Ring Nut External Thread Analysis

[tugowar]

Hello,
I am anlysing external threads on a ring nut. Unlike a bolt this ring nut will be in compression. I have tried to look for method/data in handbook but so far no luck. How will the anlalysis differ from the analysis of bolt threads.

Currently I am using formulas for bolts/screws.

 

[CoryPad]

Do you mean something that is similar to this:

If so, then you need to subtract the hollow area when calculating the stress area A_s.

Nothing else jumps out at me at the moment.

Regards,

Cory

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

 

[Cockroach]

I suppose if you have knowledge of the external loads causing the compression, then perhaps Pressue Vessel Theory may be of use.

Triaxial Wall Stress (Von Mises-Hencky) would be:

S = sqrt(3) P [R^2 / (R^2 - 1)]

for S=stress, P=external pressure, R=D/d for D=outer diameter and d=inner diameter.

This equation is derived from the stress vector given hoop, radial and longitudinal stresses. I'm not sure the longitudinal is of consequence in your case, the JPEG from CoryPad obviously has open ends so I can't see axial load coming into play. The equation would then tend to overstate your wall stress.

I still can't see your problem. The external thread is used to hold the piece in place axially. Would not those threads see some sort of shearing action? I suppose you wouldn't want the damn thing popping out from compression, perhaps this is your intent. This is why I provided you with the above equation.

Anyway, I regress. Good luck with it.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada