I need to find a solution to this problem.

I could probably figure it out myself if I had the proper resources, (textbooks, etc.) but I don't.

There is a 2" SCH 40 Black Steel pipe coming out of the ground. It is threaded on the end. The OD is 2.375". The ID is 2.067". Screwed onto the pipe is a 2" SCH 40 Galvanized Steel Coupling with a 2.75" OD and a 2.375" ID. Screwed into the coupling is a 2" SCH 40 Galvanized Steel pipe with a 2.375" OD and a 2.067" ID. If I want to machine a groove into the coupling to make sure it breaks there, rather than above or below it, how deep does the groove need to be?

Oh yeah, I don't want it to break until there is a 600lb, or .6kip load 2' above the center of the coupling (moment=14.4 kip-in). Is this possible given the section modulus of the pipe?

3/18/2008 2:25:02 PM

the answer is 5

3/19/2008 12:16:29 PM

Yes

3/19/2008 1:20:51 PM

I should have rephrased the question.

What is the new OD of the coupling at the machined "weak point" such that it would break under the .6kip load?

3/19/2008 3:42:59 PM

max. axial stress = (internal moment*outer radius)/(moment of interia about centroid)

you also have a shear stress (.6 kip) at that point, but i think it'll break by the bending moment first

[Edited on March 19, 2008 at 5:43 PM. Reason : also need to make sure it doesn't break either of the pipes first]

3/19/2008 5:42:25 PM

do your own hw, moron

3/23/2008 5:08:44 PM