Bending Strength of a deformed section
Bending Strength of a deformed section
(OP)
I work in an industrial plant and I get a lot of small questions to support other projects, usually their pretty easy. This one made me think twice.
A blind flange on a davit port to a tank is suspended from a 1 1/2" sch40 pipe bent to a 90 deg angle. I know a bent shape should keep a strength of Mp until failure, but does that apply at a bend of 90 deg? wont their be a significant change in area?
In this situation the loading is small (250#) but this could fall on a worker. The dims of the arm are 24" high reaching out 14" with a bend radius of 6".
Thanks in advance for any help.
Adam
A blind flange on a davit port to a tank is suspended from a 1 1/2" sch40 pipe bent to a 90 deg angle. I know a bent shape should keep a strength of Mp until failure, but does that apply at a bend of 90 deg? wont their be a significant change in area?
In this situation the loading is small (250#) but this could fall on a worker. The dims of the arm are 24" high reaching out 14" with a bend radius of 6".
Thanks in advance for any help.
Adam






RE: Bending Strength of a deformed section
RE: Bending Strength of a deformed section
prex
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http://www.levitans.com : Air bearing pads
RE: Bending Strength of a deformed section
aisc has an Mp = 1.11 K' = 13.32 K" for an undeformed 1 1/2" std pipe in tbl 3-15 e13
-but I wasn't sure if this applies since it's been plastically deformed.
RE: Bending Strength of a deformed section
Apparently bent pipe has reduced strength properties due to the severe bend, and the failure mode may be vastly different compared to a straight pipe loaded to failure. Buckling mode etc.
RE: Bending Strength of a deformed section
I found an eq on pg 40 of B31.1 - this checks out. But it says that this is for
"elbows, miter bends, and full size outlet branch connections"
which are (or made of) hot rolled sections. Correct me if I'm wrong.
RE: Bending Strength of a deformed section
The kids over in the FEA corner of the industry would perhaps have fun with this.
RE: Bending Strength of a deformed section
Adam
RE: Bending Strength of a deformed section
You say... “A blind flange on a davit port to a tank is suspended from a 1 1/2" sch40 pipe bent to a 90 deg angle. I know a bent shape should keep a strength of Mp until failure, but does that apply at a bend of 90 deg? wont their be a significant change in area?” Whatever that means? I wonder how many hundreds of free body diagrams could be drawn which fit that verbal description. Each one, of course, causing slightly different stress configurations and considerations. Generally speaking, you should take into account and changes in thickness and shape which may have occurred due to the pipe bending process, they change the mechanical properties of the section. Also, the bending process causes yielding in some areas of the pipe shape. Instead of thinking in terms of Mp whatever that really means to different people, look up Bauschinger Effect. You have strained the material in the bending process, or you are now working the material further up the stress/strain curve. With loading or reloading the steel will still follow essentially the same “E” slope on reloading, and if you increase the loading it will move further up the stress/strain curve, still following the same “E” slope, until it reaches failure at Fu. Today, Mp is kinda a nebulous thing with all the multiplying and reducing factors which have been introduced to loads, strengths, probabilities, etc. Today, with Mp we are taking about the section being able to tolerate some plastic deformation without failing drastically, but that is probably not your situation.
RE: Bending Strength of a deformed section
You might want to measure the bend and estimate the actual section properties there.
Mike Halloran
Pembroke Pines, FL, USA