scholarly journals Snowbreeder 5: a Micro-CT device for measuring the snow-microstructure evolution under the simultaneous influence of a temperature gradient and compaction

2017 ◽  
Vol 63 (238) ◽  
pp. 355-360 ◽  
Author(s):  
MAREIKE WIESE ◽  
MARTIN SCHNEEBELI
Keyword(s):  
Temperature Gradient ◽  
Constant Temperature ◽  
Snow Sample ◽  
Micro Computed Tomography ◽  
Peltier Element ◽  
Constant Temperature Gradient ◽  
New Device ◽  
Isothermal Conditions ◽  
Snow Metamorphism ◽  
Simultaneous Influence

ABSTRACTThe instrumented sample holder Snowbreeder 5 is used to investigate the simultaneous influence of settlement on temperature-gradient snow metamorphism in time-lapse micro-computed tomography experiments. So far, experiments have only been done on temperature-gradient snow metamorphism without settlement or settlement under isothermal conditions. With the new device we can impose a constant temperature gradient on a snow sample and induce settlement by placing a passive load on top of the snow sample. The weight of the load can be varied, simulating various snow heights on top of the snow sample. Snow-temperature measurements on the passive load are possible due to wireless data transfer via Bluetooth. The temperature gradient is set by controlling the air temperature inside the computer tomograph and by a Peltier element at the bottom of the snow sample. First experiments under isothermal conditions and a constant temperature gradient of 43 K m−1 showed that the settlement was reduced to almost half as soon as a temperature gradient was applied under otherwise almost equal snow conditions. The compactive viscosity in the isothermal experiment was in the range of literature values.

INFLUENCE OF GROWTH RATE ON MICROSTRUCTURE AND MICROINDENTATION HARDNESS OF DIRECTIONALLY SOLIDIFIED TIN–CADMIUM EUTECTIC ALLOY

2009 ◽  
Vol 16 (02) ◽  
pp. 191-201 ◽  
Author(s):  
E. ÇADIRLI ◽  
H. KAYA ◽  
M. GÜNDÜZ
Keyword(s):  
Growth Rate ◽  
Temperature Gradient ◽  
Directional Solidification ◽  
Constant Temperature ◽  
Eutectic Alloy ◽  
Directionally Solidified ◽  
Constant Temperature Gradient ◽  
Microindentation Hardness ◽  
Solidification Furnace ◽  
Eutectic Melt

Sn – Cd eutectic melt was first obtained in a hot filling furnace and then directionally solidified upward with different growth rate ranges (8.1–165 μm/s) at a constant temperature gradient G (4.35 K/mm) in the Bridgman-type directional solidification furnace. The lamellar spacings (λ) were measured from both transverse and longitudinal sections of the samples. The influence of the growth rate (V) on lamellar spacings (λ) and undercoolings (Δ T) was analyzed. λ2V, ΔTλ and ΔTV-0.5 values were determined by using λ,ΔT and V values. Microindentation hardness (HV) was measured from both transverse and longitudinal sections of the specimens. HV values increase with the increasing values of V but decrease with increasing λ values. λ-V, λ - ΔT and λ2V results have been compared with the Jackson–Hunt eutectic model and similar experimental results, HV - V and HV - λ results were also compared with the previous work.

scholarly journals Evolution of crystal orientation in snow during temperature gradient metamorphism

2013 ◽  
Vol 59 (213) ◽  
pp. 47-55 ◽  
Author(s):  
Fabienne Riche ◽  
Maurine Montagnat ◽  
Martin Schneebeli
Keyword(s):  
Computed Tomography ◽  
Temperature Gradient ◽  
Crystal Orientation ◽  
Initial Density ◽  
Snow Sample ◽  
Micro Computed Tomography ◽  
Thin Sections ◽  
Two Samples ◽  
The Difference ◽  
Snow Samples

AbstractThe physical properties of snow are tied to its microstructure. Especially for the slow, plastic deformation of snow and firn, the crystal orientation is an important factor in addition to the geometry of the ice matrix. While micro-computed tomography measures the snow microstructure precisely, it gives no information about the orientation of the ice crystals. In this study, we applied a temperature gradient of 50 K m−1 to large blocks of undisturbed decomposed snow and sieved snow during 3 months. The mean temperature of the snow samples during the temperature gradient experiment was −20°C. Two closely spaced snow samples were taken before the experiment, then every week during the first month and afterwards every month. From each sampling, one sample was analyzed by micro-computed tomography and the other was used for thin sections. The orientation of the c-axis was measured in the thin sections using an automatic ice texture analyzer. Initial density was 30% higher in the sieved snow sample. Density and specific surface area evolved alike, while the fabric showed a different evolution between the two samples. The undisturbed snow evolved from a weak single-maximum fabric towards a weak girdle fabric, while the sieved sample showed no evolution. The undisturbed snow sample converged toward the sieved sample fabric after 6 weeks, but continued its evolution thereafter. We suggest that the main factor causing this different behavior is the difference in density and in pore size.

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