3 ms·
Certainly a discovery, but a new one? Ok, this is based on an article from Nature and I'm just a random dude from the Internet, so take this with a grain of sa
by weinzierl 3y ago
Certainly a discovery, but a new one?
Ok, this is based on an article from Nature and I'm just a random dude from the Internet, so take this with a grain of salt:
What they claim is what I've learned in materials science class 20 years ago.
Metals fatigue under cyclic loading because of micro-cracks. This effect can be quantified by the Wöhler curve, which very simply put tells you how often you can bend a piece of metal until it breaks.
From what I remember, it is well known that this fatigue reverses by itself slowly and depending on the temperature and type of metal.
It is true that the effect is negligible for steel at room temperature, which admittedly is the most interesting case.
But for other metals this self healing effect can actually be exploited at room temperature. The example we learned in class was the leaden rulers everyone of us owned back then. These are rulers you can bend to draw nice curves in technical drawings. They are made out of pure lead. If you bend them very very often in one sitting they can eventually break. But if you stop before and you leave them alone over night they will be like new.
At least that is how I remember the story.
- harimau777 3y agoFunny story about lead rulers: An alternative name for them (and the name that I originally learned for them) is a "Lesbian curve" because the lead to make them originally came from Lesbos. I once went up to a woman working at an art store and asked if they had lesbian curves. Immediately after the words left my mouth I noticed that she was wearing a lesbian pride pin and based on her reaction probably misinterpreted what I was saying. I awkwardly made some excuse and left the store in embarrassment as quickly as possible. -_-
- gcr 3y agoStatisticians borrowed the idea of “simulated annealing” and used it as a regularization technique for some time now.
- dreamcompiler 3y agoAnnealing metal requires starting at a high temperature and gradually lowering it. Simulated annealing does the same thing with some appropriate analog of temperature. There's no temperature lowering happening in TFA.
- alanbernstein 3y agoYou owned a lead ruler 20 years ago? I get the idea but I had never heard of such a thing. I know about physical splines, but I thought those were flexible wood, or maybe plastic later on.
- weinzierl 3y agoOh yes, and apparently you can still buy them[1]. Mine was blue and probably a different brand (Faber-Castell, maybe) but otherwise looked the same. I didn't use it much for drawing, though, because I liked the French Curves (or Burmester Schablonen, as they are called in German) much better. The lead ruler, on the other hand, was fun to play with during boring lessons, I like to think of it as my generations fidget toy. [1] https://www.praehistorika-archäologenbedarf.de/produkt/kurvenlineal-40-cm-bleikern/ https://www.xn--praehistorika-archologenbedarf-dtc.de/produk...
- rkagerer 3y agoSounds super useful for tracing curves onto a material you need to cut. Is there still lead in it? Any health issues? Is that why I can't find them in North America? EDIT: I do find hits for Flexible Curve Ruler on Amazon but several reviews complain they don't hold their shape well. Are they made of a substitute that doesn't perform as well as lead?
- Zancarius 3y agoJust looked them up and found some on Amazon from $17-40ish depending on brand, length, and probably other factors. I had no idea these were a thing!
- Tao3300 3y agohttps://en.wikipedia.org/wiki/Lesbian_rule https://en.wikipedia.org/wiki/Lesbian_rule
- civilitty 3y agoOff topic but that lesbian rule would have been a great punchline to this sketch: https://m.youtube.com/watch?v=QIBwSHZAOU0 https://m.youtube.com/watch?v=QIBwSHZAOU0
- sandworm101 3y agoFrom anothet perspective, i was taught that metals in a non-oxidizing environment, if touching, will reform crystal bonds. So a crack deep inside a metal, if given time, can heal across a previous break. But this wound heeling will not realign complex structure, so the effect is more noticeable in non-alloy, such as a lead spline.
- v8xi 3y agothis is called cold welding https://en.wikipedia.org/wiki/Cold_welding https://en.wikipedia.org/wiki/Cold_welding