I’m very curious.
In: 141
Might be a bit off the ELI5, but I’ll try:
Due to rapid cooling of the outside of the drop it shrinks. (insert human analogue)
Not only does this shrinking occur all the way around (more or less) at once, it also means that the material has no where to go. Cold and hard on the outside, still hot and expanded on the inside; that puts it quite under a bit of – not only existential – stress.
And then the goo on the inside starts to cool down and contracts, wanting to pull the rest in. The rest that is already cooled and would love to move but can’t due to being cold.
What have we then? Stuff on the inside that pulls in all it can. Stuff on the outside that gets smushed together because someone couldn’t stand to let it relax.
And now you, with your puny hammer, start smacking around. You just don’t bring enough energy onto this table of high and unlovely mechanical stresses to throw those molecules out of order. Get a bigger hammer or grow muscles, puny human.
Well, that is until you start to attack the weak spot. The tiny tail that is so fragile, the whole thing explodes. Same thing actually, but here your puny human-arms are strong enough to overcome the residual stresses.
You monster.
We do the same thing for high pressure pipes btw. (e.g. common rail injection)
We blow them slowly up to a controlled pressure way beyond the future operational goal so that the inside starts to deform a bit. Then, after relieving them of that burden, they feel a bit weird, with all that pressure gone and the residual compression stress still there after the plastic deformation.
So, when the actual operation pressure comes along, they just laugh it off because they’ve seen way worse and won’t give in without a fight.
That completely unrelated thing is called: autofrettage
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