the answer because i want to understand .
So, i want to use the constituve law for the Hertz-Mindlin formulation.
And i want to use a non linear damping in both the normal and tangential direction.
So the problem is : when i specify "en" and "es" in my script like
 InteractionLoop(
  [Ig2_Sphere_Sphere_ScGeom(),Ig2_Facet_Sphere_ScGeom()],
  [Ip2_FrictMat_FrictMat_MindlinPhys(
   en=0.1,es=0.2)],
  [Law2_ScGeom_MindlinPhys_Mindlin()]
 )
I create a linear or a non-linear viscous damping!!!
Really i'm confused , because when i read (
https://github.com/yade/trunk/blob/master/pkg/dem/HertzMindlin.cpp
https://github.com/yade/trunk/blob/master/pkg/dem/HertzMindlin.hpp
)
I find two meaning , one time you tell that when I specify "en" and "es" , automatically betan and betas will be computed from the formulation and this means that a linear viscous damping will be used .
on the other hand , you tell that when i specify en or es alpha will be computed and this means that we use a non-linear viscous damping .
Thanks a lot for help . This help me to undrestand a lot of thing