spallation

May. 19th, 2011 07:14 am
prettygoodword: text: words are sexy (Default)
[personal profile] prettygoodword
spallation (spaw-LAY-shun) - n., the process whereby pieces are ejected from a body due to an impact; esp., the ejection of numerous smaller particles from a nucleus that has been hit by a high-energy particle.


The chips and fragments that come off something you hit are spalls, as are the ejecta from a meteorite impact. The verb form is, of course, to spall, and there is such a thing as a spalling hammer. Spallation was coined in the 1940s (possibly in a nuclear physic context?), but to spall is much older: at least the 15th century, in the sense of a chip, of uncertain origin but possibly germanic root (Old High German had a cognate verb spaltan, to split).

---L.

Date: 2011-05-19 05:20 pm (UTC)
From: [identity profile] movingfinger.livejournal.com
Huh. I'm only familiar with the weathering-peeling meaning (also applies to concrete).

Date: 2011-05-19 06:17 pm (UTC)
From: [identity profile] prettygoodword.livejournal.com
Hmm -- and the dictionaries don't seem to know of it being used in a weathering context, only impacts and (in deeply engineering contexts) stresses.

---L.

Date: 2011-05-19 08:18 pm (UTC)
From: [identity profile] movingfinger.livejournal.com
Huh. Surprisingly, Wikipedia has it right, with most emphasis on nuclear physics related usage. (Which is an example of how biased Wikipedia can be; discussion of and illustration of the weathering aspect would surely be more helpful to many looking up spalling and its causes.)

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