Variable Sensitivity Piezometric Equations for Dislocation Density and Subgrain Diameter and their Relevance to Olivine and Quartz
- B.E. Hobbs and
- H.C. Heard
Published Online: 18 MAR 2013
Copyright 1986 by the American Geophysical Union.
Mineral and Rock Deformation: Laboratory Studies: The Paterson Volume
How to Cite
Twiss, R. J. (1986) Variable Sensitivity Piezometric Equations for Dislocation Density and Subgrain Diameter and their Relevance to Olivine and Quartz, in Mineral and Rock Deformation: Laboratory Studies: The Paterson Volume (eds B.E. Hobbs and H.C. Heard), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM036p0247
- Published Online: 18 MAR 2013
- Published Print: 1 JAN 1986
Print ISBN: 9780875900629
Online ISBN: 9781118664353
- Rocks—Testing—Addresses, essays, lectures;
- Rock deformation—Addresses, essays, lectures
A review of the metallurgical literature leads to the suggestion that the stress dependence in the piezometric equations for dislocation density and subgrain diameter should be written in terms of the sum of the differential stress and an empirical stress constant, rather than simply the differential stress alone as is commonly assumed. The resulting piezometers show a sensitivity of substructure to stress that decreases with decreasing stress, especially at low stresses.
Analysis of existing experimental data for olivine and quartz indicates that the values of the stress constant could be large enough to be significant, but that they cannot be determined because the experimental data do not extend to a sufficiently low stress. Extrapolation of experimental data to low stress conditions is not reliable without the determination of this constant, and use of such incomplete piezometric equations may lead to overestimates of the stress for stresses beyond the range of the experimental data.