铆接结构中缺陷的脉冲远场涡流定量评估技术

针对飞机机身铆接结构检测中难以对缺陷进行定量评估的问题,将脉冲远场涡流检测技术运用于铆接结构缺陷检测之中。利用脉冲激励频谱成分丰富、可提取特征信息较多的优势对铆接结构中缺陷的定量评估技术展开研究。首先,建立铆接结构脉冲远场涡流三维检测模型,对缺陷进行检测,从而确定缺陷位置。在此基础上,分析缺陷类型、尺寸对检测信号的影响发现直接耦合分量幅值与上下表面缺陷深度之间具有不同的变化关系,从而实现对缺陷的分类识别。最终,利用信号的过零时间变化量实现对缺陷深度的定量,在缺陷深度已知的情况下,进一步利用直接耦合分量幅值变化对上表面缺陷长度进行定量;利用间接耦合分量幅值变化对下表面缺陷长度进行定量。

A Crack Quantitative Technology in Riveted Structure Based on Pulsed Remote Field Eddy Current

Aimed at the problem that crack is very hard to be evaluated quantitatively in the riveted structure at aircraft fuselage, pulsed remote field eddy current testing technology is used to detect the crack of riveted structure. The cracks quantitative evaluation in riveted structures are studied by utilizing the advantages rich in the pulsed spectrum components and more information. Firstly, a three dimensional model of remote field eddy current riveted structure is established to detect crack so as to get crack position. Then, the influence of crack type and size on detection signal is analyzed and the classification of surface and sub surface cracks is realized according to the different relation between direct coupling component and crack depth. Finally, the quantitative detection of crack depth is realized by zero cross time changes. Under the premise of knowing crack depth, direct coupling component amplitude and indirect coupling component amplitude are used for quantitative evaluation of the crack length on surface and sub surface respectively.