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A rate‐ and state‐dependent ductile flow law of polycrystalline halite under large shear strain and implications for transition to brittle deformation
Author(s) -
Noda Hiroyuki,
Shimamoto Toshihiko
Publication year - 2010
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2010gl042512
Subject(s) - brittleness , strain rate , materials science , flow stress , power law , mechanics , law , deformation (meteorology) , halite , shear stress , shear (geology) , thermodynamics , geology , physics , metallurgy , composite material , mathematics , statistics , gypsum , political science
We have conducted double‐shear biaxial deformation experiments in layers of NaCl within its fully‐plastic (FP) regime up to large shear strains ( γ < 50) with velocity steps. From this, we have empirically formulated a rate‐ and state‐dependent flow law which explains the transient mechanical behavior. The steady state flow stress in the FP regime can be explained by a power‐law with a stress exponent ∼8.5 and an activation enthalpy of ∼1.3 eV, with the instantaneous response having a higher stress exponent (13 ± 8), although there is data scatter. The transition to brittle regime is associated with weakening from the ductile flow law. In FP regime, the mechanical response is characterized by a monotonic decay to a new steady state while in the transitional regime, by a peak‐decay behavior. The transient flow law obtained here is of considerable importance in the study of the brittle‐ductile transition in rocks.