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Full-Text Articles in Physical Sciences and Mathematics
Does The Normal Stress Parallel To The Sliding Plane Affect The Friction Of Ice Upon Ice?, Andrew L. Fortt, Erland M. Schulson
Does The Normal Stress Parallel To The Sliding Plane Affect The Friction Of Ice Upon Ice?, Andrew L. Fortt, Erland M. Schulson
Dartmouth Scholarship
Sliding experiments were performed at –10 degrees C on smooth surfaces of freshwater columnar-grained S2 ice sliding against itself at a velocity of 8X10 –4 ms –1, with the purpose of examining whether normal stress parallel to the sliding plane affects frictional resistance. This component of the stress tensor was varied (0.20–1.83 MPa) using a loading system operated under biaxial compression, by orienting the sliding plane at two different angles, 26 degrees and 64 degrees, with respect to the principal loading direction. Under these conditions, no evidence was found to indicate that the normal stress in the direction of …
A New Technique For Firn Grain-Size Measurement Using Sem Image Analysis, N.E. Spaulding, D.A. Meese, I. Baker, P.A. Mayewski
A New Technique For Firn Grain-Size Measurement Using Sem Image Analysis, N.E. Spaulding, D.A. Meese, I. Baker, P.A. Mayewski
Dartmouth Scholarship
Firn microstructure is accurately characterized using images obtained from scanning electron microscopy (SEM). Visibly etched grain boundaries within images are used to create a skeleton outline of the microstructure. A pixel-counting utility is applied to the outline to determine grain area. Firn grain sizes calculated using the technique described here are compared to those calculated using the techniques of Gow (1969) and Gay and Weiss (1999) on samples of the same material, and are found to be substantially smaller. The differences in grain size between the techniques are attributed to sampling deficiencies (e.g. the inclusion of pore filler in the …
The Effect Of Particles On Creep Rate And Microstructures Of Granular Ice, Min Song, Ian Baker, David M. Cole
The Effect Of Particles On Creep Rate And Microstructures Of Granular Ice, Min Song, Ian Baker, David M. Cole
Dartmouth Scholarship
The microstructures of particle-free granular freshwater ice and ice containing 1 wt.% of 50 ± 10 mm uniformly distributed particles were investigated before and after compressive creep to ∼10% strain with stresses of 1.45 MPa at −10°C and 0.4 MPa at −5°C. Creep rates of particle-containing ice were always higher than those of particle-free ice. For an initial stress of 1.45 MPa at −10°C, dynamic recrystallization occurred with new grains nucleating and growing along grain boundaries for both sets of specimens, and the ice with particles showed a higher nucleation rate. Under creep with an initial stress of 0.4 MPa …
Do Loading Path And Specimen Thickness Affect The Brittle Compressive Failure Of Ice?, A. L. Fortt, E. M. Schulson
Do Loading Path And Specimen Thickness Affect The Brittle Compressive Failure Of Ice?, A. L. Fortt, E. M. Schulson
Dartmouth Scholarship
Compressive experiments were performed on square (160 mm × 160 mm) prismatic specimens of columnar-grained, S2 freshwater ice, biaxially loaded across the columns at −10°C. The work focused on brittle behavior, achieved by deforming the specimens at an applied strain rate of 4.5 ± 1.2 × 10 3s 1 in the direction of shortening. The results show that the specimen thickness (25–150 mm) has no detectable effect on the terminal failure strength of the ice. Likewise, the strength of the ice when loaded under proportional loading, where the minor stress varies during the test, was similar to that when loaded …
Brittle Compressive Failure Of Ice: Proportional Straining Vs Proportional Loading, E. M. Schulson, D. Iliescu
Brittle Compressive Failure Of Ice: Proportional Straining Vs Proportional Loading, E. M. Schulson, D. Iliescu
Dartmouth Scholarship
Proportional straining experiments have been performed on columnar-grained S2 fresh- water ice biaxially compressed across the columns at –108C at a strain rate of (4.5 1.5) 10–3 s–1. The results are compared with those obtained earlier (Iliescu and Schulson, 2004) from the same kind of material deformed to terminal failure under the same conditions, but through proportional loading. The exercise shows that the biaxial strength is practically independent of the path taken, at least under low confinement where Coulombic shear faulting limits terminal failure. First-year sea ice is expected to exhibit the same behavior.
Using Electron Backscatter Diffraction Patterns To Examine Recrystallization In Polar Ice Sheets, Rachel Obbard, Ian Baker, Katherine Sieg
Using Electron Backscatter Diffraction Patterns To Examine Recrystallization In Polar Ice Sheets, Rachel Obbard, Ian Baker, Katherine Sieg
Dartmouth Scholarship
The fabric of polycrystalline ice is typically described using the c-axis orientation alone, but this is insufficient for a full description of grain orientations in this hexagonal material. Electron backscatter diffraction (EBSD) provides full c- and a-axis orientation of individual grains, and is used here to study Greenland Ice Sheet Project 2 (GISP2) ice specimens from depths of 1551, 1642 and 1745 m. Complete orientation data are used to compare nearest-neighbor relationships to overall fabric and to differentiate between recrystallization mechanisms. Changes in orientation between grains and subgrains in GISP2 specimens were correlated with the appearance of grain boundaries on …