The Effect of a Bimodal Grain Size Distribution on the Compressive Strength of Polycrystalline Ice.

Previous studies have shown that grain size directly affects the strength of fresh-water equiaxed polycrystalline ice Ih, where strength decreases as grain size increases. This has been shown both in tension and compression at constant strain rates over a range of temperatures (-5 C, -1o C, -20C). T...

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Bibliographic Details
Main Author: Laughlin,James L
Other Authors: ARMY MILITARY PERSONNEL CENTER ALEXANDRIA VA
Format: Text
Language:English
Published: 1985
Subjects:
Snow
Ice and Permafrost
*GRAIN SIZE
*ICE
TEMPERATURE
VOLUME
MECHANICAL PROPERTIES
DISTRIBUTION
TENSILE PROPERTIES
CRYSTALS
STRENGTH(MECHANICS)
MIXTURES
STRAIN RATE
FRESH WATER
CONSTANTS
LOSSES
DUAL MODE
COMPRESSIVE PROPERTIES
POLYCRYSTALLINE
*Polycrystalline ice
Hall Petch relation
Compressive strength
Ice
permafrost
Online Access:http://www.dtic.mil/docs/citations/ADA162361
http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA162361
Description
Summary:Previous studies have shown that grain size directly affects the strength of fresh-water equiaxed polycrystalline ice Ih, where strength decreases as grain size increases. This has been shown both in tension and compression at constant strain rates over a range of temperatures (-5 C, -1o C, -20C). The mechanical behavior of the ice is well described by the Hall-Petch relation. This thesis presents the results of a study to examine the effect of a bimodal grain size distribution on the compressive strength of equiaxed randomly oriented polycrystalline ice Ih. Laboratory prepared specimens of right circular ice consisting of different amounts of large (5.5 mm) and small(2.0 mm) grains by volume (75%/25L%, 50%/50%, 25%) were tested at -10 C in uniaxial unconfined compression. Tests were conducted at two strain rates, 0.00001/S and 0.001/s. Building on the results of Cannon (1985), this work establishes the law of mixtures for the compressive strength of a specimen composed of a bimodal mix of grains. First hypotheisized by Lee(1985), the law of mixtures states that the strength of a bimodal specimen is linearly dependent on the volume fraction of large and small grains. A single significant grain size may be used to charcterize the mechanical behavior of the specimen. Two possible candidates of a significant grain size are examined, one derived from the use of the Hall-Petch relation and the second being the average of the two grain sizes. Results show the use of the average is more expedient with little loss in accuracy. Master's thesis.

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