A 2-D granular system featured in a University of Pennsylvania study about how disordered systems fail. Blue shows overpacked regions, green shows under packed regions and red shows a transient shear band of the type the researchers are trying to understand.
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Dropping a smartphone on its glass screen, which is made of atoms jammed together with no discernible order, could result in it shattering. Unlike metals and other crystalline materials, glass and many other disordered solids cannot be deformed significantly before failing and, because of their lack of crystalline order, it is difficult to predict which atoms would change during failure.
"In order to understand how a system chooses its rearrangement scenario, we must make connection with the underlying microscopic structure," said Douglas Durian, a professor of physics and astronomy at the University of Pennsylvania (Penn). "For crystals, itís easy; rearrangements are at topological defects such as dislocations. For disordered solids, itís a very hard 40-year-old problem that weíre now cracking: What and where are structural defects in something thatís disordered?"
To find a link between seemingly disparate disordered materials and their behavior under stress, Penn researchers studied an unprecedented range of disordered solids with constituent particles ranging from individual atoms to river rocks. Understanding materials' failure on a fundamental level could pave the way for designing more shatter-resistant glasses or predicting geological phenomena like landslides.
In a published paper, Penn researchers revealed commonalities among these disordered systems, defining a counterpart to the "defects" implicated in crystalline materials failure. This so-called "softness" in disordered systems predicts the location of defects, which are the collection of particles most likely to change when the material fails.
The research was conducted at Pennís Materials Research Science and Engineering Center (MRSEC), supported by the National Science Foundation (grants DMR 17-20530 and 11-20901).
Learn more about this research in the Penn news story Penn researchers establish universal signature fundamental to how glassy materials fail. (Date image taken: 2017; date originally posted to NSF Multimedia Gallery: April 13, 2018)