Acquisition and analysis of continuous acoustic emission waveform for classification of damage sources in ceramic fiber mat
Acquisition and analysis of continuous acoustic emission waveform for classification of damage sources in ceramic fiber mat
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DOI：
10.2320/matertrans.i-mra2007850
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发表时间：
2007-06-01
影响因子：
1.2
通讯作者：
Enoki, Manabu
中科院分区：
文献类型：
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作者：
Ito, Kaita;Enoki, Manabu
当声发射(AE)活动很高时，声发射(AE)事件的波形接近，有时相互重叠。传统的处理离散声发射事件的声发射测量系统不适合这种情况，因为声发射事件的漏检频繁发生。为解决这一问题，研制了一种名为连续波存储器(CWM)的新型声发射测量系统，该系统在整个测试过程中将声发射波形连续记录在硬盘上数小时。这种新的系统可以用不同的滤波参数对一个波形进行多个分析。短时傅立叶变换(STFT)给出了连续声发射波形的时频-幅度特征，为材料退化的评价提供了有用的信息。在本研究中，利用这一新系统评估了陶瓷纤维毡在循环压缩试验中的退化情况以及粘结剂的添加效果。STFT结果清楚地显示了板坯的降解分类；纤维断裂是早期压缩循环的主要来源，而纤维之间的零星摩擦是后期压缩循环中声发射的主要来源。并对有机粘结剂对防止垫子降解的效果进行了评价。结果表明，在加入粘结剂的试样中，摩擦信号消失，断裂信号减弱。
Waveforms of acoustic emission (AE) events come close and sometimes overlap each other when AE activity is very high. Conventional AE measurement systems which handle discrete AE events are not suitable for this situation because miss-detection of AE event occurs frequently. A new AE measurement system named as Continuous Wave Memory (CWM) was developed to solve this problem by recording the AE waveforms continuously to hard disks for several hours throughout the testing time. This new system enabled multiple analysis of one waveform with different filtering parameters. Short time Fourier transform (STFT) gave the time-frequency-magnitude characteristic of continuous AE waveforms and useful information for evaluation of degradation of materials. In this study, the degradation of ceramic fiber mat during cyclic compression test and the effect of binder-addition were evaluated by this new system. STFT results clearly showed the classification of degradation of the mat; breakage of fibers was the main source in the early compression cycles and sporadic friction between fibers became the main source of AE in the later compression cycles. The effect of organic binder to prevent the degradation of the mat was also estimated. It was observed that the friction signal disappeared and the breakage signal weakened in the binder-added specimens.