How to calculate Allowance for Shinkage Fits – Thin Walled applications

How to calculate Allowance for Shinkage Fits - Thin Walled applications

I am trying to verify some shrink fits do not exceed the material mechanical properties. The ratio of diameters I have is quite low & thus the Engineers data handbook does not cover it.

Can anyone help with reference matrial.

Info
Hub is heated to expand onto shaft.
Shaft (4140:
OD 99.644
ID 82.5

Hub (4140):
OD 114.3
ID 99.39

Regards
James

Mabye I can help. I just learned this stuff like a week ago. I believe only experts in things can teach them, but I will try to help.

Considering the 2 parts are the same material, and I am assuming you want to find the amounts of stresses on the materials, then you can compare them to the yield strength of AISI 4140 and see if they will bust. Here are the equations you would use:

p=(Eq/2b)[((c^2-b^2)(b^2-a^2))/2b^2(c^2-a^2)]

Where:
p=Pressure Created by Force Fit
q=Total Diameteral Interference
E=Modulus of Elasticity

****IN THIS CASE
a=0
b=OD of Shaft (99.644)
c=OD of Hub (114.3)

From there, take your p and do the following:

To=p[(c^2+b^2)/(c^2-b^2)]
To= Tensile stress in outer member (hub)

Ti=-p[(b^2+a^2)/(b^2-a^2)
Ti= Compressive stress in the inner member (shaft)

There are also equations for the amount of diameter change in each member. Lemme know if you want those.

There is also an equation for the amount of heat needed to be added or taken away to achieve the shrink fit, but I dont feel like typing more and if I can do it you can do it!!! Haha, no, but let me know if you want it.

Hope this helps, Someone correct me if Im wrong

NOTE: The diametral interference comes from a table of force and shrink fits (an FN1-FN5)

I cant give you one because you didnt specify your units on you IDs and ODs

for ref, just search table of force and shrink fits

This is not my field, but I hope this helps.
http://www.engineeringtoolbox.com/stress-thin-walled-tube-d_948.html
http://www.engineeringtoolbox.com/stress-thick-walled-tube-d_949.html

I’m sure I’ll oversimplify, but it seems you could calculate the pressure exerted on the shaft by the hub and then calculate the stresses from the above link.