Book Description

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. (EDC).