Compute contact pressure (Hertz) and friction torque
 E1 GPa  v1 default ball bearing steel
 E2 GPa v2 default Sapphire
 R1 mm R2 mm enter R2=0 for sphere on flat
  H GPa Hardness weakest body
 F N n rpm ω=2πn/60
 E' GPa R' mm
 r mm d m
 pm GPa pmax GPa
 M Nmm q mW

 1) Half elliptic contact pressure assumed (Hertz) if pm<H/3
     Uniform contact pressure assumed if pm>H
     if H/3<pm<H then M, q and r are computed by interpolation