Shocking Snowbird Meeting Explores Materials at High Pressures
Researchers keen on hearing the latest advances in shock compression science flocked to the 11th biennial International Conference of the APS Topical Group on Shock Compression of Condensed Matter (SCCM), held June 27 through July 2 in Snowbird, Utah, a year-round resort located in the Wasatch mountains, about 30 miles from Salt Lake City.
The meeting kicked off with two special keynote sessions on Monday morning focusing on issues related to the U.S. Department of Energy. DOE Deputy Assistant Secretary, Gilbert Weingard, summarized current progress on the Accelerated Simulation Initiative (ASCI), a mission-based program that seeks to enable the use of computer simulation to move from a test-based to a science-based assessment of the nuclear weapons stockpile. "Such simulations are extremely complex and will require computers that are orders of magnitude more powerful than the largest systems in place today," he said, adding that software environments must also be expanded in order to use such large systems effectively. Later that morning, Hans Mark, director of the DOE's Defense Research and Engineering division, outlined the financial outlook and potential results of defense technology R&D.
The technical focus of this year's SCCM meeting was the physics of materials at elevated pressure or stress. Tuesday morning featured a lecture by this year's recipient of the Shock Compression Award, Lynn Barker, of Valyn International. He discussed the development of the VISAR technique in 1972, which first made laser interferometry applicable to a wide range of shock experiments, such as a plate impact study of phase transitions in iron. Since then several subsequent improvements have been made to the device, most recently Valyn International's "multi-beam" VISAR, capable of measuring several points on a specimen simultaneously. He was followed by a plenary address on bridging length scales in dynamic plasticity simulations by Rodney Clifton of Brown University, who reviewed recent computer simulation methodology ranging from atomistic to macroscopic scales.
On Wednesday morning, Mel Baer, of Sandia National Laboratories, described new three-dimensional simulations of shock impact on a realistic ensemble of crystalline grains, which demonstrated that rapid material distortion occurs at crystal boundaries. Such advanced simulations are now possible because of the vastly improved new parallel computing machines able to provide improved resolution of shock processes at the mesoscale. In a third plenary session later that morning, Brad Holian, of Los Alamos National Laboratories, discussed recent advances in simulations of shock waves and related phenomena, including plastic deformation, high-speed interfacial sliding, and fragmentation. "As experimental observations become more and more refined, and molecular dynamics simulations become larger, even approaching the mesoscale, fruitful overlap is achievable in the near future," he concluded.
The topical group also organized several special events to balance out the technical aspects of the program. Tuesday afternoon featured an outdoor picnic on the deck of the Snowbird Center, complete with a complimentary ride on the 125-passenger tramcars to the top of the 11,000-foot mountain. On Wednesday, participants were given the option of choosing between two tours. The first began at Bear Hollow, Utah's state-of-the-art winter sports park and one of the venues for the 2002 Winter Olympics, and proceeded on to the Deer Valley Resort and Park City's Historic Main Street, a former mining town that now houses specialty shops, art and history museums, and restaurants The second tour focused on Salt Lake City's most famous sites, beginning with the Kennecott Copper Mine, from which 5 billion tons of ore have been extracted since operations began in 1905. [The mine is so enormous it is actually visible from space.] The tour then proceeded to the Great Salt Lake, the largest saltwater body of its kind in the world, where participants were given a summary of the lake's history from the Ice Age to the present.
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