straight pole light 2

[engahmadalqwaqnh]

hello

how i can calculate the force required to straight light pole after welding if i have a diameter 200mm

 

[drawoh]

engahmadalqwaqnh,

Perhaps you mean "straighten"?

What did you weld, how did you weld it, and how far out of straight is it? Do you have a photo or sketch?

--
JHG

 

[MintJulep]

With the geometry of the pole, the geometry of your straightening fixture and the material properties.

 

[HPost]

he posted this in the fluid power forum...

"I need to straight light pole after welding process because the pole after welding become a deflection ( banana effect )(no straight)then i need to determine the force to return the pole straight by hydraulic press .
the pole have curricular cross section with diameter 200mm and 5mm thickness and material is A36 steel. and length the pole is 12 m"

Until we know how it's deformed, there is not much that can be done to help.

Other than to say that A36 steel has a yield strength of 250MPa.

If we assume that its bent in the middle, supported at both ends, it will need 500N to deflect 4.95m. However, I can't imagine its that straight forward though.

He just needs a big press, suggest he gets a 5 ton bench press or, as has been suggested in the other forum, change the welding process.

 

[drawoh]

HPost,

Actually, it is not that simple. Welding along a beam bends it into a circle segment. Applying force in the middle and at the ends creates a non-constant bending moment, and a resulting non-constant radius, especially since some of the bending will be elastic.

Could they apply a weld bead on the side opposite the original weld?

--
JHG

 

[SnTMan]

There are services that flame straighten stuff like this.

http://www.flameoninc.com/

No affilation

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[HPost]

drawoh...

You seem to confusing me with someone that cares.

This person has posted an obscure and random question with no data to allow us to help.

I really don't care how he or she sorts it out.

 

[engahmadalqwaqnh]

Hpost.....

this not random question and really its not simple as you imagine. and yes "I need to straighten light pole after welding process because the pole after welding become a deflection ( banana effect )(no straighten)then i need to determine the force to return the pole straight by hydraulic press,
the pole have curricular cross section with diameter 200mm and 5mm thickness and material is A36 steel. and length the pole is 12m.

and the weld process its automatic along the pole

thanks

 

[berkshire]

Run an oxy propane flame on the opposite side of the pipe as the weld is taking place. With some fine adjustment your poles should come out straight.
B.E.

You are judged not by what you know, but by what you can do.

 

[3DDave]

Look for stress = Mc/I; there is no 'force' involved until a moment load is decided on. Once the needed moment is determined, then you look at how much leverage you have and divide the moment by the leverage. You will need enough stress to plastically deform the beam.

Alternatively you could hammer the weld to cause the required deformation by thinning the weld material.

The advantage to hammering is that near the ends of the tube the leverage available becomes smaller; it is zero at the end, which means the required load to produce a moment become infinite.

 

[ameyerrenke]

This article doesn't address round tube, but you're answer is heat straightening.

http://www.fhwa.dot.gov/bridge/steel/02.cfm

 

[drawoh]

3DDave,

Bending the pole like a cantilever beam does not result in a constant moment along the full length. Read up on plastic hinges.

--
JHG

 

[3DDave]

JHG - I had assumed one would have to progress along the length of the beam. Not sure why you think it would be a cantilever beam. What I was getting at was that a 3-point bending system can't correct curvature at the end of the beam as the reaction points need to be 0 inches apart, so infinite load is required to produce a moment.

Since the distortion is from a localized shrinkage from the welding material a localized hammering will expand the metal in a useful direction and eliminate the bend and this can be done at any location, including the ends.

 

[tbuelna]

Sounds like the pole is rolled from plate and seam welded along one side using an automated process. This would likely result in a "banana" shape of the welded pole. But I don't know if the curvature would be constant from the end of the pole where the weld started to the opposite end of the pole where the weld terminated. Straightening the pole using a press would require applying enough force to yield the material, but this would need to be performed over short sections of the pole to get a good result. I think it might be better to use a rolling process between dies to straighten the round pole.

 

[IFRs]

Put it through a 3-roll bender. Gently at first. With a rubber cushion.

It would help to know how close to straight the final pole needs to be ( and why ).

 

[berkshire]

The other factor not mentioned here, is that most fabricated light poles tend to be tapered, otherwise you could just use rolled steel tube or pipe.
B.E.

You are judged not by what you know, but by what you can do.