Pamela Burnley (Geoscience) wrote an article, "The Importance of Stress Percolation Patterns in Rocks and Other Polycrystalline Materials" that was published in the journal last month. She has discovered a new paradigm for understanding the deformation behavior of polycrystalline materials. Many familiar solid objects are composed of polycrystalline materials. Common examples include metals, ceramics, and rocks. Her work demonstrates that when these materials are forced to deform (change shape), their response is governed by a branch of mathematics known as percolation theory. Familiar examples of percolation behavior include the path water takes as it moves through dry sand the tracks made by raindrops running down a windshield. She used mathematical models to show that stress travels through polycrystals in much the same way, focusing in some parts of the polycrystal while leaving other parts relatively untouched. Her work provides a single theoretical framework for a surprising diversity of phenomena ranging from the formation of gneissic banding (the layering of light and dark minerals that defines the metamorphic rock referred to as gneiss) to the formation of faults deep in the Earth's lower crust and mantle. Her work has broad applications in geoscience, solid state physics, mechanical engineering, and materials science.
