Pick up a handful of sand, and it flows through your fingers like a liquid. But when you walk on the beach, the sand supports your weight like a solid. What happens to the forces between the jumbled sand grains when you step on them to keep you from sinking?
An international team of researchers collaborating at Duke University have developed a new way to measure the forces inside materials such as sand, soil or snow under pressure.
Physicists are using this computerized 3-D rendering of beads in a box to serve as a model for soil, sand or snow. Colored lines show the network of forces as the virtual particles are pushed together. Thick red lines connect the particles that are experiencing the brunt of the force. By studying the forces inside granular materials as they're pressed, pushed or squeezed, the researchers hope to better understand phenomena like the jamming of grain hoppers or the early warning signs of earthquakes and avalanches.
Credit: Video courtesy of Nicolas Brodu.
Described in the March 5 issue of Nature Communications, the technique uses lasers coupled with force sensors, digital cameras and advanced computer algorithms to peer inside and measure the forces between neighboring particles in 3-D.
The new approach will allow researchers to better understand phenomena like the jamming of grain hoppers or the early warning signs of earthquakes and avalanches, said study co-author Nicolas Brodu, now at the French institute Inria.
Whether footprints in sand, or the force of gravity on a mountain slope, physicists have long sought to understand what happens inside granular materials as they're pressed, pushed or squeezed.
For centuries this simple question has been surprisingly difficult to answer. But more recently, thanks to advances in 3-D imaging techniques and the number-crunching power of computers, researchers are starting to get a better picture of what happens when granular materials like soil or snow are pushed together.
Brodu, along with physicists Robert Behringer of Duke University and Joshua Dijksman of Wageningen University in the Netherlands, describe how they use simple tools to measure the network of forces at it spreads from one particle to the next.
The researchers use a solution of hundreds of translucent hydrogel beads in a Plexiglass box to simulate materials like soil, sand or snow.
A piston repeatedly pushes down on the beads in the box while a sheet of laser light scans the box, and a camera takes a series of cross-sectional images of the illuminated sections.
Like MRI scans used in medicine, the technique works by converting these cross-sectional "slices" into a 3-D image.
Custom-built imaging software stacks the hundreds of thousands of 2-D images together to reconstruct the surface of each individual particle in three dimensions, over time. By measuring the tiny deformations in the particles as they are squeezed together, the researchers are able to calculate the forces between them.
The new approach will help researchers better understand a range of natural and manmade hazards, such as why farmworkers stepping into grain bins sometimes experience a quicksand effect and are suddenly sucked under.
"This gives us hope of understanding what happens in disasters like a landslide, when packed soil and rocks on a mountain become loose and slide down," Brodu said. "First it acts like a solid, and then for reasons physicists don't completely understand, all of a sudden it destabilizes and starts to flow like a liquid. This transition from solid to liquid can only be understood if you know what's going on inside the soil."
The team has already used results from their technique to create a new model for the way particulate matter behaves, which is concurrently published in the journal Physical Review E.
This research was supported by grants from the National Science Foundation (DMR1206351, DMS1248071), the National Aeronautics and Space Administration (NNX10AU01G), and the U.S. Army Research Office (W911NF-1-11-0110).
CITATION: "Spanning the Scales of Granular Materials through Microscopic Force Imaging," Brodu, N., J. A. Dijksman and R. P. Behringer. Nature Communications, March 2015. DOI: 10.1038/ncomms7361
Robin Ann Smith | EurekAlert!
Astronomers release most complete ultraviolet-light survey of nearby galaxies
18.05.2018 | NASA/Goddard Space Flight Center
A quantum entanglement between two physically separated ultra-cold atomic clouds
17.05.2018 | University of the Basque Country
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...
A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.
The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...
Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.
Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...
A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.
Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...
02.05.2018 | Event News
13.04.2018 | Event News
12.04.2018 | Event News
18.05.2018 | Power and Electrical Engineering
18.05.2018 | Information Technology
18.05.2018 | Information Technology