Acoustic Emission from Columnar Grained Ice

Acoustic emission (AE) from two types of columnar grained ice specimens, plain and sharply notched, subjected to bending load at -5°C was examined. Two different levels of thresholds, 25 mV and 125 mV, were set for the "average signal" of AE, and the signals which exceeded these levels were counted. The count of the AE signal from the sharply notched specimen was less than that from the plain specimen. The Kaiser effect on AE was observed in the reloading stage and it vanished when the pause time was over after about three minutes. The pop-in of the sharply notched specimen can be detected by AE. The ratio of σAES and σf, which express the calculated stress at the start of AE and the broken stress respectively, was nearly proportional to the value of σAES.