1) The value of the
diametrical interference is typically about δ/d=0.001. The
calculator is based on elastic deformation (Lame's equation),
i.e. the stresses should be smaller than the elastic limit Rp0.2
of the elements. The interference should be corrected for the effect of
surface roughness. The flattening of roughness peaks by mounting
under high pressure is generally estimated at 10% of the Rz-value
where Rz=6Ra (ISO 6336-2).
The correction at the diametrical interference thus becomes
0.1·2·(Rz1+Rz2). If the surface roughness
of the shaft Ra1=0.5μm and that of the bore Ra2=1μm then dδ=0.1·2·6·(0.5+1)=1.8μm
and δeff=δm-dδ where δeff=effective value of diametrical
interference, δm=measured value of diametrical interference and
dδ=correction for surface roughness.
2) Approximate value for the coefficient of friction
μ are: for steel - steel contacts dry
between 0.1 and 0.15, lubricated between 0.05 and 0.1, for steel
- yellow metal contacts dry between 0.05 and 0.1.
3) Thin walled elements are usually press fitted in the full
plastic regime of the material. |