SHRINK-FIT CONNECTION

[teom]

I have to compute a shrink-fit connection between a shaft and a hub on a Ø100 mm.
In order to determine if we have an elastic deformation we have to compare if the maximum compressive stress in shaft is smaller than the yield point of the shaft (flange) material.
The material for both parts(shaft and hub) is 17CrNiMo6.
The material is case hardened (30HRC-core, 60HRC-outer layer). In the formula should use the value for the core or for the outer layer?
Does anybody know a way to compute a shrink-fit connection for such a case (a harder layer and a softer core)?

Thank you in advance!

 

[EdDanzer]

A shrink fit doesn’t care about the hardness. The coefficient of expansion of the material doesn’t change with case hardness enough to have an effect. The temperature that you heat the case hardened piece is limited so you may need to cool the other part, this will limit the amount of shrink you can obtain. If you are trying to hold a size on the OD of the shrink fit area it will need to be undersize before mating the to parts.