Aerospace Material Specification Notes 1

[Papasaurus]

Hi All,

It sure has been awhile...

Okay, in the past, I've become blindly accustomed to stating material specifications in my material callouts on my drawings, ex. MATERIAL: AL ALY 6061-T651 PLATE IAW AMS-QQ-A-250/11. That was all in defense and aerospace, and as far as I can remember the requirement was a given. Now I'm in more of a consumer electronics sector of aerospace, and such detail seems to not be as required. So I'm stuck with: AL 6061-T6, .250 thk.

I'm perusing back thru MIL-HDBK-5 and the MMPDS for guidance on these inclusions, but I wanted to hit up the community for your advice as well. As far as I know, all material certs are provided according to the contracts with the shops, but it still makes me itch not having it on the drawings.

I'm also uncomfortable with our basic aluminum abbreviation AL, instead of AL ALY, but that just makes me feel pedantic.

Thanks!

Ed Lee
CAD Admin / Sr. Mechanical Designer

https://www.linkedin.com/in/edwinlleejr/

 

[drawoh]

Ed Lee,

If you are designing light weight, safety critical structures, you need to be very picky about material. If you are doing consumer electronics, you need to be very picky about cost. Allowing your vendor to pick the cheapest acceptable material saves you money, as noted by Joe Osborn. If you were really serious about strength, you would have ordered ALUMINIUM 7075-T6.

Consumer electronics in aerospace? I have designed airborne "appliances". This stuff must remain attached to the aircraft in a survivable crash. That makes you pickier. By the time I got my stuff rigid enough to be functional, it was strong. This definitely is true of optics. Once you make your electronics vibration resistant, they are fairly strong too. I would worry more about the fasteners than the fabricated material.

ALUMINIUM 6061-T6. The word "ALLOY" is redundant.

--
JHG

 

[btrueblood]

Except you mispelled aluminum.

 

[cowski]

http://www.worldwidewords.org/articles/aluminium.htm

 

[drawoh]

btrueblood,

It is "aluminium" in the Oxford dictionary. The Oxford dictionary is always right, except when I disagree with it.

--
JHG

 

[Papasaurus]

Thanks drawoh, it's going to be no small feat relinquishing that level of liability to the fabricator for the sake of cost. Oh well, I'll get used to it.

I've been specifying AL ALY for over twenty years, redundant or not. It shows as such everywhere from NASA to Raytheon to the titles of the AMS sheets themselves(not abbreviated). Apparently it's more of an esthetic preference. Again, I guess I'll get used to some austerity in my notes.

And the spelling argument is an ongoing friendly discussion my wife and I have every time it's pronounced on Top Gear / Grand Tour. I like to shake the Reynolds Wrap box at her. =D

Ed Lee
CAD Admin / Sr. Mechanical Designer

https://www.linkedin.com/in/edwinlleejr/

 

[WKTaylor]

OK guys... I'm gonna get in trouble for over-nerd'ing this post...

As an aero-materials engineer, specifying any metal alloy, is fraught with anal minutia... EVERY aspect important.

"If you were really serious about strength, you would have ordered ALUMINIUM 7075-T6."

OH Yeah....?

NOTE. The alloy number-temper combined with the material specification is, by definition, ‘aluminum alloy’ What is more important than saying ‘aluminum alloy’ are the many ‘form’ descriptors.

Here is just a fraction of material definitions I have used a to-nail-down a concise material description for a part delineated on a ASME Y14.100 drawing [Flag Note].

NOTE. IF strictly coded into a PL line/column format, then there would be a distinct short hand used... depending on space available and needed clarity of definition... interpreter BEWARE... a lot of coded details are often missed, due to lack of intimate knowledge about the meanings or the details!

There are various ways that ‘clarity’ make a distinct difference for just a final product made from 7075 and in a standard ‘-T6xxx’ temper state. Here is how complex the definition of 7075-T6 can become... and EACH ONE of these represents a separate and distinct materials representation...

PS: I hope there are no 'spec' boo-boos or typos... my eyes are crossed...

0.062 thick clad sheet, 7075-T6, AMS4049 or AMS-QQ-A-250/13

0.062 thick clad sheet, 7075-O, AMS4048 or AMS-QQ-A-250/13. Heat treat to –T62 after forming in the W temper, per AMS2770

0.500 thick clad plate, 7075-T6, AMS4049 or AMS-QQ-A-250/13

0.062 thick bare sheet, 7075-T6, AMS4045 or AMS-QQ-A-250/12.

0.062 thick bare sheet, 7075-O, AMS4044 or AMS-QQ-A-250/12. Heat treat to –T62 after forming in the W temper, per AMS2770

0.500 thick bare plate, 7075-T651, AMS4045 or AMS-QQ-A-250/12

0.500 thick bare plate, 7075-O, AMS4044 or AMS-QQ-A-250/12. Heat treat to –T62 after forming in the W temper, per AMS2770

0.500 Dia drawn round bar, 7075-T6/-T651, AMS4122, AMS4123 or AMS-QQ-A-225/9

0.500 Dia drawn round bar, 7075-O, AMS4186 or AMS-QQ-A-225/9. Heat treat to –T62 after forming in the W temper, per AMS2770

0.500 Dia extruded round bar, 7075-T6/-T6510/-T6511, AMS4154 or AMS-QQ-A-200/11

AMS10133-1003 extruded profile/angle, 7075-T6/-T6510/-T6511, AMS4154 or AMS-QQ-A-200/11

0.500 Dia extruded round bar, 7075-O, AMS4476 or AMS-QQ-A-200/11. Heat treat to –T62 after forming in the W temper, per AMS2770

AMS10133-1003 extruded profile/angle, 7075-O, AMS4476 or AMS-QQ-A-200/11. Heat treat to –T62 after forming per AMS2770

Die forging, 7075-T6, AMS-QQ-A-367

Die forging, 7075-T6, AMS4126

Die forging, 7075-T6, AMS-A-22771

Die forging, 7075-T652, AMS-QQ-A-367

Die forging, 7075-T652, AMS-A-22771

Die forging, 7075-T652, AMS-QQ-A-367 or AMS-A-22771

8.0-ST X 10.0-LT X 40.0-L forged block, 7075-T6, AMS-QQ-A-367

8.0-ST X 10.0-LT X 40.0-L forged block, 7075-T6, AMS4126

8.0-ST X 10.0-LT X 40.0-L forged block, 7075-T6, AMS-A-22771

8.0-ST X 10.0-LT X 40.0-L forged block, 7075-T6, AMS4126, AMS-A-22771 or AMS-QQ-A-367

8.0-ST X 10.0-LT X 40.0-L forged block, 7075-T652, AMS-QQ-A-367

8.0-ST X 10.0-LT X 40.0-L forged block, 7075-T652, AMS-A-22771

8.0-ST X 10.0-LT X 40.0-L forged block, 7075-T652, AMS-QQ-A-367 or AMS-A-22771

NOTE. this is by no means a complete listing of possible '7075-T6 [-T6xxx]' cases....

BTW... 7075-T6xxx almost any form... over certain very low 'as produced' thicknesses is generally prohibited on aircraft due to low stress corrosion cracking and exfoliation corrosion thresholds... and poor Short Transverse [ST] grain fatigue crack initiation toughness [rapid crack initiation/growth].


Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[SwinnyGG]

The point of the thread is that Aerospace applications are an outlier in the engineering world, with regard to the level of specificity and quality control required when specifying and procuring materials.

Your TV probably has a bunch of little aluminum brackets holding up various electrical parts... is there any impact to life safety if those parts are made from 5052 or 6061? Not likely.

If you're in aerospace you just live in an environment where more stringent requirements are needed than the rest of the world.

 

[3DDave]

jgKRI - yes there is. The 5052 parts will be bent. The 6061 parts will have cracked at the bends. However, will there be a big pile of paper in a file cabinet with all the certs buried in it just in case a TV stops working and a bracket is to blame? Not a chance.

 

[SwinnyGG]

I didn't say bent brackets.

You're missing my point here. In Aerospace, nearly EVERYTHING is a life safety issue. This drives very intense materials certifications and requirements.

In most other engineering endeavors, very few things are life safety issues, so cost becomes more important than finding a material that is the absolute best engineering option.

 

[3DDave]

jgKRI - there aren't any flat brackets holding anything up. I already mentioned traceability not being a problem in TVs; the converse is what you are after.

 

[SwinnyGG]

Uh.. ok.

 

[drawoh]

3DDave,

This is why you follow Joe Osborne's advice and specify ALUMINIUM, on your TV parts anyway. You inspect them and reject anything with cracked bends. If your vendor is dumb enough to use 7075-T6, he will have to re-fabricate everything.

There is a further issue. If your anal retentive designer systematically specifies 8.0-ST X 10.0-LT X 40.0-L forged block, 7075-T6, AMS-QQ-A-367, sooner or later, purchasing and manufacturing will understand that you all don't really mean it. It will be too bad when you run into a functionally critical part that does require the reliable, high strength material.

I have specified ALUMINIUM 7075-T6. I designed a mirror pre-loader. I could not get Delrin to work. My stresses were too high for ALUMINIUM 6061-T6. It was a critical part in a $1M+ Lidar system.

--
JHG

 

[WKTaylor]

NOTE, RE bent sheet metal.

In aero industry we have minimum allowed bend radii for each alloy-temper combo to prevent cracking down the BR during forming [straight/compound] and/or premature in-service.

These BR allow for 'cold-bending of hard materials', 'cold-bending of soft materials [annealed or post solution heat treated, etc]' and 'hot-bending of hard materials'. These tables also allow for adverse orientations of bends... such along the sheet grain... and with minor sheet metal defects... without cracking and while still attaining good service life.

NOTE.
The bend allowance tables presumes that the sheet metal surface is free of significant defects and imperfections [scratches, gouges, corrosion, pits, dents, wrinkles, etc]... and that all sharp edges are lightly deburred. Significant [not minor] pre-existing defects can become a source of crack initiation during forming or in-service.

NOTE.
Tighter bend radii are possible under strictly controlled circumstances...but that's another story.

See FAA-H-8088-31-V1, Figure 4-125. Minimum bend radius (from the Raytheon... ...) for typical 'cold-bending of hard and soft materials', as follows...

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1505407105/tips/FAA-H-8088-31_V1_Sheet_Metal_Bend_Radius_Table_Alloy-Temper_VS_Sht_Thickness_svgh5t.pdf[/url]



Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[ctopher]

Communicate with your suppliers/vendors. Call out materials/specs that work with your company.
For the aerospace side, the material specs called out are important and are needed. For consumer electronics, probably not. It may be an overkill and may run the cost up for your parts because of suppliers/vendors ignorance in materials.

Chris, CSWP
SolidWorks '17
ctophers home
SolidWorks Legion

 

[drawoh]

WKTaylor,

I have seen an electronics chassis that must have been fabricated by some aircraft facility out of 2024-T4. The bends and the relieved corners were beautiful. Everything else was cut out with a nibbler.

The regular sheet metal shops have bend tools with standard inside radii. The shops I am using now like to do 1mm[ ]radii on 1.6 and 2.03mm[ ]sheet. To do specific radii, they "bend in air". This is inaccurate and expensive. Most non-airframe parts are not highly stressed. If they are not cracked in fabrication, they won't break. Most of our failures are fasteners or vibration. We recently broke a frame when we drop tested it. We redesigned that frame section to be thicker. The weight penalty was well below a kilogram.

--
JHG

 

[Papasaurus]

Well, we're certainly a hybrid of consumer electronics and aerospace. In fact, high-end consumer electronics mounted into high-end (private) aircraft. In my opinion, the certifiable quality of the materials we use should be absolutely accountable. All the way back to our fabricators. But thus far, that has not been required here. And unless I come up with a terribly compelling reason, we will continue not to.

Most of the parts that currently concern me are sheet metal structural. For the most part I'm sticking with 5052-H32 or 2024-T3, from .030 to .050 thick. When designing each piece according to its expected function, I'd like to work with confidence that the material will behave in the manner my experiences tell me it should. In one case, I've deviated from using a default alloy-temper.

Before I came on to the task, an industrial designer dictated sharp outer corners for the enclosure. During the development process, it's been determined that the previous material, 5052-H32 .030 thk, was too easily dented or dimpled in shipping and general handling, but it could handle the smaller bend radii. So I'm specifying the material to be 2024-T42 .040 thk, either by starting with -O, forming, then treating to T42, or by starting with T3, annealing, forming, then treating back to T42. All so I can meet the ID proposal and keep the outer enclosure from denting. Am I crazy for wanting some assurance that the material is properly spec'ed? If they use some bargain sheet and crack it at R.06, am I SOL?



Ed Lee
CAD Admin / Sr. Mechanical Designer

https://www.linkedin.com/in/edwinlleejr/

 

[SwinnyGG]

In the world in which I work, if a supplier can't meet the drawing they quoted against, that is not my problem.

 

[Papasaurus]

Yeah, I've been having other issues with this fabricator's capabilities. But this is who I'm stuck with. I think I've just been spoiled in the past.

Ed Lee
CAD Admin / Sr. Mechanical Designer

https://www.linkedin.com/in/edwinlleejr/

 

[CWB1]

Something to be aware of is that the print is often NOT the be-all-end-all of a part's specification, very often there is a whole bookshelf of corporate standards adding details to which the part must be made unless the print specifies otherwise. At a former employer I commonly called out simply "cast grey iron" which required outside suppliers to reference a large book's worth of material, process, and quality standards to mimick very specific details of our own high quality castings. From the print alone an outside observer might think we cared little about material, in reality the company had owned multiple foundries over almost a century and was well regarded for its material science.