Welding breakthrough could transform manufacturing | Hacker News Reader

Welding breakthrough could transform manufacturing

phys.org

105 pointsgooseus35 comments

"The process relies on the incredibly short pulses from the laser. These pulses last only a few picoseconds — a picosecond to a second is like a second compared to 30,000 years."

Nice bit of exposition.

You might enjoy this video of Grace Hopper explaining how to visualize a nanosecond http://www.youtube.com/watch?v=JEpsKnWZrJ8

Wonderful. For the time it takes an electron to travel in 1 microsec (in vacuum, yada, yada):

> 984 feet ... We oughta hang one over every programmers desk, or over their neck (:audience chuckles:), so they know what they're throwing away when they're throwing away microseconds.

That would be incredibly useful today for web development.

Very interesting. Welding glass and metal together instead of using an adhesive. This could be big, depending on how long-term testing comes out. The trick seems to be to use picosecond laser pulses to avoid running into thermal issues with the very different materials.

This seems to be the original press release from the university website: https://www.hw.ac.uk/about/news/2019/welding-breakthrough-co...

Have we forgotten lightbulbs, CRTs, and a myriad of other vacuum tubes used to be a thing? They used the alloy 'kovar' for much greater temperature variation tolerance than this new tech was tested for.

Kovar is still widely used. Besides the low thermal expansion coefficient, the thermal expansion is extremely close to quartz which makes it ideal for optic purposes.

I wonder how long until no one can repair phones anymore, because they are welded shut.

Seems unlikely IMHO. Devices need or will need to be serviceable or recyclable in some places.

It's kind of dubious whether phones can really be repaired now. It's often possible to get a phone running again but it's never going to be quite the same after it's been pulled apart. I'd draw the line at the point where they started gluing them shut instead of using screws and (reusable) clips.

We have glues that for practical purposes would be just as hard to repair.

Repairability is generally a choice of the designer/manufacturer.

Cars have lots of welding on them and are still plenty repairable.

This won’t eventually lead to the glass cracking as temperature changes cause the metal to expand and contract?

No, the terms picosecond and micron are pretty integral to the process. Imagine using a propane torch to heat up the side of a single brick in an apartment building wall for a few seconds. The temperature change in that brick, considerable compared to all the others, will have effectively no impact on the building itself.

Yeah, but it's about long term stresses leading to cracking. I wonder how big elements you can weld with this. Centimeter scale windows for chips will probably have no problems. While screens in mobile phones - I suppose they will crack within weeks/months.

It is very much possible that such essentially atomic level weld will be more resilient than the glass itself.

The interesting bit is if anyone can make new and exciting multilayer material composites using this kind of welding.

Definitely possible, but I think that's something you could engineer your way out of by being very selective with materials, building in strain relief. Then of course test test test.

> Then of course test test test.

That's what customers are for.

Well they are paying for it either way, why delay gratification?

As long as the thermal strain(deformation) and therefore stress is managed, it would be fine. There are design tables and values that one can refer to that limit maximum cyclic stress which might be particularly applicable here.

This could make titanium rimless glasses even more minimal, no longer needing to drill through the glass.

I'm kind of confused...Isn't laser welding a pretty well studied technique? Laser welding is pretty common for high tech industrial products. Is the breakthrough the mix of materials? Even then I've seen different plastics laser welded together. Also, pico laser has been the industry standard for lasers for a while now. The main race is getting a robust fempto laser.

So could we see the return of square windows to aircraft? This would allow that right?

https://en.m.wikipedia.org/wiki/De_Havilland_Comet

The square windows didn't do the Comet in, it was poor engineering and testing, leading to improper fuselage reinforcement.

It's covered in that wikipedia article that you linked under 'Window shape misconception'.

Ok I'm trying to parse that, and marry that with my own understanding.

The linked article seems to suggest that window corners weren't the cause of the crashes. My understanding is that corners can lead to propagation of cracks etc, thus why modern aircraft window have a large window radius. And large radius windows require less reinforcement, and thus weight.

They aren't contradictory are they?

Edit: Missing word.

The hard rectangular angles lead to fatigue failure from stress concentration. If more testing had been done and this had been known during the design phase, it would have been possible to reinforce the rest of the airframe around the windows such that the airframe would be able to withstand the forces while retaining rectangular windows. No cracks, no crashes. However, the tradeoff for such strength would have been complexity, weight, and manufacturing difficulty; thus, modern airplanes have curved window ports to allow for windows while being light and simple. Aerospace and sports cars are the places in industry where lightness pays compounding dividends over raw strength. For a plane, if you can shave a pound off the design, you do it, since that's a pound you're not going to have to burn fuel to keep aloft for the entire lifetime of the aircraft. Or, for equivalent fuel, you could go faster instead.

I suppose there's another question I never asked myself: What is the merit of a rectangular window? Why would we want rectangles on our airplanes? They're on our houses because they're simple to frame and create openers for, neither of which are important for planes.

Thanks for your input.

"What is the merit of a rectangular window" Marketing gimmick? Square panels = easier construction?

I was just trying to think of practical applications (planes), that led to trying to reason about whether this would solve the problem of fractures in this situation.

> What is the merit of a rectangular window?

less blind spots! cockpits in fact tend to maximize the window surface area and you'll find square/trapezoid on most of them. (counterpoint: SpaceShip One went for rounded windows because they maximized for strength).

Probably not, using square windows will still have stress points on the corners regardless of the manifacturing process used.

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