Inelastic properties of ice I/sub h/ at low temperatures and high pressures
The aim was to explore the rheological behavior of H/sub 2/O ices under conditions appropriate to the interiors of the icy satellites of the outer planets in order to give insight into their deformation. To this end, we have performed over 100 constant-strain-rate compression tests at pressures to 500 MPa and temperatures as low as 77 K. The effect of increasing confining pressure on stress-strain behavior and deformation mechanisms depends on the test temperature. At a strain rate of 3.5 x 10/sup -5/ s/sup -1/, ice I/sub h/ fails catastrophically at temperatures below 165 K at all pressures tested (0.1 to 350 MPa). Failure strength increases sharply with increasing pressure. At P > 30 MPa, ice I/sub h/ fails by a shear instability producing faults in the maximum shear stress orientation and failure strength typically is independent of pressure. We have also studied the frictional sliding characteristics of ice I/sub h/ by shortening cylindrical specimens sawn and ground at 45/sup 0/ to the cylindrical axis. We observed sudden (stick slip) frictional sliding with the maximum shear strength necessary to overcome static friction tau obeying the simple law tau (MPa) = 8.5 + 0.2 sigma/sub n/ (MPa) where sigma/sub n/ is the normal stress on the sliding surface. This law was determined over the range 17 less than or equal to sigma/sub n/ less than or equal to 240 MPa and is insensitive to temperature and sliding rate over the range of conditions we explored. Stress-strain curves under ductile conditions typically display a linear quasi-elastic stage followed by macroscopic yield, strain softening and finally a flat steady state flow. Optical study of thin sections of samples taken to various strains shows that macroscopic yield corresponds to the first optical evidence of internal plastic deformation, that nucleation and rapid growth of new grains accompanies strain softening and that steady-state flow corresponds to the attainment of a steady-state recrystallization structure.
- Research Organization:
- Geological Survey, Menlo Park, CA (USA); Lawrence Livermore National Lab., CA (USA); Cornell Univ., Ithaca, NY (USA). Dept. of Materials Science
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6697275
- Report Number(s):
- UCRL-95941; CONF-8609269-1; ON: DE87007334
- Resource Relation:
- Conference: 7. symposium on the physics and chemistry of ice, Grenoble, France, 1 Sep 1986; Other Information: Paper copy only, copy does not permit microfiche production
- Country of Publication:
- United States
- Language:
- English
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