5 ms·

Sounds really interesting. The only potential downside I see is that metal and glass generally expand differently under heat and have different tensile strength

Sounds really interesting. The only potential downside I see is that metal and glass generally expand differently under heat and have different tensile strengths etc. I wonder how they plan to deal with that.

crispyambulance 8y ago
I think it depends on the application and scale whether or not that is an issue. For joints that are intended to remain at a constant temperature, no problem. For very small structures where thermal expansion amounts to very little relative displacements, also no problem. But, yeah, this isn't a solution for joining outdoor windows to metal frames.
- MichaelApproved 8y ago
  > But, yeah, this isn't a solution for joining outdoor windows to metal frames. Says who? Welds held up to pretty harsh conditions -50C to 90C.
  - dsfyu404ed 8y ago
    Just because a test joint of unknown size and shape held up over that range doesn't mean an actual real world assembly can hold up over that range. We know nothing about the nature of the weld they tested or the nature of the testing. Even with two of the same materials it's very possible to design a joint that doesn't work very well in the real world.
  - ddingus 8y ago
    That would work in much of the world on paper. Not that the world sees the upper range as ambient. The metal may well approach the upper range during a sustained heat exposure. Wonder what the safety factor actually is? There are three basic types of temperature exposures: One, a journey. Got super hot, or cold for a while, then returned to moderate, or acceptable range. Two, excursions. Got extreme and stayed there for a non trivial time. (Scaled to the properties of whatever it is) Three, wild ride! Journeys all over the place. In addition, these can be one off events, or cyclic. Windows get a kind of cyclic ride in many places. A bond holding "for a while" always has the question of what "while" really means. Microfractures due to highly localized stress and strain, pre loaded in as an artifact of welding, would be my primary concern.
  - crispyambulance 8y ago
    The glass-metal weld itself might be perfectly fine! The glass portion, however, could crack depending on its size/geometry and the temperature change. The article doesn't make clear exactly what kind of manufacturing operation they're intending. I suspect this is a technology to replace glue/epoxy in certain scenarios where one joins metal and glass.
abduhl 8y ago
Isn’t that the whole reason this is a breakthrough? It’s even discussed in the article... Professor Duncan Hand, director of the five-university EPSRC Centre for Innovative Manufacturing in Laser-based Production Processes based at Heriot-Watt, said: “Traditionally it has been very difficult to weld together dissimilar materials like glass and metal due to their different thermal properties - the high temperatures and highly different thermal expansions involved cause the glass to shatter.
- AllegedAlec 8y ago
  I read that more as being about the welding process, while I'm more thinking about how it would function during its use.
- deleted 8y ago
  [deleted]
tk75x 8y ago
“We tested the welds at -50C to 90C and the welds remained intact, so we know they are robust enough to cope with extreme conditions.”
- AllegedAlec 8y ago
  They don't specify anything about the nature of that weld though, for example how big the glass and the iron pieces were, and whether it was a point weld or a continuous weld, and the geometry of the weld itself (for example if it had an inside/outside corner).
  - dsfyu404ed 8y ago
    They also didn't mention if it was heated evenly or not. This sounds like a "we have to hype up the practical applications of our research because that's what you do if you want more funding for next year" type of article. They don't even include hypothetical example applications.
danmaz74 8y ago
They say that “We tested the welds at -50C to 90C and the welds remained intact, so we know they are robust enough to cope with extreme conditions.” So, it seems like they're aiming for applications where temperatures stay in the ranges of human habitats.
- AllegedAlec 8y ago
  Even in that range, you can run into issues. I know of local buses in my home town where a lot of them would have cracks in the front window because when they went over speed bumps, the frame would flex enough that strain was placed on the window. If you remove the silicone glue or whatever it is they use to afix windows, this problem would get a lot worse.
MisterTea 8y ago
Plenty of glass to metal sealing is done for hermetic purposes. One use is glass sealed connectors for aerospace use. Also components for ultra high vacuum systems which use metal to glass (or ceramic) joints to transition between materials or electrical isolation.
- hadlock 8y ago
  Generally these metal-glass joints use a sealant that also acts as an expansion joint. The California Academy of Sciences (that building with the grass on the roof with the circular windows) has a rainforest sphere made out of 8x8 foot panels, if you inspect the joints they are sealed with 1" of silicone caulking to account for different rates of expansion of the glass in four directions. This silicone caulking is almost the consistency of chewing gum. Without that expansion joint, directly welded together, I'm curious how say, a Pixel 3 with the screen welded to the metal case would do. I can imagine a situation where the case and screen expand differently and end up cracking the screen.
  - MertsA 8y ago
    No, there are special alloys and techniques for directly bonding metal to glass. In a lot of cases the approach is to keep the bonded area close together to minimize the distortion of the metal from the different expansion rates. Materials like Kovar are designed such that it very closely matches the expansion curve of glass so that it forms a hermetic seal without any kind of sealant between the glass and the metal. https://en.wikipedia.org/wiki/Kovar https://en.wikipedia.org/wiki/Kovar
  - Ma8ee 8y ago
    Not in Ultra High Vacuum systems. There's no surface on the inside except glass or metall that can be outgased for some time at high temperature. Since we need to heat the system to speed up the outgasing process, the expansion coefficients for the joints between metall and glass must be very closely matched.
adrianmonk 8y ago
I also wondered about this. Seems like it has to be taken into account. Still, the article says that glass and metal are already put together with adhesive. Unless the adhesive is stretchy, it must mean that, within certain limits, it's already OK. Presumably it gets worse as the length increases since expansion is cumulative, which suggests that smaller lengths are OK. Also, there are probably ways you can design around it like creating gaps in the metal or shaping it so that the metal can bend.

crispyambulance 8y ago

I think it depends on the application and scale whether or not that is an issue. For joints that are intended to remain at a constant temperature, no problem. For very small structures where thermal expansion amounts to very little relative displacements, also no problem. But, yeah, this isn't a solution for joining outdoor windows to metal frames.

MichaelApproved 8y ago
> But, yeah, this isn't a solution for joining outdoor windows to metal frames. Says who? Welds held up to pretty harsh conditions -50C to 90C.
- dsfyu404ed 8y ago
  Just because a test joint of unknown size and shape held up over that range doesn't mean an actual real world assembly can hold up over that range. We know nothing about the nature of the weld they tested or the nature of the testing. Even with two of the same materials it's very possible to design a joint that doesn't work very well in the real world.
- ddingus 8y ago
  That would work in much of the world on paper. Not that the world sees the upper range as ambient. The metal may well approach the upper range during a sustained heat exposure. Wonder what the safety factor actually is? There are three basic types of temperature exposures: One, a journey. Got super hot, or cold for a while, then returned to moderate, or acceptable range. Two, excursions. Got extreme and stayed there for a non trivial time. (Scaled to the properties of whatever it is) Three, wild ride! Journeys all over the place. In addition, these can be one off events, or cyclic. Windows get a kind of cyclic ride in many places. A bond holding "for a while" always has the question of what "while" really means. Microfractures due to highly localized stress and strain, pre loaded in as an artifact of welding, would be my primary concern.
- crispyambulance 8y ago
  The glass-metal weld itself might be perfectly fine! The glass portion, however, could crack depending on its size/geometry and the temperature change. The article doesn't make clear exactly what kind of manufacturing operation they're intending. I suspect this is a technology to replace glue/epoxy in certain scenarios where one joins metal and glass.

abduhl 8y ago

Isn’t that the whole reason this is a breakthrough? It’s even discussed in the article... Professor Duncan Hand, director of the five-university EPSRC Centre for Innovative Manufacturing in Laser-based Production Processes based at Heriot-Watt, said: “Traditionally it has been very difficult to weld together dissimilar materials like glass and metal due to their different thermal properties - the high temperatures and highly different thermal expansions involved cause the glass to shatter.

AllegedAlec 8y ago
I read that more as being about the welding process, while I'm more thinking about how it would function during its use.
deleted 8y ago
[deleted]

tk75x 8y ago

“We tested the welds at -50C to 90C and the welds remained intact, so we know they are robust enough to cope with extreme conditions.”

AllegedAlec 8y ago
They don't specify anything about the nature of that weld though, for example how big the glass and the iron pieces were, and whether it was a point weld or a continuous weld, and the geometry of the weld itself (for example if it had an inside/outside corner).
- dsfyu404ed 8y ago
  They also didn't mention if it was heated evenly or not. This sounds like a "we have to hype up the practical applications of our research because that's what you do if you want more funding for next year" type of article. They don't even include hypothetical example applications.

danmaz74 8y ago

They say that “We tested the welds at -50C to 90C and the welds remained intact, so we know they are robust enough to cope with extreme conditions.” So, it seems like they're aiming for applications where temperatures stay in the ranges of human habitats.

AllegedAlec 8y ago
Even in that range, you can run into issues. I know of local buses in my home town where a lot of them would have cracks in the front window because when they went over speed bumps, the frame would flex enough that strain was placed on the window. If you remove the silicone glue or whatever it is they use to afix windows, this problem would get a lot worse.

MisterTea 8y ago

Plenty of glass to metal sealing is done for hermetic purposes. One use is glass sealed connectors for aerospace use. Also components for ultra high vacuum systems which use metal to glass (or ceramic) joints to transition between materials or electrical isolation.

hadlock 8y ago
Generally these metal-glass joints use a sealant that also acts as an expansion joint. The California Academy of Sciences (that building with the grass on the roof with the circular windows) has a rainforest sphere made out of 8x8 foot panels, if you inspect the joints they are sealed with 1" of silicone caulking to account for different rates of expansion of the glass in four directions. This silicone caulking is almost the consistency of chewing gum. Without that expansion joint, directly welded together, I'm curious how say, a Pixel 3 with the screen welded to the metal case would do. I can imagine a situation where the case and screen expand differently and end up cracking the screen.
- MertsA 8y ago
  No, there are special alloys and techniques for directly bonding metal to glass. In a lot of cases the approach is to keep the bonded area close together to minimize the distortion of the metal from the different expansion rates. Materials like Kovar are designed such that it very closely matches the expansion curve of glass so that it forms a hermetic seal without any kind of sealant between the glass and the metal. https://en.wikipedia.org/wiki/Kovar https://en.wikipedia.org/wiki/Kovar
- Ma8ee 8y ago
  Not in Ultra High Vacuum systems. There's no surface on the inside except glass or metall that can be outgased for some time at high temperature. Since we need to heat the system to speed up the outgasing process, the expansion coefficients for the joints between metall and glass must be very closely matched.

adrianmonk 8y ago

I also wondered about this. Seems like it has to be taken into account. Still, the article says that glass and metal are already put together with adhesive. Unless the adhesive is stretchy, it must mean that, within certain limits, it's already OK. Presumably it gets worse as the length increases since expansion is cumulative, which suggests that smaller lengths are OK. Also, there are probably ways you can design around it like creating gaps in the metal or shaping it so that the metal can bend.