Time to formation of first cracks in ice

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Volume1, Part 1
Pages359370; # of pages: 12
Subjectice; compressive stresses; internal cracks; temperature cracks; dislocation; creep
AbstractObservations have been made at two temperatures on the time to formation of the first internal cracks in columnar-grain ice subjected to a constant compressive load applied perpendicular to the long direction of the grains. Crack formation was observed to be a thermally activated process, with the time to formation of the first large crack (2 or more mm wide and 20 or more mm long) following the general law t=t(0)exp[(U[0]-alpha rho)divided by kT]. The value of U(0), the activation energy for zero applied stress rho, was found to be about 25 kcal/mole, t(0) about 4.6 X 10(-17) sec and alpha about 1.4 X 10(-20) cm(3)/molecule. The amount of strain associated with the formation of the first crack was observed to increase with decreasing stress, but to be independent of temperature to within the accuracy of the experiments. The results were found to be consistent with the models for crack nucleation by pile-up of dislocations discussed by Stroh (1954) and Bullough (1964). It was observed that dislocation cracks could initiate Griffith cracks if the stress exceeded about 7 kg/cm(2), and no cracks were observed when the applied stress was less than about 5 kg/cm(2).
Publication date
AffiliationNRC Institute for Research in Construction; National Research Council Canada
Peer reviewedNo
NRC number10226
NPARC number20373898
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Record identifier9dd1de58-3298-49b2-ae91-7ba8b5153c16
Record created2012-07-23
Record modified2016-05-09
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