基于电磁声效应的涡流成像无损检测技术基础研究

The defect of aero-craft component and skin is a major cause of flight accidents since it is hard for detection. The research of nondestructive testing technology for aircraft has vital practical significance to promote the development of national defence and safeguard the people's lives and property. Currently, aerial magneto-optic imager (MOI) is monopolized by developed countries of occident. The magneto-optical film, which is at a low level in China, limits the domestic development of this instrument. These problems restrict the rapid development of aviation industry of China. A new eddy current imaging technology based on electromagnetic-acoustic effect is proposed in this application. The project focuses on the visualization of eddy current testing for aviation materials. Firstly, the defects are detected with transient eddy current, and the electromagneto-acoustic signals with defect information are excited using the single vector Lorentz force in pulse excitation. Secondly, The electromagneto-acoustic signals are synchronously picked up surrounding the measured region, and the inverter model for the electromagneto-acoustic effect is studied so as to model the Lorentz force gradient dispersion. Finally, a rapid reverse method is researched to reconstruct a two-dimension eddy current density and implement real-time imaging. In this scheme, "ultrasound" is used as the carrier of defect information instead of "laser", and "electromagnetic-acoustic effect" is used as an alternative to "magneto-optical effect" in MOI. Through the studies in the project, the nationalization of aerial eddy current imager can be realized rapidly, and it will achieve lead level in flexibility and portability. The portable prototype of electromagnetic-acoustic eddy current imager will be developed to take series of practical testings on airplane. This project will provide a crucial technical support for its further industrialization.

航空器构件和外蒙皮的损伤具有隐蔽性，是造成重大航空事故的主要原因。研究航空器的无损检测技术，对推动国防、运输、保障人民生命财产都有十分重要的现实意义。目前，航空涡流成像MOI仪几乎全部为欧美垄断，而我国磁光薄膜研制水平较低，短期内难以实现MOI仪的国产化。申请人首次提出一种基于电磁声效应的涡流成像无损检测新技术，重点针对航空构件实现涡流探测的可视化。项目中，使用瞬时涡流场来检测缺陷，并利用单矢量洛仑兹力来激发携带缺陷信息的磁声信号。再拾取磁声并通过声场、电磁场逆模型构建洛仑兹力密度散度，最后反求检测区域的涡流密度分布并实现成像。本项目是利用“声”代替MOI中的“光”作为缺陷信息的载体；利用“电磁声效应”代替“磁光效应”实现涡流分布的提取，可以较快实现涡流成像仪的国产化，而且在便携性方面形成局部国际领先。项目中研制新型涡流成像仪原型机，并进行实际飞机检测的工程验证，为国产化提供关键技术支持。

航空器是我国国防与航空运输的战略基础，也是国民经济发展与科技创新的重要动力。但航空器构件和外蒙皮在长期服役中易出现隐蔽性疲劳损伤，若未能及时排查与检修，将引发严重的航空事故。因此研究航空器无损检测技术，提高其运行的安全性与可靠性，对我国国防、运输和保障人民生命财产安全具有重要意义。国内现有的航空涡流检测技术仅依靠涡流信号难以实现对隐蔽性损伤的快速识别。只有实现涡流检测的可视化，才能快速准确地发现隐藏于蒙皮表面及亚表面的损伤，保障飞行安全。为此，项目研究了一种基于电磁声效应的涡流成像无损检测新技术，首先利用缺陷会改变材料内部瞬时涡流密度的特性，建立了涡流密度数值解析模型，实现了航空铝材表面二维涡流场分布的重构。然后，课题组以偏置磁场下的单向洛仑兹力为研究对象，建立了非铁磁性材料的电磁声换能模型，并在此基础上实现了航空铝材表面的电磁超声信号瞬时激发与拾取的技术突破。与此同时，课题组还研究了电磁声-涡流正、逆模型，并实现了洛仑兹力散度到涡流密度旋度分布的重构。最后课题组研究了缺陷的快速反求与定位算法，结合差分迭代与神经网络优化模型实现了缺陷的精确定位与快速成像。此外项目组还基于电磁声涡流成像原理自主研发了便携式电磁声-涡流成像仪原型机及配套缺陷检测软件，实现了电磁声-涡流检测系统一体化。成像仪原型机在工程测试中能够有效实现缺陷的精准定位与成像，为电磁声-涡流成像仪的进一步产业化提供了关键技术。