Finite Element Modeling of Remote-Field Eddy Current Problems for the Nondestructive Testing of Metal Tube

1989 ◽  
Vol 111 (2) ◽  
pp. 101-108 ◽  
Author(s):  
R. Palanisamy
Keyword(s):  
Finite Element ◽  
Nondestructive Testing ◽  
Wall Thickness ◽  
Eddy Current ◽  
Early Recognition ◽  
Detection Sensitivity ◽  
Oil Well ◽  
Phase Lag ◽  
Apparent Contradiction ◽  
Lift Off

The remote-field eddy current effect refers to a low frequency eddy current nondestructive testing (NDT) phenomenon in tubular conductors (magnetic or nonmagnetic) in which the behavior of both amplitude and phase of induced magnetic field are in apparent contradiction to the conventional eddy current theory. Equal detection sensitivity across the wall thickness, linear relationship between the output signal phase-lag and the wall thickness, and absence of the lift-off problem are some of the attractive and contradicting features of this technique. Despite its early recognition and useful application in down-hole inspection of oil-well casing, no development of adequate scientific base that could explain this phenomenon has been reported. This paper describes modeling of this phenomenon using the finite element numerical analysis technique. Amplitude and phase of the sensor coil output have been predicted using this model for different axisymmetric test geometries, material properties, and excitation frequencies.

scholarly journals Research on Detection Mechanism of Weld Defects of Carbon Steel Plate Based on Orthogonal Axial Eddy Current Probe

Sensors ◽  
2020 ◽  
Vol 20 (19) ◽  
pp. 5515
Author(s):  
Linnan Huang ◽  
Chunhui Liao ◽  
Xiaochun Song ◽  
Tao Chen ◽  
Xu Zhang ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Eddy Current ◽  
Steel Plate ◽  
Difficult Problem ◽  
Eddy Current Testing ◽  
Detection Sensitivity ◽  
Detection Mechanism ◽  
Current Testing ◽  
Weld Defects ◽  
Lift Off

The uneven surface of the weld seam makes eddy current testing more susceptible to the lift-off effect of the probe. Therefore, the defect of carbon steel plate welds has always been a difficult problem in eddy current testing. This study aimed to design a new type of eddy current orthogonal axial probe and establish the finite element simulation model of the probe. The effect of the probe structure, coil turns, and coil size on the detection sensitivity was simulated. Further, a designed orthogonal axial probe was used to conduct a systematic experiment on the weld of carbon steel specimens, and the 0.2 mm width and 1 mm depth of weld defects of carbon steel plates were effectively detected. The experimental results showed that the new orthogonal axial eddy current probe effectively suppressed the unevenness effect of the weld surface on the lift-off effect during the detection process.

Eddy Current Testing Probe to Improve the Defect Detection Sensitivity of Metal Tube

2014 ◽  
Vol 945-949 ◽  
pp. 1987-1990
Author(s):  
Si Quan Zhang ◽  
Yu Liu ◽  
Hao Jun Xu ◽  
Chang Yin
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Defect Detection ◽  
Eddy Current ◽  
Experimental Results ◽  
Detection Sensitivity ◽  
Metal Tube ◽  
Current Testing ◽  
Element Simulation ◽  
Axial Defects

The structure of conventional bobbin probe was modified to improve the detection sensitivity of defects in metal tube. Based on the results of finite element simulation, several types of modified probes are fabricated and used to detect artificial defects in tube and the defect signals are acquired and analyzed. The simulation and experimental results verified that the modified eddy current probes are more sensitive to non-axial defects than conventional bobbin probe and can improve the reliability of tube inspection.

Study on extraction of electrical runout in eddy current measurement using finite element method

2013 ◽  
Vol 228 (6) ◽  
pp. 1077-1086 ◽  
Author(s):  
Xiaolong Chen ◽  
Yanlong Cao ◽  
Zaiyu Lin ◽  
Jiangxin Yang ◽  
Xiaoqi Hu
Keyword(s):  
Finite Element ◽  
Relative Permeability ◽  
Imaginary Part ◽  
Eddy Current ◽  
Material Properties ◽  
Ferromagnetic Material ◽  
Current Sensor ◽  
The Real ◽  
Eddy Current Sensor ◽  
Lift Off

Electrical runout is a bottleneck problem of eddy current sensor, which is caused by the maldistribution/variation of material electromagnetic properties of measurement target. However, extraction methods of electrical runout in eddy current displacement measurement remain ambiguous. Here, a 2D finite element model for the influence analysis of conductivity and permeability of ferromagnetic material on coil impedance of eddy current sensor is reported, which will be beneficial for detecting material properties and guiding manufacturing process. The relationships between the real and imaginary part of coil impedance with the varied material conductivity, relative permeability and the lift-off, which indicates the detecting distance, are investigated. When the conductivity, relative permeability of ferromagnetic material and the lift-off vary within a certain range, the relationships between the real and imaginary part of coil impedance are all nearly linear. This paper further shows that the character of distribution of resistance and reactance in diagram under different material properties and same measuring distance is linear. Furthermore, these lines under different measuring distances are parallel. Also the character under different measuring distances and same material property is linear, but these lines under different material properties are diffuse with same intercept. Altogether, the study shows that this method based on redesign of signal processing and its circuit is feasible and instructive in separating electrical runout from the output of eddy current sensor.

A Novel Technique for Eliminating Probe Lift-Off in Eddy Current Nondestructive Testing

2013 ◽  
Vol 291-294 ◽  
pp. 2474-2478
Author(s):  
Bo Ye ◽  
Ming Li ◽  
Fang Zeng
Keyword(s):  
Nondestructive Testing ◽  
Eddy Current ◽  
Measurement Accuracy ◽  
Excitation Frequency ◽  
Eddy Current Testing ◽  
Basic Principles ◽  
Current Testing ◽  
Novel Technique ◽  
Simulation Results ◽  
Lift Off

The lift-off problem is a very important problem in eddy current testing, which will influence the measurement accuracy. This paper proposes a novel technique for eliminating the probe lift-off in eddy current nondestructive testing. Firstly, the basic principles and characteristics of eddy current testing were introduced. Secondly, this paper analyzed and studied the coil impedance responses caused by the variations of the probe lift-off. Based on simulation results, this paper presents that choosing proper probe excitation frequency can eliminate the disturbance of coil impedance caused by the lift-off, and obtains better results.

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