Explosive forming of a metal sphere

Originally published at: https://boingboing.net/2020/12/22/explosive-forming-of-a-metal-sphere.html

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The ‘paper on it’ is behind a paywall.

How do they trigger the explosives inside, which I assume must be somehow held in the centre of the ‘sphere’ prior to detonation. So I guess there are some internal structural members, too?

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It turns a Death Star into a moon after all!

A commenter links another video that shows more spheres being created and gives a better sense of scale:

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That is cool; like getting tires back on to rims with lighter fuel.

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Mind blown expanded…

Mind Blown - Bill Nye|nullxnull

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Are we going to start to see giant metallic orbs appearing everywhere soon?

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thank you for this. not sure why I’m finding this so fascinating but I am.

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ds

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Sometimes the back tire on my lawnmower comes off the rim, and after seeing videos like this on youtube / here I started doing this (much to the concern of my family). It works great, but I wear a face shield just in case a bit of the tire explodes away.

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It’s filled with water which is what distributes the forces evenly… somehow. I’ve seen it done in person and it was like magic to the people doing it too.

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OK - so no structural members inside. So where is the explosive and how is it mounted? And detonated?

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I was intrigued by this process some time ago, when I read an article on artist Evelyn Rosenberg. Found a book in the campus library on the technique that outlined how it was used to make large low-run forms like fuel-tank ends for rockets.Tooling was a fraction of that it would take to make a steel die, as it could be made out of epoxy-coated concrete. (And the process can be used to make objects that would be impossible due to their size and the capacity of existing presses.) The interior is filled with water (Incompressible) to make the transfer of the shock safe® and more efficient. There were some great examples of how a seamless tube was formed into a complex shape by placing it between the mold halves with a strand of primacord strung end-to-end.

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Filling it with water keeps it from actually exploding. It’s the same way boilers are tested- filled and pressurized with water because water doesn’t compress, so there’s no explosion if a leak exists- just sprays of water. This is called hydrostatic testing.

After hydroforming, I’m sure they have to go around and weld up all the leaks (assuming this sphere is a tank of some sort) that appeared from the process.

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I’m sure this won’t put undue strain on any part of the vessel

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A scuba diver, with a box of matches. It costs a lot in health benefits, but the final effect is worth it.

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The trails of the L118 Light Gun/M119 Howitzer are explosively formed. They’re lovely to behold.

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Best I can tell from what little I read on the subject, is that the charge is suspended in the center of the object with a wire. Detonated electrically. Tube-like forms have primacord running through its length.

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I read the article - they do the math to get it just right without bursting and mention using a series of charges if they require “too much”.

Discussed is a 4 m diameter steel vessel with 18 mm wall thickness.

Clever Mongolians!

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What are the benefits / drawbacks vs more conventional hydroforming?

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Quoting the article: “The method needs no special dies and it is easy to change size and
variety; there is no need of forming equipment and the method is highly energy-
efficient.”