Post by Chicago Astronomer - Astro Joe on Nov 5, 2005 5:28:12 GMT -6
What Actually Causes Glass to Break?
After 2,000 years of making and breaking glass, one might think there would be a definitive answer. But at the Third International Workshop on the Flow and Fracture of Advanced Glasses, held Oct. 2 to 5 at The Penn Stater Conference Center Hotel, 50 or so of the world's top glass scientists scratched their heads as researchers presented sharply conflicting views on the topic.
the classical model, which says that glass fractures through the stretching and breaking of individual inter-atomic bonds one after another, and that this process is accelerated by the condensation of water at the tip of the crack."
A subscriber to the cavity model, Bouchard presented experimental evidence that both common silicate glasses and newly developed metallic glasses, as well as some ceramics, fracture via cavities that form and flow together ahead of the crack tip. The size of the cavities she observed ranged from a few nanometers in fast-moving cracks, to hundreds of nanometers in ultra-slow stress fractures, she said.
Mecholsky showed the fracture process as a series of changes in the atomic bonds at the crack tip," said Pantano. "His simulations showed the glass's atomic structure pulling apart like stretched rubber bands through the rearrangement of atoms -- not the rupture of bonds -- to propagate the growing crack."
Full story here: www.physorg.com/news7864.html
============
It's rather fractal in nature and I find atomic behavior just facinating...
