Torque Capability Of an Intereference fit joint

[desertfox]

Hi

Can anyone help me with this query:-

thread725-314067


regards

desertfox

 

[dhengr]

Desertfox:
I’m not quite sure what you are doing or trying to prove or disprove... but some food for thought.

How are you achieving your interference fit? That interference fit contact force is in compression in the shaft, it’s akin to a bearing stress on the shaft. The yield stress in bearing is actually higher than the yield stress in tension, due in part to confinement by surrounding material. Furthermore, we typically pick (or the material spec., ASTM min. is) a tensile yield stress at a .2% strain offset, but the stress strain curve continues to climb to ultimate. So, I think the yield stress would be a lower limit for the normal stress in your torque calc. Also, at those kinds of contact stresses you could probably consider a fairly high coef. of friction, since you would probably actually be getting some mechanical or almost atomic/molecular level bonding or forge welding bonding btwn. the two surfaces, I would think.

Check out a slight taper press fit btwn. the shaft/axle and the hub/wheel, just as the railroads mount wheels to axles. They use a little white lead lubricant, press to some very high pressing forces and can develop some significant torques as on locomotive drive wheels. I would think that this method also develops significant mechanical or almost atomic/molecular level bonding or forge welding bonding btwn. the two surfaces.

 

[Cockroach]

I know this answer, DesertFox.

There is a paper written in 1962 for the Shell Oil Conference that discusses premium oilfield connections, loading, shear of Box and Pin, that sort of discussion. I can't remember the author name, popular paper still in the patch. I have it, found it online in PDF format.

Let me look for it and get it to you via this forum.

Regards,
Cockroach

 

[Cockroach]

Two papers which may be of help, Clinedinst is the author. Both can be found on line using "Strength of Threaded Joints for Steel Pipe" or by searching under the author name.

Hope this helps with your computations.

Regards,
Cockroach

 

[Cockroach]

This is the second Clinedinst paper. I've used this information with good results on Casing and steel Tubing.

Regards,
Cockroach

 

[desertfox]

Hi Cockroach

I'll study those papers with interest thank you very much.

desertfox