压电骨料及其在砂浆试块加载中声发射响应研究

Piezoelectric Aggregate and Its Acoustic Emission Response in Mortar Block During Loading

本文以PZT压电陶瓷为元件、水泥和环氧树脂混合物为封装材料,制备一种埋入式压电骨料,通过试验分析PZT陶瓷封装前后电阻抗谱变化及压电骨料在砂浆试块加载过程中的声发射响应特性。研究结果表明,PZT压电陶瓷封装后谐振峰强度显著减弱,但平面谐振频带宽度有一定程度增加;压电骨料对铅笔断铅产生的声发射信号具有良好灵敏度且波形衰减较快,当断铅距离保持不变,压电骨料能接收到来自不同断铅方向的声发射信号;根据声发射撞击随加载时间变化可将埋入砂浆试块的压电骨料声发射响应分为加载初期的小概率声发射事件、加载中期的快速发展阶段和加载后期的裂纹扩展三个阶段。本文试验表明压电骨料能够用于服役混凝土结构动载损伤监测。

In this paper, PZT piezoelectric ceramic was used as sensing element, and mixture of cement and epoxy resin as packaging material to fabricate a kind of embedded piezoelectric aggregate. The electrical impedance of PZT ceramics before and after packaging was analyzed as well as the acoustic emission response in mortar block during loading. The results showed that the strength of the resonance peaks of PZT piezoelectric ceramic after packaging weakened remarkably, however, its planar resonance bandwidth increased to some extent. The piezoelectric aggregate had good sensitivity to the acoustic emission signal from pencil lead broken, and there existed a quick attenuation for the acoustic waveform. When the distance between piezoelectric aggregate and location of pencil lead broken kept unchanged, the piezoelectric aggregate could receive the acoustic emission signal from different directions. According to the change of acoustic emission impact with loading time, the acoustic emission response of the mortar block with piezoelectric aggregate inside could be classified into three periods during loading, that is, the small probability acoustic emission event in the initial loading period, rapid developing period and the latter crack propagation period. The experimental results proved that the piezoelectric aggregate could be used for the dynamic damage monitoring of the concrete structures in service.