共查询到19条相似文献,搜索用时 156 毫秒
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应用脉冲涡流检测金属表面裂纹的研究 总被引:1,自引:0,他引:1
脉冲涡流检测方法是涡流检测技术的一个新兴的分支.本文介绍了脉冲涡流检测技术应用于检测金属表面裂纹.实验结果表明:经综合考虑了裂纹深度、材质对测量结果的影响之后,发现裂纹深度和涡流信号幅值峰值之间有着深远的关联.借此可以初步的量化的判断裂纹深度. 相似文献
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电磁超声检测和涡流检测因其非接触、检测速度快、对试件表面要求低等优点而被广泛应用于金属材料的缺陷检测中,但电磁超声检测存在近表面的检测盲区,涡流检测对内部深层缺陷灵敏度不高。基于电磁超声和涡流的复合检测方法,设计了能同时满足电磁超声检测和涡流检测的复合式探头,建立了电磁超声和涡流复合检测有限元模型,并对金属试件中不同类型的缺陷进行了检测实验。仿真和实验结果表明,该复合探头不仅能快速检测表面裂纹,而且可激发出具有明显指向性的纵波,一定程度上削弱了波形转换产生的干扰波,可实现对内部缺陷的准确定位、识别,为电磁超声和涡流复合式检测技术在板材的复杂缺陷检测中的应用提供了基础。 相似文献
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本文针对连铸钢坯表面裂纹缺陷,采用小波分析方法模仿人工视觉对连铸钢坯表面图像信号进行模式识别检测,由此实现对热状态下连铸钢坯表面裂纹进行不间断检测。 相似文献
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提出了一种基于预多频涡流检测技术的钢球硬度分选系统,介绍了系统组成、工作原理及硬软件设计。该系统以工业控制PC机为核心,采用8个频率工作,通过对每个频率的测量信号的综合评价,可确定钢球的硬度。试验和实际生产应用均证明该系统可对钢球硬度进行100%自动分选,且灵敏度高,可靠性好。 相似文献
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S. I. Aks'onova A. P. Lyubchenko V. M. Uchanin V. Yu. Melanchuk B. V. Tykhomyrov S. I. Yavorovych 《Materials Science》2005,41(3):406-409
We describe a dynamic eddy current flaw detector for the testing of thin-walled brass tubes with rotation of the eddy current
transducer around them. We show that the eddy current method makes it possible to detect the greatest number of defective
tubes as compared with the visual and hydraulic-test methods. The productivity of the eddy current method is 8 – 10 times
as high as that of other methods. It enables one to evaluate the depths of defects and, correspondingly, the degree of their
danger by the signal amplitude of the eddy current flaw detector. We show the possibility to set an optimal reject criterion
and the corresponding level of operation of the threshold device of the flaw detector. The rejection of tubes with defects
deeper than the assigned value makes it possible to decrease the number of wrongly rejected tubes. The LEOTEST VD-5D dynamic
eddy current flaw detector was introduced in the technological process of full-scale locomotive production.
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Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 3, pp. 109 – 111, May – June, 2005. 相似文献
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Haiting Zhou Chi Xu Hongliang Pan Jianjun Chen 《Research in Nondestructive Evaluation》2018,29(4):212-220
Eddy current method has been recently developed to characterize mechanical properties of materials and assess internal hydrogen content of high strength low alloy steels. The application of eddy current testing in evaluating hydrogen embrittlement state of 2.25Cr-1Mo-0.25V ferritic steel has been investigated using tensile test and electrochemical hydrogen charging test. The relationship between the embrittlement index and eddy current signal is well established. It found that there is a good linear relation between the hydrogen-induced plasticity loss and the eddy current signal. This shows eddy current testing is an effective method for evaluating hydrogen embrittlement state of 2.25Cr-1Mo-0.25V steel. 相似文献
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This paper presents some recent studies dealing with flaw reconstruction using eddy current testing. The locations of parallel planar cracks in an Inconel 600 plate specimen are determined and the shapes of them are reconstructed at the same time using the signals from a multi-pancake coil probe. The reconstruction strategy, consisting of a data base used fast forward solver and a first order optimization algorithm, relies on the minimization of the nonlinear least square residual function. Validity of the inverse analysis method is investigated with respect to the influence of the arrangement of scanning paths. The efficiency of the computation is also discussed. 相似文献
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We present a new method for characterizing the performance of eddy current probes by mapping their electromagnetic fields. The technique is based on the photoinductive effect, the change in the impedance of an eddy current probe induced by laser heating of the material under the probe. The instrument we developed maps a probe's electric field distribution by scanning an infrared laser beam over a thin film of gold lying underneath the probe. Measurements of both photoinductive signals and flaw signals for a series of similar probes demonstrate that the impedance change caused by an electrical-discharge-machined (EDM) notch or a fatigue crack is proportional to the strength of the photoinductive signal. Thus, photoinductive measurements can supplant the use of artifact standards to calibrate eddy current probes. Furthermore, the shape and symmetry of the probe's field pattern can reveal defects in probe construction. By combining photoinductive measurements of a probe's field strength with a theoretical model, we are able to quantitatively predict the probe's performance under hypothetical conditions. To model commercial eddy current probes with ferrite cores, we developed a procedure to treat them as effective air-core probes. We obtained good agreement between the flaw signals calculated using this effective-coil approach and actual fatiguecrack signals measured with commercial probes. We also calculated probabilities of detection for target flaws in titanium alloys for a series of commercial probes. The results reveal how probe sensitivity can affect the reliability of an eddy current inspection.This article is dedicated to Professor Bertram A. Auld on the occasion of his 70th birthday and his retirement from Stanford University. 相似文献
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M. Khelil Jean-Hugh Thomas L. Simon R. El Guerjouma M. Boudraa 《Journal of Nondestructive Evaluation》2017,36(2):31
The aim of this study is to characterize the structural noise for a better flaw detection in heterogeneous materials (steels, weld, composites...) using ultrasonic waves. For this purpose, the continuous wavelet transform is applied to ultrasonic A-scan signals acquired using an ultrasonic non destructive testing (NDT) device. The time-scale representation provided, which highlights the temporal evolution of the spectral content of the A-scan signals, is relevant but can lead to misinterpretation. The problem is to identify if each pattern from the wavelet representation is due to the structural noise or the flaw. To solve this problem, a detection technique based on statistical significance testing in the time-scale plane is used. Information about the structural noise signals is injected into the decision process using an autoregressive model, which seems relevant according to the spectral content of the signal. The approach is tested on experimental signals, obtained by ultrasonic NDT of metallic materials (austenitic stainless steel) then on a weld in this steel and indeed enables to distinguish the components of the signal as flaw echoes, which differ from the structural noise. 相似文献
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The authors gather eddy current signals due to artificial stress corrosion cracking so that the data may be available to other researchers. Three cracks are introduced into an austenitic stainless steel plate, eddy current measurements are performed, and then the plate is destroyed to observe the cross-sectional profiles of the cracks. The authors will offer the data, as well as the true profile of the stress corrosion cracking revealed by destructive tests, to anybody who are interested in utilizing it in their studies. 相似文献