6 ms·

Discovery: Metals can heal themselves

90 points by bobvanluijt 3y ago

bobvanluijt 3y ago
Article in nature: https://www.nature.com/articles/s41586-023-06223-0 https://www.nature.com/articles/s41586-023-06223-0
tempodox 3y ago
Metals have been known to have a kind of memory. If you bend a cable out of shape, it will bend itself right back. I have to think that this self-healing is an instance of the same principle.
- iancmceachern 3y ago
  Yeah, there are formulations of wire you can buy that are specifically designed to have this property to increase fatigue resistance and bend life.
  - cwkoss 3y ago
    Nitinol is neat
    - PennRobotics 3y ago
      if you bend a thick wire of nitinol (nickel titanium alloy, discovered on accident, aka shape memory alloy) quickly, it heats at the site of the bend and that is cool, but paper clips do the same thing. once you've let the thick wire settle back to room temperature---here's the cool part---quickly force it straight again and it gets suddenly very cold at the site where the bend was. nitinol is neat
wanderingmind 3y ago
No preprint although government labs have direction to make their research openly available asap. Probably a paper written just for other researchers to cite and not for any generic interest.
- rsfern 3y ago
  It seems the paper isn’t in sandia’s publications database yet, but it’s only been a few days since the journal version was published. I’m not sure how it works at sandia, but at NIST one of the authors has to get around to uploading the manuscript and there’s no way to get an automated reminder. Then our publications database only updates once a day I think. I’m sure if you send a polite request for the manuscript they would be happy to share. Maybe even responsive to a polite request that they post a preprint next time, but in MatSci that’s much more common with modeling than experimental work. https://www.sandia.gov/research/publications/search/?pub_s=Autonomous+healing+of+fatigue+cracks+via+cold+welding&sort=date https://www.sandia.gov/research/publications/search/?pub_s=A...
nickelpro 3y ago
[flagged]
- progfix 3y ago
  You are wrong. I work in the construction industry and the term is commonly used and understood. https://en.m.wikipedia.org/wiki/Self-healing_material https://en.m.wikipedia.org/wiki/Self-healing_material
- rewmie 3y ago
  I'm afraid you'll throw a fit when you find out there's a whole field called structural health monitoring. https://en.wikipedia.org/wiki/Structural_health_monitoring https://en.wikipedia.org/wiki/Structural_health_monitoring
slater 3y ago
[flagged]
Terr_ 3y ago
[Recycling a comment from an earlier submission yesterday] Isn't this a bit like cold welding? [0] Unless something is in-between them or some force is pulling them apart, there's no big reason for two exactly-fitted pieces of the same crystalline metal to _not_ join together. It's not like the atoms "know" which side they belong to. Actually... [tap tap tap] It looks like that's explicitly in the original Nature title: "Autonomous healing of fatigue cracks via cold welding." [1] [0] https://en.wikipedia.org/wiki/Cold_welding https://en.wikipedia.org/wiki/Cold_welding [1] https://www.nature.com/article https://www.nature.com/article
- jacquesm 3y ago
  Cold welding can really mess you up when you deal with precision ground stuff.
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 ago
  Funny 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 ago
  Statisticians borrowed the idea of “simulated annealing” and used it as a regularization technique for some time now.
  - dreamcompiler 3y ago
    Annealing 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.
phyzome 3y ago
It's cool that they observed this, but I'm a little confused why this is seen as surprising. Unless there's oxidation at the fissure, metals seem like they should be able to glue back together pretty easily...
- dreamcompiler 3y ago
  ...unless the metal at the crack location reconfigures itself to a lower energy crystal structure due to the boundary condition. Which apparently is not happening here.
mensetmanusman 3y ago
Prof. Demkowic was a very good instructor at MIT. Once I learned about the amazing world of dislocation growth/glide in materials, it helped me see physical objects in a whole new way. https://youtu.be/EXbiEopDJ_g https://youtu.be/EXbiEopDJ_g The math describing these defect strings was also interesting and challenging :) I wondered if they could be used for one-way computation.
frankreyes 3y ago
Isn't this the same effect as vacuum welding? Eg NASA doors in space station has to have some kind of isolation painting?
Tanoc 3y ago
I thought reforming the bonds of microfractures was already well known as a differentiator between metalloids and true metals? So does this mean that metalloids just shouldn't be a group anymore, or that they instead have to be expanded to include more materials? And certain substitutional alloys can be argued to be self healing. In bronze the copper will replace any displaced tin and zinc bonds without heat, for example.

90 points by bobvanluijt 3y ago

Article in nature: https://www.nature.com/articles/s41586-023-06223-0 https://www.nature.com/articles/s41586-023-06223-0

tempodox 3y ago

Metals have been known to have a kind of memory. If you bend a cable out of shape, it will bend itself right back. I have to think that this self-healing is an instance of the same principle.

iancmceachern 3y ago
Yeah, there are formulations of wire you can buy that are specifically designed to have this property to increase fatigue resistance and bend life.
- cwkoss 3y ago
  Nitinol is neat
  - PennRobotics 3y ago
    if you bend a thick wire of nitinol (nickel titanium alloy, discovered on accident, aka shape memory alloy) quickly, it heats at the site of the bend and that is cool, but paper clips do the same thing. once you've let the thick wire settle back to room temperature---here's the cool part---quickly force it straight again and it gets suddenly very cold at the site where the bend was. nitinol is neat

wanderingmind 3y ago

No preprint although government labs have direction to make their research openly available asap. Probably a paper written just for other researchers to cite and not for any generic interest.

rsfern 3y ago
It seems the paper isn’t in sandia’s publications database yet, but it’s only been a few days since the journal version was published. I’m not sure how it works at sandia, but at NIST one of the authors has to get around to uploading the manuscript and there’s no way to get an automated reminder. Then our publications database only updates once a day I think. I’m sure if you send a polite request for the manuscript they would be happy to share. Maybe even responsive to a polite request that they post a preprint next time, but in MatSci that’s much more common with modeling than experimental work. https://www.sandia.gov/research/publications/search/?pub_s=Autonomous+healing+of+fatigue+cracks+via+cold+welding&sort=date https://www.sandia.gov/research/publications/search/?pub_s=A...

nickelpro 3y ago

[flagged]

progfix 3y ago
You are wrong. I work in the construction industry and the term is commonly used and understood. https://en.m.wikipedia.org/wiki/Self-healing_material https://en.m.wikipedia.org/wiki/Self-healing_material
rewmie 3y ago
I'm afraid you'll throw a fit when you find out there's a whole field called structural health monitoring. https://en.wikipedia.org/wiki/Structural_health_monitoring https://en.wikipedia.org/wiki/Structural_health_monitoring

slater 3y ago

[flagged]

Terr_ 3y ago

[Recycling a comment from an earlier submission yesterday] Isn't this a bit like cold welding? [0] Unless something is in-between them or some force is pulling them apart, there's no big reason for two exactly-fitted pieces of the same crystalline metal to _not_ join together. It's not like the atoms "know" which side they belong to. Actually... [tap tap tap] It looks like that's explicitly in the original Nature title: "Autonomous healing of fatigue cracks via cold welding." [1] [0] https://en.wikipedia.org/wiki/Cold_welding https://en.wikipedia.org/wiki/Cold_welding [1] https://www.nature.com/article https://www.nature.com/article

jacquesm 3y ago
Cold welding can really mess you up when you deal with precision ground stuff.

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 ago
Funny 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 ago
Statisticians borrowed the idea of “simulated annealing” and used it as a regularization technique for some time now.
- dreamcompiler 3y ago
  Annealing 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.

phyzome 3y ago

It's cool that they observed this, but I'm a little confused why this is seen as surprising. Unless there's oxidation at the fissure, metals seem like they should be able to glue back together pretty easily...

dreamcompiler 3y ago
...unless the metal at the crack location reconfigures itself to a lower energy crystal structure due to the boundary condition. Which apparently is not happening here.

mensetmanusman 3y ago

Prof. Demkowic was a very good instructor at MIT. Once I learned about the amazing world of dislocation growth/glide in materials, it helped me see physical objects in a whole new way. https://youtu.be/EXbiEopDJ_g https://youtu.be/EXbiEopDJ_g The math describing these defect strings was also interesting and challenging :) I wondered if they could be used for one-way computation.

frankreyes 3y ago

Isn't this the same effect as vacuum welding? Eg NASA doors in space station has to have some kind of isolation painting?

Tanoc 3y ago

I thought reforming the bonds of microfractures was already well known as a differentiator between metalloids and true metals? So does this mean that metalloids just shouldn't be a group anymore, or that they instead have to be expanded to include more materials? And certain substitutional alloys can be argued to be self healing. In bronze the copper will replace any displaced tin and zinc bonds without heat, for example.