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Shifting Nature of Grains
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Shifting Nature of Grains

June 25, 2010
Shifting Nature of Grains Graduate student Eric Corwin (seated) and physics professor Heinrich Jaeger at the University of Chicago review data from their study on how the behavior of granular materials changes from a jammed to a flowing state. The screen in the foreground displays lines of force as they are transmitted from one class bead to another in response to the application of force from above. The work was performed at the Chicago Materials Research Center, a National Science Foundation Materials Research Science and Engineering Center. Working in conjunction with physicist Sidney Nagel, Jaeger and Corwin developed a different testing system that was comprised of a cylinder filled with up to 100,000 glass beads compressed over hour-long periods by a rotating piston. Their goal was to study shear forces in granular materials. They were able to quantify a characteristic change in the way stresses propagate through the materials when the grains shift from a jammed state to a flowing one. The researchers suspect the underlying mechanism, whereby grains acquire an "effective temperature" in their flowing state, has wide-reaching implications for better understanding materials that are jammed at the atomic level, such as glass. [Jaeger and Nagels work was published in the June 23, 2005 issue of Nature.] (Date of Image: June 20, 2005)


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