High-sensitivity phase imaging eddy current magneto-optical system for carbon fiber reinforced polymers detection

This paper proposed a high-sensitivity phase imaging eddy current magneto-optical (PI-ECMO) system for carbon fiber reinforced polymer (CFRP) defect detection. In contrast to other eddy current-based detection systems, the proposed system employs a fixed position excitation coil while enabling the detection point to move within the detection region. This configuration effectively mitigates the interference caused by the lift-off effect, which is commonly observed in systems with moving excitation coils. Correspondingly, the relationship between the defect characteristics (orientation and position) and the surface vertical magnetic field distribution (amplitude and phase) is studied in detail by theoretical analysis and numerical simulations. Experiments conducted on woven CFRP plates demonstrate that the designed PI-ECMO system is capable of effectively detecting both surface and internal cracks, as well as impact defects. The excitation current is significantly reduced compared with traditional eddy current magneto-optical (ECMO) systems.

The lift-off effect analysis of flexible differential pick-up koch fractal eddy current probe

This study utilized finite element simulation and experimental methods to investigate the evolution of crack detection performanceof a flexible differential fractal Koch eddy current probe at different excitation frequencies as the lift-off distance increases.As the lift-off distanceincreased,the distribution shape of induced eddy currents changed,leading to reduced similarity in the shape of the excitation coil and an expandeddistribution range of induced eddy currents,ultimately resulting in weakened output signal strength.The experimental results showed that forexcitation frequencies of 10 kHz,20 kHz,50 kHz,100 kHz,200 kHz,500 kHz,and1000 kHz,the maximum lift distances of the real partof the output signal when cracks were detected were 5.0 mm,7.0 mm,8.0 mm,8.0 mm,8.0 mm,6.5 mm,and 4.0 mm,respectively.Theimaginary parts were 6.5 mm,6.5 mm,7.5 mm,5.5 mm,8.0 mm,6.5 mm,and 6.5 mm,respectively.

Eddy current quantitative evaluation of high-speed railway contact wire cracks based on neural network

Purpose–The purpose of this study is to study the quantitative evaluation method of contact wire cracks by analyzing the changing law of eddy current signal characteristics under different cracks of contact wire of high-speed railway so as to provide a new way of thinking and method for the detection of contact wire injuries of high-speed railway.Design/methodology/approach–Based on the principle of eddy current detection and the specification parameters of high-speed railway contact wires in China,a finite element model for eddy current testing of contact wires was established to explore the variation patterns of crack signal characteristics in numerical simulation.A crack detection system based on eddy current detection was built,and eddy current detection voltage data was obtained for cracks of different depths and widths.By analyzing the variation law of eddy current signals,characteristic parameters were obtained and a quantitative evaluation model for crack width and depth was established based on the back propagation(BP)neural network.Findings–Numerical simulation and experimental detection of eddy current signal change rule is basically consistent,based on the law of the selected characteristics of the parameters in the BP neural network crack quantitative evaluation model also has a certain degree of effectiveness and reliability.BP neural network training results show that the classification accuracy for different widths and depths of the classification is 100 and 85.71%,respectively,and can be effectively realized on the high-speed railway contact line cracks of the quantitative evaluation classification.Originality/value–This study establishes a new type of high-speed railway contact wire crack detection and identification method,which provides a new technical means for high-speed railway contact wire injury detection.The study of eddy current characteristic law and quantitative evaluation model for different cracks in contact line has important academic value and practical significance,and it has certain guiding significance for the detection technology of contact line in high-speed railway.

MAPOD Analysis in Eddy Current Testing of Flaws Considering Multiple Response Signals and Multiple Flaw Parameters

The reliability of the eddy current testing (ECT) in flaw detection is quantitatively evaluated by theprobability of detection (POD). Precise and efficient modeling of POD gives direction for the implement of ECTon sites to avoid false or missing flaw detection. Traditional POD analysis focuses on single uncertain factor orsingle response signal with limited credibility in engineering. This paper considers multiple response signals andmultiple flaw parameters to perform POD. The flaw length, the flaw depth, the coil impedance, and the magneticflux density are comprehensively studied under various lift-off distances. A finite element model (FEM) of ECT isestablished and verified with experiments to obtain sufficient simulation data for discrete POD modeling. Thecontinuous POD function is then fitted based on the discrete values to show the superiority of integrating multiplefactors. A comparison with conventional POD analysis further demonstrates the higher reliability of ECT flawdetection considering multiple flaw parameters and multiple response signals, especially for small flaws.

Investigation of Eddy Current Nondestructive Testing for Carbon Fiber-Reinforced Plastic （CFRP） Based on Electromagnetic Field Analysis

CFRP （carbon fiber reinforced plastic） is used extensively in aircraft and spacecraft structures, because of its excellent mechanical properties. Ultrasonic testing, which is used as a non-destructive testing technique for CFRP, requires a contact medium. In contrast, eddy current testing does not require a contact medium, and when used for CFRP testing it has advantages not available with other techniques. CFRP is a laminate, with each layer being anisotropically conductive, and the distribution of the induced eddy current is yet to be determined. Here, to determine the eddy current distribution in the detection of flaws in cross-ply CFRP （0°/90°） by using a cross-point probe, we performed an FEM （finite element method） analysis of electromagnetic fields. We investigated the nature of the flaw signals and the differences in eddy current distributions between materials with and without flaws.

高速列车关键部件涡流自动成像检测方法

涡流检测是一种非破坏性检测方法。以高速列车构架为检测对象,结合涡流与自动化设备检测技术,针对人工涡流检测效率低、结果一致性差等问题,提出涡流自动成像检测方法。通过建立构架焊缝的涡流探头仿真模型,分析激励电流方向对检测信号的影响,优化激励线圈相关参数并制作涡流探头;设计开发构架涡流自动成像检测系统,开展构架焊缝表面缺陷自动化检测试验。对比分析激励频率、激励电压等涡流检测工艺参数以及探头扫查速度、扫查轨迹间距等路径参数对缺陷涡流信号的影响,研究结果表明,利用涡流自动成像检测系统可以对构架整车进行自动探伤,能够将构架焊缝处缺陷以图像形式呈现,可以有效检出0.3、0.5 mm深的人工缺陷,对构架批量产线化检测具有参考价值。

长输油气管道内检测技术

管道内检测技术是长输油气管道内检测最有效的方法之一,是长输油气管道缺陷检测、评估与完整性评价的重要手段。随着我国能源行业的高速发展,管道成为能源输送的最有效载体,这对管道内检测技术提出了新的挑战,应运而生多种新的检测方法与解决方案。梳理了长输油气管道内检测技术的发展过程,阐述了长输油气管道内检测技术的国内外研究现状,针对长输油气管道内检测现存在的问题,对新技术、新方法的原理、应用情况进行归纳总结,并提出管道内检测行业的未来展望。

基于多频技术的涡轮叶片涡流检测边缘效应抑制

涡轮叶片是航空发动机的重要组成部件,对其进行质量检测有着重要意义。在对涡轮叶片进行涡流检测的过程中,当使用单一频率的涡流探头扫查叶片边缘时,检测线圈易受到边缘效应的信号干扰,叶片边缘的缺陷信号有可能淹没在干扰信号中,因此必须消除边缘效应对信号的干扰才能保证检测的质量。为此,提出一种通过多频涡流技术对涡轮叶片检测中边缘效应的干扰信号进行抑制的方法,并进行验证试验。试验结果表明,多频涡流检测技术能够有效抑制边缘效应的干扰,可提高涡轮叶片检测准确率,降低漏检率。

航空锂电池焊缝的多通道多频涡流检测

为了实现航空锂电池极耳极板激光焊缝的高效准确检测,设计制作了带有层析成像功能的多通道多频涡流检测系统.采用该系统及5通道防干扰差分结构涡流传感器对极耳极板焊缝中的局部断焊、整体漏焊、焊缝变形内凹、微小缺陷等典型缺陷进行检测,并基于趋肤效应原理,采用层析成像技术对焊瘤缺陷进行扫查成像.结果表明,研发的带有层析成像功能的多通道多频涡流检测系统可有效检测出锂电池极耳极板焊缝中的多种典型缺陷,最小可检测1 mm的缺陷,层析成像技术可实现不同深度下缺陷的形貌观测.通过对大量检测结果的对比分析,总结了缺陷种类、位置及长度的判别方法,提出了一套缺陷判别流程与评定准则,为实现锂电池极耳极板焊缝检测的工程化奠定了良好的基础.

基于多TMR的涡流无损顶锤裂纹检测系统设计

针对碳化钨顶锤的表面及近表面裂纹的快速精准无损检测需求,开发了一套基于多个隧道磁阻的涡流裂纹探伤检测系统。系统设计了电源供电电路、频率可调节的信号发生电路、功率放大电路、检测探头,能检测出微缺陷引起的叠加磁场的变化。有限元仿真与顶锤检测实验的对比分析表明该检测系统可以准确识别顶锤的细微裂纹损伤,实现了基于涡流原理的顶锤钨合金试块近表面微小裂纹的检测。

脉冲涡流检测中核电运行机组电磁干扰研究

脉冲涡流主要应用于壁厚的腐蚀检测工作,因其可在带保温的情况下进行检测工作而受到无损检测行业的关注。由于脉冲涡流对于在役运行的核电机组的检测,更容易受到电磁环境的干扰,研究从脉冲涡流检测信号的频谱分析入手,论证了核电在役机组低频电磁场干扰对检测信号的强干扰作用。研究在役机组空间电磁干扰的频谱识别,并通过实验验证了其对脉冲涡流时域检测信号的影响。根据研究结果,提出用检测信号与空间参考信号作差,来消除空间电磁干扰的差分检测模式,可较好地抑制在役机组的电磁干扰问题。在核电机组运行状态下,通过现场实验验证了探头差分模式下脉冲涡流在役检测效果。

在役油管内壁腐蚀缺陷脉冲涡流检测方法

为实现采油管柱中的在役油管内壁腐蚀缺陷高精度离线检测,本文提出了一种基于双磁场传感的脉冲涡流外检测及深度定量评估方法。在试验研究中,以检测信号下降沿对数曲线斜率作为信号特征。在建立信号特征与油管剩余壁厚间映射关系的基础上,通过分析感应涡流在油管内分布范围与成像检测所识别腐蚀缺陷区域间的互相关关系,引入腐蚀缺陷深度评估补偿系数β。结合所建立映射关系,形成油管内壁腐蚀缺陷深度高效可视化定量评估方法。通过对缺陷成像及深度定量评估结果与真实情况的对比分析发现:所提方法不仅可实现对油管内壁腐蚀缺陷的三维形貌重现,且对其深度的定量评估具有较高的精度,满足工程实际在役油管的检测精度要求。

脉冲涡流-电磁超声复合检测方法的可靠性评估

金属结构广泛应用于现代工业的各种领域,在其从生产、制造到服役各个阶段都有可能产生各类复杂缺陷。例如金属结构的表面和底部都出现复合缺陷的情况,单一的电磁无损检测方法难以满足所有需求。而使用两种或多种具有针对性的电磁无损检测方法进行检测,又存在检测效率低、成本高等问题。为解决这一难题,本文开发了一种新型的脉冲涡流-电磁超声一体化复合检测方法。该复合检测方法仅需使用一套检测系统和检测探头,基于同时解调出的电磁成分和超声成分,即可同步检测出金属结构的表面缺陷和底部缺陷,大大简化了实验系统,提高了复合缺陷的检测效率。此外,基于检出概率开发了一种可靠性评估方法,对脉冲涡流-电磁超声复合检测方法的检测能力进行评估。通过数值模拟和实验对脉冲涡流-电磁超声复合检测方法进行检出概率分析,以确定复合缺陷检测的最小可检尺寸。

基于CoKriging代理模型的涡流无损检测模型辅助探测概率问题的研究

无损检测模型辅助探测概率问题的研究需要大量仿真数据,而高精度的物理模型计算模型响应需要大量时间,往往是无法实现的。代理模型是一种高效的数学模型,可以替代费时复杂的物理模型,广泛应用于设计优化问题。CoKriging模型可以融合高精度和低精度的数据,融合了大量计算成本低的低精度数据和少量计算成本高的高精度数据,提高了建模效率,是一种非常有应用潜力的代理模型。文中将CoKriging模型应用于涡流无损检测模型辅助探测概率的研究,在有限截面线圈探测金属平板表面槽缺陷算例中,利用物理模型计算部分训练点,构建CoKriging模型,精度验证通过后的CoKriging模型可以代替物理模型进行MAPoD分析,通过对比物理模型计算的MAPoD关键参数验证CoKriging模型的精度和效率。结果表明,相较于Kriging模型,CoKriging模型只需要更少的样本点训练模型就可以达到求解精度的要求,其构建元模型所需时间仅为Kriging元模型所需的7%,提高了涡流无损检测模型辅助探测概率研究的效率。

基于锁相放大器的电涡流金属分类系统设计

电涡流检测是一种通过检测金属导体感应出的微小涡流信号来识别被测材料性质的方法。在利用电涡流检测技术进行金属分类时,微弱信号甚至会被噪声信号完全淹没,这使提取有效信号变得非常困难。针对这种实际问题,根据相关检测法设计了基于锁相放大器的金属分类系统。在设计中,微弱待测信号经过低噪声放大后与两路正交参考信号进行互相关,再经过低通滤波电路后被采集,对被采集的信号进行计算即可实现对微弱信号的检测。实验结果表明,系统具有较高的精度和灵敏度,能够极大地提高信号的信噪比,实现对金属材料的快速分类,分类准确率可达93%。

非侵入式电解质溶液电导率测量的研究

针对电解质溶液这种低电导率物质测量,传统的侵入式电极类传感器具有容易污染被测溶液,电极污损以及电极表面极化等缺点。为了改进以上不足,该文利用电涡流效应的原理设计了一款基于FPGA芯片的非侵入式电解质溶液电导率测量系统。改进了传统的信号处理电路,通过信号频率的变化来显示电导率的大小。实验结果证明该测量系统具有较高的灵敏度,约为44.5 Hz/(S/m)。

钢桥面板顶板贯穿裂纹长度涡流检测及其影响因素

针对正交异性钢桥面板顶板贯穿型疲劳裂纹隐蔽性强、难以精确检测的问题,提出通过涡流检测方法对裂纹长度进行测量。首先,对试验获取的涡流检测信号进行分析,探究信号特征与裂纹长度之间的关系,据此拟合出裂纹长度的测量公式,并通过有限元模拟对其有效性进行验证;其次,研究线圈参数与扫查速度对检测效果的影响;最后,通过有限元模拟分析了水平裂纹相邻顶点间距、裂纹与线圈中心的偏移距离、裂纹与线圈扫查方向的夹角对检测结果的影响。结果表明:增加圆柱形线圈外径与内径之比并适当减小线圈内阻可提高检测灵敏度;裂纹长度的测量值随着线圈扫查速度的增大而减小;水平裂纹相邻顶点间距越大,越利于精确测量裂纹长度;随着裂纹与线圈中心偏移距离的增加,检测信号的变化幅值逐渐减小,裂纹长度测量值也随之下降;此外,线圈扫查方向与裂纹长度方向的夹角越大,越不利于检测。该钢桥面板疲劳裂纹长度涡流检测方法可实现高效、便捷、精准的无接触式检测,为钢桥的运营维护提供相关技术参考。

基于刀片式激励线圈旋转的脉冲涡流探头

脉冲涡流检测裂纹时,微裂纹在感应涡流中产生的扰动微弱,检测信号的信噪比低;另一方面,单向扫查下的常规脉冲涡流探头难以获得多向裂纹检测的最大灵敏度和判断裂纹方向。提出一种采用机电旋转脉冲涡流激励线圈的检测方法,实现了多方向微裂纹的高灵敏度检测。刀片式激励线圈具有明显的聚磁性与方向性,机电旋转激励线圈后可以获得不同转角下的接收信号,将该接收信号与基准信号进行差分,提取出微小的峰值变化量,得到角度与峰值变化量之间的图谱。试验验证与测试结果表明:基于刀片式激励线圈在空心接收线圈内旋转的脉冲涡流探头不仅具有亚毫米级裂纹深度区分的检测能力,且能有效分辨裂纹方向,误差为±5°。

基于多项式混沌展开法的涡流无损检测高效元模型辅助探测概率的分析

探测概率对于量化涡流无损检测系统的检测能力非常重要。模型辅助探测概率的参数需要大量试验或仿真数据才可以确定,往往难以实现。应用基于退化核函数加速的边界元法的数值模型,提出使用基于普通最小二乘法的多项式混沌展开算法的元模型提升三维涡流无损检测问题探测概率的效率。通过有限截面线圈检测金属板面槽的算例,引入线圈位置和提离距离为不确定传播的参数,测试结果表明,该元模型预测的模型参数与基于退化核函数加速的边界元法物理模型计算的模型参数相对误差在1%以内,极大降低了所需的计算开销。

基于差分脉冲涡流的大提离下坑蚀检测方法研究

针对大提离下铁磁性材料坑蚀检测的难题,提出基于差分脉冲涡流的线圈结构。通过实验定性分析3种差分布置方式对信号的影响,表明外部差分可保证信号对称性。进而对比不同提离下外部180°、90°差分结构缺陷信号幅值,表明外部180°差分结构更优。最后在100 mm提离下采用外部180°差分接收线圈3检测直径20 mm、深2.4 mm平底孔,其幅值为0.3 mV,表明该结构可在大提离下检测坑蚀。