Yield Strength in Pipe. 2

[_Yoda_]

I have a 1" NPS x 70" Schedule 80 steel pipe vertically cemented in the ground. A force is applied at the top of the pipe at a 45 degree angle downward.
A deformation happened at the very bottom of the pipe, the cement did not fail. The pipe failed from one side in tension and the other in compression.

Question: How can I find the yield strength of the pipe? Using that information I will find the minimum amount of rotational force that had to be applied to cause the pipe to fail.

Am I looking at this problem the correct way?
Any help and advice will be greatly appreciated. Thank you.

 

The pipe failed from one side in tension and the other in compression.

That's called bending. In this scenario of a skinny, long pipe under a bending force, no amount of yield strength will give
resistance to failure. No surprise that it failed at the base.

Designers know the secret is not so much a material's inherent strength as the shape of the part made from it that gives it rigidity. In other words it's not so much how much metal you use but where you put it. Hence we see wide flange beams, tubular elements, honeycomb construction, geodesic domes, space frames, etc.

Do some second moment of inertia calculations on various diameter and wall thickness combinations and it will point you to a solution that will resist the applied bending force. A pipe of twice the diameter and half the wall thickness would be substantially stiffer.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[oldestguy]

In answer to your question, get the section modulus of the pipe and assume a reasonable yield strength stress. My bet you will find you can't put much of a pull on the top of that tall pipe before it bends. Bottom of the pipe obviously had the most bending stresses due to longest lever.

 

[Tmoose]

Did the pipe buckle and kink ?

https://i.pinimg.com/originals/e3/84/d7/e384d7f36b8e33476ae5415ff8da4c76.jpg

That is sometimes the failure, and can happen well below the failure predicted just from "I".

 

[1503-44]

Kink type failures are more likely on thin walled pipe, maybe started by ovaling effects from a bending moment, progressing to local compressive stress buckling. 1" sch80 wall is a bit thick for that, but not saying it couldn't happen. If it was tension yielding elongation that casused the failure, rather than bluckling on the compression side, or an ultimate strength snap, then try about 30,000 Lbs/in2 x Section_modulus_in3 / 12in/ft to get Bending Moment M Ft-Lbs that existed at the time of failure. If it was tension failure at ultimate strength, the 30,000 might be higher. 40-45,000? A picture might help a lot.
Divide M by vertical height in Ft from failure point to the application point of the force to get its horizontal component Fh.
Multiply Fh by 1.41 to get the force that was applied at 45deg.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"