FRACTURE-TOUGHNESS OF FRESH-WATER ICE .1. EXPERIMENTAL-TECHNIQUE AND RESULTS

Experiments have been performed to determine the effect of loading rat e and temperature on the fracture toughness of both granular and S2 co lumnar freshwater ice. Loading rare was varied from 0.04 to 40.0 kPa r oot m s(-1), and over this range the fracture toughness was observed t o decrease from 201 to 109 kPa root m. Examination of load-CMOD curves indicate that at a loading rare of 40 kPa root m s(-1), the crack tip plasticity was sufficiently limited that the specimen behavior can be considered linear elastic, thus providing a valid K-Q measurement. Wh en test temperature was varied from -5 to -45 degrees C for the S2 col umnar ice, no significant variation in toughness was observed. In cont rast, for granular ice, a higher toughness (144 kPa root m) was observ ed in the -5 to -20 degrees C range than for the S2 columnar ice. Howe ver, the toughness of the granular ice at -45 degrees C is not signifi cantly different from that of the S2 columnar ice. A companion paper ( Weber and Nixon, 1996) analyzes the results in greater detail comparin g them with previous work, and presents a detailed fractographic analy sis of the failure surfaces.