News Release 

Groovy! These grooved patterns better mitigate shock waves

University of California - San Diego

A team of engineers at UC San Diego has discovered a method that could make materials more resilient against massive shocks such as earthquakes or explosions. Undergraduate researchers in the structural engineering lab of Professor Veronica Eliasson used a shock tube to generate powerful explosions--at Mach 1.2 to be exact, meaning faster than the speed of sound. They then used an ultra high-speed camera to capture and analyze how materials with certain patterns fared.

Previous research from Eliasson's lab had shown that obstacles laid out in a logarithmic spiral--picture a Nautilus shell spiraling around and around--were better able to diminish the energy of a shock wave and reduce overall damage than when arranged in other patterns. The researchers took that a step further, testing whether cutting three grooves into each side of the obstacle materials would be an even better attenuator of the shock when compared with similar obstacles laid out in a logarithmic spiral but with no grooves.

They found that these grooves did diminish the impacts of what's called the reflected shock wave--once the initial wave has hit the spiral of obstacles and bounced back. Results were inconclusive for the initial transmitted shock wave. The researchers reported their findings in a recent issue of the journal Multiscale and Multidisciplinary Modeling, Experiments and Design.

"This research can be used in military applications and civil applications too, to design materials and buildings to better withstand high-intensity blasts," said Christina Scafidi, one of the authors of the paper, who graduated in 2019 with a degree in structural engineering.

"The coal industry has had many fatal accidents and we believe this research presents a strong case for protecting the workers from blast waves that can easily propagate throughout an entire coal mine," added Alexander Ivanov, a recent aerospace engineering graduate and co-author of the paper. "If the entire wall of the coal mine could be lined with these solid geometric obstacles, it could provide a cheap way to protect all of the workers in the mine."

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The research was funded by a grant from the National Science Foundation.

Paper title: "Shock wave attenuation using rigid obstacles with large- and small-scale geometrical features." Authors include Alexander Ivanov, Nicolas Fassardi, Christina Scafidi, Tal Shemen and Veronica Eliasson from UC San Diego.

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