融合电磁超声载波的声发射传播特性分析

Propagation Characteristics Analysis of Acoustic Emission Integrating Electromagnetic Ultrasonic Carrier

电磁声发射是通过对缺陷导电结构件施加非接触式电磁载荷,进而激发声发射应力波,并据此效应来进行构件无损检测。本文针对电磁声发射信号不适合较远距离传播问题,融合电磁超声技术,实现对声发射应力波的载波远距离传输。文章首先从自由电子运动理论出发,从微观层面上研究电流对金属位错激活能的影响,推导出定向漂移的自由电子与位错碰撞时所产生的能量交换;其次搭建了融合电磁超声载波的电磁声发射有限元模型,分析了多个特征源激励下的应力波传播位移;最后利用希尔伯特黄变换方法对载波实验信号进行了分析比较。本文通过对传统的电磁声发射激励端研究、改进,提升电磁超声对电磁声发射应力波的传输特性,拓宽了电磁声发射检测的应用范围。

Electromagnetic acoustic emission technology（ EMAE） does nondestructive detection with the effect of contactless electromagnetic loading to generate a stress field stimulating stress waves from the defective conductive structure. The most significant problem faced by the metallic structural health monitoring method of EMAE is that EMAE signal is not suitable for long distance transmission,this problem was improved by integrating electromagnetic ultrasonic carrier method. Firstly,based on free electron theory,the mechanism of EMAE was studied at a microscopic level which based on the activation energy changed from the electrical current to mobile dislocations. Secondly,the difference of stress wave propagation characteristics under various electromagnetic stimulating conditions was researched by building finite element model. Finally,the comparison between the energy percentage intrinsic mode functions of carrier experiment was discussed by Hilbert-Huang transformation. The stress wave propagation characteristics of EMAE was improved by integrating electromagnetic ultrasonic method which based on the study and improvement of traditional exciting,and the range of EMAE application will be widened.