Slashdot Mirror
Super Strong Metal Foam Discovered
MikeChino writes to tell us that a North Carolina State University researcher has discovered what appears to be the strongest metal foam yet, capable of compressing up to 80% of its original size under load and still retain the original shape. The hope is that this amazing material could be used in cars, body armor, or even buildings to absorb the shock from earthquakes. "Metal foam is exactly what you might think – a cellular structure made from metal with tiny pockets of space inside. What makes Rabiei’s metal foam better than others is that she’s been able to make the tiny pockets of space more uniform. And that apparently is what gives it the strength as well as elasticity it needs in order to compress as much as it does without deformation. Many tests are being performed in the laboratory to determine its strength, but so far Rabiei says that the spongy material has 'a much higher strength-to-density ratio than any metal foam that has ever been reported.' Calculations also predict that in car accidents, when two pieces of her composite metal foam are inserted 'behind the bumper of a car traveling at 28 mph, the impact would feel the same to passengers as an impact traveling at only 5 mph.'"
Is it simply the uniformity in the cellular structure? What is the difficulty/breakthrough in achieving higher uniformity?
Fuck systemd. Fuck Redhat. Fuck Soylent, too. Wait, scratch the last one.
Some hot metal, a tiny straw, and a guy who's really good at measuring his breaths.
Needless to say, scaling is a problem.
The enemies of Democracy are
"...behind the bumper of a car traveling at 28 mph, the impact would feel the same to passengers as an impact traveling at only 5 mph,,,"
George Carlin used to point out that if you put a large spike on the steering wheel so that the driver would suffer badly in a collision, the numbers of collisions would drop dramatically.
Best regards.
http://www.rexresearch.com/rabiei/rabiei.htm
Place this behind an existing body armor compound (one that stops the bullet) and use the foam to absorb the remaining shock. Then you could survive being shot and also continue to return fire without being thrown back or suffering bad bruising.
Maybe, maybe not. Elasticity is not the same thing as softness... steel is pretty elastic, but you don't necessarily want a face full of it in a car wreck. OTOH, landing in a bed of inelastic potato chips wouldn't be particularly painful (though it would be itchy).
The foam is made by filling a mold with hollow steel spheres and then filling the gaps with molten aluminum. VERY scalable.
I wonder how it would fair if, instead of using molten aluminum to fill the gaps, you coated the steel spheres with aluminum (or other binder that melts at a temp lower than the spheres would start to collapse at) and sintering it into a solid block. More air gaps means it's lighter, but still very uniform.
=Smidge=
You'd rather have a big hunk of metal than an airbag? Don't let the "foam" fool you: slamming your face into a block of it at 35mph would only be a little better than running face first into a brick wall at the same speed.
It's squishy and springy...for metal. But it's not what you'd call soft.
ad logicam Claiming a proposition is false because it was presented as the conclusion of a fallacious argument.
Airbags and bumpers serve two entirely different purposes.
If this material lives up to the hype (unlikely), your next car will feature both items.
I'm curious to know more about the 28mph -> 5mph assertion. That stat was given to the media because it sounds impressive (grant guff), but how does it compare to the deceleration of a traditional auto bumper.
Two youtube videos about the material:
http://www.youtube.com/watch?v=mI5ZzfOlbKA - earlier video
http://www.youtube.com/watch?v=wfFcs25KmMc - one week old video
Shows among other things compression tests of the material.
It's The Golden Rule: "He who has the gold makes the rules."
TFA is a poor re-blog of the original article here, which has this video, where you actually hear how it is made: Hollow steel balls are pored into a from, (and presumably agitated to settle them in a uniform matrix), then aluminum is pored over them to fix them there. So yes, should scale up well.
Well, and elastic just describes it's tendency to return to it's original shape, it says nothing about how much energy it's going to take to make it change shape in the first place...We're talking about a block of aluminum filled with hollow steel balls here. Anything short of a sledgehammer isn't going to change it in the least.
ad logicam Claiming a proposition is false because it was presented as the conclusion of a fallacious argument.
I hate seeing this comment on every science article mentioned. It reflects a common attitude among people and corporations, and it is, in many ways, the wrong attitude. Yes, many ideas aren't scalable. But there is, and needs to be a lag time between discovering something and then figuring out how to manufacture and apply it. If we only concern ourselves with something we can bring to market tomorrow then a lot of items will never see the light of day. Some science needs time to develop, and it isn't any less impressive if they haven't already started building the factories to put these in [insert application here].
The foam is made by filling a mold with hollow steel spheres and then filling the gaps with molten aluminum. VERY scalable.
Well, yeah, if you assume hollow steel spheres are "off the shelf". Kind of like saying starships are very scalable, you just make them with warp drives, problem solved.
I have cast aluminum and have had porosity problems. Basically some gasses dissolve better in hot aluminum and bubble out as it cools. Preventing porosity in castings is very old technology. I always assumed metal foams did the opposite of preventing porosity, and tried to supersaturate molten metal with hydrogen or argon or something under pressure and then froze it at a rate that grew the bubbles to just the right size. Metallurgists have no problem doing all kinds of complicated heat treatments and all kinds of weird alloys, so I figured the limitation was dissolving enough "whatever" in the metal to make it work.
"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
Think China, lots of guys, lots of straws.
Au contraire! Some of the impact force will compress the foam, instead of compressing the child's head.
My testing has conclusive shown that a child's head, impacted at 25 mph by a block of this foam, will compress only 3 inches, compared to 5 inches when hit by a piece of solid aluminum.
Clearly this means that children will be 40% less dead when hit by a Canyonero driven by a soccer mom texting her neighbor's landscaper about getting her garden tilled*, provided that the Canyonero is equipped with this foam.
*And by getting her garden tilled, I mean having her bushes trimmed**
**And by having her bushes trimmed, I mean having bulbs planted***
****And by having bulbs planted, I mean having roots... oh screw it. I mean having a tryst.
"Trolls they were, but filled with the evil will of their master: a fell race..." -- J.R.R. Tolkien on Olog-hai
I think I'd rather have some of this between me and a potential impact than a classic airbag, if it came to the crunch. What do they use for an inflation gas generator - sodium azide is it? Nasty stuff. Like driving around with a firecracker held in front of your face.
I'm thinking if your face is traveling at 80+ kph into metal foam there is a going to be a lot of crunch going around. Airbags made of cloth and gas which deflate when you hit them do enough damage. I'd be more concerned with inhaling the fragments of my teeth and skull that resulted from my face colliding with a metal "pillow" than about inhaling the byproducts of the airbag detonation.
Damn, and we already shipped all of our tiny straw manufacturing over to China!
The enemies of Democracy are
It sounds like a cool material, but the last thing we need is for something to make the idiot behind the wheel feel SAFER.
Oddly, the vehicles that make you FEEL safest are the most dangerous on the road -- SUVs. More people die in SUVs per passenger mile than any other kind of vehicle, and the reasons are simple. Their weight makes braking and handling problematic, their height makes handling problematic and rollovers easier, and they have no crumple zones. This stuff wouldn't make you feel safer, but it would make you BE safer.
George Carlin first talked about the metal spike, but he was joking. You're not supposed to take a comedian seriously, you know.
If I have a choice between hitting a pedestrian or a utility pole, I'll hit the pole. With the spike, one might not make that choice. You have to be crazy to think dangerous cars are safer; cars used to be a lot less safe then they are now; metal dashes, no ABS, no airbags. And then as now it was said "the most dangerous part of the car is the nut behind the wheel", and the people who said that were the ones who were against seat belts. With today's safer cars the death rate per passenger mile has plummeted.
Free Martian Whores!
I read it as his desire to use this foam as a replacement for the bumper and crumple zones. It would turn the existing crumple zones into something in the car's frame and bumper system that would absorb a great deal more of the impact and, therefore, largely eliminate the need for airbags.
I'm not sure I'm buying it, though. Airbags are an "also need" feature, and cannot be replaced wholly by a better crumple zone.
The problem lies in the elasticity and the distance. If you hit a brick wall doing 65MPH and your crumple zone is too squishy, it will continue crumpling up until you are included in the crumple zone. In other words, you're dead.
Make it too hard, and the car will stop more quickly than your flesh can handle. The airbag is a crude but effective way of allowing a relatively stiff crumple zone that can manage to keep your passenger cabin intact during a VERY major impact, and still accommodate your body's need to decelerate as gradually as possible. If you hit a brick wall doing 65MPH, the crumple zone decelerates the car from 65MPH - 0MPH in the distance represented by the zone (usually a few feet at best), and materials aren't going to improve on that a whole hell of a lot. You are still going from 65MPH-0MPH in just a few feet. That's a SERIOUS amount of deceleration.
The airbag is what takes your head and torso and slows them down as gently and slowly as possible, leveraging the deceleration already provided by the crumple zone and making the best use of it to keep your brains from splashing around in your noggin, and/or snapping your neck. Which is not to say the airbag is gentle or slow at all, far from it, just more gentle and slower than making your dainty neck bones absorb all of the force as your torso is stopped by the seatbelt and your several pounds of head really wants to keep going to make Newton happy.
Could be worse, though. You could be wearing no seatbelt at all and expect your chest and head to absorb all of the speed when they impact the steering wheel and windshield respectively. That always ends colorfully, particularly in shades of red and grey.
"This post contains words, known to the State of California to cause thought. Wash brain thoroughly after reading."
Clearly this means that children will be 40% less dead when hit by a Canyonero
That might be enough for Miracle Max to work with!
****And by having bulbs planted, I mean having roots... oh screw it. I mean having a tryst.
I'm still confused... What's a tryst? Are they perennials? What's this landscaper's number, I think I could use a tryst or two.
The enemies of Democracy are
This stuff is nice, but it's a mistake to look at it as a drastic improvement in terms of safety.
The benefit of this is the reduction in weight without loss of strength.
ad logicam Claiming a proposition is false because it was presented as the conclusion of a fallacious argument.
This material reminds me of the lunar module's landing gear, made out of collapsible aluminum honeycomb. Look here for the word aluminum. Highly interesting.
In 1976 I was driving a 1974 Gremlin at 50 mph, and had a head on collision with a quarter ton pickup truck that was doing 70. Back then they didn't even have padded dashes, let alone airbags; it was naked steel. I wasn't wearing a seat belt. I bent the steering wheel, and bent the dash where my shoulder hit it. The shoulder was permanently dislocated, but I had no organ damage (well, I may have suffered a concussion) or broken bones.
After the wreck you couldn't even tell what kind of car it was. I'll tell you though, it hurt like hell! My then-fiancee didn't fare nearly as well, her pelvis was broken in six places and she was in the hospital for a long time.
I've worn my seat belt ever since. You're in the most danger in the city at 30 mph where these new bumpers wouldn't help -- the deaths come from being t-boned.
Free Martian Whores!
Nah. All you need is a straw-transistor: You blow in a small straw, which controls a huge turbine, blowing out of a bazillion straws into a bazillion glasses of fresh metal milk.
Any sufficiently advanced intelligence is indistinguishable from stupidity.
On a day where grammar and spelling made the front page, surely we can use the correct "its" ?
100MPH+ crashes are fairly common in Formula 1. The driver almost universally survives. In fact, the last Formula 1 fatality happened in 1994. This material might be too heavy to work for Formula 1, but if it can give other cars a bit of the same safety, I'm all for it. If the car magically springs back into shape after a crash, so much the better.
Finally! A year of moderation! Ready for 2019?
You know what’s ignored and missing in this discussion?
The question of what the spheres are filled with!
Because they are certainly not “filled” with a vacuum.
But I think there got to be cool properties and applications, when you fill them with something else than air.
Any sufficiently advanced intelligence is indistinguishable from stupidity.
When they develop an airbag that can detect your position and avoid punching you in the face, I'll want one. I had one in my Subaru and was always thinking about replacing the steering wheel and getting rid of it in the process. Neither of my vehicles have them and I like them that way.
If you really care about safety, the thing to do is to wear a helmet and a five- or six-point harness (males prefer six) when driving. The helmet is there not so much to protect your head as to give you a place to mount a head strap.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
"Can a car with magic foam in the bumper really make a 30mph collison feel like 5mph?"
In the end - they blow up the foam!
Do you have physics to back you up? No, I didn't think so.
Take a new Toyota Tacoma. Assume weight savings in replacing bumper with foam metal is used elsewhere so you have the same mass vehicle. A Tacoma weighs approximately 4000 pounds, which is approximately 1800 kg.
Kinetic energy is given by:
e=0.5*m*v^2
m = mass
v = velocity (or speed for our purposes).
The kinetic energy of a Tacoma moving at 28 miles per hour is approximately 141 kJ.
The kinetic energy of a Tacoma moving at 5 miles per hour is approximately 4.5 kJ.
That is, the foam bumper only has to absorb 31 times as much energy as the solid bumper to perform to the quoted standard.
See quote below, which is from here: http://www.rexresearch.com/rabiei/rabiei.htm
We see they estimate a factor of 80 improvement of energy absorption over the foam metal's equivalent bulk material. They don't say, but let's assume (reasonably) that they are talking about linear compression. Let's assume for a second that the stock bumper is made of a block of solid steel that doesn't absorb any energy. It's not, and it does, obviously.
If their estimate is correct, and a foam bumper of the same size will absorb 80 times as much energy as its solid counterpart, then the passenger in the 28 mph impact would feel 1-2 kJ of energy instead of ~140 kJ of energy. Obviously the bumpers are not solid metal, and they already have some energy absorption capabilities built into them.
Based on the factor of 31 between the kinetic energies of the vehicle at different speeds, I think their claim is the opposite of bullshit. It's reasonable.
For a steering column, you want a structure with very high torsional stiffness, but very low longitudinal stiffness. You don't want it to deform at all when you turn it, but if it's compressed along its length, it should do so readily.
I believe today's steering columns already do this to some degree.
As well as delicious.
Towards the Singularity.
It's not just about absorption of energy - a solid, stiff bumper can absorb energy. It's about rate of deceleration. The the theoretical minimum is total change in speed over total change in distance (constant deceleration). The minimum change in speed is fixed by the impacting speed and end speed. The maximum change in distance is fixed by the depth of the bumper. The way to minimize deceleration is to get the declereation to happen over a greater distance than the bumper: allow the engine compartment to crumple and cushion the deceleration, not just the bumper.
Maybe, maybe not. Elasticity is not the same thing as softness... steel is pretty elastic, but you don't necessarily want a face full of it in a car wreck.
Correct. For an example, take a large steel ball bearing and a solid rubber ball the same size. Drop them on a concrete floor from the same height.. The steel ball, being more elastic than the rubber(!) will bounce higher.
The ability of a metal to deform under compressive stress is malleability (the counterpart of this is ductility, which is a measure of tensile stress). Elasticity is an entirely different 'ticity.
Do not mock my vision of impractical footwear
But moderation will not do the job. If you want me to stop telling the truth even over the objections of liars, you're going to have to ban me from slashdot.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"