Electromagnetic Methods Of Nondestructive Testing Research Articles

Analytical Solutions to Eddy-Current-Induced Field in Cylindrical Conductor Considering Velocity Effect

Electromagnetic nondestructive testing methods to inspect metal rods and pipes are widely used in industrial production. When the scanning speed of the electromagnetic coil is close to the magnitude of eddy current diffusion speed in conductive specimens, the coil motion will significantly affect the distribution of the eddy current field and detection signal. In this article, based on the basic equations and boundary conditions of electromagnetic field problems for moving conductors, the eddy-current analytical model of coaxial relative motion between the coil and the cylindrical conductor rod is solved by using Fourier transform method, and the impedance change expression of the pick-up coil is obtained. The theoretical results are in excellent agreement with the experimental results, which verify the analytical expression of impedance change. Furthermore, the effects of a conductor moving velocity and excitation frequency on impedance-change modulus values for differential and absolute pick-up coils are analyzed, respectively. The theoretical methods proposed in this article quantitatively analyze the velocity effect on the eddy current field, which can be applied to fast real-time eddy current testing for conductive specimens.

Electromagnetic and magnetic methods of non-destructive testing for control of damage accumulation in structural steels and alloys (review)

Control of the stress-strain state, compressive and tension stresses, accumulated fatigue damage is one of the goals of non-destructive testing. We consider data of current research in the field of eddy current and electromagnetic methods of non-destructive testing aimed at solving the problem of monitoring the accumulated damage in structural steels and alloys. Developments for practical implementation of the coercive force method, the eddy current structurescopy of non-magnetic materials, the method of higher harmonics and remanence-based control, the method of magnetic noise (Barkhausen noise) are considered. The physical foundations of non-destructive testing methods are considered along with their brief comparative analysis. Examples of non-destructive testing of critical units, such as operating oil and gas pipelines, aircraft parts, bearing parts, pressure vessels, crane parts, etc. are given. The possibility of using the eddy current method for control of the austenitic phase of cold rolled austenitic steels (AISI 304, AISI 321, AISI 316) is analyzed. The examples of static and fatigue tests of the samples of various steels and alloys are given: St3, St20, St45, D16T, AMg6, AMg6N, 12Kh18N9T, 08Kh18N9, 40Kh, R91. Metrology issues and the impact of interfering parameters affecting the measurement error are considered. The equipment used for a number of methods is discussed. Conclusions regarding the limits of applicability and limitations of the considered methods are drawn. The review provides links to both the fundamental works in the field of electromagnetic structurescopy and to modern research in this area which is important for the practical implementation of the devices based on electromagnetic and magnetic methods of non-destructive testing.

Guest Editorial: Recent Advances in Non-destructive Testing Methods

A wide range of engineering and geoscience applications today rely on the extensive employment of specialist non-destructive testing (NDT) methods. The standalone use of these techniques has become established in many areas given the research progress achieved in the use of electrical, electromagnetic, optical and acoustic NDT methods. The capabilities and potential of these methods have been comprehensively explored and assessed, bringing research up to date. Research efforts have been mostly focussed on achieving new theoretical developments, the advancement of hardware and software components, and on finding new surveying and data processing methods and interpretations. As a result of this, the standard of quality is excellent, and data can be collected very accurately with available technology. At the same time, the concept of integration between sensing methodologies, in terms of modelling data of different scale domains and resolutions, is becoming a real challenge within the scientific community, and is starting to be recognised as a key research area that could drastically enhance the capabilities of existing NDT technology when faced with new and complex scenarios. This trend is driven by an increase in the demand for more effective solutions for the investigation of non-conventional scenarios. These investigations need to be carried out while maintaining reasonable costs and within feasible time requirements, as multiple methods and equipment and interdisciplinary expertise are involved.

A wall-thinning measuring method based on magnetic permeability perturbation

In the determination of metal thickness by traditional electromagnetic nondestructive testing methods, the material’s electrical conductivity and magnetic permeability are required but practically unavailable or inexact. In this paper, a wall-thinning measuring method based on magnetic permeability variation of steel pipes is proposed. The direct current magnetization is applied to the ferromagnetic material, the internal magnetic field perturbation caused by the wall-thinning brings the permeability perturbation in the surface layer and be sensed by eddy current probe. The simulation results show that the permeability perturbation is closely related to wall thickness loss. The experiment results show that the signal amplitude increases with the thickness of the wall-thinning and the new method can measure the 10% wall-thinning of pipe. Finally, theoretical range of magnetization current values are discussed. The new method takes advantage of the changes in permeability and is not limited by thickness of object to be detected.

A Millimetre-wave Probe for Fast Screening and Evaluation of Corrosion in Planar Conductors: Numerical Simulations

Planar conductors are commonly used in critical mechanical structures. Due to high-temperature and high-pressure environment, corrosion may occur in in-service planar conductors, and seriously threatens structural integrity and safety. Hence, it is indispensable to detect and evaluate corrosion using Non-destructive Testing (NDT) techniques before structural failure. As a technique complementary to other Electromagnetic NDT methods, Microwave NDT is found to be advantageous in terms of high efficiency and accuracy in inspection of conductors subject to surface flaws. In this paper, a millimetre-wave probe for efficient detection and evaluation of corrosion in planar conductors is proposed and intensively investigated via simulation. A 3D Finite Element (FE) model of the proposed probe is established based on electromagnetic wave theory. The characteristics of the microwave propagation along with the mechanism regarding corrosion detection are intensively analysed. The probe structure and parameters are subsequently optimised in an effort to enhance the detectability, sensitivity and accuracy in corrosion evaluation. Besides, signal processing techniques involving extraction of features from the S-parameter in the function of frequency are investigated.

Development of electromagnetic NDT methods for structural integrity assessment

Nondestructive testing (NDT) methods are widely used for inspection of long term exploited structures as important part of maintenance strategy. NDT methods can create the background for material optimization under the engineering procedures (e.g., welding) influence also. Principal attention taken into consideration is the investigation of the correlations between measured nondestructively material properties (e.g., specific electrical conductivity, coercive force) and parameters of fatigue crack growth resistance (FCGR) needed for residual life estimation. In this study the evaluation of aluminum alloys (AA) degradation in aging aircraft and AA welded joints characterization based on the specific electrical conductivity (SEC) measurements are presented. Eddy current (EC) device for local noncontact SEC with lift off suppression was developed. For ferrous steel components (steam pipelines, ship bearing elements) the NDT method based on coercive force (CF) measurements by attachable type probes are applied. The EC method based on the magnetic anisotropy (MA) changes under mechanical stress was proposed.

Thickness Measurement of Metal Plates Using Swept-Frequency Eddy Current Testing and Impedance Normalization

Electromagnetic nondestructive testing signals generally change with the electromagnetic properties of the test objects. In the determination of metal thickness by electromagnetic nondestructive testing methods, the material's electrical conductivity and magnetic permeability are required but practically unavailable or inexact. This paper investigated the use of swept-frequency eddy current testing (SFECT) and impedance normalization to measure a metal plate's thickness, without the prior knowledge of its exact conductivity and permeability. Analytical and experimental studies were conducted separately on nonmagnetic and ferromagnetic metal plates. For nonmagnetic metal plates, it was found that the plate thickness can be determined by using the extreme values (maximum or minimum) of the normalized SFECT impedances' phases. For ferromagnetic metal plates, phase and resistance of very low frequency normalized impedance were found to be “permeability-independent,” and a conductivity-insensitive function was constructed. The thickness of a ferromagnetic plate was evaluated by using this function. This paper concludes that it is possible to measure a metal plate's thickness by SFECT and impedance normalization even without the prior knowledge of the conductivity and permeability of the test object.

Evaluation of chloride contamination in concrete using electromagnetic non-destructive testing methods

We present the results of the sensitivity of some electromagnetic non-destructive testing (NDT) methods to chloride contamination. The NDT methods are resistivity, using a quadripole probe, capacitive technique, with few sets of electrodes, and radar technique, using different bistatic configurations. A laboratory study was carried out involving three different concretes with different water to cement ratios. The concretes were conditioned with different degrees of NaCl saturation by means of three solutions containing 0g/L, 30g/l or 120g/l. The solution was homogenized in the concrete by using a specific procedure. Results show that the EM techniques are very sensitive to the chloride content and saturation rate and, on a second level, to the porosity. Multi-linear regression processing was performed to estimate the level of sensitivity of the NDT measurements to the three indicators. Values of ten ND observables are presented and discussed. At last, the uncertainties of the regression models are studied on a real structure in a tidal zone.

Electromagnetic Nondestructive Testing by Perturbation Homotopy Method

Now electromagnetic nondestructive testing methods have been applied to many fields of engineering. But traditional electromagnetic methods (usually based on least square and local iteration) just roughly give the information of location, scale, and quality. In this paper we consider inverse electromagnetic problem which is concerned with the estimation of electric conductivity of Maxwell's equations (2D and 3D). A perturbation homotopy method combined with damping Gauss-Newton methods is applied to the inverse electromagnetic problem. This method differs from traditional homotopy method. The structure of homotopy function is similar to Tikhonov functional. Sets of solutions are produced by perturbation for every homotopy parameterλ=λi,i=0,…,L. At each iterative step of the algorithm, we add stochastic perturbation to numerical solutions. The previous solution and perturbation solution are regarded as the initial value in the next iteration. Although the number of solution in set increased, it increased the likelihood of obtaining correct solution. Results exhibits clear advantages over damping Gauss-Newton method and testify that it is an available method, especially on aspects of wide convergence and precision.

Utilization of two-directional AC current distribution for enhancing sizing ability of electromagnetic nondestructive testing methods

This paper proposes a novel method for accurately evaluating the depth of a defect using electromagnetic phenomena. The novel method induces AC currents inside a conductive medium and detects the disturbance of the currents. Whereas the principle itself has been utilized in conventional methods, the uniqueness of this new method lies in realizing a current distribution in which there is a region where currents near the surface and those deeply inside the specimen flow opposite to each other. The novel method provides a clear indication corresponding to the depth of the inspected defect. In addition, it enables one to evaluate the depth of a defect that is much deeper than the depth of penetration. After the physical background of this new method is explained, the results of experimental verifications and subsequent numerical simulations are presented.

Recent advancement of electromagnetic nondestructive inspection technology in Japan

In this paper, the electromagnetic nondestructive testing (NDT) of present interest for research and industrial applications in Japan is described. Besides ac and pulsed eddy-current testing, magnetic flux leakage testing, passive magnetic flux leakage for characterization of material degradation, and various inversion techniques are presented. Both simulation and experimental results are used to demonstrate validity of the electromagnetic NDT methods.

Flux density measurement in ferromagnetic tubular product: Spierer E.D. Electromagnetic Methods of Nondestructive Testing. Edited by William Lord. Nondestructive Testing Monographs and Tracts, Vol. 3, pp. 161–173. Gordon and Breach Science Publishers (1985)

Flux density measurement in ferromagnetic tubular product: Spierer E.D. Electromagnetic Methods of Nondestructive Testing. Edited by William Lord. Nondestructive Testing Monographs and Tracts, Vol. 3, pp. 161–173. Gordon and Breach Science Publishers (1985)

Capacitor discharge magnetization of oil country tubular goods: Moake, G.L.; Stanley, R.K. Electromagnetic Methods of Nondestructive Testing. Edited by William Lord. Nondestructive Testing Monographs and Tracts, Vol. 3, pp. 151–160. Gordon and Breach Science Publishers (1985)

Capacitor discharge magnetization of oil country tubular goods: Moake, G.L.; Stanley, R.K. Electromagnetic Methods of Nondestructive Testing. Edited by William Lord. Nondestructive Testing Monographs and Tracts, Vol. 3, pp. 151–160. Gordon and Breach Science Publishers (1985)

Basic principles of magnetic flux leakage inspection systems for the evaluation of oil country tubular goods: Stanley, R.K. Electromagnetic Methods of Nondestructive Testing. Edited by William Lord. Nondestructive Testing Monographs and Tracts, Vol. 3, pp. 97–149. Gordon and Breach Science Publishers (1985)

Basic principles of magnetic flux leakage inspection systems for the evaluation of oil country tubular goods: Stanley, R.K. Electromagnetic Methods of Nondestructive Testing. Edited by William Lord. Nondestructive Testing Monographs and Tracts, Vol. 3, pp. 97–149. Gordon and Breach Science Publishers (1985)

Flaw detection in mine hoist transportation systems : Electromagnetic Methods of Nondestructive Testing. Edited by Williams Lord. Nondestructive Testing Monographs and Tracts, Vol. 3, pp. 35–69. Gordon and Breach Science Publishers (1985)

Flaw detection in mine hoist transportation systems : Electromagnetic Methods of Nondestructive Testing. Edited by Williams Lord. Nondestructive Testing Monographs and Tracts, Vol. 3, pp. 35–69. Gordon and Breach Science Publishers (1985)

Magnetic flux leakage inspection of wire rope : Electromagnetic Methods of Nondestructive Testing. Edited by William Lord. Nondestructive Testing Monographs and Tracts, Vol. 3, pp. 21–33, Gordon and Breach Science Publishers (1985)

Magnetic flux leakage inspection of wire rope : Electromagnetic Methods of Nondestructive Testing. Edited by William Lord. Nondestructive Testing Monographs and Tracts, Vol. 3, pp. 21–33, Gordon and Breach Science Publishers (1985)

Eddy current inspection of steam generator tubing : Electromagnetic methods of nondestructive testing. Edited by William Lord. Nondestructive testing monographs and tracts, vol. 3, pp. 175–193. Gordon and Breach Science Publishers (1985)

Eddy current inspection of steam generator tubing : Electromagnetic methods of nondestructive testing. Edited by William Lord. Nondestructive testing monographs and tracts, vol. 3, pp. 175–193. Gordon and Breach Science Publishers (1985)

Pulsed eddy current flaw detection and flaw characterization Electromagnetic methods of nondestructive testing. Edited by William Lord. Nondestructive testing monographs and tracts, Vol. 3, pp. 307–320. Gordon and Breach Science Publishers (1985)

Pulsed eddy current flaw detection and flaw characterization Electromagnetic methods of nondestructive testing. Edited by William Lord. Nondestructive testing monographs and tracts, Vol. 3, pp. 307–320. Gordon and Breach Science Publishers (1985)

Multifrequency eddy current examination of heat exchanger tubing : Electromagnetic methods of nondestructive testing. Edited by William Lord. Nondestructive testing monographs and tracts, vol. 3, pp. 195–305 Gordon and Breach Science Publishers (1985)

Multifrequency eddy current examination of heat exchanger tubing : Electromagnetic methods of nondestructive testing. Edited by William Lord. Nondestructive testing monographs and tracts, vol. 3, pp. 195–305 Gordon and Breach Science Publishers (1985)

Eddy current inspection of steam generator tubing Electromagnetic methods of nondestructive testing. Edited by William Lord. Nondestructive testing monographs and tracts, vol. 3, pp. 175–193. Gordon and Breach Science Publishers (1985)

Eddy current inspection of steam generator tubing Electromagnetic methods of nondestructive testing. Edited by William Lord. Nondestructive testing monographs and tracts, vol. 3, pp. 175–193. Gordon and Breach Science Publishers (1985)