Skip to comments.Scientists solve 400-year-old mystery of Prince Rupert's drops
Posted on 05/09/2017 10:39:25 AM PDT by Red Badger
Prince Ruperts drop.
(Phys.org)Researchers have finally answered a question that has stumped scientists since the early 1600s: Why are the heads of tadpole-shaped pieces of glass called "Prince Rupert's drops" so strong?
In the 17th century, Prince Rupert from Germany brought some of these glass drops to England's King Charles II, who was intrigued by their unusual properties. While the head of the drop is so strong that it can withstand the impact of a hammer, the tail is so fragile that bending it with your fingers will not only break the tail, but cause the entire droplet to instantly disintegrate into a fine powder.
Prince Rupert's drops are easily made by dropping red hot blobs of molten glass into water. Although researchers have tried to understand what causes the unusual properties of these drops for many years, it was not until recently that modern technology has allowed researchers to thoroughly investigate them.
In 1994, S. Chandrasekar at Purdue University and M. M. Chaudhri at the University of Cambridge used high-speed framing photography to observe the drop-shattering process. From their experiments, they concluded that the surface of each drop experiences highly compressive stresses, while the interior experiences high tension forces. So the drop is in a state of unstable equilibrium, which can be easily disturbed by breaking the tail.
One open question, however, is how the stresses are distributed throughout a Prince Rupert's drop. Understanding the stress distribution would help to more fully explain why the heads of these drops are so strong.
To do this, Chandrasekar and Chaudhri began collaborating with Hillar Aben, a professor at Tallinn University of Technology in Estonia. Aben specializes in determining residual stresses in transparent three-dimensional objects, such as Prince Rupert's drops.
Fringes throughout a Prince Ruperts drop indicate residual stresses. Credit: Aben et al. ©2017 American Institute of Physics ==============================================================================================================================
In the new study published in Applied Physics Letters, Aben, Chandrasekar, Chaudhri, and their coauthors have investigated the stress distribution in Prince Rupert's drops using a transmission polariscope, which is a type of microscope that measures the birefringence in an axi-symmetrical transparent object, such as a Prince Rupert's drop.
In their experiments, the researchers suspended a Prince Rupert's drop in a clear liquid, and then illuminated the drop with a red LED. Using the polariscope, the researchers measured the optical retardation of the light as it traveled through the glass drop, and then used the data to construct the stress distribution throughout the entire drop.
The results showed that the heads of the drops have a much higher surface compressive stress than previously thoughtup to 700 megapascals, which is nearly 7,000 times atmospheric pressure. This surface compressive layer is also thin, about 10% of the diameter of the head of a drop.
As the researchers explain, these values give the droplet heads a very high fracture strength. In order to break a droplet, it's necessary to create a crack that enters the interior tension zone in the drop. Since cracks on the surface tend to grow parallel to the surface, they cannot enter the tension zone. Instead, the easiest way to break a drop is to disturb the tail, since a disturbance in this location allows cracks to enter the tension zone.
Overall, the researchers believe that the results finally explain the great strength of Prince Rupert's drops.
"The work has fully explained why the head of a drop is so strong," Chaudhri told Phys.org. "I believe we have now solved most of the main aspects of this area. However, new questions may emerge unexpectedly."
More information: H. Aben et al. "On the extraordinary strength of Prince Rupert's drops." Applied Physics Letters. DOI: 10.1063/1.4971339
Journal reference: Applied Physics Letters
Read more at: https://phys.org/news/2017-05-scientists-year-old-mystery-prince-rupert.html#jCp
Or we could make a bullet out of it (and cut the tail off with a laser, so as not to shatter the whole thing). It’d be interesting to see what’s its ability to penetrate armored targets would be.
Alternatively, do the same with some kind of metal...if the same or a similar effect can be produced in metal.
Oh, and what about transparent aluminum...this is already in use for some military aircraft. Imagine if a window could be made super hard from that stuff!
That is frames per second for the camera. That would be a respectable velocity for a rifle though.
That’s FRAMES PER SECOND for the camera........................
The process of makin Price Rupert’s Drops is sort of like making Fried Marbles, except you don’t heat them until they’re molten. Always wear goggles or safety glasses. In making fried marbles you take pretty swirl pattern marbles, place them in a skillet or other suitable vessel and heat them to 400 - 500 degrees. Then, using a pair of tongs, drop them into ice water. The glass will instantly develop all sorts of crazy stress cracks internally in the marbles, making their translucent patterns even more interesting.
I tried frying marbles when I was a kid.
Never could get them tender................
Bummer! I hate it when that happens!
I wonder if that would work. The original object is a complicated equilibrium of internal forces. i'm not convinced that one could heat any part of it until molten and not disturb the whole thing. Doing this might make another very interesting series of videos.
I tried cutting a piece of tempered glass from a storm door with a tile saw once.
what a mess........................
I had the same thought, it would be quite interesting if it were possible.
What/who am I?....Bill Clinton?
Prince Rupert was a first cousin to King Charles II—his mother was a daughter of James VI&I. The region drained by Hudson’s Bay used to be called Prince Rupert’s Land—now divided between several Canadian provinces and the Northwest Territories, but a small part is in the US.
What would also be interesting would be having a high-technology metallurgy lab try to make these things symmetrical. Otherwise, making bullets - large or small - out of these would be impractical; tail or no tail, you won’t get any kind of accuracy. Or, possibly, these things could be encased inside of a very symmetrical bullet (like a lot of AP ammo already is). Then the only question would be whether the cost/benefit ratio is high enough to develop the damned thing in the first place...but that’s what R&D budgets are for, aren’t they?
Here’s a thought. We have a MOP (Massive Ordnance Penetrator) bomb that is designed to penetrate many meters underground, even through concrete, and then blow up. Wonder if a Prince Rupert drop made of tungsten would help the penetration?
This just gets at the ridiculousness of Metric measures.
The metric unit for force is a Pascal. This is a stunningly small amount of force. One Newton per Square Meter. So, one atmosphere of pressure which for most people is not a very familiar measure (kind of like a furlong per fortnight) is equal to 101,000 Pascals. This is why Mega-Pascals are used for many situations needing to be described in the “real world” however, this unit kind of sucks for that purpose too.. because 1 Megapascal = approx. 145 psi. So your normal water pressure in your pipes should be 80 psi or less. That is .5517 Megapascals. Arrg. Or 552 Kilopascals. Argg again. The concept was to avoid conversion constants in basic units.. but this is a hopeless idea. What you get is a series of wrong sized units that are not practical for human usage. So you still end up multiplying and dividing and applying many more conversions.
Science designed by a committee and enforced by the mouth of a gun. One wonders if the whole global warming hoax would have been possible without the forced introduction of Metric units to make people unable to estimate anything but the most basic units in their heads. When we get to beams and strength of materials this issue makes the most brilliant scientist liable to huge errors due to slipped decimal places.
To get a quick idea of this problem.. it would seem that 8 chicken feathers would produce about 1 pascal of force on sensitive enough scale. But, this might be in error.. because these calculations need to be worked at e-5 scales. A chicken feather is 0.0082 grams approx. So, a 9.8 Meters per second squared conversion might be needed to convert grams into newtons. Fun. Yes. this was designed by the French to be easier. SO my question is 0.8 chicken feathers? 8 chicken feathers or 80 equal to one pascal?
“This is an allegory/riddle.
Can be hit on the head with out any effect.
But tweak the tail, and everything shatters.
What/who am I?”
If you want to tweak Hillary’s tail, that’s your business. I find it disgusting.
They may have quantified it better, but I have seen this principle explained on numerous you tube videos, where people have actually shot the head of them with bullets and broken the tails with special cameras so that you can see what happens.
I just answered the riddle, I didn’t propose actually doing it. Heck, I wouldn’t touch that will someone else’s @#$%.
“with” not “will”
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