Bending of aluminum sheet 5

[mte12]

It looks like welding aluminum decreases strength in weld/heat affected zones.

As an alternative, I was thinking of bending a single sheet and cutting voids (in order to reduce weight).

Bending sheet seems like it would cold work the material, hence assuming no loss of strength at least. Would this assumption be correct?

Also is radii shown in table below achievable for arrangement shown. Currently looking at 6mm or 8mm Grade 5083.

[URL unfurl="true"]https://www.australwright.com.au/wp-content/uploads/2019/02/Aluminium_Catalogue.pdf[/url]

 

[rb1957]

we don't use 5082 ... presumaby more ductile than 2024 or 6061. But you have data so run with it. I'd do some tests first. how much does the metal thin in the corner ? There's probably some learning required.

I wouldn't cut the holes first, as they'll affect the strain of the sheet. If you must have holes, cut them later, but seriously, how much weight are you saving ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[dvd]

Be aware of rolling direction effects on bends - bending parallel to rolling direction is more difficult

 

[mte12]

Thanks for the comments guys.

 

[JStephen]

Welding aluminum reduces the allowable stress near the welds.
But if the strength of the overall section is governed by elastic buckling, that may not be an issue at all.
And if you do lose strength in the area immediately adjacent to the weld, with a cross section that large, it may be a negligible loss in the overall strength. I'm not sure how that's accounted for in the design.
On the bend radius- if you're having this done at an outside shop, ask them what bend radius to use- they may have tooling that makes it easier with specific radii.
It might be advantageous to put a lip on those legs, see figure below.
There is an aluminum design manual, last I checked, it was pretty pricy. But that might help you optimize the design.
With a cross section that large and thin, working out details of supports and attachments may be more of an issue than overall bending.
I would think you could drop the thickness slightly and get a lighter design without the holes.
Adding those holes just complicates the heck out of any kind of design work. I'd especially omit them in the flange area.

 

[mte12]

OK thanks JStephen, will take note of your comments.

 

[Stress_Eng]

In addition to introducing the holes, have you considered flanging them? Doing so will introduce additional stiffness. I use to do this quite often in my “shop floor” days.

 

[Stress_Eng]

Just adding to the point of flanging the free edges. Analytically, doing so can effectively give you a ‘simply supported edge condition’, when compared to a ‘free edge’ without flanges.

 

[mte12]

Thanks for advising Stress_Eng.

 

[dhengr]

Mte12:
I would grind a slight radius on the two corners and clean up the plate edges in the areas of the bends, over and above what Dvd showed. Otherwise edge imperfections will likely induce cracking at the edges of the plates when you do your bending.

 

[mte12]

Thanks dhengr, the comment from dvd relating to cracking is a concern actually.

 

[Stress_Eng]

In my experience of aluminium alloy sheet development and fabrication work (late 80’s), the developed sheet had to be solution heat treated, after which the part needed to be fabricated within 2 hours. The heat treatment made the part more workable and less susceptible to cracking when folded. After this period, the part would have naturally aged and was no longer capable of being folded. If fabrication is a concern, it may be worth getting recommendations from fabricators with aluminium alloy experience.

 

[mte12]

OK thanks Stress_Eng.

 

[3DDave]

Heat treat of 6061 and similar is desirable for small (<2T) bends. I don't recall annealing and heat treating being used otherwise for bending.

 

[Stress_Eng]

Just out of interest, I’ve found my old A/C Fitting Apprenticeship log books, surprised I found them! Just went through and found a few examples. Avionics equipment holder, made from 18-16G Alu. Alloy parts, 1.2mm thick Alu. Alloy Frame, Reinforcing Plate and fabricated flanged edge (free edges and holes) Bracket (similar to yours), they all involved heat treatment. That took me down memory lane! It’s a process that just may be worth investigating.