The behavior seen here is similar to "shear thickening," which has been used when manufacturing bulletproof vests that present as a soft material when worn, but hardens upon impact of a bullet.
"The research shows that friction can fundamentally change the nature of granular materials in intriguing ways," says Daryl Hess, program director for condensed matter and materials theory at the National Science Foundation. "Friction and shear reveal the richness of possible states of granular matter, pointing us down a road paved with new discoveries. These may expose deeper connections between jamming and seemingly unrelated phenomena spanning from earthquakes to transformations occurring in other kinds of matter, like water to ice."
In industries where hoppers are used, like loading rice grains onto a truck for example, jamming can be a problem. One possible solution, says Chakraborty, is to change the traditional shape in order to both prevent and break up jams.
"We need these sort of laboratory-based experiments to construct and test theories," says Chakraborty. "Once you get into an industrial situation things are not controlled enough to understand."
|Contact: Susan Chaityn Lebovits|