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Materials science key for stockpile stewardship

Gray classified colloquium Wednesday

The importance of materials science to stockpile stewardship, and specifically how materials properties affect the performance of weapon secondaries, is the topic for the next Director's Classified Colloquium, scheduled for 1:10 p.m., Wednesday in the Administration Building Auditorium at Technical Area 3.

Laboratory Fellow George "Rusty" Gray of Structure and Property Relations (MST-8) will describe the technical challenges, direction and advances in the determination and modeling of the causes and impact of high explosive-induced case performance in his talk entitled "Case Dynamics."

All attendees must hold "Q" clearances and have sigmas 1-10 assigned by line management. To register for the colloquium and others in the classified colloquium series, write to the Security Help Desk at security@lanl.gov by electronic mail and include name, Z number, group, e-mail address and phone number. Gray's talk is limited to U.S. nationals.

"An essential task of the weapons program has always been to determine, with confidence, the performance of nominal, aged and rebuilt stockpile weapons," Gray said.

The secondary stage of stockpile weapons is responsible for much of their yield, so confidence and precision in understanding the factors that control secondary yield is crucial. The related problem of determining the margins and uncertainties associated with understanding secondary performance is a key issue for stockpile stewardship, he added.

Gray said the Laboratory's case dynamics program seeks to understand the key elements of the sequence of events leading to secondary explosion and weapon performance, and to resolve the physics and computational issues related to them.

"During the high-explosive phase and subsequent primary explosion, the radiation case is simultaneously subjected to strong shocks, large radiation doses and high pressure, and changes in the case can impact the subsequent radiation flow from the primary to the secondary," Gray said.

Understanding case behavior requires experiments to characterize the materials properties of the radiation case, closely linked to validation modeling and simulation through the Advanced Simulation and Computing program, he said.

"My talk will describe the technical challenges, direction, and advances in the determination and modeling of the causes and impact of high explosive-induced case performance," Gray said.

Gray's research interests for the last 19 years have been in the area of structure/property effects of high-rate and shock-wave loading on a broad range of materials. His research has been focused on utilizing shock recovery and split-Hopkinson-bar experiments as part of an interdisciplinary research team combining real-time experiments, theoretical modeling, and post-shock / high-strain-rate material studies to investigate the generation of defects and storage during shock- and impact-loading events. Gray has actively pursued the application of high-rate / shock research to civilian applications such as foreign-object damage, crash-worthiness, and advanced manufacturing in addition to conventional and nuclear defense thrusts.

Gray is project leader for a Department of Defense (DoD) Office of Munitions program on Processing, Mechanical Response and Modeling of Defense Materials and Los Alamos' Case Dynamics - Materials project. He co-chaired the Physical Metallurgy Gordon Conference in 2000 and served on the board of directors of the Minerals, Metals and Materials Society as the chair of the Structural Materials Division from 2001 to 2003. He is a fellow of the American Society for Metals International and serves on the International Scientific Advisory Board of the European Association for the promotion of research into the dynamic behavior of materials and its applications, or DYMAT. He has authored or co-authored more than 230 technical publications.

The goal for the Director's Classified Colloquium series is to disseminate important and interesting information on classified scientific topics to Los Alamos technical staff. The talks are planned to help inform a wide audience of Los Alamos' major classified scientific research and to stimulate discussions within an appropriate, secure environment, ultimately leading to future ideas and initiatives that will advance classified programs.

More information about the Classified Colloquium series and upcoming colloquia is available at http://stbblue.lanl.gov/colloquium.html online.

--Jim Danneskiold

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