How much force does it take to shatter a Humvee, a soldier’s body armor, or a submarine?
In his cavernous laboratory at the University of Rhode Island, Arun Shukla—the Simon Ostrach Professor of Mechanical Engineering at URI—is finding answers to those questions and more as he studies how and why things break apart. His research is taking on greater importance and relevance during these turbulent times.
A world leader in fracture and experimental mechanics, Shukla has been working with the American government since the early 1980s to create stronger materials that can withstand damage from explosions and other catastrophic events. Most recently, he has conducted experiments for the U.S. Department of Homeland Security and the U.S. Department of Defense.
“Our objective is to find better ways to protect soldiers and civilians—and make our infrastructure stronger and more durable,’’ says Shukla. “As the world becomes more violent, this type of research is crucial to make us safer.’’
In his laboratory in the Kirk Center for Advanced Technology on the Kingston campus, he and his students simulate bomb blasts and other explosions in two devices: a huge pressurized steel water capsule and a 33-foot aluminum shock tube. With that equipment, he creates a controlled explosive environment so he can test how materials stand up to blasts—and also ensure that his students are doing safe experiments.
The shock tube simulates the rush of high-pressure gases from an exploding bomb to test materials. Helium is pumped into the tube to break a covering, then the gases race down the tube at three to four times the speed of sound and hit the material at the end. The 7-foot-tall, 1,800-gallon water capsule simulates the pressure deep in the ocean to measure how underwater shock waves and explosions affect materials and structures at that depth. Both devices evaluate different materials and structures. With the shock tube, Shukla examined how blasts damage glass windows and buildings. Using the tank, he is looking at how structures in submarines collapse from water pressure and blasts.
Shukla built the shock tube with Carl-Ernst Rousseau, now chair of Mechanical, Industrial and Systems Engineering at URI. Shukla designed the water capsule, which was built in Virginia and shipped to URI three years ago. Both devices loom large in Shukla’s Dynamic Photomechanics Laboratory, where the equipment hums steadily as it readies for the experiments.
The tests often last less than one millisecond, so three high-speed cameras that can take photos ranging from 30,000 to 200 million frames per second record the action. “This allows us to see the event, as it evolves, in slow motion,’’ says Shukla. His team examines the photos to understand how damage happens and how it can be prevented. Sensors on the shock tube and tank also pick up high pressures generated by the blast. Those results are analyzed on computers.
His list of sponsors is long—and impressive. Besides Homeland Security and the U.S. Office of Naval Research, he has collaborated with the U.S. Air Force Office of Scientific Research, the Naval Undersea Warfare Center in Newport, the National Science Foundation, the U.S. Army Research Office, and the Rhode Island Department of Transportation.