Experimental investigation of rate dependency of freeze bond strength

Abstract

The effects of deformation rate on the shear strength of freeze bonds have been investigated through a series of Asymmetric Four-Point Bending (AFPB) experiments. Two submersion times of 30 min and 24 h have been considered, while the deformation rate has been varied from 0.01 to 100 mm/s. Ice specimens with an initial temperature of −18 °C have been subjected to a constant confinement of 25 kPa during formation and shearing of the freeze bonds. Failure of the bonds proved to be highly dependent on deformation rate, where more strain was observed prior to failure of the bond for slower deformation rates. The shear strength of the bond for both submersion times showed a general decreasing trend with increased deformation rate, which is of significant importance in characterizing the properties of ice ridge/rubble strength. Previous ice rubble strength experiments, as well as ice ridge keel gouging tests, have reported the same failure rate-dependency, highlighting the role of freeze bond failure on rate effects. Compressive strength measurements of solid ice presented in the literature have been observed to follow similar trends within the range of strain rates used in present study, where the failure mode appears to transition from ductile to brittle with increasing deformation rate. While more work is needed to understand the mechanisms associated with the rate dependency of freeze bond, this general observation suggests the rate dependency of ice ridges/rubble may indeed be related to the behavior of ice as a material, rather than being associated primarily with factors such as inertial and pore pressure effects, which have been previously proposed as the principal controlling mechanism.