柱状多結晶氷のアコースティック・エミッションに関する研究

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  • チュウジョウ タ ケッショウゴオリ ノ アコースティック エミッション ニ カ
  • Research of Acoustic Emission from Columnar Grained Ice

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Acoustic emission (AE) from the columnar grained ice specimen subjected to the bending load was examined. Two types of specimen, plain and sharply notched, were used. Three point bending tests were conducted at -5℃. The AE transducer was attached to the specimen by pouring a bit of water between the surface of the AE transducer and that of the specimen, which froze into ice and fixed the AE transducer to the specimen. Two different levels of threshold, 25mV and 125mV, were set for "average signal" of AE and the signals which exceeded these levels were counted. The number of thus counted AE signals are expressed as N25 and N125, respectivety. The results of this study are as follows; (1) In the bending tests of plain specimen the values of N25f and N125f, which expressed the total number of N25 and N125 untill the fracture of the individual specimen, showed a considerable scatter. The scatter decreased as the loading rate increased. (2) The calculated value of σAES, which expressed the stress where AE started, was 0.2～0.4 MPa under low loading rate and 0.1～0.4 MPa under high loading rate. (3) In the bending tests of sharply notched specimen, the count of AE signal was less than that of plain specimen. (4) The pop-in will be detected by AE. (5) The Kaiser effect on AE was observed in the reloading, when the pause time was zero, and it vanished when the pause time was over about three minutes.

長崎大学工学部研究報告, 17(29), pp.100-109; 1987

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