Car Science: buckling under pressure
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Hey,
Sorry for not sending a Car Science for ages again. I had this like, vague idea I'd do some video stuff but honestly it's overambitious, this already takes me kind of a long time to write because - idk, I try and make it reasonably good or at least an accurate summary of the science. It probably isn't sometimes, I'm not really on any level qualified to review papers in nanomaterials or whatever. This was all a terrible idea.
What have I been up to instead? Well, being depressed tbh. Working a lot behind a bar. Waiting to be able to pay the subscription to send my newsletter because there's too many people subscribed (a good problem!) for me to send it free. Reengaging with some old self-destructive behaviours. The usual autumnal stuff.
It's difficult not to feel like everything's collapsing under stress. Which is a good intro to today's topic: what if someone invented an incredibly strong material that was resistant to vibrations?
In making cars (and many other things) there are two key things you want: very rigid materials and materials that can withstand the vibrations of movement, power generation, etc. Cars are very vibrate-y things; you hear Formula 1 drivers having a moan about getting shaken around a lot but even the world's most trundly road car has an engine thrumming away in it that's going to shake it to its very core. And also its outer bits. All the seals. Every interlocking bit of plastic. Wiring. Every screw and bolt and welded join in the frame. The windows. You get the idea.
I went to McLaren Applied the other week and they showed me the inside of a Formula 1 ECU (electronic control unit) that has to withstand, y'know, Formula 1. That's a lot of heat and vibration and put anything through but the fact for the past 17 years it's also been an odd wedge shape because of where Adrian Newey wanted to put it in the car, which means the chip housing is truly a bespoke experience. Trying to make something strong enough to not be instantly shattered in a crash is one thing. Trying to get it to survive the vibrations is another thing entirely, especially with such severe constraints to package it. Also they have these teenytiny little heat sinks you can apply directly to a chip for when it's pretending to be in a Formula 1 car but actually just roped up to a server, which for obvious reasons they wouldn't let me take a photo of but: fun stuff. By the standards of this newsletter, anyway.
Where were we. Oh yeah, being under so much constant stress that you fall apart. Like in the paper Buckling metamaterials for extreme vibration damping which is the sort of thing ya girl here likes to read on the bus to Le Mans.
So: although the metamaterial this edition is about wasn't specifically developed for automotive purposes, it is basically the holy grail of things that can withstand extraordinary amounts of vibration AND are extremely rigid. It's easy to make floppy things that don't mind wobbling but not harder stuff. Insert your own - actually, no, let's just end this paragraph here.
So: metamaterials. They're the loosely defined category of 'things that don't occur in nature' and can range from things measured in metres to microns and they've gotta be made of two different types of stuff. Mechanical metamaterials, which this stuff'd definitely come under, are generally (although inevitably because this is science and even in the DIY shop of materials no one can escape the exception) things that have properties involving negative stiffness.
What's interesting - if you find yourself cornered by me in the kitchen at a party and have to feign it - is that most of the materials that use bucking on an atomic level for vibration damping have been reclassified as extreme composites. There's like, a reasonably micron-measurable line between extreme composites and metamaterials and some people say it doesn't exist but in theory it's that many metamaterials are made of composites but not all composites are metamaterials and vice versa or some shit. Really, who cares but science do be making these distinctions and I'm sure someone's getting a postgrad thesis out of it.
Anyway, the paper I'm gradually getting to discussing here is about a new method of using a buckling structure internal to the material that creates a damping coefficient tanδ ≈ 0.23 in a metal metamaterial. That's, as the paper is keen to lede on, so many times better than previously achieved and tbh I just wrote like three attempts at explaining damping coefficients and no one needs to know, frankly, except that it's good. Better. Than other things. Progress, y'know.
What's different here than before is that previous buckling metamaterials have basically acted quite a lot like car suspension with scronkled dampers that can absorb a lot of vibration but are not by themselves load-bearing. This tries a new thing by making something that looks less absorbtive but actually turns out to be moreso, as well as much lighter by default of having less material:
Do we truly want to get any further into the physical weeds of how this works? Probably not. But some further exciting details include the fact that this stuff doesn't get worse under bigger oscillations, unlike spring dampeners (meta or otherwise) and that it was developed with a computational framework that makes it non-hideously expensive to predict the behaviour of. Something that's important if you're actually going to use it in any applied contexts like design.
It can also absorb, in a more complex, net-like structure, multidirectional vibration. There's plenty of maths in the paper if you're into the weeds of it but frankly, we all know I'm not a material scientist and we're probably reaching the outer limits of my fraudulent attempts at explaining without saying something completely inaccurate. So, in the spirit of actually sending this, that's about it for today.
What am I going to do about Car Science, given I'm probably too depressed to write a free newsletter with any level of enthusiasm? Who knows. I will try and send it more frequently but isn't that the one main theme of this all along. Who knows, maybe this is the 'finally doing that task you've been avoiding for four months' that'll restart the newsletter production line.
Until, uh, whenever I next send this
Hazel