Torque and preload calculations for threaded tubing

[homebrewdude]

I am trying to define torque and preload requirements for threaded tubing.

I am using standard fastener equations to determine pre-load at a particular torque value.

I used standard fastener equations to determine the tensile stress area. I then subtracted the area that is considered hollow on the tube. (Tensile area is less for tubing then bolts)

The part I am stuck on...
I have a pre-load value and a Tensile area.
How do I know if I am overstressing the threads on the tube?

My pre-load is 47,000 lbs

My material is 50,000 yield

Is my actual stress on the threads =Preload/Tensile area?

 

[CoryPad]

There are three failure modes for threads: 1) tensile fracture of externally threaded member; 2) shear fracture of externally threaded member; 3) shear fracture of internally threaded member. You have started work on number 1, and yes, you can use stress = force/area.

Regards,

Cory

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