40Cr钢淬硬层深度的涡流无损检测

利用涡流方法和常规硬度分析法对常用的淬火钢-40Cr钢的淬硬层深度进行了检测。通过对检测所得涡流信号的分析、计算及其与硬度实验法测算结果的对比，发现涡流无损检测拟合计算方法与硬度分析法的结果最大相对偏差平均小于6％。本研究将最小二乘法用于涡流硬度检测拟合，拟合值与实测的最大相对偏差为0．55％，拟合率达到了99％，并由此得出了涡流检测淬火钢淬硬层深度的规律。研究结果表明，涡流检测方法可以作为一种可靠的无损检测方法来进行淬硬层深度的测算，且所得结果的误差较小。     

涡流新技术在油罐底板腐蚀检测中的应用

突破了传统涡流检测的应用局限，介绍了油罐底板腐蚀涡流检测新技术，如远场涡流技术，相控阵技术和磁饱和技术等。建立了试验远场涡流检测系统。试验结果表明，采用涡流方法检测罐底腐蚀是可行的，探头的改进方式及质量对试验结果影响较大。为了达到对各种形状缺陷的有效诊断，提高检测灵敏度和准确性，还需进一步改进和完善远场涡流检测系统。     

40Cr铜淬硬层深度的涡流无损检测

利用涡流方法和常规硬度分析法对常用的淬火钢-40Cr钢的淬硬层深度进行了检测.通过对检测所得涡流信号的分析、计算及其与硬度实验法测算结果的对比,发现涡流无损检测拟合计算方法与硬度分析法的结果最大相对偏差平均小于6%.本研究将最小二乘法用于涡流硬度检测拟合,拟合值与实测的最大相对偏差为0.5%,拟合率达到了99%,并由此得出了涡流检测淬火钢淬硬层深度的规律.研究结果表明,涡流检测方法可以作为一种可靠的无损检测方法来进行淬硬层深度的测算,且所得结果的误差较小.     

非接触式无损探伤设备

目前，我国钢铁业和有色金属业已逐步同国际经济接轨，加入到国际经济发展的大循环之中。因此，产品的质量问题越来越被生产厂家所重视。钢材的质量主要以同类产品在组织结构、尺寸规格和钢材表面及内部的各种缺陷的控制上反映出来。钢材的各种缺陷和纵、横向裂纹可用非接触式无损探伤的方法来检验，如涡流无损探伤法、射线法等。涡流无损探伤是通过在探头部位的差动式组合线圈对钢材表面产生涡流，再通过高速传感器探头对涡流在钢材本身产生的磁场进行扫描，通过对扫描数据的处理可以比较出涡流在有、无缺陷钢材部位产生的磁场差别，从而对…     

涡流技术在球墨铸铁硬度检测中的应用

介绍了涡流法检测硬度的原理及特点,阐述了在检测过程中检测电流频率、线圈形状和结构以及检测方式等相关参数的选择,并通过对轿车零件MA差速器壳体进行相关的试验和验证。得出以下结论:在涡流检测时,零件硬度的变化会引起零件阻抗的变化,导致零件在阻抗平面图位置产生变化。虽然涡流检测不能进行定量检测得到具体硬度值,但可以通过检测零件在阻抗平面图中的位置来分选出零件是否异常,对零件硬度进行定性分选,并快速有效判定零件是否异常。因此,涡流检测分选球墨铸铁零件的硬度是一种高速有效的无损检测方法。     

一种专用涡流检测换能器的设计

介绍了涡流检测换能器的工作原理和设计方法，并根据检测特殊结构金属工件的要求，对涡流检测中换能器结构尺寸等参数进行了分析和优化，为设计一种专用涡流检测换能器提供了思路。     

油气长输管道管体损伤的高速涡流磁场检测

针对油气长输管道外壁缺陷影响管道安全运行的问题，提出了一种基于动生涡流磁场的无损检测方法。借助ANSYS Electronics有限元分析软件分析了管道表面缺陷参数、检测速度与动生涡流磁场之间的关系，发现在不同管道表面缺陷参数下，动生涡流磁场会根据缺陷形状、尺寸的差异反馈出不同的磁感应强度信号，缺陷尺寸越大，信号反馈越强烈；随着检测速度的提高，动生涡流的磁感应强度逐渐增大，但整体变化趋势基本一致。根据工程实际研制了基于动生涡流磁场的管道无损检测试验装置，开展了试验研究，得到了与仿真相同的规律性结果，从而验证了该技术的可行性，表明动生涡流磁场无损检测方法能够对管道缺陷进行精准定位与辨别。     

基于小波分析的涡流信号去噪处理

涡流检测方法是常规无损检测技术之一。但微小裂缝、穿孔引起的涡流检测信号很微弱，客易被各种噪声湮没，分辨起来较困难。用小波分析方法对涡流信号进行处理，能分辨出较微弱的缺陷信号，得到比较满意的结果。     

压力容器无损检测--涡流检测技术

综述了压力容器用管材制造和压力容器使用过程中的涡流检测技术，包括制造过程中的铁磁性钢管和非铁磁性金属管材的涡流检测技术、在用铁磁性钢管的远场涡流检测技术、在用非铁磁性金属管的涡流检测技术和金属压力容器壳体焊缝表面裂纹的复平面分析涡流检测技术。     

有限元方法用于涡流电磁场计算的有效性分析

利用有限元方法，对涡流检测中的电磁场问题进行数值计算，有助于涡流检测线圈的优化设计、检测缺陷的识别与定量，从而提高涡流检测的效果与精度。为验证有限元数值计算结果的有效性，对TEAM（Testing Electromagnetic Analysis Methods）组织提出的Workshop问题（Problem 15）进行了求解与分析。利用解析方法计算了空芯线圈的阻抗，然后通过二维有限元模型进行了阻抗求解，对比结果有较好的一致性。针对厚板上裂纹的涡流检测，建立了三维有限元计算模型，对影响计算结果的因素进行了分析，得到了比较好的数值模拟结果。     

Hardness profile plotting using multi-frequency multi-output electromagnetic sensor

Induction hardening technique was used to produce different case depths on nine AISI 1045 steel rods. Determining the optimum frequency for each depth below the surface, relations between eddy current outputs (primary and secondary voltages and normalized impedance) and hardness at each specific depth were investigated. Finally, the hardness values for each depth with the optimum eddy current output were determined and hardness profiles were plotted nondestructively. Comparisons were made with destructive hardness results.     

Characterization of ductile cast iron by eddy current method

Eddy current method was applied for evaluation of material properties of ductile cast iron. Measurements of eddy current response signals from FCD 450–600 grades of cast iron demonstrated good correlation with their hardness and tensile properties. Alternative ultrasonic method was explored for assessment of hardness of the studied samples and showed its inadequacy for specimens with similar graphite nodularity.     

Detection of milled 100Cr6 steel surface by eddy current and incremental permeance methods

Hard milling was applied to 100Cr6 steel of 50 HRC hardness using cutting tools with different flank wear. The modified surface layers were investigated by eddy current and incremental permeance measurements at magnetizing frequencies from 0.2 to 10 kHz. The signals were studied as a function of a low-frequency magnetic field applied to the sample. Both methods showed growth of magnetically harder peak in the measured curve with tool flank wear and magnetizing frequency increase. New parameters were introduced to evaluate the flank wear and corresponding surface damage in the material. The incremental permeance method showed much higher sensitivity comparing to the eddy current testing.     

On the Relationship of Magnetic Response to Microstructure in Cast Iron and Steel Parts

Nondestructive eddy current technique has long been used to detect discontinuities in materials. However, recently, its application has been extended to characterize materials' microstructure and properties. In the present article, four mild carbon steel bars with different chemical compositions (AISI 1015, 1035, 1045, and 1080) were obtained in annealed condition. Besides, to determine the effect of microstructure, six ductile cast iron bars with the same chemical composition and different pearlite contents were prepared. The pearlite percentage and estimated hardness values were determined by eddy current nondestructive technique, and the results were compared with the data obtained from conventional metallographic and hardness testing methods. The results indicate that the eddy current is a sensitive comparative technique to detect the microstructure (directly) as well as the mechanical (indirectly) changes of mild carbon steel and ductile cast iron parts.     

Magnetic NDT Technology for characterization of decarburizing depth

From practical point of view, determining the decarburizing depth is important in quality control of steel parts as it has undesirable effects on the mechanical properties such as hardness, wear and fatigue resistance. Traditional destructive methods of determining the depth of decarburized layer include metallographic and hardness test which are time-consuming and costly. Since response to eddy current is sensitive to chemical composition as well as microstructure of the material under consideration, the non-destructive method can be used in determining the depth of the decarburized layer in steel parts. It is mainly due to the difference in the microstructures, and as a result, in the magnetic properties of the decarburized layer with other parts of the specimen. In the present study at the first step, the magnetic properties of decarburized carbon steel bars (0.45 wt.% C) were evaluated using an electromagnetic sensor and correlated with the microstructure changes from surface to the core of the sample. At the second step the steel bars were held in 900 °C for different period of times and the depth of decarburizing layers were measured using hardness testing. Finally, the non-destructive eddy current technique was used and the response of test samples to the induction current including primary and secondary voltages, normalized impedance, phase angle and harmonic analysis parameters were investigated. Results show an acceptable accuracy in comparison to the destructive method.     

Relation between mechanical microhardness and impedance variations in eddy current testing

According to the state of the art, eddy current testing (EC) has a strong application in defect detection. The sensitivity to characterize defects and other parameters can be improved by an optimal choice of probes and operation frequency.The work discussed here is a study to materials microstructure characterization and especially the heat affected zones (HAZ) near welds using eddy current techniques.These zones are sometimes brittle and characterized by a microstructure gradient. The aim of this work is to study by eddy current the behavior of such cases. For each damage mechanism, the authors have prepared series of samples. These specimens were tested using NDT methods based on magnetic and electric properties.Electric conductive material samples were made of Aluminum and steel and heated at different temperatures with variable exposure times.The aluminum samples were then exposed to corrosion using an electrochemical process.The applied NDT methods can characterize grain size changes, microstructure types, micro structural changes, hardness changes after thermal treatment.The objective of our work is to detect some metallurgical characteristics by non-destructive methods. The characterization of the microstructure modifications by eddy currents allows detecting mechanical and metallurgical parameters of materials.     

电磁超声和涡流组合检测方法

两栖装甲车工作环境恶劣,车体尤其是底部容易破损。提出了一种电磁超声和涡流组合检测的快速方法,利用电磁超声的激励信号在被测金属表面感应的涡流,实现表面和近表面缺陷的涡流检测,无须额外增加专门的涡流线圈及其激励电路。设计了组合检测系统和探头,对带有表面缺陷和内部缺陷的装甲钢试块进行了检测试验。结果表明,该方法可以实现装甲钢试块内部缺陷和表面裂纹的检测,比单一的电磁超声检测或涡流检测能获取更全面的有用信号。     

加氢裂化在役高压空冷器翅片管束的涡流检测

针对炼油加氢高压空冷器翅片管的腐蚀特点,采用远场涡流和常规涡流检测技术相结合的方法进行检测。重点介绍了在役空冷器翅片管的涡流检测方法,并将检测结果和解剖结果进行了对比验证。对此表明,采用远场涡流和常规涡流相结合的方法可以比较准确可靠地检测出空冷器翅片管的腐蚀情况,为判断空冷器的使用情况提供了可靠的依据。     

磁饱和后的涡流检测信号的非涡流效应

系统地进行了实验规划和验证,最后应用等效源法对实验结果进行了分析。分析表明,钢管在磁饱和状态下的涡流检测信号并不是由涡流效应产生的,而是由漏磁场引起的。缺陷的漏磁信号可视为一等效电流源,产生的扰动磁场被调制在高频载波上而引起涡流仪的信号显示。     

预防性多滤波技术在丝材涡流检测中的应用研究

针对小径丝材检测的要求,介绍了一种基于预防性多滤波技术的新型涡流检测方法,从原理出发,比较了预防性多滤波涡流检测与常规涡流检测的不同,即在一个宽的、全面的频率带宽内设置了多个中心频率不同的带通滤波器,并通过试验得到预防性多滤波涡流检测在丝材检测中的周向灵敏度、端头盲区及检测灵敏度。通过检测应用证实能够有效检出宽度约为30 μm、深度为225.7 μm的纵向裂纹。