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Elninio
12-08-2012, 11:47 AM
How is it made?
Can it be machined?
Is it expensive?
Can it be made at home?
http://upload.wikimedia.org/wikipedia/commons/a/ae/Aluminium_foam_sandwich.jpg

chipmaker4130
12-08-2012, 12:07 PM
That's interesting. Can't answer any of your questions but I have one of my own...
What does the end-view of that piece look like (cross section)?
Thanks,
Gordon

Duffy
12-08-2012, 12:19 PM
I first saw aluminum foam in about 1960. A fellow student at university got a piece from his dad. The story that I was told was that it was developed at NRC while working on stuff for the Avro Arrow. They were looking for a way to produce seamless, rivetless wing sections by moulding. It did not work.
I believe that it is foamed with a high-temperature sulfur-based foaming agent, likely similar to the one used to produce Foamglas. They both stink!
Is it expensive? Almost certainly, (after all, it is likely made from molted BILLET!):rolleyes:
Can it be made at home? Not likely, although a gassey casting MIGHT be called foamed aluminum!:)
I have always thought that this was an idea that just never went anywhere.

Grind Hard
12-08-2012, 12:28 PM
http://en.wikipedia.org/wiki/Metal_foam

Wiki has some information and dates.

winchman
12-08-2012, 12:48 PM
Where did you get a picture of my welding?

Paul Alciatore
12-08-2012, 01:12 PM
Yes, HOW IS IT MADE? Precisely, how was this sample made with foam in the middle and fairly consistent solid sides? I mean, the obvious answer of "blowing a gas through the molten metal" does not answer that question. Was this made in one step? Or is it an assembly of two sheets of solid metal with the foam metal between them? The flat sides of some of the bubbles seem to support this sandwich method. But how would you do that? If it is assembled, the welds look almost perfect.

Probably getting into trade secrets here, but something must be known about how it is done.



How is it made?
Can it be machined?
Is it expensive?
Can it be made at home?
http://upload.wikimedia.org/wikipedia/commons/a/ae/Aluminium_foam_sandwich.jpg

Grind Hard
12-08-2012, 01:42 PM
Ok I know a bit about how they make closed-cell skinned foam out of styrene-plastic.

The outer layer "skin" is created by maintaining the die/mold at a specific temp. Basically, the skin forms first while the bubbles churn within.

If you get blowout or skin ruptures you adjust the die/mold temps, then you adjust your fill-rate/extrusion rate, finally you adjust your chemistry.

One assumes the principles are the same for metal-foams just at different heats and chemistry.

Mark Rand
12-08-2012, 02:31 PM
I would envisage casting the part with mould wall and injecting gas to foam the middle of the material when an appropriate skin thickness had solidified. That would probably be far more reliable than trying to fabricate a composite structure.

Edit:- Like what Grind-Hard says :-)

oil mac
12-08-2012, 02:57 PM
Shame on you guys for not sussing the production methods out before this , It is made in a top secret underground factory somewhere in the mid west of the U.S A, I might get into a lot of hassle for giving you all the low down, It is simple Great big economy size wasps, making nests in the stuff , The workforce are very highly paid, for danger money.:D

Grind Hard
12-08-2012, 02:59 PM
Shame on you guys for not sussing the production methods out before this , It is made in a top secret underground factory somewhere in the mid west of the U.S A, I might get into a lot of hassle for giving you all the low down, It is simple Great big economy size wasps, making nests in the stuff , The workforce are very highly paid, for danger money.:D

ABSOLUTE Bull**** and you know it.

This was outsourced years ago as Asian Hornets have a much lower cost per unit than American Wasps.

Evan
12-08-2012, 03:08 PM
I do know that there is a great deal of interest in producing foamed metals in micro-gravity conditions. That would be one of the highest priority applications for orbital manufacturing along with production of medical materials including drugs where convection does not cause separation of the constituents. They have been discovering some unanticipated effects that operate at high temperatures (and low) when gravity is absent. Flames in particular work in ways not at all predicted. A little known form of combustion of plain diesel fuel was recently verified on the ISS. The fuel actually burns at a temperature of about 120C, just above water boiling temp.



Cool Flames and Autoignition: Thermal-Ignition Theory of Combustion Experimentally Validated in Microgravity

At temperatures as low as 120 °C, fuel-air mixtures react chemically and produce very weak flames called cool flames. Unlike conventional flames—which generate large amounts of heat, carbon dioxide, and water—cool flames generate very little heat (e.g., a temperature rise of only 10 °C), carbon dioxide, and water. At low temperatures, the fuel and oxygen molecules have little energy and therefore do not react vigorously. The reaction never proceeds to complete combustion; rather, the molecules break down and recombine to produce a variety of stable chemical compounds including alcohols, acids, peroxides, aldehydes, and carbon monoxide. The weak temperature rise is produced by the breaking and reforming of the chemical bonds.

http://www.grc.nasa.gov/WWW/RT/RT1999/6000/6711wu.html

Foamed metals would be of high value if the material can be held in zero gee for a long enough time for the foam to arrange itself in a least energy packing configuration, unlike the sample shown. Such a configuration would produce predictable and consistent properties, the lack of which makes current products much less useful.

oil mac
12-08-2012, 03:10 PM
ABSOLUTE Bull**** and you know it.

This was outsourced years ago as Asian Hornets have a much lower cost per unit than American Wasps.

Still bigger labor problems using Asian hornets ,Grindhard, They are bad tempered, vindictive & stubborn , The work study guys found, You will never get inside the mind of a hornet , Better importing some of our Scottish wasps, "Dear little things" Speak to Alistair Hosie he has a cheap source for them & stop outsourcing work, & bring jobs back home!

Evan
12-08-2012, 03:15 PM
If you read through this long list there may be information on foamed materials. I haven't looked yet.

http://www.grc.nasa.gov/WWW/RT/RT1999/intro/contents.html

Black_Moons
12-08-2012, 03:44 PM
Where did you get a picture of my welding?

That was my first thought, Someone just forgot to turn on the shielding gas when they welded those two sheets of steel. :P

Elninio
12-09-2012, 06:20 PM
I guess that, the heat dispersion in aluminium occurs so fast, that heating the mold or cooling it would not be like pouring bubbly aluminium onto some chilled surfaces. There's no foamy steel and aerogel (foamed glass) has much smaller pores. It's used for sound and heat insulation, and outperformed honeycomb aluminium, which has been used for a long time (in crumple zones for example). The homogeneity of the foaming agent is amazing - look at some larger pieces, they are very consistent.

darryl
12-09-2012, 07:42 PM
A good material might be aluminum coated mini or micro balls of some viscous compound made from recycled plastic bottles and tires. It would be stored dry and in an oxygen-free container, and just prior to use it would be mixed into a solution of lye and oxalic acid and cast like concrete. The molds would be heated, and the heat would break down the compound so the walls of the mold get a layer of higher aluminum content at the surfaces. Because the average density would be reasonably low you would cast in enough ribs so the resulting module would actually have a lot of strength without being too rigid. Now you have something to build a spacecraft out of.

Micrometeorites would likely punch through the outer layer, but they would get swallowed up in the viscous, multi-directional passageways in the material. It would be able to absorb considerable vibration, so it should be able to withstand multiple rocket launchings. Plus, being fairly light and foamy, it would float. That might be a good feature for splashdown landings.

The bottom of this craft could be cast as a solid block, with the largest component of this being a vaporizable material- ion engine fuel. There would of course be a barrier layer that would remain intact when all the fuel has been vaporized.

You would probably begin by spraying this mixture onto the outside of the crew compartment, which itself could be made from a denser version of this material, then you'd add outer mold sections and just continue to fill it as you go up. At a certain point you'd turn it upside down and align the structure into the nose cone made of unablatium, and you'd fill that. The junction of this nose cone and the previously cast body of the craft would be where you fit all the access hatches, windows, grappling hardware, instrumentation, etc.

Around the outside of this craft you might have several deployable booms, swinging out from the side. These would do double duty- they would be rocket motors to start with, then they would swing out to become docking points for visiting spacecraft. Another version of this PRANK compound (plastic, rubber, aluminum, no-meltum, and kryptonite would be resilient enough to act as a gasket for air-locks, etc.

NASA should be knocking on my door soon- :)

Machine
12-09-2012, 09:12 PM
I'll take a stab at how that aluminum foam is made: They might have poured molten aluminum into a chilled mold. That would get the outer shell to solidify quickly (kinda like a hollow chocolate bunny). Then quickly plunge a hollow steel or tungsten tube with a "sprayer head" down into the molten metal in the core of the mold. Air or some other chilled gas (possibly cryogenically cooled) is pumped through the tube and out the sprayer head as it is quickly withdrawn through the molten core. The sprayer head is designed to create and evenly distribute bubbles of a certain size based on a certain pressure and flow rate. This would leave a column of rapidly solidifying bubbles in its wake, neatly encapsulated within the already cooled and solidified perimeter.

That's my guess, anyway.

john hobdeclipe
12-09-2012, 10:08 PM
Yeast

Black_Moons
12-10-2012, 03:50 AM
Micrometeorites would likely punch through the outer layer, but they would get swallowed up in the viscous, multi-directional passageways in the material.

Yeaa... Except no :)
Iv seen test videos of simulated micrometeorites hiting multiple inchs of solid steel.
It looks like what you would expect to see if you shot water straight on with a very high powered rifle. Except I think water would slow the bullet down faster! The highest power rifles only reach about 0.9km/second, Micrometeorites range from 8km to 80km/s :)

Basicly it would just go through anything like a hot knife through.. air.

Now, a more intresting material might be able to self seal after a puncture event, maybe having a high pressure gooie center that trys to fill any void. Theres not much you can do to actualy stop something going several KM per *second*

They have developed self sealing gas tanks and such.. I wonder if the space station is 'self sealing' in event of (minor) puncture?

derekm
12-10-2012, 08:49 AM
Yeaa... Except no :)
... Theres not much you can do to actualy stop something going several KM per *second*
..

What you need is a large envelope of stuff that slows it down by causing the leading edge to get hot and burn and eject parts of the meteorite, and eventually cause it to explode before it reaches the target...

bob_s
12-10-2012, 12:31 PM
see:

Isotech, Inc.
777 Schwab Road, Suite T
Hatfield, PA 19440
Toll Free: 800-314-3332
Phone: 267-663-5555
Fax: 215-631-9148
E-mail Isotech


http://www.isotechinc.com/foamed-aluminum.html

philbur
12-10-2012, 02:55 PM
From Bobs' link, second page of this pdf:

http://catalog.isotechinc.com/Asset/foamed-aluminium.pdf

Phil:)

philbur
12-10-2012, 03:03 PM
and some more background:

http://www.tms.org/pubs/journals/JOM/0012/Banhart-0012.html

Phil:)

Evan
12-10-2012, 03:13 PM
The standard method for shielding against micrometeors is double wall shielding. The inner wall is the true hull of the spacecraft. The outer wall is a layer of thin material spaced a couple of inches away from the inner wall. When the outer wall is hit the particle penetrates but in the process is turned to plasma which then strikes a much larger area of the inner wall and fails to penetrate. That works up to fairly large sizes of several millimetres or so. Above that the energy involved become very large. A piece of steel the size of a marble at orbital velocity has the same energy as a 1200 lb block moving at 60 mph.

Fortunately, as is often the case in nature, the size distribution of particles in space follows 2nd power law. As the mass of particles grows the number of them grows exponentially fewer.


.

JoeLee
12-10-2012, 06:04 PM
Just start TIG welding some crappy aluminum and you'll end up with the same stuff. If I knew there was a market for it I would have saved all my aluminum welding projects.

JL................