厚度振动模式下背衬结构PZT的声能特性

为了充分利用埋入混凝土中压电陶瓷所激励的声能,采用了一种在压电陶瓷圆片结构的一面设置金属背衬的方法将压电陶瓷双侧的声能集中到一侧,提高了声指向性和声能。实验表明:该方法能使同距离下压电陶瓷圆片轴向声能提高10倍以上,并且得到了声能的相对增量随背衬厚度和声激励频率之积变化的特性曲线。声信号的谱分析还表明:背衬没有改变声信号的主频和主峰区间的频率带宽;当声激励频率为谐振频率79kHz时,最优背衬厚度为2.4mm;当声激励频率f为60kHz～100kHz时,接收端声能相对较大,适合用于实际的压电埋入式超声无损检测。

Study on the acoustic energy characteristic of PZT based backing structure on thickness vibration mode

Conventional ultrasonic non-destructive method cannot process real-time health monitoring to the concrete structure,instead piezoelectric embedded concrete module that embedded the piezoelectric ceramic in concrete,can achieve the on-line monitoring of concrete structures.But the acoustic excitation efficiency of piezoelectric ceramic disc is severely affected after the piezoelectric ceramic is embedded in concrete.Moreover,both attenuation and noise affect the receiver acoustic signal.In order to enhance the acoustic signal created by the embedded piezoelectric materials,a method of using metal backing combined the embedded piezoelectric ceramic disc is proposed,which can concentrate both sides of the piezoelectric ceramic disc to one side so that the acoustic directivity and the energy of the acoustic signal is increased.Experiments show that this method allows the receiver on the axial direction of the embedded ceramic disc receives acoustic signal with 10 times more energy.And a characteristic curve of the energy of the relative increment of the acoustic signal changes as the product of backing thickness and acoustic excitation frequency is got.The spectral analysis shows that the metal backings do not change the peak frequency and frequency bandwidth range of the acoustic signal power spectrum.