scholarly journals Evaluation of Eddy Current Response Due to the Applied Stress on a Steel Plate Using Phase Diagram

2020 ◽  
Author(s):  
Sanjeema Bajracharya ◽  
Eiichi Sasaki
Keyword(s):  
Phase Diagram ◽  
Stress State ◽  
Relative Permeability ◽  
Eddy Current ◽  
Steel Plate ◽  
Stress Measurement ◽  
Excitation Frequency ◽  
Steel Structures ◽  
Probe Size ◽  
Lift Off

Structural health monitoring of steel structures is crucial for inspection of corrosion and cracking in structural members, compromising their safety and serviceability. In the present study, the prospective of evaluation of change in stress state of structural member due to corrosion and cracking through eddy current based stress measurement is investigated. For this, three-dimensional numerical simulations are carried out in the FE software COMSOL Multiphysics 5.2a for a steel plate subjected to change in relative permeability, representative of change in stress state, whereby the eddy current indices are characterized, including the effects of additional influential parameters namely, lift-off, excitation frequency, and probe size. Phase Diagram is then proposed as a concise method to evaluate the variation of relative permeability and lift-off concurrently in a single graph for an excitation frequency and probe size. It further facilitates the selection of suitable excitation frequency and probe size to conduct the eddy current based stress measurement.

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.

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.

scholarly journals Investigate the effect of lift-off on eddy current signal for carbon steel plate

2018 ◽  
Vol 225 ◽  
pp. 06005
Author(s):  
Moneer A Faraj ◽  
Fahmi Samsuri ◽  
Ahmed N AbdAlla ◽  
Damhuji Rifai ◽  
Kharudin Ali ◽  
...  
Keyword(s):  
Eddy Current ◽  
Steel Plate ◽  
Current Signal ◽  
Independent Variables ◽  
Investigation Methods ◽  
Interaction Equation ◽  
Lift Off ◽  
The Relationship ◽  
Factor Interaction ◽  
Two Independent Variables

In this study, the effect of various factors like lift-off and depth defect on the eddy current signal was investigated. Investigation methods like response surface methodology (RSM) and composed central design (CCD) were employed to establish the relationship between lift-off distance, depth of a defect and the eddy current signal by the two-factor interaction equation, and would provide a reference in further to accurate the depth defect. The regression analysis suggested that eddy current signal was well fitted by the two-factor interaction equation (R2 = 0.9656). The eddy current signal was investigated by varying the levels of these two independent variables, in which all have significant influences on eddy current signal. There would be a change in the amplitude and when lift-off distance is altered, and lift off distance increased, the increase of the amplitude of output signal decrease gradually.

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.

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.

Design of orthogonal eddy-current probe for weld crack detection of carbon-steel plate

2020 ◽  
Vol 64 (1-4) ◽  
pp. 1347-1355
Author(s):  
Tao Chen ◽  
Xiaoqi Xiao ◽  
Lihong Zhang ◽  
Cheng Lv ◽  
Zhiyang Deng ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Eddy Current ◽  
Crack Detection ◽  
Steel Plate ◽  
Signal To Noise Ratio ◽  
Detection Sensitivity ◽  
Scanning Angle ◽  
Length Width ◽  
Lift Off ◽  
Detection Effect

Due to uneven surface and lift-off effect, it is difficult to detect weld crack by eddy-current testing. A new orthogonal eddy-current probe for weld crack detection of carbon-steel plate was designed in this paper. Based on COMSOL Multiphysics, the influence of scanning angle on detection sensitivity of the probe was compared firstly. Then, the effects of coil width, coil side length, detection coil height, and lift-off distance on detection sensitivity of the probe were studied, respectively. Finally, the test piece of carbon-steel plate weld with crack, and the physical probe used to verify the crack detection effect were made. The experimental results show that the weld crack of carbon-steel plate with length × width × depth of 20.0 mm × 0.3 mm × 1 mm can be effectively identified, and the lift-off noise can be effectively suppressed by the method presented in this paper. At the same time, the signal-to-noise ratio of the probe keeps constant in the lift-off distance range of 0.3 mm–3.0 mm.

scholarly journals Subsurface Defect Evaluation of Selective-Laser-Melted Inconel 738LC Alloy Using Eddy Current Testing for Additive/Subtractive Hybrid Manufacturing

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Sai Guo ◽  
Guanhui Ren ◽  
Bi Zhang
Keyword(s):  
Influencing Factors ◽  
Eddy Current ◽  
Excitation Frequency ◽  
Eddy Current Testing ◽  
Experimental Investigations ◽  
Hybrid Manufacturing ◽  
Current Testing ◽  
Lift Off ◽  
Inconel 738Lc ◽  
Subsurface Defects

AbstractNew materials and manufacturing technologies require applicable non-destructive techniques for quality assurance so as to achieve better performance. This study comprehensively investigated the effect of influencing factors including excitation frequency, lift-off distance, defect depth and size, residual heat, and surface roughness on the defect EC signals of an Inconel 738LC alloy produced by selective laser melting (SLM). The experimental investigations recorded the impedance amplitude and phase angle of EC signals for each defect to explore the feasibility of detecting subsurface defects by merely analyzing these two key indicators. Overall, this study revealed preliminary qualitative and roughly quantitative relationships between influencing factors and corresponding EC signals, which provided a practical reference on how to quantitively inspect subsurface defects using eddy current testing (ECT) on SLMed parts, and also made solid progress toward on-line ECT in additive/subtractive hybrid manufacturing (ASHM) for fabricating SLMed parts with enhanced quality and better performance.

scholarly journals Numerical Simulation on Stress Measurement with Eddy Current Thermography

2020 ◽  
Author(s):  
Shuwen Deng ◽  
Suixian Yang ◽  
Yong Yao
Keyword(s):  
Stress State ◽  
Temperature Distribution ◽  
Eddy Current ◽  
Material Properties ◽  
Stress Measurement ◽  
Heating Process ◽  
Parameter Distribution ◽  
Induction Current ◽  
Electromagnetic Characteristics ◽  
Nondestructive Testing Method

Stress in components will lead to the change of material properties and even failure. Therefore, the assessment for the stress state of components is play an important role in testing industry. As a non-contact and multi-physical field nondestructive testing method, eddy current thermography (ECT) can be applied to detect non-homogeneous electromagnetic characteristics parameter distribution in conductive materials. Internal stress and its distribution in a material will affect the value of electromagnetic characteristic parameters. If induction current applied on conductive material, the Joule’s heat, which generate in the sample will lead to the temperature rise on the surface of the specimen by induction heating process. The temperature distribution on the specimen surface can be recorded by infra camera and stored as IR images or videos. The feature of the temperature distribution and its variation can be used to express the stress state in the specimen. It is concluded that there is an approximate linear relationship between the surface temperature appreciation and the loading force when the excitation source condition remains unchanged.

Detection of internal defects in CFRP strengthened steel structures using eddy current pulsed thermography

2021 ◽  
Vol 282 ◽  
pp. 122642 ◽  
Author(s):  
Jing Xie ◽  
Changwei Wu ◽  
Lemei Gao ◽  
Changhang Xu ◽  
Yinsheng Xu ◽  
...  
Keyword(s):  
Eddy Current ◽  
Steel Structures ◽  
Internal Defects ◽  
Pulsed Thermography

scholarly journals Evaluation of Coating Thickness Using Lift-Off Insensitivity of Eddy Current Sensor

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 419
Author(s):  
Xiaobai Meng ◽  
Mingyang Lu ◽  
Wuliang Yin ◽  
Abdeldjalil Bennecer ◽  
Katherine J. Kirk
Keyword(s):  
Eddy Current ◽  
Coating Thickness ◽  
Thickness Measurement ◽  
Eddy Current Testing ◽  
Thickness Variation ◽  
Testing Technique ◽  
Current Testing ◽  
Thin Skin ◽  
Embedded Algorithms ◽  
Lift Off

Defect detection in ferromagnetic substrates is often hampered by nonmagnetic coating thickness variation when using conventional eddy current testing technique. The lift-off distance between the sample and the sensor is one of the main obstacles for the thickness measurement of nonmagnetic coatings on ferromagnetic substrates when using the eddy current testing technique. Based on the eddy current thin-skin effect and the lift-off insensitive inductance (LII), a simplified iterative algorithm is proposed for reducing the lift-off variation effect using a multifrequency sensor. Compared to the previous techniques on compensating the lift-off error (e.g., the lift-off point of intersection) while retrieving the thickness, the simplified inductance algorithms avoid the computation burden of integration, which are used as embedded algorithms for the online retrieval of lift-offs via each frequency channel. The LII is determined by the dimension and geometry of the sensor, thus eliminating the need for empirical calibration. The method is validated by means of experimental measurements of the inductance of coatings with different materials and thicknesses on ferrous substrates (dual-phase alloy). The error of the calculated coating thickness has been controlled to within 3% for an extended lift-off range of up to 10 mm.

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