Crack-Bridging Analysis for Alumina Ceramics under Monotonic and Cyclic Loading |
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Authors: | Xiaozhi Hu Yiu-Wing Mai |
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Affiliation: | Center for Advanced Materials Technology, Department of Mechanical Engineering, University of Sydney, Sydney, N.S.W. 2006, Australia |
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Abstract: | Frictional degradation of grain-localized bridges behind a crack tip has been recognized as the major cyclic fatigue mechanism in alumina ceramics. Such a fatigue mechanism implies that the crack growth resistance ( R ) curve behavior during cyclic fatigue is different from that of monotonic loading due to the reduction in crack-tip shielding. A recent crack-bridging theory based on crack compliances is used to study the bridging stresses under monotonic loading and during cyclic fatigue. The bridging-stress distributions of two coarse-grained aluminas under monotonic loading are determined using compliance measurements. Because the interlocking grain bridges at the crack wake are subject to frictional damage from cyclic loading, the bridging-stress distribution evaluated during cyclic fatigue is distinct from that for monotonic loading. These results indicate that it is incorrect to incorporate the R -curve behavior from monotonic loading to the analysis of cyclic fatigue of alumina ceramics. |
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Keywords: | alumina crack bridging degradation friction fatigue |
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