UNIVERSITY OF NEVADA, LAS VEGAS PROJECT TITLE: DEFORMATION OF POLYCRYSTALLINE MATERIALS UNDER EXTREME CONDITIONS: STRESS PERCOLATION, SHEAR LOCALIZATION AND GRAIN BOUNDARY RHEOLOGY PROJECT DESCRIPTION: THE GOAL OF THE RESEARCH IS TO IMPROVE THE ABILITY TO PREDICT MECHANICAL CONSTITUTIVE OF PROPERTIES OF POLYCRYSTALLINE MATERIALS AT EXTREME CONDITIONS. THE PROJECT WILL TEST A NOVEL THEORY OF POLYCRYSTALLINE BEHAVIOR THAT POSITS THAT THE MECHANICAL CONSTITUENTS (GRAINS AND GRAIN BOUNDARIES) IN A POLYCRYSTAL INTERACT SO AS TO GENERATE PERCOLATION PATTERNS IN THE STRESS STATE WHICH IN TURN LEAD TO VARYING DEGREES OF SHEAR LOCALIZATION, FRACTURE OR VOID FORMATION. TO TEST THIS HYPOTHESIS, THEY WILL INTEGRATE DEFORMATION EXPERIMENTS, MICROSTRUCTURAL OBSERVATIONS AND NUMERICAL SIMULATIONS. THE EXPECTED OUTCOME OF THIS PROJECT WILL BE AN IMPROVED UNDERSTANDING OF THE MECHANICAL BEHAVIOR OF POLYCRYSTALLINE MATERIALS, INCLUDING A BETTER UNDERSTANDING OF THE ROLE OF GRAIN BOUNDARIES IN REDISTRIBUTING STRESS DURING DEFORMATION AND THE ROLE OF STRESS DISTRIBUTION IN CONTROLLING MECHANICAL BEHAVIOR. THIS UNDERSTANDING WILL ALLOW US TO BUILD BETTER MODELS OF MATERIALS DEFORMATION THAT ARE CRITICAL TO PREDICTING RHEOLOGY AT EXTREME CONDITIONS THAT ARE INACCESSIBLE TO LABORATORY STUDIES.