Use of Welding for Aircraft Frames
Use of Welding for Aircraft Frames
(OP)
I wonder why it is not used instead of machining massive aluminum blocks to frame parts. I understand that bolt to hole and hole to hole connections are safer when compared to welding but machining of an Al plate to a frame part is extremely costly when compared to welding.
Answer to this question may be the change of microstructural properties after welding, crack growth through welding, QC of weld seams in detailed frame parts can be a problem. However, I think that these all can be solved by design solutions like in pressure vessels or other industries. Is there another reason that I missed which makes use of welding non applicable.
Thanks
Answer to this question may be the change of microstructural properties after welding, crack growth through welding, QC of weld seams in detailed frame parts can be a problem. However, I think that these all can be solved by design solutions like in pressure vessels or other industries. Is there another reason that I missed which makes use of welding non applicable.
Thanks





RE: Use of Welding for Aircraft Frames
however, research "friction stir welding" ... a new method that's fashionable (A380) for attaching stringers to the fuse skins without rivets.
RE: Use of Welding for Aircraft Frames
RE: Use of Welding for Aircraft Frames
Also note that CNC mills can run unattended, so the labor cost associated with ~95 pct stock removal is not as great as you might first expect.
Mike Halloran
Pembroke Pines, FL, USA
RE: Use of Welding for Aircraft Frames
In the old days radial engine mounts were all welded tubing, and any fittings welded to the tubing as well.
We all know it can be done and last look at some of the motorcycle frames made of Al.
RE: Use of Welding for Aircraft Frames
Several older light aircraft fuselages were welded steel tube spaceframe.
It's hard to weld good aluminum. Getting the combination of strength and fracture toughness that makes stuff like 2024-T3 and 7475-T76 so useful is hard enough as it is. You can weld up 2219 quite well, but it's not really good for anything except elevated temperature use. I think the A400M inlet, which is hot air anti-iced/de-iced, is 2219.
To get adequate fracture properties a lot of Al alloys need the -51 (or -52) temper, which has cold word before aging. Re-solution treating and aging would be needed after welding for adequate properties, and it's hard to do cold work on an assembly, never mind the distortion that tends to occur on quench.
NASA has done quite bit of work on weldable aerosapce alloys, including (it tends to be older work):
http://nt
RE: Use of Welding for Aircraft Frames
http://ww
RE: Use of Welding for Aircraft Frames
What you almost described is precision die-forgings. Available in somewhat limited alloys, they have tremendous potentical for material savings and minimal machining... for sizeable production runs of parts.
For onsey-twosy parts... can't beat ecconomy of machining from a forged block or thick plate, but mechanical properties are alway an issue.
FSW has good potential for material savings.. but the metallurgy in the stir/HAZ zone is always an issue.... although can be improved by re-heat treatment and peening
Regards, Wil Taylor
RE: Use of Welding for Aircraft Frames
Although they're not specifically airframe structures, many highly stressed turbofan engine or gearbox parts are welded using various solid state and fusion processes:
-Shaft and gear blanks are commonly solid state friction welded (direct drive or inertia processes) where there is a large change in diameter.
-Compressor blades are sometimes linear friction welded to the hubs.
-Large hollow titanium fan blades have the skins and honeycomb cores diffusion bonded (solid state process).
-Compressor drums are electron beam or laser welded (fusion process in a vacuum environment).
As the others have noted there are some examples of flight structures using solid state joining:
-Eclipse used friction stir welding to join stringers to skins.
-Boeing uses friction stir welding to build cryo fuel tanks on their Delta IV rocket. They also used conventional TIG welding on the older Delta II alum. cryo tank structures.
-Rockwell used several diffusion bonded titanium pieces on the Space Shuttle.
If you want to get an idea of why few conventionally welded structures are used on aircraft, take a look at sec. 8 & 9 in MIL-HBDK-5 to see what allowables and knockdown factors apply to fusion welded joints.
Hope that helps.
Terry
RE: Use of Welding for Aircraft Frames
Not too sure about this, but with FSW you can (to what degree I don't know) bond disimilar metals.
http://www.solveering.com: Multidisciplinary Engineering Services
RE: Use of Welding for Aircraft Frames
RE: Use of Welding for Aircraft Frames
That said, a lot of them are still riveted though.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Use of Welding for Aircraft Frames
Wichita State University [WSU] has a VERY active R&D Friction Stir Welding [FSW] program in the National Institute for Aviation Research [NIAR]. They receive funding for fundamental aviation research from US government [FAA, DoD] and aero-industry in Wichita KS [aviation capitol of the world]. Engineering MS and PhD candidates are leading the hands-on charge... with an outstanding cadre of PhD-level research instructors guiding the process and interfacing with the outside world. Some incredibly ambitious goals for a university!
One thing they are pursuing is the solid state [FSW] welding of pieces together to form a basic shape that would be be basis for a replacement extrusion or a forged bulkhead with integral reinforcement, etc. Concept is that thin sections have superior grain directionality (orientation) and mechanical properties that could be enhanced (after finish machining) using Laser Shock Peening [LSP]. They are currently attempting to make L, T, U, Z etc sections from thick extruded bar-stock that match the mechanical, SCC and DaDn properties of the extrusion they mimic [replace]. The concept could be expanded to plate with integral stiffener made from bar-stock, for bulkheads, etc....
Go to NIAR website and "search NIAR" for FSW & LSP.
http://www.niar.twsu.edu/
May also find some of the other research fascinating and informative [human factors, composites, aging acft, crash dynamics, mechanical testings, Virtual Reality, etc...].
Regards, Wil Taylor
RE: Use of Welding for Aircraft Frames
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RE: Use of Welding for Aircraft Frames