Accession Number:

ADA256300

Title:

Shock Response of Snow: Analysis of Experimental Methods and Constitutive Model Development

Descriptive Note:

Corporate Author:

COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH

Report Date:

1992-07-01

Pagination or Media Count:

24.0

Abstract:

A shock impact test was conducted on snow with an initial density of 400 kgcu.m using a large-diameter gas gun and Lagrangian stress gauges between layers of snow. The shock propagation velocity ranged from 240 to 2O7 msec., the peak stresses in the snow were between 20 and 40 MPa, and the compacted snow density was less than 860 kgcu.m. Interpretation of the stress records was complicated by the unsteady nature of the shock, impedance mismatching between gauges and snow, multiply-reflected pulses, and release waves generated at the edge of the target. A dynamic finite-element analysis was used to interpret the data, to construct a constitutive relationship for the snow, and to examine the importance of the release waves. Model calculations indicate two release wave sources the free edge of the target aluminum buffer and the edge of the snow in contact with the copper container. The aluminum buffer release waves contain both shear and dilatational components. Transmission across the aluminumsnow interface significantly attenuated dilatational waves and essentially eliminated the shear waves. The snowcopper release wave did not arrive at the stress gauge position until after the end of the experiment. With the aid of model calculations, the pressure volumetric-strain P-V curve for initial shock loading was determined from arrival time information and stress measurements at the embedded gauges. Stress signals caused by reflected waves were used to determine the reloading and unloading P-V curve. The P-V response for shock loading was found to be much stiffer than that for quasi-static loading. The unloading P-V curves used in model calculations were nonlinear functions of volumetric strain with linear reloading.

Subject Categories:

  • Snow, Ice and Permafrost

Distribution Statement:

APPROVED FOR PUBLIC RELEASE