The non-linear behavior of aqueous model ice in downward flexure

TL;DR

This paper investigates the non-linear flexural behavior of aqueous model ice used in ship ice tank tests, highlighting the effects of plasticity, vertical property variations, and top layer formation, with implications for better modeling of sea ice.

Contribution

It demonstrates that all types of aqueous model ice behave non-linearly in flexure regardless of composition, and critiques the Hertz method for estimating the Cauchy number.

Findings

All model ice types exhibit non-linear flexural behavior.

Top layer formation significantly impacts ice sheet behavior.

Hertz method for Cauchy number estimation is inadequate.

Abstract

As aqueous model ice is used extensively in ice tanks tests on the performance of ship hulls in sheet ice, it is imperative that such model ice replicate the main flexural strength behavior of sheets of sea ice and freshwater ice. Ice tanks use various types of aqueous model ice types, each of which contain brine dopants to scale-reduce ice-sheet strength. Dopants, though, introduce non-linear trends in the scaled flexural behavior of model ice sheets, and can affect ice loads and ice-rubble at ship-hulls and structures. This paper analyzes the non-linear behavior of model ices, and shows that all types behave non-linearly in flexure independent from crystal structure or chemical dopant. Such behavior is attributable to plasticity and vertical variations in stiffness and strength through sheets of model ice. Additionally, the problematic formation of a top layer in model ice sheets is shown to have a greater impact of sheet behavior than the literature reports heretofore. There remains a significant knowledge gap regarding the freezing and movement of brine dopants within ice sheets and their impact on the non-linear behavior. Additionally, it is found that the Hertz method for estimating the Cauchy number of model ice does not reflect the actual deformation behavior of model ice and should be revised.