How Glass Breaks: Four Theories
1.
Brittleness
on the macroscopic scale
can be deceiving. Measured
in microns, the fracture surface
resembles the long-lost, infinitesimal
twin of a rent in metal –
that famously elastic break.
So too, then, with glass:
cavities as narrow as a few nanometers
open ahead of the crack,
not-glass
flowing together
in the last fraction of a second before
the wineglass shatters under
the bridegroom’s shoe.
2.
Atom separates from
individual atom
in rapid sequence
wherever the amorphous
solid – glass –
encounters stress.
The blind cane of an atomic
force microscope can tap
all along the edge of a crack
& find no sign of deformation,
no pits or pockmarks.
Glass must therefore be
as we’d always thought:
immaculately brittle.
3.
Atoms under pressure slip
& slide across each other;
nothing is simple. Friction
leads to atom-sized cracks
& the cracks widen into
the necessary cavities, yes.
But all along the fracture zone,
the same pressure
responsible for the break
makes the gaps snap shut
immediately thereafter.
Let’s call them nanovoids,
these model wounds,
healing as perfectly as if
they had never been.
4.
Approaching the fracture origin,
the surface of a crack appears
increasingly smooth. But under
an electron microscope, each region
shows the same kinds of features
at a finer & finer scale – a fractal
self-affinity. Beginning at ground
zero, we name these regions
mirror, mist, hackle,
macroscopic crack branching:
energy magnified in chaotic order.
Given an opening, given vibration,
atoms in the amorphous silica will
change partners – a choreography
of rings that first contract, then
join together, encircling ever
larger volumes until the last
bonds fail & the atoms
dance irrevocably
apart.
__________
Inspired by an article in Research: Penn State, “What Makes Glass Break,” by Walt Mills (online, 2005). Also consulted:
F. Célarié, S. Prades, D. Bonamy, L. Ferrero, E. Bouchaud, C. Guillot, and C. Marlière, “Glass Breaks like Metal, but at the Nanometer Scale.” Physical Review Letters 90, 075504 (2003).
J.-P. Guin and S. M. Wiederhorn, “Fracture of Silicate Glasses: Ductile or Brittle?” Physical Review Letters 92:21, 215502 (2004).
R. K. Kalia, A. Nakano, P. Vashishta, C. L. Rountree, L. Van Brutzel and S. Ogata, “Multiresolution atomistic simulations of dynamic fracture in nanostructured ceramics and glasses.” International Journal of Fracture 121:1-2, 71 (2003).
J. J. Mecholsky, J. K. West, and D. E. Passoja, “Fractal dimension as a characterization of free volume created during fracture in brittle materials.” Philosophical Magazine A, 82:17/18, 3163 (2002).
by Dave Bonta of Via Negativa
qarrtsiluni 
impressive,…and beautiful
“under
an electron microscope, each region
shows the same kinds of features
at a finer & finer scale – a fractal
self-affinity.”
and
“the same pressure
responsible for the break
makes the gaps snap shut
immediately thereafter.
Let’s call them nanovoids,
these model wounds,
healing as perfectly as if
they had never been.”
worlds within worlds
That’s lovely, Dave.
The first stanza is my favorite — I love both its opening lines and its closing lines.
Terrific poem, Dave. Like Rachel, I especially loved the first stanza and its surprising concluding image of the bridegroom, bringing us suddenly into the picture.
Yup, make that three of us! I think it left me looking for similar “returns” from the microscopic world in the other stanzas. There is a bit of that, I think, in the last stanza – the changing of partners, the bonds fail and dance irrevocably apart – so much for the wedding!
You’ve proved it. The world of science can yield some amazing poetry. So much hard truth is encapsulated in a term like “fractal self affinity”.
Whew… marriage in the 21st century- the fractal conceit, the wine glass at the Jewish wedding, brilliantly done. To a beautiful, slow shattering dance, “until the last
bonds fail & the atoms
dance irrevocably
apart.”
Thanks for the comments. It’s gratifying to realize that I may have succeeded in making some fairly dry material come alive – and of course it’s always fun to see what people will respond to in something as strange as this. My personal favorite was the third stanza; the fourth was the most challenging to write because of the extreme stangeness of the material. It was easy to forget, when reading these papers, that they were actually talking about something breaking – it sounded so much more like a wedding than a divorce! But then it occurred to me that if we are to have any chance of conceptualizing things at the atomic level, we have to turn all our convential notions upside-down…
Ah, that’s neat, Dave. Like Rachel, I love the first stanza best, but the whole thing is pretty cool. Nice work!