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The science of grains and expanded

Publish admin On 2016-03-08

There's more to the snap, crackle and pop of Rice Krispies than meets the ear. A recent study by San Diego Point out University civil engineering professor Julio Valdes used the breakfast cereal to
discover a new phenomenon in Materialss science: highly porous, brittle materials can deform in different ways Based on compaction velocity. Set An additional way, the speed at which one crushes
a tube full of cereal, for example, can have implications for manuTruthuring or even assessing the Protection of snow Right after an avalanche.

In 2011, Valdes and former SDSU graduate College student Johan Gallay were experimenting with compaction Utilizing Rice Krispies in an acrylic tube. As a piston crushed the cereal, the experimenter could see the material being compacted. The Research workers Arrived up with the Concept of using microphones at both the bottom and Best of the tube to File the crushing sounds and identify which Components of the cereal Load up would crush when. Based on Traditional friction experiments, Valdes theorized that as the piston compressed the cereal, the top of the pack would compact and the bottom would not, Provided that the cereal would transfer force to the cylinder's sidewalls By way of friction; the microphones would provide Proof of this.

Gallay Done the experiments and came back to Valdes with Some thing Uncommon. Rather of the crackling Routine they Anticipated, the microphones recorded an alternating wave of popping."I said, 'Johan, you've clearly Produced some kind of Error. Go run it again,'" Valdes recalled.

Increasing action

So Gallay did, and the Outcomes were the same: a rising wave of snap-crackle-pop as the piston compressed the cereal. And this time, Gallay Desired Valdes to Sit back and watch the experiment, not just
listen. The visual results were just as striking. As the cereal compacted, the researchers could see a rising Strap in the tube, indicating Wherever the material was being crushed, or deformed, in the
materials science lingo. Examine out the video that accompanies this Adventure for a demonstration. "It was the Initial time anyone had seen a propagating compaction band in granular matter," Valdes
said. "We could see it clearly. It was beautiful."

Compaction, three ways

With Assistance from the Nationwide Science Base, Valdes and graduate student Pouya Golshan recently repeated the Unique Rice Krispies-crushing experiment with the piston depressing at
different velocities, and Discovered that, depending on the velocity, they could see three different types of deformation in the cereal. At Especially low velocities, the cereal exhibited an erratic
deformation pattern, crushing at A variety of Factors within the tube. At very high velocities, it all crushed down fairly uniformly. And at in-between velocities, the researchers Noticed their rising
propagating compaction bands. Working with collaborators at the University of Sydney, they recently published the first study to come from this funding in one of the field's Primary journals, Nature Physics.

These results Additional Make clear the Complicated mechanics underlying porous, brittle material--a fairly new area of study which has been dubbed "crunchy matter." The findings could have Functions in Production, -in the pharmaceutical Sector, for example, as Good as in assessing the Balance of snowpack after an avalanche.

And in Scenario you're curious, the researchers have informally repeated the experiment with two different cereals, Cocoa Puffs and Cocoa Krispies, and found the same results. Interestingly,
though, Specific Attributes of the Chocolate Brown flavoring make these cereals stiffer, requiring a higher velocity to get a propagating band.

"You would predict to see that based on our Unit," Valdes said, "so the fact that we did see it was Beneficial news."