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J. Korean Ceram. Soc. > Volume 35(6); 1998 > Article
Journal of the Korean Ceramic Society 1998;35(6): 551.
AE에 의한 알루미나 세라믹스의 Microcrack 생성과 파괴거동의 평가
장병국, 우상국
Evaluation of Fracture Behavior and Formation of Microcrack of Alumina Ceramics by Acoustic Emission
Detection of microcrack in {{{{ {Al }_{2 } {O }_{3 } }} ceramics were studided by AE(acoustic emission) technique with 4-point bending test in order to evaluate the fracture process and formation of microcrack. Fully-dense alu-mina ceramics having a different grain size were fabricated by varing the hot-pressing temperature. The grain size of alumina increased with increasing the hot-pressing temperature whereas the bending strength decreasd. The microcracks were observed by SEM and TEM. The generation of AE event increased with increasing the applied load and many AE event was generated at maximum applied load. Alumina with smaller grain size shows the generation of many AE event resulting in an increase of microcrack formation. An intergranular fracture is predominantly observed in fine-grained alumina whereas intragranular fracture occurs predominantly in coarse-grained alumina,. Analysis of micorstructure and AE prove that primary mi-crocracks occur within grain-boundaries of alumina. The larger microcracking were formed by the growth and/or coalesence of primary microcracks. Then the materials become to fracuture by main crack gen-eration at the maximum applied load.
Key words: Fracture, Microcrack, Microcracking, Microstructure, Acoustic emission, Al$_2$O$_3$, Bending strength
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