Hello. I have 2 large diameter cylindrical shells that are "rabbetted" together. I am trying to determine the approximate load required to pull them apart without much success. The parameters are as follows (all length dimensions in inches) and result in a .005" (diametric) interference:(adsbygoogle = window.adsbygoogle || []).push({});

Outer Shell(female):

OD2 = 40.525

ID2 = 40.175

t2 = .350

Inner Shell(male):

OD1 = 40.180

ID1 = 39.98

t1 = .200

The axial engagement length of the fit is:

L = .125

The materials are the same for inner & outer shell:

v= 0.3

E = 221 GPa

I have tried a couple of approaches that yield very different numbers. I first tried just considering the force required to deflect the inner shell by the interference value (radially .0025") and then using this "normal force" to determine the frictional load to overcome. I used a formula in Roarks to determine this force. This requires a significant amount of force compared to using a "shaft/hub" press fit calculator such as the one at this tribology site. The difference in answers is from about 1200 lbf to 20 lbf, respectively.

I think a couple of things are happening here, but could use some guidance:

1) I believe that the Roarks approach might be overly conservative since it does not consider the outer shell and that it will expand a little to accommodate the inner shell.

2) For a shaft/hub equation, I am guessing that they might not be too accurate for "shafts/hubs" as large as the ones I am looking at. But maybe someone could comment on this?

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# Large Diameter Interference Fit: Removal Load

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