Originally published at: https://boingboing.net/2021/01/12/huge-crystal-ball-vs-a-50-caliber-round.html
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Weird story; this guy has a few different Youtube channels. I used to watch his home remodeling channel as he does take on some odd junk. I was aware that his main channel glorified guns and bro culture, but wasn’t that affected by it. One night I had a dream where I was visiting him in his kitchen and he literally fed me a shit sandwich. I haven’t watched any of his videos since.
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Neat.
The spalling effect just begs to have a high speed camera to see if you can see the shock waves move through the glass or not. Call that Smarter Every Day guy. I had heard of spalling for things like body armor and armored vehicles, didn’t think it would apply to glass balls.
It also shows how when Dirty Harry blasts a bad buy in the movies with a .44 magnum and they go flying back is pure Hollywood BS. That ball barely moved.
Neat A-Team looking Mini-14.
ETA - oh and the heat transfer. I wonder if the large ball felt hot at all.
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I think there may be significant differences in the results when a softish target is hit versus a harder target. Elastic versus inelastic collisions. I don’t really want to think about it in more detail, though.
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There is - soft targets will generally have a less transfer of energy, especially if the round exits.
They did a Mythbusters on this where they shot a dead pig hanging with various rounds, including a .50cal BMG and it didn’t move at all. While bullets do lots of damage, if a bullet was powerful enough to knock you off your feet getting shot by it, the shooter would also be on their butts.
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It has to do with interactions (constructive and destructive) of the pressure waves in the material. I suppose under certain conditions anything can spall - it’s due to the dimensions, the impact velocities and the equations of state of the materials getting whacked.
It would be fun to model!
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Oh, wonderful. I’m sure these fine fellas are going to clean up all of those tiny glass shards off of the forest floor.
/s
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I’m not sure how much there would be to see under standard lighting; but if you used the crossed polarizer technique for birefringent materials you’d probably get pretty dramatic results.
That works great for showing patterns in internally stressed glass(Prince Rupert’s drops seem to be the usual object to photograph; but any deliberately stressed or improperly annealed glass works).
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That’s a good point. Newton’s laws and all.
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I think your subconscious detected that with the gun stuff, there is an underlying dark psychic vibe that no amount of fun, relaxed presentation really washes out.
To state the obvious, being very interested in guns is not just like being interested in woodturning or collectible teapots. Guns exist to maim and destroy by pointing; you aren’t interested in guns if you’re not interested in that. And that is interesting, but in a dark and serious way. Framing it as silly fun and nothing else is a statement in itself. I mean, he didn’t just pick up that comedy-sized .45 for $5 in the checkout line. I don’t mind if he wants to talk about what made him crave such a murder-forward object, but it makes me cumulatively queasy to watch people pointedly pretending these things are just unremarkable household objects like spoons or carpets.
Yes, I am being very prudish here. It turns out I don’t mind that. Guns are distasteful.
I think it’s more about shock waves moving around the glass. The reason you get spalling at the antipode is that a wave traveling along the surface will always interfere constructively with itself at the antipode of its starting point, so the displacement will be twice as great there as anywhere else on the surface. That would actually be true of a soft body as well, though it’d be hard to notice if the bullet traveled straight through and exited at the same place.
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I am not familiar with that. Is it anything like Schlieren imaging?
I have seen slow motion footage of a Prince Ruperts Drop breaking and it is amazing.
So, as above, would Schlieren imaging work to show that?
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The clear transition in power from even big pistol rounds to the .223/5.56mm rifle illustrates the rule of a gunfight, in that a pistol is best used to fight your way to a rifle.
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I’m all for LNT, but this is private land and that’s just quartz, ie large form, pre-ground sand.
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Ah, private land, that makes it a-ok. I’m sure that nocturnal and other non-human creatures trespassing in that area do fully understand that their cut up paws are just a result of their criminal behavior and the sand’s form factor. I’m all clear now.
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I’m not 100% sure what the arrangement of polarizers is; but it takes advantage of the fact that the magnitude of a birefringent material’s effect on polarization varies with its stress; so you get fairly dramatic rainbow patterns in stressed areas and the usual dimmed-by-polarizer-but-otherwise-uninteresting color elsewhere.
Good for verifying that Prince Rupert’s drops are super angry; excellent for verifying that your not-intentionally-stressed glass is annealed properly; also pretty cool for observing the effects of injection molding on transparent plastic objects.
I assume, in this case, that it would allow the internal pressure waves to be visualized pretty well with a sufficiently high speed camera; even if the deformation isn’t great enough to noticeably change the refractive index.
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Crossed polarizers show the stresses because the medium “rotates” the light as a function of stress.
Schlieren shows changes in density/refractive index, which I suppose would also change with compressive or tensile stress, but I’m not so sure what it would look like in a sphere - you’re looking for tiny changes in the refractive index and that might get funky.
Another cool diagnostic would be high-speed Digital Image Correlation (DIC). You put a pattern of speckles on the surface and watch it from a few angles. After some calculations/image processing you can measure the strain to a pretty precise level. I’ve never done it on something so dynamic but I’ve used it to watch pressure vessels change as you add pressure. In this case you’d probably see some resonance, the result of which are likely the internal cracks on the sides/back of the sphere.
Breaking stuff is fun, regardless of your energy source! I don’t do it for a living, but many of my colleagues do. I usually look at broken stuff afterwards.
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Be sure to pick up every single sharp rock on your ranch.
You all might be interested in this video of a similar nature, but what drops the glass rather than shooting it: https://youtu.be/8V5wjfAS3Do?t=473
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Oh, cool. I’m sure all the wildlife will understand. And I’m sure this guy will live forever and no one else will have to worry about their children and dogs having their feet and paws sliced up. Seriously, Google images of glass in animal paws or stomachs.
A couple of years ago my wife’s organization purchased woodland that had been “lightly” harvested for hardwood. You cannot imagine the ecological devastation it took. There are now strips of fetid water pools filled with mosquito and fly larva that are a constant source of irritation to people and animals for miles around. It is also one of the few places in North America that feature true American Chestnut trees, many of which were cut down to make way for logging vehicles (that dug huge ruts that now fill with water every spring). But, hey, it was private land and that Chestnut wood commands a pretty penny!
ETA: @RobJ beat me to it.
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Sure, because clearcutting a forest and distributing a few rocks are exactly the same.
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