压电型声发射传感器的校准方法研究

Acoustic Emission (AE) technology has been applied widely in pressure vessels, aerospace engineering and other fields, and AE sensor is an indispensable component used to collect information in AE testing. Most AE sensors are piezoelectric transducers. The calibration of piezoelectric AE sensors is the premise of AE quantitative testing. The present research indicated that there were some difference between the sensitivity results calibrated by the surface pulse method and the reciprocity method suggested by the present standards. At the same time the reference capacitance sensor is difficult to develop and remain. This project is aiming to adopt the laser doppler technique to measure the micro-displacement of the medium.With the function modification of the pulse force,the comparison of analytic solution of the Lamb equation under the condition of different possion ratio with the laser measurement result is to be implemented, and the exact reference velocity is expected to be confirmed and used to do the AE sensor calibration. The surface pulse method and reciprocity method, as well as the Longitudinal wave reciprocity and optical method, will be compared with each other . The calculation result by the ratio of the frequency component of the normal velocity to the frequency component of the adding pulse force, will be compared with the reciprocity constant in the same frequency, system error of the different methods is to be discussed. The calibration work is helpful to unify the value of the surface wave and the longitudinal wave in AE field,and accelerate the application of the quantitative AE technique.Ihis work will also redound to imporve the Lamb problem's solution and the reciprocity theory of sensors.

声发射检测在压力容器等大型结构件的状态监测中具有广泛的应用，压电型声发射换能器是声发射检测的重要部件，其灵敏度的准确校准是实现声发射定量技术的前提，而现有校准方法中的表面脉冲法和互易法所得的灵敏度数据存在较大差异，且电容传感器作为参考传感器，在制作和使用中存在诸多限制。本项目拟：1）引入激光多普勒测振技术实现微小动态位移的精确测量，通过研究脉冲力的大小和波形，优化载荷函数，将不同泊松比条件下Lamb问题中垂直点源问题的解析解与激光多普勒测量值相对照，获得准确的参考位移和参考速度。2）对表面脉冲法引入等效互易常数，即法向振动速度的频率分量与所加力脉冲的频率分量比值，与互易法中的互易常数进行比较，探讨其差异并研究如何修正。压电型声发射传感器校准方法的研究，有助于推进声发射定量技术的应用，完善垂直点源作用下Lamb问题解析解和声发射传感器的互易校准理论。

材料中局部区域快速释放能量产生瞬态弹性波的现象称为声发射，声发射传感器的灵敏度定义为每单位机械输入（位移、速度、加速度）的输出电压，通常以速度灵敏度或位移灵敏度表示。尽管声发射检测技术已经应用很长时间，但现有校准方法中，表面脉冲法和互易法所得结果存在较大差异，统一的声发射测量标准和可溯源的校准方法尚未完全建立，限制了声发射定量技术在关键安全构件上的应用。.项目针对现有声发射传感器校准方法中表面波脉冲法与互易法校准结果之间的差异，引入激光多普勒单点测振技术，取代参考电容传感器获得实际位移和速度的测量值，同时试图通过脉冲力的测量，得到垂直点源作用下Lamb问题的法向位移精确解析解，探讨计算值与测量值之间的一致性。在获得可靠的参考速度和参考位移的基础上，得到传感器的灵敏度，研究表面脉冲法和互易法校准结果之间的差异，将单位简谐点源作用时的法向速度视为等效互易常数，与互易法中对应频率的互易常数进行比较分析，探讨如何获得声发射传感器统一的表面波灵敏度和纵波灵敏度。.项目建立了基于激光多普勒测量系统的表面脉冲法校准装置和互易校准装置，从试验上证明两者校准结果的一致性；同时探讨了激光多普勒测量值与弹性波方程计算值的差异，并从等效互易常数的角度阐述了表面脉冲法和互易校准的一致性。项目从实验和理论上证明了互易法校准适用于多种模态弹性波共存时的压电型声发射传感器校准。但解析解自身获得的等效互易常数计算结果却存在一定差异，后续工作将围绕解析解中的参数以及解析解模型自身的修正开展。