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Nucleation and growth of cracks in vitreous-bonded aluminum oxide at elevated temperatures

Journal Article · · J. Am. Ceram. Soc.; (United States)
The nucleation and growth of cracks was studied at elevated temperatures on a grade of vitreous-bonded aluminium oxide that contained approx. =8 vol% glass at the grain boundaries. Cracks were observed to nucleate within the vitreous phase, close to the tensile surface of the flexural test specimens used in these experiments. Crack nucleation occurred at a strain of approx. =0.08% to 0.12% which corresponded to a crack nucleation time of approx. =35% of the time to failure by creep rupture. Once nucleated, cracks propagated along grain boundaries, as long as the stress for crack propagation was maintained. The crack velocity for cracks that were nucleated by the creep process was found to be linearly proportional to the apparent stress intensity factor, whereas for cracks that were nucleated by indentation, the crack velocity was proportional to the fourth power of the apparent stress intensity factor.
Research Organization:
Dept. of Mechanical Engineering, Univ. of Massachusetts, Amherst, MA
OSTI ID:
6656128
Journal Information:
J. Am. Ceram. Soc.; (United States), Journal Name: J. Am. Ceram. Soc.; (United States) Vol. 69:10; ISSN JACTA
Country of Publication:
United States
Language:
English