The Viscoelastic Fracture and Indentation of Sea Ice

Abstract

The fracture of sea ice is modeled using a viscoelastic fictitious crack (cohesive zone) model. The sea ice is modeled as a linear viscoelastic material. The fictitious crack model is implemented via the weight function method. The impact of assuming viscoelastic behavior in the bulk as opposed to elastic behavior is studied. The model is applied to large scale in-situ sea ice fracture tests. Two coupled influences are back-calculated: the shape of the size-independent rate-independent stress separation curve, and the relevant creep compliance function. Next, the high pressure zones that arise during ice-structure indentation are examined. The influences of scale and indentation speed on the formation of these high pressure zones are explored. Line-like and localized high pressure contact zones are modeled via quasi-brittle hollow cylinder and hollow sphere idealizations, respectively. For both simultaneous and non-simultaneous contact, the critical lengths of stable cracking that may occur prior to flaking and flexural failure are strongly linked to the current level of specific pressure parameters for both line-like and localized high pressure zones. The stability aspects of the in-plane cracking, and the link between the maximum possible crack lengths and the relative magnitudes of the local and far-field pressures help explain the transitions observed within the realms of ductile, intermittent, and brittle crushing.