“For the process of deformation, this offers a new universal theory in which the gap between microscopic rearrangements and macroscopic flow is bridged by simple, self-similar scaling relations.”Peter Schall, University of Amsterdam
The rearrangement of particles in materials during deformation, such as when a spoon is bent, resembles highly collective avalanches that span the entire material. This is the conclusion of experimental research conducted by a team of researchers from the University of Amsterdam (UvA) in the Netherlands and the University of Illinois at Urbana-Champaign. The team’s findings, which are published in Nature Communications, provide the basis for a new universal theory of deformation.
Within the field of physics, the everyday deformation of materials has traditionally been described in very different contexts. For example, when a spoon is bent or a mobile phone cover shaped during production, small sporadic atomic rearrangements occur that ultimately give rise to the changing shape of the material. In soft materials such as cream or tooth paste, similar rearrangements occur, but with much larger constituent particles giving rise to the overall shape change.
Until now, attempts to describe exactly what happens during the deformation process have been impeded by the large difference in length scales between microscopic rearrangements and macroscopic deformation. This has precluded a complete understanding of deformation processes.
To gain a better insight into deformation, the researchers made use of a new method that involved directly imaging the three-dimensional motion of fluorescently-labelled particles inside a model system using a laser-scanning technique. This allowed them to track the motion of the individual particles in space and time and connect this motion to the applied deforming force, thereby bridging the gap between micro and macro scales.
What they discovered was that the motion of the particles strongly resembles an ‘avalanche’, in that the particles do not rearrange themselves individually but move collectively to a new position. Moreover, by analyzing variations in the applied force, the researchers also determined that the particle movement was very similar to the seismic activity of earthquakes.
“Avalanches are important phenomena that occur not only in the surge of snow down an incline, but also in a wider context such as through the spread of forest fires, diseases or in the dynamics of stock markets,” says Peter Schall, professor of soft condensed matter physics at UvA and one of the researchers who took part in the project. “They typically develop in highly collective systems that are distinct by their critical state and in which a small event can trigger a large effect.”
The beauty of this finding is that deformation – like many other avalanche phenomena – are described by identical statistical distributions, thereby allowing unification of widely differing phenomena. “For the process of deformation, this offers a new universal theory in which the gap between microscopic rearrangements and macroscopic flow is bridged by simple, self-similar scaling relations,” says Schall. “These are independent of the material and can include anything from nanorods to rocks to everyday materials. This greatly reduces the complexity of the phenomenon into a unifying framework and should ultimately lead to the better prediction and design of material properties.”
This story is adapted from material from the University of Amsterdam, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.