Date/Time: Tuesday, January 31, 2012 9:00AM PST, 16:00 UTC
Presenter: Jerome Johnson, PhD. University of Alaska, Fairbanks.
The “Excavation and Mobility Modeling” task of the Scientific Exploration Potential of the Lunar Poles project is to develop physically based discrete element method (DEM) models of the interaction ofwheeled mobility platforms and excavation tools with lunar regolith at the poles and elsewhere. The DEM explicitly models the dynamics of assemblies of particles, such as regolith (the layer of loose rock particles covering bedrock). It is particularly useful when a material undergoes large-scale discontinuous deformations that depend on micro-scale contact processes, internal breakage of contact bonds, and compaction of broken fragments, such as occur during excavation and mobility processes. The goal is to develop a DEM modeling capability that is usable by non-specialists and that can be configured to accurately simulate a wide range of applied and basic science and engineering problems beyond the current focus on mobility and excavation problems. For example, asteroid properties and processes, volatile migration in regolith, impact weather of crater walls and other problems that involve contact processes of particulate materials. Experimental data describing measurement of the geotechnical properties of lunar regolith, the interaction between wheels and regolith, and excavation interactions with regolith are being used to guide development of, and to validate the DEM models. Of particular interest is percussive excavation, which can greatly reduce the mass requirements of excavation machines on the moon. DEM modeling capabilities have progressed to the stage that accurate simulations of wheel digging tests for laboratory and Mars experiments have been completed. Simulations are also underway for percussive excavation, penetration and bevameter tests in JSC-1A lunar simulant. DEM simulation results demonstrate the importance of accurately representing regolith shape characteristics. CT scanning technology is being used to construct 3-d digital particles of JSC-1A. The COUPI DEM is undergoing beta testing at Glenn Research Center and the Cold Regions Research and Engineering Laboratory. The next phases of development are to configure COUPI to run on a range of computer platforms from laptops to massively parallel supercomputers. The webinar will present further detailsabout project progress, results, and planned future work.