Validity of FEM Method

By FEM analysis a value of  0.7 for the friction coefficient results for the steel rolls with Ra equal to 10.30 μm

In order to controll the FEM validity an experimental test has been conducted with the same rolls to evaluate the maximum height reduction Δh_max . Knowing maximum height reduction the friction angle value has been calculated by formula: 

Δh=2r(1-cosρ)             with r rolls radius and  ρ angle of friction

  Δh _max =64 mm  ----->   ρ= 34.5°----->  μ = tg ρ = 0.69