Low temperature elastic constants and nonlinear acoustic response in rocks and complex materials.

Darling, T. W. ; Johnson, P. A.

Technical Information Center Oak Ridge Tennessee

关键词: Acoustics;    Rocks;    Materials;    Elasticity;    Sandstones;   

RP-ID  :  DE2001784309

学科分类：工程和技术（综合）

美国|英语

来源: National Technical Reports Library

【 摘 要 】

The P-M Space model of Guyer and McCall has some success in describing the large nonlinear effects ('slow dynamics') observed by Johnson et al in rocks. The model uses elements which couple classical nonlinear elasticty with hystertic components. The actual processes and scales corresponding to the model elements are not yet defined, however it is reasonable to seek energy scales by studying the low-temperature dependence of the elastic constants. We have measured qualitative elastic properties of basalt and Berea sandstone from room temperature down to 4 K using Resonant Ultrasound Spectroscopy (RUS). A simple elastic solid should show a monotonic increase in the elastic constants as temperature decreases. The basalt samples show this gross behavior but the sandstone shows a very unexpected anomalous regime between 40 K and 200 K where the elastic constants decrease with decreasing temperature. Both rocks show temperature dependent structure in both the modulus and internal friction, and also significant hysteresis, indicating history and rate-dependent properties. This data provides insight into the time and energy scales of dynamical effects observed in sandstones.