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Structure-property relationships for sea ice: Modeling and experimental validation

Presented by: 
David Cole
Monday 6th November 2017 - 13:30 to 14:30
INI Seminar Room 1
This talk addresses the constitutive behavior of sea ice, with a focus on the relationships between measurable physical properties and the elastic, anelastic and viscous components of strain. To accommodate attendees with a limited knowledge of sea ice, the presentation includes a brief overview of the microstructure and flaw structure of naturally occurring sea ice. Some attention is paid to the structure and mechanics of columnar and granular freshwater ice for completeness. The components of strain are quantified in terms of crystallographic characteristics (primarily c-axis orientation), dislocation density for the inelastic components, and temperature. The mechanisms of anelastic strain (e.g., time-dependent but recoverable) are associated with basal dislocation glide and grain boundary sliding. Viscous straining is quantified in terms of drag-controlled dislocation glide on the basal planes. It is shown that dislocation density exerts an overwhelming influence on the constitutive behavior of sea ice both at the scale of laboratory experiments (0.1 m) and in-situ experiments ( ≤ 30 m). Recent efforts to account for certain high temperature effects and differences between in-situ vs. in-vitro constitutive behavior of sea ice are described and the associated modifications to the published constitutive model are discussed. An analysis of existing cyclic loading and creep experiments makes it possible to identify the physical basis for the apparent increase in activation energy of inelastic behavior with proximity to the melting point. Additionally, brine drainage from specimens harvested for laboratory experiments is shown to cause a major discrepancy between the in-situ elastic response of warm sea ice vs. that found in laboratory experiments. 
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University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons