Material ID/Capacity Question

[TravisR100]

I'm curious if any of you might have a clue as to the material this item is made from. It very much looks and feels like aluminum however it has a very odd gold tint to it. The attached photo is very representative of what the metal looks like in real life. At first I thought maybe it had some type of zinc chromate treatment. It almost looks like it's very lightly gold anodized. I'm pretty sure it's aluminum but not sure if it's the standard 6061.

I'm also curious what anyone thinks the weight bearing capacity is. For clarification, this is an aircraft jack adapter. The aircraft this is made for sits too low to the ground for a typical aircraft jack to jack it up. The protruding cylinder fits in the wheel axle and the jack goes under the half sphere at the top. I'm looking at creating one of these myself out of 6061 but I'm curious what the weight bearing capacity would be. The part is uniformly thick except for the tapered "nose" at the top where the half sphere is at. Other than this tapered nose, it's about 2 to 2-1/1 thick. Any help or suggestions are appreciated.

[punish3r]

I'm curious if any of you might have a clue as to the material this item is made from.

No real idea, but I can throw a guess or two your way. It's an 'aircraft' part (or at least aircraft associated) so if it isn't 6061, it's 2000 series or 7000 series. 7000 series have a higher UTS (generally), but your 'gold' coloration could be from the high(er) percentages of copper found in 2000 series aluminum alloys. Or it could just be a corrosion resist (Alodine, Iridite, etc).

In short, if I had to guess I would say tempered 7075 (GUESS) given the application, fatigue requirements, appearance and industry. But I also recognize that even with the part in my hand I'd be HARD pressed to give you an accurate answer without the proper testing. (And even then it would be ridiculously expensive to get much more than the first digit of the series)

Oh, and I probably should have said this at the outset, but call the manufacturer and ask. It's the type of situation where they want you to know that they know, you know?

[TravisR100]

Thanks for the reply. I suppose I asked the wrong question. The better question is, what should I make it out of? The max weight it would need to support is about 3000 lbs. Would 6061 do?

[punish3r]

Thanks for the reply. I suppose I asked the wrong question. The better question is, what should I make it out of? The max weight it would need to support is about 3000 lbs. Would 6061 do?

[Short answer: no. Read on if you've got some time to waste ]

Aye, there's the rub. To make a recommendation would require more information. Minimum cross section, moment of inertia, strict definition of the material and its provenance, safety factor, number of uses before retirement, some FEA, etc, etc... You get the picture.

(This is not a recommendation, just a note on aluminum alloys)

IN GENERAL... 6000 series aluminum alloys are of a group known as "precipitation hardenable". This means that the yield strength can be varied as a function of the cure time and temperature of the alloy. 7000 series are also precipitation hardenable but much more so than 6000 series alloys. In point of fact, of all of the precipitation hardenable aluminum alloy series, 6000 series (as a group) are the weakest. 6000's are generally seen more often due to the fact that their silicon content makes them easier to machine.

For a slapdash comparison, the oft quoted yield strength of 6061-T6 is 276 MPa (roughly 40 ksi) whereas 7075-T6 (same temper) has a quoted yield strength of 503 MPa (roughly 73 ksi). This means: one would require a cross section of 6061-T6 to be in the neighborhood of 185% larger than a piece of 7075-T6 in order to yield at the same tensile load, perpendicular to the cross section. And yes, I know that's a gross oversimplification.

This of course does not account for elongation at load, fatigue strengths (which really, really matter in these types of alloys), crack growth rate, thermal expansion, Young's modulus, toughness, shear strength, etc, etc... You get the picture.

That being said, I wouldn't recommend that any replacement part for an airplane, on an airplane or even NEAR an airplane be made without the properly vetted tools and materials. Sorry, but there's just too much at stake. I realize that a part like this is in a 'non-critical' application with relatively low risk, but bad habits are born of lax enforcement.

And there I go lecturing again. Sorry about that. To summarize, I personally do not feel that 6061 would do the trick and more importantly I would recommend that you purchase a ready-made part from an authorized manufacturer rather than manufacture one yourself and risk having it fail.