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

建立了声发射源特征和这些空间定位系统，用于分析裂纹尖端的微裂纹。利用<Al_2><O_3>这种声发射波形分析方法对陶瓷材料的微断裂过程进行了评价。用声发射源定位技术确定了微裂纹形核于人工缺口前端。其中大多数已被评估为模式I裂纹，因为相同的相位辐射模式的AE源表征。这些微裂纹可分为两类，它们对陶瓷断裂行为起着相反的作用。第一种是有效的微裂纹，提高了陶瓷的抗断裂能力，而其他微裂纹则成为不稳定断裂的起源。

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.