Making Protective Mesh Stronger
Date: February 17, 2010
Making Protective Mesh Stronger
Braden Lusk with the University of Kentucky has been developing a mining research program at UK focused on the use of explosives, and he admits that this research interest began a long time ago—when he was 10 years old.
“As a kid growing up in Hutchinson, Kansas, I liked to blow up my toys,” he says, chuckling at the memory. “I would horde all kinds of fireworks, but I didn’t use them on the 4th of July. I had ‘greater uses’ for them, I guess. My parents had a lot of trouble understanding this hobby,” adds Lusk, an assistant professor of mining engineering.
He describes his current research focus as a two-sided coin. “We’re looking both at how to make explosives more effective and also how to design materials to lessen the effects of a blast,” says Lusk, a robust and effusive man who came to UK from the University of Missouri-Rolla in 2005. His main project during the last year has been the study of an aluminum mesh product for blast mitigation. This product development work is being funded for $433,000 by the U.S. Navy through a company called Innovative Productivity Inc., in Louisville.
Lusk explains that this aluminum mesh could be attached to the windows of buildings near blasting sites, ship holds or as protective layers on mine-resistant, ambush-protected trucks, referred to as MRAPs. Large numbers of MRAPs have been shipped to Iraq. “And it’s possible that soldiers in the field could use this mesh for protection,” Lusk adds.
And in his work there is a direct tie to the mining industry. Lusk talks about the Sego Mine disaster in January 2006 in Tallmansville, West Virginia, where an explosion trapped 13 miners beneath the surface, leaving only one survivor: “At the heart of that disaster was a seal failure that followed a methane explosion. The seals that failed at Sago had been tested and approved for a methane blast that was much less powerful than the blast that caused them to fail,” Lusk explains. “Even before this tragedy happened, there was a big push for the development of more blast-resistant mine seals, and I’ve thought about this material I’m working on and others like it as a good solution to protect mine seals.”
With the help of Kyle Perry, who has a degree in civil engineering (and also happens to be Lusk’s brother-in-law), Lusk has been testing the mesh product in the field—an underground quarry in Georgetown, Kentucky. For “donating this space” to his work, he says he’s indebted to Frank Hamilton, who owns the property, and his son Richard, both UK alums.
Perry and Lusk set up different thicknesses of mesh around an explosive charge with sensors directly behind the mesh, stand back a safe distance, and then detonate the charge. A sensor, with no mesh in front of it, collects a reference pressure measurement from each blast to see how much the pressure is reduced with various layers of mesh.
“We’re doing some numerical simulations using Autodyn,” Lusk explains, “a software program that models blast events in conjunction with physical testing to validate the mitigating strengths of this mesh.” So far the researchers have shot over 150 tests, using a total of around 75 pounds of desensitized RDX, an explosive related to nitroglycerine and used by the military.
In corollary testing, Lusk is simulating blasts using a shock tube, a 120-foot-long reinforced steel tube with a 3/8” steel plate at the end and sensor mounts at different spots along the tube. Using less than a pound of explosives, he can send a shock wave down the tube and collect data that tell him the pressure time history of the wave.
“Field testing involves thousands of pounds of expensive explosives. Using this simulation testing is a lot less expensive and allows us to compare results between arena testing and tube testing.”
After he crunches the data from the tests he’s done, Lusk hopes to draw up some guidelines for the use of this mesh, depending on the size and location of the blast.
By Jeff Worley, University of Kentucky Odyssey