scholarly journals A Gradient-Field Pulsed Eddy Current Probe for Evaluation of Hidden Material Degradation in Conductive Structures Based on Lift-Off Invariance

Sensors ◽  
2017 ◽  
Vol 17 (5) ◽  
pp. 943 ◽  
Author(s):  
Yong Li ◽  
Haoqing Jing ◽  
Ilham Zainal Abidin ◽  
Bei Yan
Keyword(s):  
Eddy Current ◽  
Gradient Field ◽  
Material Degradation ◽  
Pulsed Eddy Current ◽  
Lift Off

Analysis of field uniformity and quantitative evaluation of subsurface pitting corrosion in conductors via GPEC

2020 ◽  
Vol 64 (1-4) ◽  
pp. 19-29
Author(s):  
Shuting Ren ◽  
Yong Li ◽  
Bei Yan ◽  
Jinhua Hu ◽  
Ilham Mukriz Zainal Abidin ◽  
...  
Keyword(s):  
Quantitative Evaluation ◽  
Eddy Current ◽  
Pitting Corrosion ◽  
Gradient Field ◽  
Uniform Field ◽  
Eddy Current Method ◽  
Optimal Position ◽  
Pulsed Eddy Current ◽  
Field Uniformity ◽  
Processing Algorithms

Structures of nonmagnetic materials are broadly used in engineering fields such as aerospace, energy, etc. Due to corrosive and hostile environments, they are vulnerable to the Subsurface Pitting Corrosion (SPC) leading to structural failure. Therefore, it is imperative to conduct periodical inspection and comprehensive evaluation of SPC using reliable nondestructive evaluation techniques. Extended from the conventional Pulsed eddy current method (PEC), Gradient-field Pulsed Eddy Current technique (GPEC) has been proposed and found to be advantageous over PEC in terms of enhanced inspection sensitivity and accuracy in evaluation and imaging of subsurface defects in nonmagnetic conductors. In this paper two GPEC probes for uniform field excitation are intensively analyzed and compared. Their capabilities in SPC evaluation and imaging are explored through simulations and experiments. The optimal position for deployment of the magnetic field sensor is determined by scrutinizing the field uniformity and inspection sensitivity to SPC based on finite element simulations. After the optimal probe structure is chosen, quantitative evaluation and imaging of SPC are investigated. Signal/image processing algorithms for SPC evaluation are proposed. Through simulations and experiments, it has been found that the T-shaped probe together with the proposed processing algorithms is advantageous and preferable for profile recognition and depth evaluation of SPC.

scholarly journals The Effects of Lift-Off from Wall Thinning Signal in Pulsed Eddy Current Testing

2012 ◽  
Vol 17 (4) ◽  
pp. 298-301 ◽  
Author(s):  
Duck-Gun Park ◽  
C.S. Angani ◽  
M.B. Kishore ◽  
C.G. Kim ◽  
D.H. Lee
Keyword(s):  
Eddy Current ◽  
Eddy Current Testing ◽  
Current Testing ◽  
Pulsed Eddy Current ◽  
Wall Thinning ◽  
Lift Off

An approach to reduce lift-off noise in pulsed eddy current nondestructive technology

2014 ◽  
Vol 63 ◽  
pp. 1-6 ◽  
Author(s):  
Yating Yu ◽  
Yue Yan ◽  
Fei Wang ◽  
GuiYun Tian ◽  
Dejun Zhang
Keyword(s):  
Eddy Current ◽  
Pulsed Eddy Current ◽  
Lift Off

scholarly journals Lift-off Invariant Inductance of Steels in Multi-Frequency Eddy-Current Testing

2021 ◽  
Author(s):  
Mingyang Lu ◽  
Xiaobai Meng ◽  
Ruochen Huang ◽  
Liming Chen ◽  
Anthony Peyton ◽  
...  
Keyword(s):  
Eddy Current ◽  
High Accuracy ◽  
Eddy Current Testing ◽  
Current Testing ◽  
Pulsed Eddy Current ◽  
Working Frequency ◽  
Lift Off ◽  
Ferromagnetic Steels ◽  
Point Of Intersection ◽  
Steel Properties

Eddy current testing can be used to interrogate steels but it is hampered by the lift-off distance of the sensor. Previously, the lift-off point of intersection (LOI) feature has been found for the pulsed eddy current (PEC) testing. In this paper, a lift-off invariant inductance (LII) feature is proposed for the multi-frequency eddy current (MEC) testing, which merely targets the ferromagnetic steels. That is, at a certain working frequency, the measured inductance signal is found nearly immune to the lift-off distance of the sensor. Such working frequency and inductance are termed as the lift-off invariant frequency (LIF) and LII. Through simulations and experimental measurements of different steels under the multi-frequency manner, the LII has been verified to be merely related to the sensor parameters and independent of different steels. By referring to the LIF of the test piece and using an iterative inverse solver, one of the steel properties (either the electrical conductivity or magnetic permeability) can be reconstructed with a high accuracy.

Pulsed Eddy-Current Measurements of Corrosion and Cracking in Aging Aircraft

1997 ◽  
Vol 503 ◽  
Author(s):  
J. C. Moulder ◽  
J. A. Bieber
Keyword(s):  
Eddy Current ◽  
Current System ◽  
Fatigue Cracks ◽  
Single Frequency ◽  
Pulsed Eddy Current ◽  
Wide Range ◽  
Lift Off ◽  
Hidden Corrosion ◽  
Time Gating

ABSTRACTPulsed, or transient eddy-current methods are an effective tool for quantitative characterization of hidden corrosion and cracking in multi-layer aircraft structures. Eddy currents are the method of choice for this task, since they penetrate multiple layers of metal, whether or not the layers are mechanically bonded. The pulsed eddy-current technique is an important advance over conventional eddy-current methods because it rapidly acquires data over a wide range of frequencies, thereby providing more information than a conventional, single-frequency eddy-current instrument. We have combined a pulsed eddy-current instrument with a portable two-axis scanner to produce an instrument capable of rapidly scanning aircraft lap splices in situ, producing pseudo-color images that reveal hidden corrosion or cracking. A unique feature of time-domain eddy-current data is the ability to selectively filter clutter from the image by time-gating the pulsed signal. Time-gating permits the user to select the inspection depth, thereby eliminating interference from upper layers, air gaps, lift-off variation and fasteners. By using a theoretical model of the pulsed eddy-current system, it is possible to interpret the data quantitatively, yielding quantitative maps of corrosion damage. Some of the same advantages of the pulsed eddycurrent technique apply to the characterization of hidden fatigue cracks as well, although the tieory for crack signals is less advanced.

Measurement of Wall Thinning through Insulation with Ferromagnetic Cladding Using Pulsed Eddy Current Testing

2011 ◽  
Vol 301-303 ◽  
pp. 426-429
Author(s):  
Zhi Yuan Xu ◽  
Xin Jun Wu ◽  
Chen Huang ◽  
Yi Hua Kang
Keyword(s):  
Eddy Current ◽  
Steel Plate ◽  
Thickness Measurement ◽  
Measurement Range ◽  
Galvanized Steel ◽  
Shielding Effect ◽  
Pulsed Eddy Current ◽  
Wall Thinning ◽  
The Common ◽  
Lift Off

Pulsed eddy current (PEC) technique has been successfully used for measuring wall thinning of carbon steel equipments without removal of the insulation. In field applications, the probe performance decreases in presence of ferromagnetic claddings. This paper presents a method based on saturation magnetization to solve this problem. The main principle of this method is to weaken the magnetic shielding effect of the cladding by magnetizing it to saturation. A U-shaped magnetizer is designed to realize this method. Contrast experiments are performed on a Q235 steel plate covered by a galvanized steel cladding. The experiment results show that the thickness measurement range and lift-off range are increased by applying this method to the common PEC probe.

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