How to count the press fit between circular model and uncircular model

[SPADEJACK]

thread404-151892.

http://www.eng-tips.com/viewthread.cfm?qid=151892&page=6

according to the thread link above.
i found that formula which given by desertfox is for circular inner body and circular outer body.
my question is, what if the outer body is not circular. For example, i want to press fit a pin to a rectangular block. Then, how to count the contact pressure (Pc) between two body.

 

[gwolf2]

Use Hertzian contact formulae - they are all over the web including some free calculators.

This is a very wierd thing to want to do - is this a joke?

 

[GregLocock]

I'm guessing something more like plastic deformation, for example forcing a ball bearing into a square tube. If that is the case then Hertz is not going to be much help.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[corus]

I'd go back to the basic theory of press fit which is based upon equating the displacements between the two bodies with the amount of interferece. In your case you'd be displacing a recatangular box section at the contact points with the ball, and vice versa displacing the ball with point contact from the rectangular block. For the recatangular block you can apporximate the displacements using Roark and assuming some end condition to the plate. For the ball I'm not sure.

corus

 

[SPADEJACK]

let me clear the problem,

i want to press a material with press machine where the puncher is an eight-shape.

my problem is, the puncher is stuck with the material and the punch holder cannot hold the puncher. (the holder and the puncher is press-fitted). I assume that the contact pressure between the puncher and the material is larger than the contact pressure between the holder and the puncher.

What i want to know is the contact pressure between the material and the puncher.

(im sorry if i cant make my self clear)

 

[GregLocock]

Photos/diagrams/drawings would help.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.