共查询到19条相似文献,搜索用时 62 毫秒
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脉冲涡流技术是一种可以对飞机多层结构中缺陷实施有效检测的方法。交变磁场测量技术是一种精确测量表面裂纹的非接触式无损检测方法。提出了脉冲涡流磁场测量(PECFM)技术,并对其进行了理论分析。在设计了相应传感器的基础上,对多层铝板结构中的缺陷进行了检测实验,实验结果与理论分析相一致。实验证明PECFM技术可以有效地实现多层结构中缺陷的识别与定量检测。可以预见,PECFM技术将会在无损检测领域中发挥很大的作用。 相似文献
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传统脉冲涡流检测技术对缺陷的检测灵敏度不高,需采用差分的方法来增强缺陷信息.本文提出了一种改进型的脉冲涡流无损检测方法,其无需差分就可以对缺陷进行定量,具有较大的理论价值和应用价值,采用改进的脉冲涡流技术对腐蚀缺陷的深度和体积进行了检测,并采用一种新的"频谱分离点"的腐蚀缺陷识别方法,提高了腐蚀缺陷分类识别的正确率. 相似文献
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脉冲涡流无损检测技术对矩形截面形状的裂纹具有良好的定量检测能力,但是,实际检测过程中遇到的裂纹缺陷的形状非常复杂,本文在前期工作的基础上,进一步研究了脉冲涡流对其它截面形状裂纹的定量检测问题,实验结果表明以前针对矩形裂纹的方法也完全适用于其它截面形状裂纹的定量检测。 相似文献
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长期以来,脉冲涡流检测中铁磁材料的磁导率多被视为常数,但这种简化的合理性及其影响尚缺乏充分的证明.本文基于有限元法,建立了探头置于Q235钢板上方的脉冲涡流检测模型,研究了钢板磁导率的空间分布和时间变化规律及其对探头信号的影响,并进行了实验验证.结果表明:钢板中瞬态磁场的工作点与激励电流幅值有关,增大激励电流,磁场可能超出磁化曲线的起始磁化区而进入到瑞利区甚至陡峭区;由于磁导率非线性的影响,激励方波高、低电平段的感应电压信号不成奇谐对称,高电平段的晚期感应电压比低电平段的大;钢板浅层磁导率的变化显著,不能简化为常数,而深层的磁导率变化很小,可视为常数. 相似文献
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A comprehensive review of advancements in eddy current (EC) modeling is presented. This paper contains three main sections: a general treatise of EC theory, the thin skin EC forward modeling, and the EC inverse problem. (1) The general treatise of eddy current theory begins with an exposition of the reciprocity formulas for evaluating probe impedance changes, which are derivable from first principles. Two versions of the reciprocity formulas, one with a surface integral and the other with a volume integral, are given. Any particular type of defect, as well as both one-port and two-port probes, can be treated. Second, a brief account of analytical and numerical methods for calculating the field distributions is presented. Third, theory of probe/material interactions with various defect types is described. (2) The paper then proceeds to the forward modeling section, which contains a detailed treatment of the eddy current forward problem for surface breaking cracks and EDM notches in the thin skin approximation. (3) The inverse problem section begins with a general review of commonly used inversion methods, exemplified by selected references from the literature, followed by more detailed examinations of EC inversions for surface breaking cracks and slots. The last part of this section is devoted to the inverse problem for layered structures. Although being a review in nature, the paper contains a number of new accounts for time-domain eddy current interactions. In particular, a modification is proposed to the reciprocity formula in order to take a better account of pulsed eddy current signals. 相似文献
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结合实际涡流无损检测应用中的含磁介质点探头的特点,分析了探头中磁介质引入的各种附加效应及其对缺陷阻抗的影响。通过引入等效电流的概念,讨论了磁介质对涡流场的作用,建立含磁介质点探头涡流无损检测模型,并给出含磁介质探头周围的电磁场方程,求得均匀半无限导体系统的磁矢量势分布和导体中涡流、电场强度分布。通过实例,计算了非铁磁性导体中无缺陷时探头信号与提离高度的关系、存在缺陷时探头阻抗变化的特点。理论计算与实验结果基本吻合。 相似文献
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电涡流传感器阵列测试技术 总被引:17,自引:1,他引:17
针对采用扁平柔性电涡流传感器阵列实现大面积金属曲面部件位置实时监测,对电涡流传感器的阵列测试技术进行了研究.采用一种基于时分多路的电涡流阵列测试的方法,通过对传感器探头和测试电路的合理设计,使系统电路得到简化,减小阵列单元之间的串扰,提高传感器系统的测试性能,实现了电涡流传感器阵列的快速、高精度测量. 相似文献
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Time-Frequency Analysis of Pulsed Eddy Current Signals 总被引:9,自引:0,他引:9
M. S. Safizadeh B. A. Lepine D. S. Forsyth A. Fahr 《Journal of Nondestructive Evaluation》2001,20(2):73-86
Detection and measurement of the material loss due to corrosion in aircraft fuselage lap splices are of great importance to life management of ageing aircraft. Pulsed eddy current (PEC) techniques have shown the potential to fully characterise these structures. However, variations in the probe lift-off, the interlayer gaps and material thinning produce similar PEC signals, making signal interpretation very difficult. This paper describes time-frequency analysis algorithms applied to pulsed-eddy current signals from lap-joint specimens containing simulated flaws. The effect of probe lift-off, interlayer gap, and material thinning on PEC signals is examined in three-dimensional space (amplitude-time-frequency). This study shows that the time-frequency analysis of PEC signals provides specific visual patterns that can be related to the interlayer gap, lift-off, and material loss. 相似文献
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L. Bettaieb M. Poloujadoff A. Sentz H. J. Krause 《Research in Nondestructive Evaluation》2013,24(3):159-177
Nondestructive evaluation (NDE) is often conducted by inducing eddy currents in the materials to be examined, and characterizing those currents by the magnetic fields that they produce. Most papers describe experimental results produced by such methods; very few theoretical approaches have been proposed. In the present article, we develop some particularly very simple but ad-hoc analytical studies, notably in the case of various calibrated flaws such as cracks. The validity of the models has been checked with a classical High Tc radio frequency SQUID, which is described. Theory and measurement have been found to be in good agreement. 相似文献
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材料的红外无损检测技术及其进展 总被引:5,自引:0,他引:5
目的 介绍材料的红外无损检测以及红外无损检测技术这一领域的最新进展 .方法 综述了材料的红外无损检测技术的理论基础和影响其测试精度的因素 ,以及国内外的进展 .结果与结论 红外无损检测技术可检测到其它检测技术所无法检测的区域 ,与其它检测技术有互补的作用 .作者综述了这种技术在近年来比较活跃的几个方面 相似文献