Swaging 2024 tubing, from T3,O, T42?

[heloman78]

I'm working on a project where I'm reproducing (PMA) an aircraft control rod. The part is made up of a center section of custom drawn seamless tubing 1.18 in diameter with a 0.065 wall thickness. The ends of the tube are swaged to 1.090 in diameter (7.7% reduction in diameter) and then threaded for attachment of clevis type rod ends. I have a lab report that says the OEM tube is 2024 T42, which sort of makes sense conceptually; the tube could have been swaged in the "O" condition, and then heat treated to T42. But this seems a little odd for a couple reasons. First, I would think that the tube would not remain straight during the heat treat process. Second, the lab report I got on the original tube was based on physical testing and I don’t see how the lab would have differentiated between T42, and T3 using only physical testing, so maybe the original was swaged straight from T3.
What I'd like to do is swage straight from T3 but I'm looking for justification that I will not create a possibility for brittle fracture at the swaged area. In fact, I have in the past made these tubes for a DER repair straight from T3 and performed destructive assembly tensile tests by attaching the tube to one end of the machine and the clevis to the other, the rods always failed at the clevis for both the original, supposedly T42, and my replacement formed straight from T3. What do you guys think of swaging straight from T3? Any thoughts on the cold working effect during the swaging process? Thank you!

 

[rb1957]

1) doesn't PMA require you to remanufacture the original part with the original processes ?
2) i don't think the T42 heat treat will distort the rod.
3) if you've experience with the T3 part, then you should be able to get an RDA to cover the difference in the material (if you can't remanufacture the original part).
4) how much thread can you fit onto an 0.065" thk wall ?

 

[heloman78]

1. No, you can change the part if there's good reason, as long as it won’t affect safety or function. I’ve made material changes and minor design changes on several PMA parts, usually they make a clear improvement to the part.
2. Thanks for your input.
3. The T3 part was a DER repair, this is going to be a PMA part so it will have ACO approval, just want to cover all my bases.
4. The swaged area has a thicker wall do to the reduction in diameter, and the threads are extra fine, UNEF.
Thanks you!

 

[rb1957]

1) then haven't you answered your own question ? you've experience with the T3 part to know/believe it's equivalent to the T42 part, the properties of T3 and T42 are near enough the same ...

4) "The swaged area has a thicker wall do to the reduction in diameter" ... yeah, ok about 1/2 of 5/8 of damn all, or roughly a 7.7% increase (about 0.005") which'd make it a 0.07" wall ... still not much to thread into. do you roll the thread by any chance ? (that'd make some sense)

 

[heloman78]

1. Your right, I don't see a problem, but I need to explain it in a clear way; I'm wondering if I can come up with a better explanation than "I did it before." What I'm looking for is a little understanding of the cold working effect when swaging.

2. Your right, the wall of the swaged area is just over 0.07", I would say best practices would require a rolled thread, but the original is not rolled, surprisingly. Wall thickness at the root of the thread is about 0.05".

Thank you!

 

[rb1957]

i'd be surprised if anyone got particularly "aerated" over a material change T3 for T42.

your previous experience is something to draw on, but not i suspect DER witnessed so i don't think it can be used directly.

"form, fit, and function"

 

[TVP]

FWIW, the minimum property requirements for drawn 2024 tubes in T42 or T3 condition is the same.

 

[dgapilot]

I used to make swaged tubes at one of the places I worked. Smae type arrangement you describe. As I recall, we used T3 tubing in a rotary swager. We also used roll taps. Is the application both push and pull? If so, verify both tension and compression loads. Perhaps as part of your manufacturing process you may want to do an eddy current or dye penetrant prior to thread forming just to be sure the swaging didn't cause any cracks.

 

[heloman78]

Thanks for the comments dgapilot! I'm going to do a penetrant inspection after swaging.

 

[WKTaylor]

Heloman78...

CAUTION.
I have been privileged to talk with push-pull control rod vendors. Art and science come together in ways they jealously guard... and are NOT necessarily expressed on drawings or in aircraft manufacturer's process manuals.

for instance...

They procure raw extruded tubes that have extremely tight wall-thickness and straightness tolerances; and are 100% ultrasonic and eddy current NDIed.

They emplace tight controls on end-fitting concentricity and tube bowing to avoid eccentricities.

They destructive/fatigue test completed tube assys to ensure the Assys meet design requirements.

They control mass of the tube assy to ensure consistencey ship-set to ship-set.

Great pains are taken to ensure corrosion protection of the ID and faying surfaces.

Etc.

Regards, Wil Taylor

Trust - But Verify!

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