Evaluation of Microcracking and Phase Transformation by AE Wave Analysis in High Temperature Ceramics

建立了声发射源表征和这些尺寸定位系统，分析了裂纹尖端的微裂纹。利用声发射波形分析对<Al_2> <O_3>陶瓷的微断裂过程进行了评价。利用声发射源定位技术明确了微裂纹在人工缺口尖端前缘成核。由于声发射源的相位辐射模式相同，大多数被评价为I型裂纹。这些微裂纹可分为两种类型，它们对陶瓷的断裂行为起着相反的作用。前者是增强陶瓷抗断裂能力的有效微裂纹，而后者则成为不稳定断裂的根源。

AE Source Characterization and these dimensional location system was established to analyze the microcracks at the crack tip. Microfracture process in <Al_2> <O_3> ceramics has been evaluated by using this AE waveform analysis. It has been made clear by using AE source location technique that micraocracks nucleated at the tip front of artificial notch. Most of them have been evaluated as Mode I cracks because of the same phase radiation pattern of by AE source characterization. Those micrlcracks can be classified into two types with opposite roles for fracture behavior of ceramics. First one is useful microcracks to enhance fracutre resistance of ceramics, while the others become the origin of unstable fracture.