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Thermally induced acoustic emission in westerly granite
Author(s) -
Yong Chen,
Wang Chiyuen
Publication year - 1980
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl007i012p01089
Subject(s) - atmospheric temperature range , acoustic emission , materials science , growth rate , thermodynamic equilibrium , thermal , range (aeronautics) , thermodynamics , composite material , physics , geometry , mathematics
The acoustic emission of Westerly granite subjected to temperature changes up to 120° at various heating rates from 0.4 to 12.5°C/min was studied. A threshold temperature of 60 to 70°C appeared to exist for this range of heating rate, above which A.E. began to occur profusely with increasing temperature. Above the threshold temperature, the rate of A.E. depended strongly on the rate of heating. However, a thermal ‘Kaiser’ effect appeared to exist such that in cyclic heating and at temperatures below the maximum temperature reached in the previous cycle, very few A.E. occurred irrespect of the heating rate in the subsequent cycles. We suggest that there is an equilibrium state of the thermally induced cracks, which is a function of temperature but is independent of the heating rate; in the slower experiment, the equilibrium state of crack extension is achieved by slower growth, which is associated with smaller amounts of acoustic emission.