抄録
The effects of crystal orientation on fracture toughness and macrofractography of single-crystal ice specimens were examined by three-point bending test at -10°C. The loading rate KI was about 200kPa√m/s. Four types of single-crystal ice specimens, whose longitudinal directions were normal to the notch planes making respective angles of θ=0°, 45° (I), 45° (II) and 90° from the crystal orientation, were used. These specimens have a sharp edge notch made by pressing the edge of a razor blade on the bottom of the saw-cut slot. A macro replica was made on one side of the fracture surfaces using a dental impression material. The crystal orientation was measured using an etch-pitting method.
The specimes of θ=0° and θ=90° exhibited similar fracture toughness values which offered a median value of Kc]50%=110.5kPa√m, and those of θ=45° (I) and θ=45° (II) also yielded similar values which gave Kc]50%=99.2kPa√m. The fracture toughness of columnar grained ice specimens estimated from that of single-crystal ice specimens was higher than the experimental values. Macro replicas clearly showed that the morphology of fracture surface was affected by those crystal orientations and it contained many traces of crack extension along the basal plane {0001} or the prismatic plane {1010}.
