HR: 0800h
AN: NG31A-0866    [Abstracts]
TI: Neutron Diffraction Study of the Contribution of Grain Contacts to Nonlinear Stress-Strain Behavior
AU: * Darling, T W
EM: darling@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop K764, Los Alamos, NM 87545 United States
AU: TenCate, J A
EM: tencate@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop K764, Los Alamos, NM 87545 United States
AU: Brown, D W
EM: dbrown@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop K764, Los Alamos, NM 87545 United States
AU: Clausen, B
EM: clausen@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop K764, Los Alamos, NM 87545 United States
AU: Vogel, S C
EM: sven@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop K764, Los Alamos, NM 87545 United States
AB: Repeatable, hysteretic loops in quasi-static loading measurements on rocks are well known; the fundamental processes responsible for them are not. The grain contact region is usually treated as the site of these processes, but there is little supporting experimental evidence. We have performed simultaneous neutron diffraction and quasi-static loading experiments on a selection of rocks to experimentally isolate the response of these contact regions. Neutron diffraction measures strain in the lattice planes of the bulk of the grain material, so differences between this strain and the macroscopic response yield information about grain contact behavior. We find the lattice responds linearly to stress in all cases, oblivious to the macroscopic unrecoverable strains, curvature, and hysteresis, localizing these effects to the contacts. Neutron diffraction shows that the more granular rocks appear to distribute stresses so that the same strain appears in all the grains, independent of crystallographic orientation. [Work supported by Los Alamos Institutional Support (LDRD) and the DOE Office of Basic Energy Sciences. The Manuel Lujan Jr. Neutron Scattering Center is a national user facility funded in part by the U.S. DOE.]
DE: 3630 Experimental mineralogy and petrology
DE: 3694 Instruments and techniques
DE: 3909 Elasticity and anelasticity
DE: 3954 X ray, neutron, and electron spectroscopy and diffraction
SC: Nonlinear Geophysics [NG]
MN: 2004 AGU Fall Meeting