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Microcracking during stress‐relief of polycrystalline ice formed at high pressure
Author(s) -
Meglis Irene L.,
Gag R. E.,
Young R. P.
Publication year - 1995
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 - 10.1029/95gl02007
Subject(s) - brittleness , materials science , crystallite , nucleation , composite material , stress (linguistics) , slurry , cracking , grain size , hydrostatic pressure , mineralogy , geology , geotechnical engineering , metallurgy , linguistics , chemistry , philosophy , physics , organic chemistry , thermodynamics
To study microcracking in a brittle material in response to stress‐relief, samples of polycrystalline ice were frozen under hydrostatic pressures up to 19 MPa and subsequently decompressed. Eight cylindrical samples (approximately 56 mm in diameter and 120 mm long) were made by freezing a slurry of crushed ice and degassed water inside a clear Teflon jacket. Four additional tests were done by reloading samples which were previously unloaded, allowing them to re‐equilibrate, and then unloading again. Tests were filmed through windows in the confining cell. Acoustic emissions were monitored in some samples. When the stress was released, intense cracking occurred for approximately 0.4 seconds and then tapered off. Thin sections showed that the stress‐relief cracks were approximately equal to the facet size (<5 mm), were primarily along grain boundaries, and were distributed throughout the samples with no obvious preferred orientation. Within a few hours of unloading, grain boundaries became cloudy, possibly a result of air trapped at the grain surfaces. Preliminary results from further tests indicate that this air plays a significant role in crack nucleation.