Punching angles prior to rolling.
Punching angles prior to rolling.
(OP)
I'm looking for the formula to calculate the hole layout for a large angle flange punched prior to rolling. The angle is 3" x 3" x 1/4" rolled leg out to a 60" inside radius with holes in the outstanding leg on a 2" gauge.I know the spaces will stretch some since they're outside the neutral axis, but I haven't been able to find out how much. Can anyone help?
Thanks,
Scotty
Thanks,
Scotty






RE: Punching angles prior to rolling.
I don’t think you are going to find any such formula. The pre-punched holes will certainly lead to localized stretching, at each hole, during the rolling process, and they may mess a bit with the rolling process. And, this could lead to some radial cracking at the holes too. I think I would roll the angles first, and let them relax for a short time. Then tack the two angles back to back, do your layout on one, and match drill them.
RE: Punching angles prior to rolling.
As dhengr notes, you might get some cracking. Inspect closely after rolling.
RE: Punching angles prior to rolling.
Dik
RE: Punching angles prior to rolling.
Thanks,
Scotty
RE: Punching angles prior to rolling.
Dik
RE: Punching angles prior to rolling.
I tend to think that the term 'x' should by closer to t/2 than the position of the N.A. because I think yielding will be in tension, not compression. If you are doing a test case, why not measure s' after bending?
BA
RE: Punching angles prior to rolling.
There is a whole vert. leg and some inner part of the horiz. leg on the compression side of the N.A./centroid of the static section. The horiz. leg also has the punched slot in it on the tension side of the N.A., so the static/calculated centroid will be moved further toward the vert. leg even before yielding. Then it will be moved still further toward the vert. leg (compression leg) during the rolling process (partial hinge formation?). Over the 1.875" slot length the section stiffness and Sx/Z will be significantly reduced, with fairly significant yielding/strain outside of the slotted hole, almost to the point of producing a flat spot or different rolled radius at the slots. Unless they really dress the slot edges and corners, I’ll bet they will get some ripping or cracking in the radial direction. The only saving grace is that this ripping will propagate across the rolling grain of angle material.
RE: Punching angles prior to rolling.
Consider that the neutral line may move outwards because there is more sectional material to compress (3" x 1/4" non-perforated leg) and much less to stretch, mainly the 1"x1/4" above the holes.
I would run a test first with a few feet of perforated angle, mainly to estimate the resultant inner diameter (critical in the case of a flange).
Once you have the actual diameter and total length figured, you could just divide a straight length in equal parts, according to the number of slots.
You will be rolling around 31 feet of 3"x3" angle and welding its ends.
Consider that the first and last few feet will not be curved by the machine.
"God will not look you over for medals, degrees or diplomas, but for scars." - Elbert Hubbard
RE: Punching angles prior to rolling.
We punched a trial piece of angle. It didn't crack but we did get a small amount of thinning between the edge of the hole and the toe of the angle. I don't know my customer's usage so I sent them pictures and asked for their blessing. On the vertical leg there is an ever so little bit of a ripple at the hole but if you weren't looking for it I don't think you'd even notice it.
We laid out our 7/8" x 1 7/8" slots on 16 7/8" centers prior to rolling. After rolling they're on 17 3/16" centers. An increase of 5/16". I expected some but not that much. I'd still like to find a proven formula for figuring this in the future.
Thanks for your suggestions.
Scotty