CN103336049B - A kind of pulse eddy current detection method and device eliminating Lift-off effect - Google Patents
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Abstract
本发明公开了一种消除提离效应的脉冲涡流检测方法及装置，所述检测方法具体包括：步骤1、对被测试件在不同的已知缺陷深度位置处获得不同提离高度下的检测信号时域曲线并且在被测试件无缺陷位置处获得无提离高度的参考信号时域曲线，并对检测信号和参考信号的时域曲线作差分处理和提取特征值处理，获取差分峰值电压拟合直线斜率与缺陷深度的关系曲线；步骤1、对被测试件的未知缺陷深度进行定量评估，获得在未知缺陷深度位置处不同提离高度下的检测信号时域曲线，并将检测信号与参考信号的时域曲线作差分处理和提取特征值，将处理结果代入求得的表达式中，获得被测试件的未知缺陷深度。该方法消除了提离效应在脉冲涡流检测系统中的影响。
The invention discloses a pulsed eddy current detection method and device for eliminating the lift-off effect. The detection method specifically includes: Step 1. Obtain detection signals at different lift-off heights for the tested piece at different known defect depth positions Time-domain curve and obtain the time-domain curve of the reference signal without lift-off height at the non-defective position of the test piece, and perform differential processing and extraction of eigenvalues on the time-domain curves of the detection signal and reference signal to obtain differential peak voltage fitting The relationship curve between the slope of the straight line and the depth of the defect; Step 1. Quantitatively evaluate the unknown defect depth of the tested piece, obtain the time domain curve of the detection signal at different lift-off heights at the position of the unknown defect depth, and compare the detection signal with the reference signal The time-domain curve is differentially processed and the eigenvalues are extracted, and the processing results are substituted into the obtained expression to obtain the unknown defect depth of the tested piece. This method eliminates the influence of the lift-off effect in the pulsed eddy current testing system.
Description
技术领域technical field
本发明属于无损检测技术领域，具体涉及一种消除提离效应的脉冲涡流检测方法及装置的设计。The invention belongs to the technical field of non-destructive testing, and in particular relates to a pulsed eddy current testing method and device design for eliminating the lift-off effect.
背景技术Background technique
脉冲涡流检测技术是涡流检测的一个新的应用领域，它以测得的磁场最大值出现的时间来确定缺陷位置，从而实现了缺陷的无损检测和定量化描述。该技术常用于飞机机身结构及发动机的安全检测、核动力设施中的蒸汽管道及石油、天然气等运输管道的可靠性检测，各种板、棒、管等金属零件生产过程中的质量监控等。脉冲涡流无损检测技术一改传统涡流检测、多频涡流检测和扫频涡流检测中采用正弦信号激励线圈的方式，采用具有一定占空比的脉冲信号激励线圈。因为脉冲信号可表示为直流成分、基波和一系列奇次谐波的总和，因此通过脉冲激励产生的电磁信号载有更丰富的特征信息。Pulsed eddy current testing technology is a new application field of eddy current testing. It uses the time when the measured maximum magnetic field appears to determine the defect position, thus realizing the non-destructive testing and quantitative description of defects. This technology is often used in the safety inspection of aircraft fuselage structure and engine, the reliability inspection of steam pipelines in nuclear power facilities and transportation pipelines such as oil and natural gas, and the quality control in the production process of various metal parts such as plates, rods, and pipes, etc. . The pulsed eddy current non-destructive testing technology changes the traditional eddy current testing, multi-frequency eddy current testing and frequency-sweeping eddy current testing using a sinusoidal signal to excite the coil, and uses a pulse signal with a certain duty cycle to excite the coil. Because the pulse signal can be expressed as the sum of DC component, fundamental wave and a series of odd harmonics, the electromagnetic signal generated by pulse excitation carries richer characteristic information.
根据涡流检测原理，当载有脉冲信号的线圈探头靠近金属导体时会在导体内部感应出涡流，任何导致涡流发生改变的因素都会影响检测结果。由于线圈和被测体间的互感系数随探头线圈到被测体表面的提离的增大而迅速减小，被测体中的涡流密度也随提离的微小变化而发生显著变化，这种效应称为提离效应。被测体表面的涂层厚度、不规则的被测体表面、操作者的微小移动及被测体的热胀冷缩都会引起提离变化，从而掩盖真实的检测信息。因此，抑制和消除提离干扰一直是脉冲涡流检测技术研究中非常重要的一个环节。According to the principle of eddy current testing, when the coil probe carrying the pulse signal is close to the metal conductor, eddy current will be induced inside the conductor, and any factors that cause the change of eddy current will affect the test result. Since the mutual inductance coefficient between the coil and the measured body decreases rapidly with the increase of the lift-off between the probe coil and the surface of the measured body, the eddy current density in the measured body also changes significantly with the slight change of the lift-off. This effect is called lift-off effect. The thickness of the coating on the surface of the measured object, the irregular surface of the measured object, the slight movement of the operator, and the thermal expansion and contraction of the measured object will all cause changes in the lift-off, thereby covering up the real detection information. Therefore, suppressing and eliminating lift-off interference has always been a very important link in the research of pulsed eddy current testing technology.
在工业实际运用时，当探头在试件进行扫描的过程中，由于结构的不平整性等其他原因在扫描的过程中产生提离，提离效应产生的信号可能淹没有效信号，通过采用新的探头设计或者先进的信号处理软件算法消除提离效应成为目前的研究热点。In practical industrial applications, when the probe is scanning the specimen, due to structural unevenness and other reasons, lift-off occurs during the scanning process, and the signal generated by the lift-off effect may submerge the effective signal. By adopting a new Probe design or advanced signal processing software algorithm to eliminate the lift-off effect has become a current research hotspot.
针对该问题，J﹒汉森和X﹒乔提出用于脉冲涡流检测的自动提离补偿，公开号为CN101413923A，已知提离处的参考信号可以用对应的计算的比率参数加权，并从测试信号减去，以补偿提离。优选获得多个参考信号，并且优选确定每个参考信号的最大幅度梯度，识别具有最接近测试信号的最大幅度梯度的对应参考信号，并在相关补偿程序中选择该对应的参考信号，但是该方法存在以下问题：①该方案为了提高检测精度需要获得多组参考数据，每次测量都需要测量参考信号，并且参考信号的提离值为已知提离，还要选择具有最接近测试信号的梯度的参考数据，来确定选择的参考信号和测试信号之间的差异；②该方法运算比较复杂，还需要对信号进行微分运算来确定梯度；③该方案所使用具有整体的发射器线圈和接收器阵列的探头，典型的接收器阵列具有16或32个传感器，装置比较复杂；④在后续的AD-LOC方法补偿程序中还要对提离是否存在进行判断，确定存在的提离，在确定提离存在以后需要选择提离参考，计算补偿比，从测试数据减去加权的提离参考数据补偿提离。In response to this problem, J. Hanson and X. Qiao proposed automatic lift-off compensation for pulsed eddy current detection, the publication number is CN101413923A, the reference signal at the known lift-off can be weighted with the corresponding calculated ratio parameter, and subtracted from the test signal to compensate for the lift-off. Multiple reference signals are preferably obtained, and the maximum magnitude gradient for each reference signal is preferably determined, the corresponding reference signal having the largest magnitude gradient closest to the test signal is identified, and that corresponding reference signal is selected in the correlation compensation procedure, but the method There are the following problems: ① In order to improve the detection accuracy, this scheme needs to obtain multiple sets of reference data, each measurement needs to measure the reference signal, and the lift-off value of the reference signal is known, and the gradient with the closest test signal must be selected The reference data to determine the difference between the selected reference signal and the test signal; ②This method is more complex in operation, and it also needs to perform differential operations on the signal to determine the gradient; ③This scheme uses an integral transmitter coil and receiver The probe of the array, the typical receiver array has 16 or 32 sensors, and the device is relatively complicated; ④ In the follow-up AD-LOC method compensation program, it is necessary to judge whether there is lift-off, determine the existing lift-off, and determine the lift-off After the lift-off exists, it is necessary to select the lift-off reference, calculate the compensation ratio, and subtract the weighted lift-off reference data from the test data to compensate for the lift-off.
发明内容Contents of the invention
本发明所要解决的技术问题是提供一种消除提离效应的脉冲涡流检测方法及装置，其能够消除提离效应对涡流检测结果的影响，提高检测精度，并且处理过程简便。The technical problem to be solved by the present invention is to provide a pulsed eddy current detection method and device that eliminates the lift-off effect, which can eliminate the influence of the lift-off effect on the eddy current detection results, improve the detection accuracy, and the processing process is simple.
本发明解决其技术问题采用的技术方案是：一种消除提离效应的脉冲涡流检测方法，具体包括：The technical solution adopted by the present invention to solve the technical problem is: a pulsed eddy current detection method that eliminates the lift-off effect, specifically including:
S1、对被测试件在不同的已知缺陷深度位置处获得不同提离高度下的检测信号时域曲线并且在被测试件无缺陷位置处获得无提离高度的参考信号时域曲线，并对检测信号和参考信号的时域曲线作差分处理和提取特征值处理，获取差分峰值电压拟合直线斜率与缺陷深度的关系曲线，具体分步骤包括：S1. Obtain the time-domain curves of the detection signal at different lift-off heights for the tested piece at different known defect depth positions and obtain the time-domain curve of the reference signal without lift-off height at the non-defective position of the tested piece, and The time domain curves of the detection signal and the reference signal are subjected to differential processing and feature value extraction processing to obtain the relationship curve between the slope of the differential peak voltage fitting line and the depth of the defect. The specific sub-steps include:
S11、产生频率和占空比均可调的脉冲激励信号；S11, generating a pulse excitation signal with adjustable frequency and duty ratio;
S12、激励探头线圈，产生激励磁场，将探头线圈置于被测试件上方，获取不同情况的响应信号的时域曲线，包括：S12. Excite the probe coil to generate an excitation magnetic field, place the probe coil above the test piece, and obtain time-domain curves of response signals in different situations, including:
1、在被测试件无缺陷位置处获取无提离高度的参考信号的时域曲线；1. Obtain the time-domain curve of the reference signal without lift-off height at the non-defective position of the tested piece;
2、在被测试件至少四处已知缺陷深度A1、A2、A3、A4处获取不同提离高度下的检测信号的时域曲线，所述A1、A2、A3、A4分别为不同的缺陷深度；2. Obtain the time-domain curves of the detection signals at different lift-off heights at at least four known defect depths A 1 , A 2 , A 3 , A 4 of the tested piece, the A 1 , A 2 , A 3 , A 4 are different defect depths;
S13、对在已知缺陷深度A1处获得的检测信号的时域曲线与参考信号的时域曲线作差分处理，获取在已知缺陷深度A1处不同提离高度下的差分信号曲线；S13. Perform differential processing on the time-domain curve of the detection signal obtained at the known defect depth A1 and the time - domain curve of the reference signal to obtain differential signal curves at different lift - off heights at the known defect depth A1;
S14、重复步骤S13，获取在已知缺陷深度A2、A3、A4处不同提离高度下的差分信号曲线；S14. Repeat step S13 to obtain differential signal curves at different lift-off heights at known defect depths A 2 , A 3 , and A 4 ;
S15、提取所述步骤S13和S14中获取的已知缺陷深度A1、A2、A3、A4在不同提离高度下的差分信号曲线的峰值电压，获取在不同已知缺陷深度A1、A2、A3、A4下差分峰值电压与不同提离高度的关系曲线，所述关系曲线分别对应在不同已知缺陷深度A1、A2、A3、A4下的差分峰值电压拟合直线斜率：K1、K2、K3、K4；S15. Extract the peak voltages of the differential signal curves of the known defect depths A 1 , A 2 , A 3 , and A 4 obtained in steps S13 and S14 at different lift-off heights, and obtain the peak voltages at different known defect depths A 1 , A 2 , A 3 , A 4 relationship curves of differential peak voltage and different lift-off heights, the relationship curves correspond to differential peak voltages at different known defect depths A 1 , A 2 , A 3 , A 4 Fitting straight line slope: K 1 , K 2 , K 3 , K 4 ;
S16、根据所述步骤S15获得的差分峰值电压拟合直线斜率K1、K2、K3、K4与对应的已知缺陷深度A1、A2、A3、A4，将其拟合为一条三次函数曲线，所述三次函数曲线为：h=aK3+bK2+cK+d，其中，所述h为对应的已知缺陷深度A1、A2、A3、A4，K为所述差分峰值电压拟合直线斜率K1、K2、K3、K4，a、b、c、d分别为所述三次函数曲线的系数，将所述A1、A2、A3、A4和K1、K2、K3、K4代入所述三次函数曲线，获得对应的a、b、c、d的值，再将获得的a、b、c、d的值代入三次函数曲线，得到差分峰值电压拟合直线斜率与缺陷深度关系：h=aK3+bK2+cK+d；S16. According to the differential peak voltage obtained in the step S15, the slopes K 1 , K 2 , K 3 , and K 4 of the straight line are fitted with the corresponding known defect depths A 1 , A 2 , A 3 , and A 4 , and they are fitted is a cubic function curve, and the cubic function curve is: h=aK 3 +bK 2 +cK+d, wherein, the h is the corresponding known defect depth A 1 , A 2 , A 3 , A 4 , K Fitting straight line slopes K 1 , K 2 , K 3 , K 4 for the differential peak voltage, a, b, c, and d are the coefficients of the cubic function curve respectively, and the A 1 , A 2 , A 3 . _ _ _ _ Function curve to get the relationship between the slope of the differential peak voltage fitting line and the depth of the defect: h=aK 3 +bK 2 +cK+d;
S2、对被测试件的未知缺陷深度进行定量评估，获得在未知缺陷深度位置处不同提离高度下的检测信号时域曲线，并将检测信号与参考信号的时域曲线作差分处理和提取特征值，将处理结果代入所述步骤S16中求得的表达式h=aK3+bK2+cK+d中，获得被测试件的未知缺陷深度，具体分步骤包括：S2. Quantitatively evaluate the unknown defect depth of the tested piece, obtain the time-domain curves of the detection signal at different lift-off heights at the position of the unknown defect depth, and perform differential processing and feature extraction on the time-domain curves of the detection signal and the reference signal value, and substitute the processing result into the expression h=aK 3 +bK 2 +cK+d obtained in the step S16 to obtain the unknown defect depth of the tested piece. The specific sub-steps include:
S21、产生频率和占空比均可调的脉冲激励信号；S21, generating a pulse excitation signal with adjustable frequency and duty ratio;
S22、激励探头线圈，产生激励磁场，将探头线圈置于被测试件上方，在未知缺陷深度Ax处的某一未知提离高度处获得检测信号B1的时域曲线；再在未知提离高度的基础上分别依次增加△x，再获得至少三处不同提离高度的检测信号B2、B3、B4的时域曲线；S22. Excite the probe coil to generate an excitation magnetic field, place the probe coil above the test piece, and obtain the time-domain curve of the detection signal B1 at an unknown lift-off height at the unknown defect depth Ax; then at the unknown lift-off height Increase △x in turn on the basis of , and then obtain at least three time-domain curves of detection signals B 2 , B 3 , and B 4 at different lift-off heights;
S23、将所述步骤S22获得的检测信号B1、B2、B3、B4的时域曲线与所述步骤S12中获得的参考信号的时域曲线作差分处理，获得不同提离高度下的差分信号曲线，提取差分信号曲线的峰值电压，获得不同提离高度与对应的差分峰值电压的关系曲线，提取所述关系曲线的差分峰值电压拟合直线斜率K，并将K代入所述步骤S16中所得的关系曲线h=aK3+bK2+cK+d，获得未知缺陷深度h，即步骤S22中的Ax的深度值。S23. Differentially process the time-domain curves of the detection signals B 1 , B 2 , B 3 , and B 4 obtained in the step S22 and the time-domain curves of the reference signal obtained in the step S12 to obtain The differential signal curve of the differential signal curve, extract the peak voltage of the differential signal curve, obtain the relationship curve of different lift-off heights and corresponding differential peak voltages, extract the differential peak voltage of the relationship curve to fit the slope K of the straight line, and substitute K into the step From the relationship curve h=aK 3 +bK 2 +cK+d obtained in S16, the unknown defect depth h is obtained, that is, the depth value of A x in step S22.
进一步的，所述至少四处已知缺陷深度A1、A2、A3、A4中，其中有一处的缺陷深度值为0。Further, among the at least four known defect depths A 1 , A 2 , A 3 , A 4 , one of them has a defect depth value of 0.
进一步的，在所述步骤S13之前还包括对检测信号和参考信号的放大滤波处理。Further, before the step S13, amplification and filtering of the detection signal and the reference signal are also included.
进一步的，在所述步骤S23之前还包括对所获得的检测信号的放大滤波处理。Further, before the step S23, amplification and filtering processing of the obtained detection signal is also included.
进一步的，所述△x为0.6mm。Further, the Δx is 0.6mm.
基于上述方法，本发明解决其技术问题还提供了一种消除提离效应的脉冲涡流检测装置，脉冲激励信号源、传感器探头、数据采集模块、提离补偿模块以及缺陷深度计算模块；Based on the above method, the present invention solves its technical problems and also provides a pulsed eddy current detection device that eliminates the lift-off effect, a pulse excitation signal source, a sensor probe, a data acquisition module, a lift-off compensation module, and a defect depth calculation module;
所述脉冲信号源用于产生脉冲激励信号；The pulse signal source is used to generate a pulse excitation signal;
所述传感器探头包括激励线圈以及位于线圈内的霍尔传感器，激励线圈用于在被测试件导体内部产生涡流，霍尔传感器用于将磁场信号转化为电信号，所述电信号即为响应信号，所述响应信号即为参考信号和检测信号；The sensor probe includes an excitation coil and a Hall sensor located in the coil, the excitation coil is used to generate eddy current inside the conductor of the test piece, and the Hall sensor is used to convert the magnetic field signal into an electrical signal, and the electrical signal is the response signal , the response signal is a reference signal and a detection signal;
所述数据采集模块用于对响应信号进行提取和保存，提取出参考信号和在不同缺陷深度、不同提离高度下的检测信号，并对所述参考信号和检测信号进行记录；The data acquisition module is used to extract and save the response signal, extract the reference signal and the detection signal at different defect depths and different lift-off heights, and record the reference signal and detection signal;
所述提离补偿模块用于对数据采集模块传输的参考信号和检测信号进行差分处理，获得在不同已知缺陷深度下提离高度和差分峰值电压的关系曲线，并对所述关系曲线提取特征值处理，获得在不同缺陷深度与差分峰值电压拟合直线斜率的关系曲线；The lift-off compensation module is used to differentially process the reference signal and the detection signal transmitted by the data acquisition module to obtain a relationship curve between lift-off height and differential peak voltage at different known defect depths, and extract features from the relationship curve Value processing to obtain the relationship curve of the slope of the fitting line between different defect depths and differential peak voltages;
所述缺陷深度计算模块用于根据提离补偿模块所得到的不同缺陷深度与差分峰值电压拟合直线斜率的关系曲线获得未知缺陷深度。The defect depth calculation module is used to obtain the unknown defect depth according to the relationship curve between different defect depths and the slope of the differential peak voltage fitting line obtained by the lift-off compensation module.
进一步的，还包括信号调理模块，所述信号调理模块用于对霍尔传感器输出的电信号进行放大滤波处理，并输出到数据采集模块。Further, a signal conditioning module is also included, and the signal conditioning module is used to amplify and filter the electrical signal output by the Hall sensor, and output it to the data acquisition module.
更进一步的，所述信号调理模块包括放大器AD620、运算放大器OP07。Furthermore, the signal conditioning module includes an amplifier AD620 and an operational amplifier OP07.
进一步的，所述脉冲激励信号源采用SPF40型数字合成函数信号发生器实现。Further, the pulse excitation signal source is realized by a SPF40 digital synthesis function signal generator.
本发明的有益效果是：本发明一种消除提离效应的脉冲涡流检测方法及装置通过在不同已知缺陷深度位置的不同提离高度下产生的结果的处理，消除了提离效应在脉冲涡流检测系统中的影响，系统能够更加精确的定量检测出被测试件的缺陷深度，与现有技术相比，检测装置简单，算法简单明了，不仅消除了提离效应的影响也能够对缺陷深度进行定量检测，提升了脉冲涡流检测技术在飞机机身结构及发动机的安全检测、核动力设施中的蒸汽管道及石油、天然气等运输管道的可靠性检测，各种板、棒、管等金属零件生产过程中的质量监控等工业运用中的市场竞争力，从而带来巨大的经济效益，解决了脉冲涡流检测技术发展多年来的核心问题。The beneficial effects of the present invention are: a pulsed eddy current detection method and device for eliminating the lift-off effect of the present invention eliminates the lift-off effect in the pulsed eddy current by processing the results generated at different lift-off heights at different known defect depth positions The influence in the detection system, the system can more accurately and quantitatively detect the defect depth of the tested piece. Compared with the existing technology, the detection device is simple and the algorithm is simple and clear, which not only eliminates the influence of the lift-off effect but also can measure the defect depth Quantitative testing has improved pulsed eddy current testing technology in the safety testing of aircraft fuselage structures and engines, the reliability testing of steam pipelines in nuclear power facilities and transportation pipelines such as oil and natural gas, and the production of various metal parts such as plates, rods, and tubes The market competitiveness in industrial applications such as quality monitoring in the process, thus bringing huge economic benefits, and solving the core problems of the development of pulsed eddy current testing technology for many years.
附图说明Description of drawings
图1为本发明实施例的一种消除提离效应的脉冲涡流检测方法的流程框图；Fig. 1 is a block flow diagram of a pulsed eddy current detection method for eliminating the lift-off effect according to an embodiment of the present invention;
图2为本发明实施例的一种消除提离效应的脉冲涡流检测装置的结构框图；Fig. 2 is a structural block diagram of a pulsed eddy current detection device that eliminates the lift-off effect according to an embodiment of the present invention;
图3为在被测试件为铝合金7075材质时无缺陷、无提离高度下的参考信号的时域曲线和缺陷深度为4mm处提离高度分别为0.2mm、提离0.8mm、提离1.4mm、提离2.0mm下的检测信号的时域曲线；Figure 3 is the time-domain curve of the reference signal when the tested piece is made of aluminum alloy 7075 with no defect and no lift-off height, and the lift-off height at the defect depth of 4mm is 0.2mm, 0.8mm, and 1.4mm respectively. mm, the time domain curve of the detection signal under the lift-off of 2.0mm;
图4为在被测试件为铝合金7075材质时缺陷深度为4mm处检测信号与参考信号的时域曲线的差分信号曲线；Figure 4 is the differential signal curve of the time domain curve of the detection signal and the reference signal at a defect depth of 4mm when the tested piece is made of aluminum alloy 7075;
图5为在被测试件为铝合金7075材质时不同的已知缺陷深度位置处提离高度与差分峰值电压的关系曲线图；Figure 5 is a graph showing the relationship between lift-off height and differential peak voltage at different known defect depth positions when the tested piece is made of aluminum alloy 7075;
图6为在被测试件为铝合金7075材质时不同缺陷深度的差分峰值电压拟合直线斜率与对应的缺陷深度的关系曲线；Figure 6 is the relationship curve between the slope of the fitting line of the differential peak voltage and the corresponding defect depth at different defect depths when the tested piece is made of aluminum alloy 7075;
图7为在被测试件为铝合金2024材质时在无缺陷、无提离高度下的参考信号的时域曲线和缺陷深度为4mm处提离高度分别为0.2mm、提离0.8mm、提离1.4mm、提离2.0mm下的检测信号的时域曲线；Figure 7 is the time-domain curve of the reference signal when the tested piece is made of aluminum alloy 2024 with no defect and no lift-off height, and the lift-off height at a defect depth of 4mm is 0.2mm, lift-off 0.8mm, lift-off The time-domain curve of the detection signal at 1.4mm and 2.0mm lift-off;
图8为在被测试件为铝合金2024材质时缺陷深度为4mm处检测信号与参考信号的时域曲线的差分信号曲线；Fig. 8 is the differential signal curve of the time domain curve of the detection signal and the reference signal at a defect depth of 4 mm when the tested piece is made of aluminum alloy 2024;
图9为在被测试件为铝合金2024材质时不同的已知缺陷深度位置处提离高度与差分峰值电压的关系曲线图；Fig. 9 is a graph showing the relationship between lift-off height and differential peak voltage at different known defect depth positions when the tested piece is made of aluminum alloy 2024;
图10为在被测试件为铝合金2024材质时不同缺陷深度的差分峰值电压拟合直线斜率与对应的缺陷深度的关系曲线；Figure 10 is the relationship curve between the slope of the fitting line and the corresponding defect depth between the differential peak voltage fitting line slope and the corresponding defect depth when the tested piece is made of aluminum alloy 2024;
附图曲线标记说明：31-参考信号（无缺陷无提离）、32-提离0.2mm、33-提离0.8mm、34-提离1.4mm、35-提离2.0mm；Description of the curve marks in the drawings: 31-reference signal (no defect, no lift-off), 32-lift-off 0.2mm, 33-lift-off 0.8mm, 34-lift-off 1.4mm, 35-lift-off 2.0mm;
41-提离0.2mm、42-提离0.8mm、43-提离1.4mm、44-提离2.0mm；41-lift off 0.2mm, 42-lift off 0.8mm, 43-lift off 1.4mm, 44-lift off 2.0mm;
51-无缺陷、52-深2mm、53-深3mm、54-深4mm、55-深5mm、56-深6mm、57-深7mm、58-深8mm；51-no defect, 52-2mm deep, 53-3mm deep, 54-4mm deep, 55-5mm deep, 56-6mm deep, 57-7mm deep, 58-8mm deep;
71-参考信号（无缺陷无提离）、72-提离0.2mm、73-提离0.8mm、74-提离1.4mm、75-提离2.0mm；71-reference signal (no defect, no lift-off), 72-lift-off 0.2mm, 73-lift-off 0.8mm, 74-lift-off 1.4mm, 75-lift-off 2.0mm;
81-提离0.2mm、82-提离0.8mm、83-提离1.4mm、84-提离2.0mm；81-lift off 0.2mm, 82-lift off 0.8mm, 83-lift off 1.4mm, 84-lift off 2.0mm;
91-无缺陷、92-深2mm、93-深4mm、94-深6mm、95-深8mm。91-no defect, 92-2mm deep, 93-4mm deep, 94-6mm deep, 95-8mm deep.
具体实施方式detailed description
下面结合附图对本发明的实施例作进一步的说明。Embodiments of the present invention will be further described below in conjunction with the accompanying drawings.
如图1所示为本发明实施例一种消除提离效应的脉冲涡流检测方法的流程框图，其步骤具体包括：As shown in Figure 1, it is a flow chart of a pulsed eddy current detection method for eliminating the lift-off effect according to an embodiment of the present invention, and its steps specifically include:
S1、对被测试件在不同的已知缺陷深度位置处获得不同提离高度下的检测信号时域曲线并且在被测试件无缺陷位置处获得无提离高度的参考信号时域曲线，并对检测信号和参考信号的时域曲线作差分处理和提取特征值处理，获取差分峰值电压拟合直线斜率与缺陷深度的关系曲线，具体分步骤包括：S1. Obtain the time-domain curves of the detection signal at different lift-off heights for the tested piece at different known defect depth positions and obtain the time-domain curve of the reference signal without lift-off height at the non-defective position of the tested piece, and The time domain curves of the detection signal and the reference signal are subjected to differential processing and feature value extraction processing to obtain the relationship curve between the slope of the differential peak voltage fitting line and the depth of the defect. The specific sub-steps include:
S11、产生频率和占空比均可调的脉冲激励信号；S11, generating a pulse excitation signal with adjustable frequency and duty ratio;
S12、激励探头线圈，产生激励磁场，将探头线圈置于被测试件上方，获取不同情况的响应信号的时域曲线，包括：S12. Excite the probe coil to generate an excitation magnetic field, place the probe coil above the test piece, and obtain time-domain curves of response signals in different situations, including:
1、在被测试件无缺陷位置处获取无提离高度的参考信号的时域曲线；1. Obtain the time-domain curve of the reference signal without lift-off height at the non-defective position of the tested piece;
2、在被测试件至少四处已知缺陷深度A1、A2、A3、A4处获取不同提离高度下的检测信号的时域曲线，所述A1、A2、A3、A4分别为不同的缺陷深度；2. Obtain the time-domain curves of the detection signals at different lift-off heights at at least four known defect depths A 1 , A 2 , A 3 , A 4 of the tested piece, the A 1 , A 2 , A 3 , A 4 are different defect depths;
其中参考信号的时域曲线和检测信号的时域曲线的获取均为本领域技术人员的公知常识，在本发明申请方案中不再做详细介绍。The acquisition of the time-domain curve of the reference signal and the time-domain curve of the detection signal are common knowledge of those skilled in the art, and will not be described in detail in the application scheme of the present invention.
为了能够实现对被测试件有无缺陷的判断，还应该测量在无缺陷位置处不同提离高度下的检测信号，以增加检测结果的准确性，具体的，在本发明实施例中，所述至少四处已知缺陷深度A1、A2、A3、A4中，其中有一处的缺陷深度值为0，也可以所述在测量了四处已知缺陷深度的检测信号后，在对无缺陷位置处单独测量其不同提离高度下的检测信号。In order to realize whether there is a defect in the tested piece, the detection signals at different lift-off heights at the non-defective position should also be measured to increase the accuracy of the detection results. Specifically, in the embodiment of the present invention, the Among at least four known defect depths A 1 , A 2 , A 3 , and A 4 , one of them has a defect depth value of 0. The detection signals at different lift-off heights are measured separately at the position.
S13、对在已知缺陷深度A1处获得的检测信号的时域曲线与参考信号的时域曲线作差分处理，获取在已知缺陷深度A1处不同提离高度下的差分信号曲线；S13. Perform differential processing on the time-domain curve of the detection signal obtained at the known defect depth A1 and the time - domain curve of the reference signal to obtain differential signal curves at different lift - off heights at the known defect depth A1;
S14、重复步骤S13，获取在已知缺陷深度A2、A3、A4处不同提离高度下的差分信号曲线；S14. Repeat step S13 to obtain differential signal curves at different lift-off heights at known defect depths A 2 , A 3 , and A 4 ;
S15、提取所述步骤S13和S14中获取的已知缺陷深度A1、A2、A3、A4在不同提离高度下的差分信号曲线的峰值电压，获取在不同已知缺陷深度A1、A2、A3、A4下差分峰值电压与不同提离高度的关系曲线，所述关系曲线分别对应在不同已知缺陷深度A1、A2、A3、A4下的差分峰值电压拟合直线斜率：K1、K2、K3、K4；S15. Extract the peak voltages of the differential signal curves of the known defect depths A 1 , A 2 , A 3 , and A 4 obtained in steps S13 and S14 at different lift-off heights, and obtain the peak voltages at different known defect depths A 1 , A 2 , A 3 , A 4 relationship curves of differential peak voltage and different lift-off heights, the relationship curves correspond to differential peak voltages at different known defect depths A 1 , A 2 , A 3 , A 4 Fitting straight line slope: K 1 , K 2 , K 3 , K 4 ;
S16、根据所述步骤S15获得的差分峰值电压拟合直线斜率K1、K2、K3、K4与对应的已知缺陷深度A1、A2、A3、A4，将其拟合为一条三次函数曲线，所述三次函数曲线为：h=aK3+bK2+cK+d，其中，所述h为对应的已知缺陷深度A1、A2、A3、A4，K为所述差分峰值电压拟合直线斜率K1、K2、K3、K4，a、b、c、d分别为所述三次函数曲线的系数，将所述A1、A2、A3、A4和K1、K2、K3、K4代入所述三次函数曲线，获得对应的a、b、c、d的值，再将获得的a、b、c、d的值代入三次函数曲线，得到差分峰值电压拟合直线斜率与缺陷深度关系：h=aK3+bK2+cK+d；S16. According to the differential peak voltage obtained in the step S15, the slopes K 1 , K 2 , K 3 , and K 4 of the straight line are fitted with the corresponding known defect depths A 1 , A 2 , A 3 , and A 4 , and they are fitted is a cubic function curve, and the cubic function curve is: h=aK 3 +bK 2 +cK+d, wherein, the h is the corresponding known defect depth A 1 , A 2 , A 3 , A 4 , K Fitting straight line slopes K 1 , K 2 , K 3 , K 4 for the differential peak voltage, a, b, c, and d are the coefficients of the cubic function curve respectively, and the A 1 , A 2 , A 3 . _ _ _ _ Function curve to get the relationship between the slope of the differential peak voltage fitting line and the depth of the defect: h=aK 3 +bK 2 +cK+d;
S2、对被测试件的未知缺陷深度进行定量评估，获得在未知缺陷深度位置处不同提离高度下的检测信号时域曲线，并将检测信号与参考信号的时域曲线作差分处理和提取特征值，将处理结果代入所述步骤S16中求得的表达式h=aK3+bK2+cK+d中，获得被测试件的未知缺陷深度，具体分步骤包括：S2. Quantitatively evaluate the unknown defect depth of the tested piece, obtain the time-domain curves of the detection signal at different lift-off heights at the position of the unknown defect depth, and perform differential processing and feature extraction on the time-domain curves of the detection signal and the reference signal value, and substitute the processing result into the expression h=aK 3 +bK 2 +cK+d obtained in the step S16 to obtain the unknown defect depth of the tested piece. The specific sub-steps include:
S21、产生频率和占空比均可调的脉冲激励信号；S21, generating a pulse excitation signal with adjustable frequency and duty ratio;
S22、激励探头线圈，产生激励磁场，将探头线圈置于被测试件上方，在未知缺陷深度Ax处的某一未知提离高度处获得检测信号B1的时域曲线；再在未知提离高度的基础上分别依次增加△x，再获得至少三处不同提离高度的检测信号B2、B3、B4的时域曲线；S22. Excite the probe coil to generate an excitation magnetic field, place the probe coil above the test piece, and obtain the time-domain curve of the detection signal B1 at an unknown lift-off height at the unknown defect depth Ax ; Increase △x sequentially on the basis of the height, and then obtain at least three time-domain curves of detection signals B 2 , B 3 , and B 4 at different lift-off heights;
S23、将所述步骤S22获得的检测信号B1、B2、B3、B4的时域曲线与所述步骤S12中获得的参考信号的时域曲线作差分处理，获得不同提离高度下的差分信号曲线，提取差分信号曲线的峰值电压，获得不同提离高度与对应的差分峰值电压的关系曲线，提取所述关系曲线的差分峰值电压拟合直线斜率K，并将K代入所述步骤S16中所得的关系曲线h=aK3+bK2+cK+d，获得未知缺陷深度h，即步骤S22中的Ax的深度值。S23. Differentially process the time-domain curves of the detection signals B 1 , B 2 , B 3 , and B 4 obtained in the step S22 and the time-domain curves of the reference signal obtained in the step S12 to obtain The differential signal curve of the differential signal curve, extract the peak voltage of the differential signal curve, obtain the relationship curve of different lift-off heights and corresponding differential peak voltages, extract the differential peak voltage of the relationship curve to fit the slope K of the straight line, and substitute K into the step From the relationship curve h=aK 3 +bK 2 +cK+d obtained in S16, the unknown defect depth h is obtained, that is, the depth value of A x in step S22.
在现有技术中，脉冲涡流检测一般应用较多的是对航天器材的检测，采用本发明所述消除提离效应的检测方法对被测试件进行检测时，只需在第一次对被测试件所属材料的已知缺陷深度进行测量分析，得到差分峰值电压拟合直线斜率与缺陷深度的关系曲线，消除不同的提离高度对检测结果的影响，就可使检测得到的结果更加准确，并且其中的算法过程简便，易于在实际中进行操作，不需借用庞大精密的仪器即可完成对未知缺陷深度的检测，消除提离效应对检测结果的影响。In the prior art, pulsed eddy current detection is generally applied to the detection of aerospace equipment. When using the detection method of the present invention to eliminate the lift-off effect to detect the tested piece, it only needs to be tested for the first time. Measure and analyze the known defect depth of the material to which the part belongs, and obtain the relationship curve between the slope of the differential peak voltage fitting line and the defect depth, and eliminate the influence of different lift-off heights on the test results, so that the test results can be more accurate, and The algorithm process is simple and easy to operate in practice. The detection of unknown defect depth can be completed without borrowing huge and sophisticated instruments, and the influence of lift-off effect on the detection results can be eliminated.
其中，因为输出的响应信号较为微弱，为了获取更好的检测结果，需要对输出的检测信号和参考信号做放大滤波处理，所以在所述步骤S13之前还包括对检测信号和参考信号的放大滤波处理，同样的，在所述步骤S23之前还包括对所获得的检测信号的放大滤波处理。Wherein, because the output response signal is relatively weak, in order to obtain better detection results, the output detection signal and reference signal need to be amplified and filtered, so the amplification and filtering of the detection signal and reference signal are also included before the step S13. The processing also includes amplification and filtering of the obtained detection signal before the step S23.
如图2所示为本发明实施的一种消除提离效应的脉冲涡流检测装置的结构框图，其包括：脉冲激励信号源、传感器探头、数据采集模块、提离补偿模块以及缺陷深度计算模块；As shown in Figure 2, it is a structural block diagram of a pulsed eddy current detection device that eliminates the lift-off effect implemented in the present invention, which includes: a pulse excitation signal source, a sensor probe, a data acquisition module, a lift-off compensation module, and a defect depth calculation module;
所述脉冲信号源用于产生脉冲激励信号；The pulse signal source is used to generate a pulse excitation signal;
所述传感器探头包括激励线圈以及位于线圈内的霍尔传感器，激励线圈用于在被测试件导体内部产生涡流，霍尔传感器用于将磁场信号转化为电信号，所述电信号即为响应信号，所述响应信号即为参考信号和检测信号；The sensor probe includes an excitation coil and a Hall sensor located in the coil, the excitation coil is used to generate eddy current inside the conductor of the test piece, and the Hall sensor is used to convert the magnetic field signal into an electrical signal, and the electrical signal is the response signal , the response signal is a reference signal and a detection signal;
所述数据采集模块用于对响应信号进行提取和保存，提取出参考信号和在不同缺陷深度、不同提离高度下的检测信号，并对所述参考信号和检测信号进行记录；The data acquisition module is used to extract and save the response signal, extract the reference signal and the detection signal at different defect depths and different lift-off heights, and record the reference signal and detection signal;
所述提离补偿模块用于对数据采集模块传输的参考信号和检测信号进行差分处理，获得在不同已知缺陷深度下提离高度和差分峰值电压的关系曲线，并对所述关系曲线提取特征值处理，获得在不同缺陷深度与差分峰值电压拟合直线斜率的关系曲线；The lift-off compensation module is used to differentially process the reference signal and the detection signal transmitted by the data acquisition module to obtain a relationship curve between lift-off height and differential peak voltage at different known defect depths, and extract features from the relationship curve Value processing to obtain the relationship curve of the slope of the fitting line between different defect depths and differential peak voltages;
所述缺陷深度计算模块用于根据提离补偿模块所得到的不同缺陷深度与差分峰值电压拟合直线斜率的关系曲线获得未知缺陷深度。The defect depth calculation module is used to obtain the unknown defect depth according to the relationship curve between different defect depths and the slope of the differential peak voltage fitting line obtained by the lift-off compensation module.
其中，还包括信号调理模块，所述信号调理模块用于对霍尔传感器输出的电信号进行放大滤波处理，并输出到数据采集模块。所述信号调理模块包括放大器AD620、运算放大器OP07。所述脉冲激励信号源采用SPF40型数字合成函数信号发生器实现。Wherein, a signal conditioning module is also included, and the signal conditioning module is used to amplify and filter the electrical signal output by the Hall sensor, and output it to the data acquisition module. The signal conditioning module includes amplifier AD620 and operational amplifier OP07. The pulse excitation signal source is realized by SPF40 digital synthesis function signal generator.
为了便于本领域技术人员能够理解并实施本发明方案，下面对本发明一种消除提离效应的脉冲涡流检测方法及装置进行详细说明：In order to make it easier for those skilled in the art to understand and implement the solution of the present invention, a pulsed eddy current detection method and device for eliminating the lift-off effect of the present invention will be described in detail below:
上述步骤S11和步骤S21中所述的激励信号的获取可以利用SPF40型数字合成函数信号发生器，由它直接得到频率、占空比及幅值均可调的高精度稳定脉冲信号f(t)，它可用式（1）进行傅里叶展开：The acquisition of the excitation signal described in the above step S11 and step S21 can utilize the SPF40 type digital synthesis function signal generator to directly obtain a high-precision stable pulse signal f(t) with adjustable frequency, duty cycle and amplitude , it can be Fourier expanded by formula (1):
式中，A0为直流分量，An为对应的各谐波分量的幅值，ω1为基波角频率，为脉冲波初始相位。In the formula, A 0 is the DC component, A n is the amplitude of the corresponding harmonic components, ω 1 is the fundamental angular frequency, is the initial phase of the pulse wave.
所述传感器探头由激励线圈和霍尔传感器组成。激励线圈为激励磁场源，由它产生构成涡流效应的一次磁场；霍尔传感器置于激励线圈底部中间位置，作为探头的检测部分，用于获取线圈激励磁场和涡流反馈磁场叠加后磁场的大小，并将其转化为电压信号反馈给后续处理部分。但是由于激励磁场比较微弱，因此，霍尔传感器所输出的电压信号同样比较小，往往只有几十毫伏，而且里面还掺杂了很多高频干扰信号，因此，需要对传感器探头输出的信号进行放大滤波处理，也就是对所获得的参考信号以及在各个不同已知缺陷深度位置处不同提离高度下所获得的检测信号进行放大滤波处理，滤除信号中的杂波干扰信号并对其进行放大，使其达到后续数据采集模块的测量范围。为实现这一功能，在本发明实施例中可以使用以仪表放大器AD620为核心的放大电路实现信号的放大，并利用高精度运算放大器OP07组成二阶低通滤波器滤除干扰信号。The sensor probe consists of an excitation coil and a Hall sensor. The excitation coil is the excitation magnetic field source, which generates the primary magnetic field that constitutes the eddy current effect; the Hall sensor is placed in the middle of the bottom of the excitation coil as the detection part of the probe, and is used to obtain the magnitude of the magnetic field after the coil excitation magnetic field and the eddy current feedback magnetic field are superimposed. And convert it into a voltage signal and feed it back to the subsequent processing part. However, because the excitation magnetic field is relatively weak, the voltage signal output by the Hall sensor is also relatively small, often only tens of millivolts, and there are many high-frequency interference signals doped in it. Amplification and filtering processing, that is, performing amplification and filtering processing on the obtained reference signal and the detection signals obtained at different lift-off heights at different known defect depth positions, filtering out the clutter interference signal in the signal and processing it. Zoom in so that it reaches the measurement range of the subsequent data acquisition module. In order to realize this function, in the embodiment of the present invention, the amplifying circuit with the instrumentation amplifier AD620 as the core can be used to amplify the signal, and the high-precision operational amplifier OP07 is used to form a second-order low-pass filter to filter out the interference signal.
在完成了对参考信号以及在各个不同已知缺陷深度位置处不同提离高度下所获得的检测信号的获取之后，需要将所得到的数据进行提取和保存，以方便对结果进行分析对比，为实现检测系统与上位机的连接，在本发明实施例中可利用上位机控制数据采集卡来实现对信号的采集和存储。再由后续的提离补偿模块和缺陷深度计算模块对获取的信号进行差分处理和提取特征值，获得对应的关系曲线。After completing the acquisition of the reference signal and the detection signals obtained at different lift-off heights at different known defect depth positions, the obtained data needs to be extracted and saved to facilitate the analysis and comparison of the results. To realize the connection between the detection system and the host computer, in the embodiment of the present invention, the host computer can be used to control the data acquisition card to realize the acquisition and storage of signals. Then, the subsequent lift-off compensation module and defect depth calculation module perform differential processing on the acquired signals and extract eigenvalues to obtain corresponding relationship curves.
下面将对参考信号和各种检测信号的获取以及对数据的差分处理和特征值的提取的过程进行详细描述：The process of obtaining reference signals and various detection signals, differential processing of data and extraction of eigenvalues will be described in detail below:
首先选取被测试件为铝合金7075材质，在无缺陷位置和至少四处已知缺陷深度位置处进行检测，在本发明的实施例中选取了八处不同已知缺陷深度进行检测，缺陷深度依次为0mm、2mm、3mm、4mm、5mm、6mm、7mm、8mm，再分别在八处不同已知缺陷深度位置处获得在不同提离高度下的检测信号，在涡流检测技术领域中，通过研究发现，提离高度在一定的变化范围内，其得出的检测结果为有效的检测范围，有效检测范围会根据脉冲涡流检测系统探头的几何结构、几何尺寸和电气特性发生变化，在本发明中所述的有效检测范围为提离高度在0mm至2mm之间变化时，在本发明实施例中选取四处不同的提离高度，分别为提离0.2mm、提离0.8mm、提离1.4mm、提离2.0mm，如图3所示为在被测试件无缺陷、无提离高度下的参考信号的时域曲线和缺陷深度为4mm处，提离高度分别为0.2mm、提离0.8mm、提离1.4mm、提离2.0mm下的检测信号的时域曲线，其他已知缺陷深度位置处的信号曲线也与此类似，在本发明实施例中不再一一列出。再分别对所获得的检测信号的时域曲线与参考信号的时域曲线作差分处理，得到如图4所示的差分信号曲线，提取其中的峰值电压，得到在缺陷深度为4mm处提离高度与差分峰值电压曲线，其他已知缺陷深度位置处也作相同处理，得到如图5所示在不同的已知缺陷深度位置处提离高度与差分峰值电压的关系图。Firstly, the tested piece is selected to be made of aluminum alloy 7075, and the detection is performed at the non-defective position and at least four known defect depth positions. In the embodiment of the present invention, eight different known defect depths are selected for detection, and the defect depths are in turn: 0mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, and then obtain the detection signals at different lift-off heights at eight different known defect depth positions. In the field of eddy current testing technology, it is found through research that The lift-off height is within a certain range of variation, and the detection result obtained by it is the effective detection range, and the effective detection range will change according to the geometric structure, geometric size and electrical characteristics of the probe of the pulsed eddy current detection system, as described in the present invention The effective detection range is that when the lift-off height changes between 0mm and 2mm, four different lift-off heights are selected in the embodiment of the present invention, which are respectively lift-off 0.2mm, lift-off 0.8mm, lift-off 1.4mm, lift-off 2.0mm, as shown in Figure 3 is the time domain curve of the reference signal when the tested piece has no defects and no lift-off height and the defect depth is 4mm, the lift-off height is 0.2mm, lift-off 0.8mm, lift-off The time-domain curve of the detection signal at 1.4mm and 2.0mm lift-off, and the signal curves at other known defect depth positions are also similar, and will not be listed one by one in the embodiment of the present invention. Then differentially process the time-domain curve of the obtained detection signal and the time-domain curve of the reference signal to obtain the differential signal curve as shown in Figure 4, extract the peak voltage, and obtain the lift-off height at the defect depth of 4mm With the differential peak voltage curve, the same process is carried out at other known defect depth positions, and the relationship diagram between lift-off height and differential peak voltage at different known defect depth positions is obtained as shown in Figure 5.
由图5可以发现当缺陷深度一定时，在不同提离高度下得到的检测信号与参考信号的差分信号的峰值电压和提离高度呈线性关系，即U=Kx+n，其中所述U为峰值电压，x为提离高度，K为直线斜率；并且同一缺陷深度，不同提离高度的差分信号的峰值电压的变化率一定，即K一定，与提离的变化情况无关，从而在检测结果的计算以及分析中消除了提离高度的影响。It can be found from Fig. 5 that when the depth of the defect is constant, the peak voltage and the lift-off height of the differential signal of the detection signal and the reference signal obtained at different lift-off heights have a linear relationship, that is, U=Kx+n, where U is Peak voltage, x is the lift-off height, K is the slope of the straight line; and the rate of change of the peak voltage of the differential signal of the same defect depth and different lift-off heights is constant, that is, K is constant, which has nothing to do with the change of lift-off, so the detection results The influence of lift-off height is eliminated in the calculation and analysis.
最后提取图5中不同已知缺陷深度下提离高度与差分峰值电压对应关系曲线的斜率K1、K2、K3、K4、K5、K6、K7、K8，将得到的斜率与对应的已知缺陷深度拟合为三次函数曲线：h=aK3+bK2+cK+d，如图6所示为差分峰值拟合直线斜率与对应的缺陷深度的关系曲线，得到系数a、b、c、d的值，从而完成了被测试件为铝合金7075材质的差分峰值拟合直线斜率与缺陷深度关系曲线的测量。Finally, extract the slopes K 1 , K 2 , K 3 , K 4 , K 5 , K 6 , K 7 , and K 8 of the curves corresponding to the lift-off height and differential peak voltage at different known defect depths in Figure 5, and the obtained The slope and the corresponding known defect depth are fitted into a cubic function curve: h=aK 3 +bK 2 +cK+d, as shown in Figure 6 is the relationship curve between the slope of the differential peak fitting line and the corresponding defect depth, and the coefficient is obtained a, b, c, and d values, thus completing the measurement of the relationship curve between the slope of the differential peak fitting line and the depth of the defect for the tested piece made of aluminum alloy 7075.
当被测试件为铝合金2024材质时，处理的方法与被测试件为铝合金7075类似，得到的测试结果如图7所示为被测试件为铝合金2024时，其无缺陷、无提离高度的参考信号的时域曲线和缺陷深度为4mm位置处提离高度分别为0.2mm、0.8mm、1.4mm、2.0mm时检测信号的时域曲线；图8所示为基于图7中的检测信号与参考信号的时域曲线的差分信号曲线；图9所示为在不同缺陷深度下提离高度与差分峰值电压的关系曲线，选取的缺陷深度分别为0mm、2mm、4mm、6mm、8mm；图10所示为图9中差分峰值拟合直线斜率与对应的缺陷深度的三次函数曲线。When the tested piece is made of aluminum alloy 2024, the treatment method is similar to that of the tested piece made of aluminum alloy 7075. The test results obtained are shown in Figure 7. When the tested piece is made of aluminum alloy 2024, there is no defect and no lift-off. The time-domain curve of the reference signal of the height and the time-domain curve of the detection signal when the lift-off height is 0.2mm, 0.8mm, 1.4mm, and 2.0mm at the defect depth of 4mm; Figure 8 shows the detection based on Figure 7 The differential signal curve of the time domain curve of the signal and the reference signal; Figure 9 shows the relationship curve between the lift-off height and the differential peak voltage at different defect depths, and the selected defect depths are 0mm, 2mm, 4mm, 6mm, and 8mm; FIG. 10 shows the cubic function curve of the slope of the differential peak fitting line in FIG. 9 and the corresponding defect depth.
再根据求得的被测试件为铝合金7075材质的拟合直线斜率与缺陷深度关系曲线：h=aK3+bK2+cK+d，对被测试件为铝合金7075材质的未知缺陷深度进行检测，具体的操作步骤如下：Then, according to the relationship curve between the slope of the fitted line and the defect depth obtained for the tested piece made of aluminum alloy 7075: h=aK 3 +bK 2 +cK+d, the unknown defect depth of the tested piece made of aluminum alloy 7075 is calculated. Detection, the specific operation steps are as follows:
步骤1、在未知缺陷深度上方的某一未知提离高度的位置处获得检测信号B1的时域曲线后，在此基础上增加已知高度的提离间隔△x=0.6mm的位置，得到检测信号B2的时域曲线；在得到检测信号B2后，再在此基础上又增加已知高度的提离间隔△x=0.6mm的位置，检测得到信号B3；最后在得到检测信号B3后，再在此基础上又增加已知高度的提离间隔△x=0.6mm的位置，得到检测信号B4的时域曲线。确定四个检测信号的有效性，如果检测信号在有效检测范围内方可使用，如果没有在有效范围内则必须重新测量进而获得有效的检测信号；Step 1. After obtaining the time-domain curve of the detection signal B 1 at a position of an unknown lift-off height above the unknown defect depth, on this basis, increase the position of the lift-off interval of known height △x=0.6mm to obtain The time-domain curve of the detection signal B 2 ; after obtaining the detection signal B 2 , on this basis, increase the position of the lift-off interval △x=0.6mm of the known height, and obtain the signal B 3 through detection; finally obtain the detection signal After B 3 , on this basis, increase the position of the lift-off interval △x=0.6mm of the known height to obtain the time domain curve of the detection signal B 4 . Determine the validity of the four detection signals. If the detection signal is within the effective detection range, it can be used. If it is not within the effective range, it must be re-measured to obtain an effective detection signal;
其中△x的值可以根据所确定的有效范围来人为定义；The value of △x can be artificially defined according to the determined effective range;
步骤2、将上面所检测出的四个检测信号B1、B2、B3、B4的时域曲线分别与参考信号的时域曲线进行差分运算，获得四个差分信号，提取出四个差分信号的峰值电压U1、U2、U3、U4；Step 2. Perform differential calculations on the time domain curves of the four detection signals B 1 , B 2 , B 3 , and B 4 detected above and the time domain curves of the reference signal to obtain four differential signals and extract four Peak voltages U 1 , U 2 , U 3 , U 4 of differential signals;
步骤3、根据步骤2中所获得的四个有效的差分峰值电压和已知的提离间隔拟合出一条直线，获得拟合直线的斜率K值；Step 3. Fit a straight line according to the four effective differential peak voltages obtained in step 2 and the known lift-off interval, and obtain the slope K value of the fitted straight line;
步骤4、将步骤3中所得到的直线斜率K值代入不同缺陷深度h与拟合直线斜率K存在的三次函数关系式中即可求得缺陷深度h值，因而消除了初始位置未知提离高度对检测结果的影响。Step 4. Substituting the straight line slope K value obtained in step 3 into the cubic function relationship between different defect depths h and the fitting straight line slope K can obtain the defect depth h value, thus eliminating the unknown lift-off height of the initial position impact on test results.
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| CN101865883A (en) * | 2010-06-21 | 2010-10-20 | 南京航空航天大学 | Pulse eddy current stress crack integrated detection system and method |
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| US7750626B2 (en) * | 2005-03-14 | 2010-07-06 | Her Majesty The Queen In Right Of Canada, As Represented By The Minister Of National Defence Of Her Majesty's Canadian Government | Method and apparatus for eddy current detection of material discontinuities |
| CN101413923A (en) * | 2007-06-12 | 2009-04-22 | 通用电气检查技术有限公司 | Automatic lift-off compensation for pulsed eddy current inspection |
| CN101865883A (en) * | 2010-06-21 | 2010-10-20 | 南京航空航天大学 | Pulse eddy current stress crack integrated detection system and method |
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