共查询到17条相似文献,搜索用时 171 毫秒
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飞机多层结构铆钉周围埋藏裂纹检测是无损检测领域的一个难点和热点,脉冲涡流能够对这种裂纹进行有效的检测。针对这种缺陷检测,本研究采用了一种双激励线圈且用隧道磁电阻(TMR)为接收的新型探头。双激励源反向联接,激励电流不至于过大,但磁场却能达到局部聚焦的作用。通过大量试验对该传感器参数进行优化选择,以提高传感器的检测灵敏度。试验结果表明:当激励线圈绕制180匝、两激励线圈间距为20~30 mm、单个线圈水平夹角为60°~90°、且TMR位于裂纹正上方时探头的检测灵敏度最大。该研究结果可为飞机多层结构铆钉周围裂纹脉冲涡流检测探头设计提供参考。 相似文献
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研究了脉冲激励下的远场涡流管道检测技术,采用有限元仿真的方法对检测系统参数对检测结果的影响做了详细的分析。表明该技术将远场涡流和脉冲激励的优势有效结合,能提取较多检测信息,可同时测量管道内径和内、外壁缺陷信息,且具有信号幅值高,功耗低的优点。 相似文献
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为了研究脉冲漏磁检测中涡流效应对漏磁信号的影响,应用有限元分析软件建立了脉冲漏磁检测仿真模型,对被测样本内磁场与涡流分布随时间变化的情况进行了分析,进而研究了基于不同激励电压和磁芯磁导率仿真模型的漏磁信号波形。仿真结果表明,当磁场激励较小时,漏磁信号在脉冲激励电压的上升阶段存在过冲现象,随后达到稳态。搭建了检测平台进行检测试验,检测结果与仿真结果相一致,研究表明在缺陷检测中应用检测信号峰值特征评估缺陷深度的方法具有更高的精度。 相似文献
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脉冲涡流检测系统影响因素分析 总被引:1,自引:0,他引:1
脉冲涡流检测系统中参数的选择对于提高缺陷的检测灵敏度具有重要的意义。分析了激励线圈的尺寸、激励脉冲的频率、占空比和电压等因素对脉冲涡流检测系统的影响,给出了实际检测过程中选择参数的原则。 相似文献
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如何检测老龄化飞机多层结构中的裂纹缺陷一直是无损检测领域的一个难点。脉冲涡流技术是一种可以对多层结构中缺陷进行有效检测的电磁无损检测技术。理论推导了脉冲涡流渗透深度的公式,得出适当的减小脉冲激励频率与增加占空比有利于检测深层缺陷。设计了实验系统与矩形传感器,对激励信号的频率与占空比进行了优化设计。对多层结构中的内层缺陷进行了实验,并对微弱的检测信号进行了必要的数据处理。实验结果证明脉冲涡流检测技术可以对内层裂纹缺陷进行有效的检测。脉冲涡流技术将会在航空无损检测领域发挥重大的作用。 相似文献
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Pulsed eddy current (PEC) is an emerging non-destructive testing technique with wide application potential. In this study, defect parameter identification in multi-layer structures is examined by using the PEC technique, and a Fisher linear discriminate analysis (FLDA)-based defect classification method is proposed. Defect localization and shape identification are investigated, and defects on the surface and subsurface of the third layer are discriminated. The time domain characterization method is introduced and researched by using the peak time and zero-crossing time of PEC response signals, the principal component analysis algorithm and the FLDA method. The feature extraction results of the three methods are used as the input values of support vector machine for defect classification and feature extraction, and the classification methods are compared. Theoretical analysis and experimental results show that the proposed method can contribute to effective classification for defect parameter identification. 相似文献
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Yunze He Feilu Luo Mengchun Pan Feibing Weng Xiangchao Hu Junzhe Gao Bo Liu 《NDT & E International》2010,43(2):176-181
The Pulsed Eddy Current (PEC) technique is an effective method of quantifying defects in multi-layer structures. It is difficult to detect defects in riveted structures of aging aircraft. Based on theoretical analysis of PEC technique, three different probes, including a differential hall probe, a differential coil probe, and a two-stage differential coil probe are designed to detect this kind of defects. The averaging method and wavelet analysis method are used to de-noise the hall response signals. By selecting peak amplitude and zero-crossing time of response signal in time domain as key features, defects in riveted structures can be detected effectively. The experimental results indicated that the differential coil probe acted as effectively as the differential hall probe. The defects between third layer and fourth layer in riveted structures can be detected by utilizing the two-stage differential coil probe. The PEC technique has a promising application foreground in the field of aeronautical nondestructive testing. 相似文献
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A signal denoising method is presented for ferromagnetic material pulsed eddy current (PEC) testing signal. The method firstly performs multiple measurements, and obtains an averaged signal and then transforms the averaged PEC signal from Cartesian domain to double logarithmic domain by the developed algorithm. A median filtering process is then performed for double logarithmic domain signal. An invert transform is optional to be performed to transform the processed signal from double logarithmic domain back to Cartesian domain. A signal-to-noise ratio (SNR) improvement quantification method is applied to evaluate the SNR improvement. The performance of the method is then verified by experiments. The effects of signal averaging number and median filter’s order are discussed. Experiment results show the method is able to increase SNR by about 40 dB. 相似文献
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脉冲涡流检测中由于探头倾斜或被测对象表面不光滑等原因容易产生提离效应,提离效应严重影响着脉冲涡流无损检测的结果。提出了一种基于差分信号二阶微分零时刻值匹配补偿的方法。首先建立相应的提离参考数据库,然后通过索引二阶微分零时刻值匹配提离参考信号,计算补偿比,利用补偿公式对提离效应进行抑制。通过试验发现,经该方法处理后的有提离差分信号能够与无提离的差分信号可以很好的吻合,消除了提离效应对差分信号的影响。试验结果表明了该方法能够对多层金属结构的内部缺陷检测具有较好的提离抑制效果。 相似文献