Press fits, or interference fits, are similar to pressurized cylinders in that the placement of an oversized shaft in an undersized hub results in a radial pressure at the interface.
Start by finding the interface pressure.
Where δr is the RADIAL interference for hub and shaft of the same material, with modulus of elasticity, E.
If the shaft is solid, ri = 0 and
If the shaft and hub are of different materials
Once we have the pressure, we can use the cylinder equations to compute the hoop stresses at the interface.
A) The ID of the hub is tensile:
B) The OD of the shaft is compressive:
= -p if shaft is solid
Strain Analysis of Press Fits
The press fit has no axial pressure, so σl= 0, and it is a biaxial stress condition.
The circumferential strain
which equals the radial strain (because C = 2pr).
Because the radial change we get the increase in Inner Radius of the outer member (hub):
And the decrease in Outer Radius of the inner member (shaft):