Bending of Aluminum Tubing 1

[domettim]

Is there any way to predict the thinning of walls and length of strain along thin wall tubing specifically aluminum bent on a radius? I'm trying to get shear calculations at points along the bend but would like to account for the reduction of area.

.06" wall w/.125" corner radii - 1"sq outside dim tube bent 75 to 80 degs on 2 1/2" inside radius

Thanks




Tim

http://www.dom-met.com

 

[BigInch]

Poisson's ratio will describe it.
If tension stress is applied to a material, stresses in the perpendicular directions will equal the tension stress x Poisson's ratio, opposite in sign, thus are compressional.
Those compressional stresses act to compress the material in the perpendicular directions, thus thin the wall.
If a length of a 1" long element of a pipe wall is stretched 0.1 inch, the thinning will be Poisson's ratio x stretched length per inch of wall thickness. Since Poisson's ratio is roughly 0.25 to 0.3 for most metallic materials (check what it is for AL), thinning of the wall in that case would be appx. 0.3 x 0.1"/ inch of original wall thickness
If original wall thickness was 0.5", then
Thinning = 0.5" x 0.3 x 0.1"/1" = 0.015"
New thickness = 0.5 - 0.015 = 0.485"

"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
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[MikeHalloran]

You might want to talk to your fabricator about tooling costs and production rate before you go predicting section properties.

Square tubing needs a lot of help to make a nice bend.

You may elect to make a faster, cheaper, and much uglier, crush bend, in which case your cross section changes to something between an E and an H.



Mike Halloran
Pembroke Pines, FL, USA

 

[BigInch]

Just noticed that's a very large angle. It won't be holding its shape for that bend.

"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
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[domettim]

Mike,

You are correct - "You may elect to make a faster, cheaper, and much uglier, crush bend, in which case your cross section changes to something between an E and an H."

The walls perpendicular to the bend change shape and are concave parabolas



Tim

http://www.dom-met.com

 

[BigInch]

Then you're also well beyond the range of calculating anything.

"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
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