tube fitted within tube w interference. Shrink i.d. of inner tube? 3

[electricpete]

Seems like this should be a standard calculation, but I can't find it.

If I have a smaller tube 1 with inner and outer diameter ID1 and OD1

Fit into a larger tube with inner and outer diameter ID2 and OD2

Where an interference delta = OD1-ID2 > 0

Perhaps different E1 and E2 (but not essential).

Where can I find the formula for reduction in ID1?


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[desertfox]

Hi electricpete

Try this calculator:-

http://www.tribology-abc.com/sub23.htm

regards

desertfox

 

[desertfox]

Hi Again

Here's another calculator:-

http://www.engineersedge.com/calculators/machine-design/press-fit/press-fit-calculator.htm

regards

desertfox

 

[desertfox]

This site gives explanation of the formula too:-

http://www.utm.edu/departments/engin/lemaster/Machine Design/Lecture 15.pdf

 

[desertfox]

Hi electricpete

The formula for inner radius change can be found from:

x = (p*Ra/E)* ((Rb^2 + Ra^2/Rb^2-Ra^2)+ v)

where Ra = inner radius

Rb = outer radius

V =poissons ratio

E = elasticity modulus

p=pressure

pressure in your case would be the pressure generated at the interface of the mating cylinders

regards

desertfox

 

[TheTick]

The key is that strain on inner and outer is equal.

 

[electricpete]

Thanks guys. Is there an obviouis reason why the strain would be the same?

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[40818]

Electric pete, "Is there an obvious reason why the stain would be the same".
Strain compatability.

Timoshenko's Strength of materials (Part 2) covers this topic.

Using the same notation as Desertfox above, the radial displacement at the outer surface due to external pressure is:

x = -(p*Rb/E)* ((Rb^2 + Ra^2/Rb^2-Ra^2)- v)

(the minus sign indicates that the displacement is towards the axis of the cylinder).

I actually think this topic was covered in eng-tips previously somewhere.

 

[desertfox]

Hi electricpete

40818 is spot on, but if you want a further explaination
see this site:-

http://www.mech.uwa.edu.au/DANotes/cylinders/compound/compound.html

desertfox

 

[ccw]

The "engineers edge" calculator is very thorough, and forces you to consider many loads that may or may not be in your situation. Very nice. Thanks!

One point to consider: If the local stresses at the faying surfaces do compute as exceeding the published proportional limit, after the joint is made, it is usually OK if ductile materials are used.