Threaded Fastener & Nut Hoop Stress 1

[cnuk]

I am working on building a spreadsheet for threaded connection design. It is for an oilfield application (or others) where you need to join two coaxial shafts together with a cylindrical coupling. The coupling has to transmit a torque and axial (tensile) load between the two shafts. One of the design goals is to make the coupling OD as small as possible while still safely transmitting the required torque and axial load. I can use the power screw calculations to figure out the axial load and torque calculations but what I am missing is the calculation for the hoop stress in the nut. For a square thread there should no hoop stress, high for a v-thread, and an acme thread somewhere in between the two. Since the goal is to reduce the OD as much as possible the hoop stress in the coupling seems critical to me.

Does anyone have any advice on calculating the hoop stress in a nut that has a cylindrical OD? I don't want to just to FEA yet and think a good spreadsheet would work for me.

 

[Cockroach]

Use API equations, try the Grant Prideco website.

Hoop stress is typically defined by the interference fit of threads. This can be found at various websites. The best one I found was at the University of Tennessee, Mechanical Engineering course notes posted by a professor.

Good luck.

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