How to calculate Buttress Threads stress for a comparison to standard threads?

[Tweedclassic]

Hello all

I am trying to calculate the strength advantage of a buttress threaded bolt and nut statically loaded in one thrust direction. I have found several examples for determining the stress's of a square thread, for example Link.

Will these same equations apply? I am having a hard time finding buttress thread specific calculations or equations anywhere. Is this something that will require FEA? . Tips on where to look or start would be greatly appreciated.

Regards,

Robert

 

[desertfox]

Hi tweed classic

I believe the only difference is the profile proportions of the thread.
Go to the link below and scroll down you will find what your looking for.

http://www.ejsong.com/mdme/memmods/MEM30009A/lifting_systems/power_screws.pdf

 

[Cockroach]

I don't think it is that easy, the first sentence in the section on stress says it all. Thread stress computations are complicated!

The Buttress is a tapered thread form and therefore, equations associated with shear and bending are not the same as those for a straight thread. Several studies from notables in the field, Clinedinst for example, are quite detailed in the analysis and have restricted the study to line pipe threads. None-the-less, the departure from classical methodologies such as that in the ANSI standard, is particularly pronounced. I have included one such paper for your review.

I have found that small adjustments in the numerical values associated with some threads are highly acceptable to field results. Many of my own studies with VAM, Tenaris-Hydril and an inhouse tapered Acme thread form came within 3% theoretical values when using the paradign laid out in the Clinedinst paper. I have not looked at Buttress threads, therefore cannot comment on accuracy. I surmise you would see similar results if pressed to do so, although the assymetry of threading may give larger errors or at least beyond standard scientific error.

Good luck with it.

Regards,
Cockroach

 

[Tweedclassic]

Thanks
I will review the paper. I really appreciate it.

Cheers

Robert