Evaluation of New Thermomechanical Constitutive Theory for Snow

The thermomechanical properties of snow have been described in terms of microstructural processes. The constitutive theory was formulated in a form consistent with the second law of thermodynamics. Deformation was described in terms of such microstructural processes as pressure sintering, shearing d...

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Bibliographic Details
Main Author: Brown, R. L.
Other Authors: MONTANA STATE UNIV BOZEMAN
Format: Text
Language:English
Published: 1989
Subjects:
Snow
Ice and Permafrost
Thermodynamics
*SNOW
*DEFORMATION
*THERMOMECHANICS
*ICE
STEADY STATE
TRANSIENTS
LOAD DISTRIBUTION
MECHANICAL PROPERTIES
MICROSTRUCTURE
SIZES(DIMENSIONS)
VAPORS
ELASTIC PROPERTIES
MATRIX MATERIALS
GRAIN SIZE
MIXTURES
RESPONSE
LENGTH
ANISOTROPY
MASS TRANSFER
PRESSURE
LABORATORY PROCEDURES
BONDING
HEAT
RADIUS(MEASURE)
SLIDING
SINTERING
IMAGE PROCESSING
COMPUTER PROGRAMS
GRANULES
VISCOPLASTICITY
THERMAL PROPERTIES
CONSTITUTIVE PROPERTIES
PORE SIZE
Ice
permafrost
Online Access:http://www.dtic.mil/docs/citations/ADA206367
http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA206367
Description
Summary:The thermomechanical properties of snow have been described in terms of microstructural processes. The constitutive theory was formulated in a form consistent with the second law of thermodynamics. Deformation was described in terms of such microstructural processes as pressure sintering, shearing deformations within the necks connecting the ice grains, and intergranular glide. The matrix material (ice) was modeled as an elastic-viscoplastic material such that transient response as well as steady state response to loading can be described. The formulation is also able to describe the development of material anisotropy which evolves as a result of sustained deformation. An experimental technique was also developed to enable one to measure the change in the microstructure of the material due to deformation. This had to be done in order to determine if the constitutive theory was correctly describing the microstructural deformation processes. This technique involved using an image analysis system to quantitatively determine the important microstructural processes (grain size, pore size, neck length, bond radius, bonds/grain). Computer software were developed to automate the processes as much as possible. Finally the changes in microstructure due to thermal effects was studied. A modern mixture theory was adopted and modified for snow to characterize the effects of heat and vapor mass transport through snow on the grain size, neck radius, density, etc. This part of the project was important since these microstructural properties determine the mechanical properties.

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