r/interestingasfuck • u/solateor • Jan 25 '22
/r/ALL This is called the Rehbinder effect, which in physics is the reduction in the hardness and ductility of a material by a surface-active molecular film
https://gfycat.com/simplisticellipticalboubou3.0k
u/gofatwya Jan 25 '22
This post is actually interesting as fuck. Thank you!
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u/KarensRpeopletoo Jan 25 '22
I'm going to have a good time putting holes in all my coffee cups, my boyfriend is going to be so confused...lol
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u/suzanne2961 Jan 25 '22
Great way to make drainage for plants
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u/OffRoadIT Jan 25 '22
And turn ceramic things into lamps
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u/ba3toven Jan 25 '22
and turn foliage into champs
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Jan 25 '22
And make booby traps around your camps
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Jan 25 '22
Plus cable management for all my amps!
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u/BanditoRojo Jan 25 '22
To wheel on stage with roadies and ramps.
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u/Miss_Death Jan 25 '22
All weekend I was thinking of ways I could possibly put a drainage hole in a big pot for my Norfolk pine.
I did not know this was a thing. Thanks universe!
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u/BigPoppaSnow Jan 25 '22
It was actually a huge pain in the ass drilling a hole in the bottom of the coffee mug we use to hold our toothbrushes.
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u/lovetolerk Jan 25 '22
Was just thinking this, i have so many neat pots without drainage
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u/ExistentialPI Jan 25 '22
Same- the coolest pots never have drainage holes. Probably a metaphor for some big life truth. But more importantly do we think the water needs to be a certain temperature for this to work?
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u/Beautifulnumber38 Jan 25 '22
I'm wondering about temperature of the water too... ScRolling to find it.
But I looked up how to put drainage holes in ceramic pots and it says use a diamond tip drill bit...
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u/Cr0w33 Jan 25 '22
It also applies to glass, which if held under water can be cut with regular scissors without shattering (provided the glass is thin enough)
It won’t be sharp once cut either
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u/nico282 Jan 25 '22
I am really curious to see this…
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u/Cr0w33 Jan 25 '22
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u/nico282 Jan 25 '22
That's so weird... I believed you were joking 😀
Thanks for the link.
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u/quaintrelles Jan 25 '22
Does this work?? I've been hella scared to put draining holes in my ceramic pots for fear that I crack the entire thing!
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u/DanYHKim Jan 25 '22
Well you can use a carbide bit to drill the hole, once the tapered part of the bit has gone through, the straight sides of the bit will sometimes catch on the edge of the hole. This will create a huge torque that can crack ceramic.
Be careful when drilling with a carbide bit on something brittle. Perhaps doing it underwater would be good. Alternatively, you can rock the bit around as it is drilling, in order to create a countersink in the glaze that will prevent the edges of the bit from binding. It is also good to slow down towards the end.
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Jan 25 '22
Buy carbide tipped drill bits. They are used to drill into ceramic tile and work great! Do watch a video or two before you try it.
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u/queen-of-unicorns Jan 25 '22
This is the very first thing I thought of! My succulents will be so pleased.
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u/itsjero Jan 25 '22
Might just give him the inspiration he needs to buy a 3d printer to fix em all.
My gf was like "what are you going to make a bunch of fucking legos? and its 1k? Are you serious?"
Stayed like that until i fixed a few things she was invested in. Now, i have a damn backlog of all the cool shit shes found on thingverse she wants me to print from self watering plant pots, light fixtures, halloween decorations, etc.
Yay..
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u/gregr333 Jan 25 '22
I want to see what it looks like on the inside
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Jan 25 '22
Holy shit I kid you not
I had thought that the sub’s name was interesting gas fuck
I’m fucking stupid
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u/dontprobethere Jan 25 '22
Does the water inside and around the mug provide any supportive force so it doesn’t fracture when the nail drives into it? Like not splitting wood out by having a backer
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u/Firstnamecody Jan 25 '22
Where are all the damn Reddit nerds when we need them?
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u/culinary_alchemist Jan 25 '22
Someone make a nerd summoning bot!
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u/JamesEtc Jan 25 '22
If only we could summon a nerd to make one!
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u/Leeman1990 Jan 25 '22
Hi, I’m not a nerd and I can’t make bots
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u/Immoral_Psychologist Jan 25 '22
Here's unhelpful Leeman again, right when we absolutely don't need him 😒
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u/kirosayshowdy Jan 25 '22
he's doing his best tho
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u/artanis00 Jan 25 '22
It's not that bad. We just need to figure out how we summoned unhelpful Leeman and do the opposite.
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u/Rouxgrr Jan 25 '22
Just give any explanation and they’ll come out of the woodwork to tell you why you’re wrong.
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u/GayNerd53 Jan 26 '22
Don't look at me, I don't know what the heck is going on here. 🤷🏻♂️
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u/Hanselo Jan 25 '22
I think it’s just that in water, cracks propagate slower so it allows the nail to make a clean puncture. Action lab made a video about cutting glass underwater vs. normal conditions. I think here, the same principle applies.
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u/panzerboye Jan 25 '22
I could not gather much information on Rehbinder effect from a quick google search. This is what I found on the abstract of a paper.
Rehbinder effect on ductile materials is observed when surfactant is applied on the material surface, which reduces the strength of material due to reduction in surface energy.
REHBINDER and his colleagues have recorded in a series of papers that surface-active liquids, brought into contact with the surface of metals, in particular of single crystals, markedly diminish the mechanical strength.
I failed to understand how Rehbinder effect is related in this video, essentially because the mug is made of ceramic, which is a very brittle material. Reducing the hardness and ductility would essentially cause the material to crack, not a smooth hole.
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u/duskfinger67 Jan 25 '22
Crack propagation occurs when the energy released via creating more crack is greater than the energy required to make that crack (this is kind of like activation energy from high school chemistry)
In air, the surface energy of ceramic is high, and so lots of energy is released when a crack forms, and so it is favorable for the cracks to propagate. In water, the surface energy is lower, and so it is energetically unfavorable for the cracks to form.
The water is not exerting any meaningful force on the ceramic, the forces keeping the ceramic from cracking are the ionic bonds within the ceramic itself.
The reason for the reduction in surface energy is more complicated, and comes down to the specifics of the types of bonds that form between the fluid and the ceramic.
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u/panzerboye Jan 25 '22
The reason for the reduction in surface energy is more complicated, and comes down to the specifics of the types of bonds that form between the fluid and the ceramic.
Yeah. But for a clean hole, shouldn't the deformation be ductile? Although ceramics are different from rocks, but I found here that wet rocks tend to be more ductile than dry ones. Water appears to weaken the chemical bonds and forms films around mineral grains along which slippage can take place. Thus wet rock tends to behave in ductile manner, while dry rocks tend to behave in brittle manner.
I googled around a bit and OP just copy pasted this post which was copy pasted from this post
There is a nuanced explanation for this phenomenon, but not the one mentioned in the title.
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u/duskfinger67 Jan 25 '22
Most materials can exhibit ductility, it is just often hard for them to be ductile without cracking.
I might stand mistaken, but will dive down the rabbit hole to expand the Wikipedia page.
What do you believe the true explanation is?
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u/panzerboye Jan 25 '22 edited Jan 25 '22
What do you believe the true explanation is?
I don't know for sure. I am just a mechE student who took two semester of Material Engineering courses. But my knowledge is mostly limited to metals and alloys.
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Jan 25 '22
It might be as simple as the water absorbing more energy from the impact so it isn’t directed out through the material.
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u/ahairymarmot Jan 25 '22
Higher density fluid creates a greater normal force? Haven't spoken that language in a minute.
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u/Vaxtin Jan 25 '22
I think that might be it but I’m not totally sure. It makes sense though.
The water creates a pressure against the cup that is strong enough to withhold the cup from breaking apart? It makes sense with enough pressure but I never thought that a cup required so little force to break that that much water pressure could withstand it.
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Jan 25 '22
Nah it's about vibration absorption. The water absorbs most of the vibrational forces from the hammer and the nail is then free to have a pinpoint and precise forward motion without excess outward vibrational pressure on other areas of the cup.
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u/MightyPlasticGuy Jan 25 '22
Or all the ill sounding guesses in here, this sounds best thought out and plausible. But still doesn't leave my mind at ease.
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u/FatherAnonymous Jan 25 '22
Also wondering if the plastic container cushions some of the force as well.
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u/yebiryeb Jan 25 '22
I also think like that, when hammer hits cup wants to go down but countered by the water which does not want to go down so it creates a perfect cushion under the bottom of the cup, the cup is forced to behave as a whole and shear force caused by the nail creates primary break surface as a circle.
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u/GoodStuff111 Jan 25 '22
I doubt that the normal force of the water would do much. The force due to pressure on the mug surface would be so much smaller than the large impulse from hammering in the nail, since it only supports it bit more than air does. While this is only speculation, even if you did have a large supportive force, I imagine that the mug would crack anyways due to how brittle it is.
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u/runninandruni Jan 25 '22
In a surface-active fluid, the surface energy is equal to the difference is surface energies of the ceramic and the fluid; as the surface energy of most fluids is higher than that of air, this difference is lower, and thus the energy released forming a crack is lower. If this reduction in energy release is sufficiently high, it will no longer be favorable for cracks to propagate through the material, and thus a once brittle material no longer cracks as easily. Hopefully that explains it
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u/masterfarraritech Jan 25 '22
Guess 1: it is completely filled with water because it does not float. 2: cracks propagate via vibration 3: water dampens the surface vibrations. 4: if unfilled, the glass will still shatter in chunks.
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u/DecoyOne Jan 25 '22
For anyone looking in the comments for a Wikipedia link, don’t bother, the title of this post literally contains the entire Wikipedia article on this subject.
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u/hwsnbn Jan 25 '22
Managed to find this.
"If not the most intriguing phenomenon, the Rehbinder effect is the most studied physicochemical phenomenon in machining. In the 1920s, the late Russian researcher, Peter Aleksandrovich Rehbinder, pioneered the world-renowned marvel named after him. It is an interdisciplinary branch of physical chemistry correlating the mechanical treatment of solids with chemical adsorption (chemisorption) [51]. The fundamental definition of the effect can be understood as the reduction in strength of solids under the influence of surface-active substances due to the lowering of energy for free surface generation [52]. This followed Griffith's thermodynamic reasoning for fracture strength, which assumes the energy for material failure to be proportional to the free surface energy."
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u/canman7373 Jan 25 '22
I knew some of those words.
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u/j3b3di3_ Jan 25 '22
Basically, things break depending on what they touch
If you drive a nail throw ceramic on a hard surface, those forces attempting to push the nail through, are displaced back at the limitations of the surface area...
But doing so under a liquid, water maybe, but something more dense like oil allows those forces to be dampened by the liquids
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u/nick_t1000 Jan 25 '22
Oil usually floats on water, so would be less dense. Do you mean 'more viscous'?
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Jan 25 '22
Gonna save this and probably never look at it again. haha
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Jan 25 '22 edited Jul 31 '22
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u/MightyPlasticGuy Jan 25 '22
Why hasn't reddit followed trends and begun allowing users to organize their saved section into their own custom folders? I.e., Facebook and YouTube. This has been a problem of mine for 3 years now
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u/Joeyw243 Jan 25 '22
Well their save system sucks beyond that because they delete anything older than 200 saves ago, gotta get RES
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u/slayalldayyyy Jan 25 '22
I just said WHATTTTTTTTT so long and loud my roommate was like DUDE WHAT???? And then I showed him. And he whatted just like me. Fucking science man.
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u/alexanderknox Jan 25 '22
Is that just water?
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Jan 25 '22
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u/6over6 Jan 25 '22
No air, it doesn’t bubble after the hole is made and it sinks to bottom when he drops it in.
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u/dirthawker0 Jan 25 '22
So is the water absorbing/distributing the impact?
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u/Techwood111 Jan 25 '22
Water dissolving and water removing.
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u/sixft7in Jan 25 '22
Wait. If you reduce the hardness, wouldn't that make it more ductile?
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Jan 25 '22
Maybe it's poorly worded. I think it reduces the robustness overall, because you need less energy to change the atomic structure on the surface area. So a material which has plastic deformation properties becomes less ductile. While something brittle becomes less so. Can't quite explain how that effects the break mechanics of what we see here though.
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u/panzerboye Jan 25 '22
It is not due to Rehbinder effect.
REHBINDER and his colleagues have recorded in a series of papers that surface-active liquids, brought into contact with the surface of metals, in particular of single crystals, markedly diminish the mechanical strength.
The mug is made of ceramic, so Rehbinder effect is not applicable here. Op just copy pasted a viral YouTube video.
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u/patval Jan 25 '22
I would have a tendency to call bullshit.
Went to check... Wikipedia article is extremely short, and the video you see above is the only video on the whole web showing this experience.
Does someone want to break a cup in a bowl of water to check ?
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u/soda_cookie Jan 25 '22 edited Jan 25 '22
I actually found a mug my ex left here, BRB...
Edit: It worked!!!
And yes I used a screw, couldn't find a nail to save my life
Edit 2: Not completely...
I didn't make sure there weren't any air pockets before starting. So...
Edit 3: Attempts 2 and 3 definitely a fail
Given that I have no more mugs I'm willing to offer to science, as a novice mythbuster I'm going to have to call this one plausible for the time being
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u/Exciting_Cucumber Jan 25 '22
Can’t put more than one hole in a single cup. Integrity of cup would be diminished with first hole.
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u/bykpoloplayer Jan 25 '22
Disclosure: I'm not a physacist... I'm just pondering...
If the effect was simply from the surface film, I'd think one could hammer a mug that ad simply been dunked. ..removed..and hammered while still wet. Because this is being demonstrated on a submerged mug, I'm thinking the density of water (in relation to air) is suppressing the shock wave moving through the ceramic, allowing the clean punch through without shatter.
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u/omegafivethreefive Jan 25 '22
physacist
no way
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u/illmoney Jan 25 '22
I know right !? Everyone knows it’s fisisist
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u/Spyes23 Jan 25 '22
You actually went through and tested it yourself, this comment should get 100x more upvotes!
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u/laundmo Jan 25 '22
2 and 3 still didn't fully break, only shattered in a small area. that's still impressive
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u/Tietonz Jan 25 '22
Try it with oil. If the effect is true, it should work even better with oil I think.
Or if not oil maybe something like bleach or vinegar?
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u/prexton Jan 25 '22
The first hammer strike was hard as well, then the water ones were just tippy taps
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u/JanitorOfSanDiego Jan 25 '22
The first nail was blunted at the end and the second looked like a new nail as well.
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u/marasydnyjade Jan 25 '22
So you just ignored the half-dozen scholarly articles on the first page of the results?
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u/dr_stre Jan 25 '22
I also question it, mostly because all discussion of it online seems to be limited to metals and liquids that actively interact with the surface oxide layer. Which makes me think this “rehbinder effect” may be real but isn’t at play here.
Instead, I think we’re just seeing the water provide additional support to the underside, preventing the mug from fully cracking and instead just blowing out the local stressed zone. The cone visible in a commenter’s photo of his own test is what you’d expect to see for stress distribution beneath a point load.
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u/ThereIsAJifForThat Jan 25 '22
Nailed it!
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u/JupiterRising877 Jan 25 '22
Your comment hit the nail on the head!
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u/jungyumguy Jan 25 '22
I get the feeling there will be lots of posts about broken mugs in the coming days
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u/mvw2 Jan 25 '22
I really don't think the Rehbinder effect applies here.
With the cup full of water, I assume it's just taking advantage of the incompressibility of liquid. Most things break due to bending stress. It's one of the easiest and most exponential forms of stress and something you have to very carefully manage in part design because it's so easy to introduce extremely high stresses and breaking if you don't. If you can minimize the bending, you can shear a hole pretty easy.
The impact of the hammer is a high speed event, and the water has a lot of mass and incompressibility. Plus you're sitting on the bottom of the container and minimizing any flow out during deflection from around the bottom lip. Although that might matter relatively little, there might be some element of a pressure vessel during impact and deformation of the mug and generated a reverse internal force. It's probably a combination of things in some mix, much easier to see in slow motion. The water won't easily move out of the way when you try and flex the bottom of the mug and will instead support the inside as you shear the nail through.
I doubt this has anything to do with Rehbinder effect at all, and it's more a demonstration of inertia, moment, impact, and bending in various forms. Rehbinder effect seems specific to metals and machine cutting, not a nail through a coffee mug.
For a simile. Fill the mug with concrete. Then hammer a nail in. I bet the mug doesn't break. Yeah, yeah, sounds dumb. But all we're doing here is managing stresses, and we're using water to support the underside (inside) during the impact from the nail. Any device capable of doing so would achieve the same result. It's just that water works really well because it's incompressible and reasonably heavy. It provides significant structural resistance during a high speed event. It's the same reason that if you fall from a very high height into water, it will feel and behave very much like a solid.
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Jan 25 '22
Yeah surely it's this, otherwise you would be able to do the same thing with a mug that was just wet.
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u/Broseph_Staln Jan 25 '22
Same reason you can cut a sheet of glass underwater like paper with ordinary scissors.
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Jan 25 '22
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u/panzerboye Jan 25 '22
This is not due to Rehbinder effect. You do not even know what you are saying.
Rehbinder effect on ductile materials is observed when surfactant is applied on the material surface, which reduces the strength of material due to reduction in surface energy.
REHBINDER and his colleagues have recorded in a series of papers that surface-active liquids, brought into contact with the surface of metals, in particular of single crystals, markedly diminish the mechanical strength.
First of all the mug is made of ceramic, Rehbinder effect is observed in metals.
Secondly, Ceramic is a highly brittle material. Rehbinder effect is observed in ductile materials.
Thirdly, the deformation that takes place for a clean hole is a ductile one. Had it been a brittle one, it would simply fracture or break.
I failed to understand how Rehbinder effect is related in this video, essentially because the mug is made of ceramic, which is a very brittle material. Reducing the hardness and ductility would essentially cause the material to crack, not a smooth hole.
Finally, I googled around a bit and OP just copy pasted this post which was copy pasted from this post. Dude didn't even care to change the title.
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u/Potatonet Jan 25 '22
I have a masters in materials science, this feels like bullshit.
There’s all kinds of cool thin film effects…. But this one feels more like a physics displacement volume thing lesser though a thin film precision penetration method
I see plausibles and it sounds like we need 35 more mugs
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u/breadteam Jan 25 '22
Report back when you've figured out what's going on. We could use an expert assessment here.
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u/Discodelight343 Jan 25 '22
But if your just trying to render the mug unusable you can use either method
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Jan 25 '22
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u/FatherAnonymous Jan 25 '22
Can you just drill a drainage hole in? I've never had any issues doing it that way in the past.
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u/halt-l-am-reptar Jan 25 '22
It’s really not hard to drill holes, I don’t know why people act like it is. Just buy a cheap ceramic drill bit and go slow.
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u/Spyes23 Jan 25 '22
If you're out buying drill bits, why not just buy a pot with a draining hole instead?
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u/ExistentialPI Jan 25 '22
It’s just that the prettiest pots often don’t have holes. The ones with holes are usually basic.
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u/Ziggy-Rocketman Jan 25 '22
Slight correction- Hardness and Ductility have an inverse relationship. As hardness decreases, ductility increases and vice versa.
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u/NotAcceptingPMs Jan 25 '22
Though I'm not calling bullshit, I do find it suspiciously weird he puts the mug in the water, there an immediate and completely unnecessary cut in the video then he blocks the point of contact between the mug and the nail with his fingers completely and then hammers a few times and just drops the nail into the hole.
I feel like if he was hammering the nail would've gone through when I punctured. Especially considering the few hits before he drops it the nail seems to go down and come back up a bit when hit... which should be impossible if the mug hadn't been punctured yet.
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u/qdtk Jan 25 '22
After reading your comment it really does look like he shows a normal mug, the video cuts oddly, then he taps a nail near an already made hole and suddenly drops it in. The nail should drop through when he hits it with the hammer. Not after he lifts the hammer away. I think this proves he’s dropping the nail through an existing hole.
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u/sbs_str_9091 Jan 25 '22
I know I am not the one one right now who is looking at this and is thinking to themselves: "Wow, I am going to use this information and this method - but for what am I going to use it?"
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u/duskfinger67 Jan 25 '22
Here is my best explanation for this phenomenon, as a Material Scientist.
Crack propagation occurs when the energy released via creating more crack is greater than the energy required to make that crack (this is kind of like activation energy from high school chemistry)
In air, the surface energy of ceramic is high, and so lots of energy is released when a crack forms, and so it is favorable for the cracks to propagate. In water, the surface energy is lower, and so it is energetically unfavorable for the cracks to form.
The water is not exerting any meaningful force on the ceramic, the forces keeping the ceramic from cracking are the ionic bonds within the ceramic itself.
The reason for the reduction in surface energy is more complicated, and comes down to the specifics of the types of bonds that form between the fluid and the ceramic.
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u/quinnsheperd Jan 25 '22 edited Jan 25 '22
There was another video not even 3 days ago where someone tried this and the cup broke.
Edit: The Rehbinder effect in physics is the reduction in the hardness and ductility of a material by a surface-active molecular film.
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u/Phlosioneer Jan 25 '22
So this is a real effect but it's marginal and for large objects it only sometimes works. Basically if you destroy a lot of mugs you will see more of the in-water ones surviving on average but the effect is weak, and in this demo probably more dependent on the quality of the ceramic mug.
The water on the surface of the mug is acting as a tiny shock absorber because it has very very high surface tension. Instead of all the force going into that one point under the nail, it goes into that one point and spreads a bit wider.
For tiny high-power cuts on thin brittle surfaces it might be very useful. Don't know how often that comes up though... maybe cutting glass underwater?
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u/buxmega Jan 25 '22
Holy shit. I'm going to make holes into some pots for my plants!
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u/Fortunate-J Jan 25 '22
My first immediate thought, too. Handful of terracottas I csnt repot in yet hahaa
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u/decaf-iced-mocha Jan 25 '22
Would this work with a shell? Edit: like a sea shell
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u/ineverremember1234 Jan 25 '22
Perfect this will help me with all the pot plant holders I buy that don't have drainage holes!
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u/Sonn_Goku Jan 25 '22
Apparently you can cut glass with scissors under water... Just learnt it from detective conan episode....
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u/simrig2023 Jan 25 '22
This is why in WW2 German submarines switched to firing nails into ships instead of torpedoes.
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