Eddy Current Testing Of Tubes Research Articles

Efficient calculation of transient eddy current response from multi-layer cylindrical conductive media.

The transient response from a transmitter-receiver coil system inside a multi-layer cylindrical conductive configuration is obtained. The particular set-up applies to well logging as well as to eddy current tube testing. In this work, a number of improvements are presented to existing models for an efficient calculation of the induced voltage. These include: domain truncation, novel treatment of arbitrary number of layers in order to avoid computational overflows and efficient time response calculation. The latter is based on a combination of Laplace inversion techniques for short- and long-time transient responses. This article is part of the theme issue 'Advanced electromagnetic non-destructive evaluation and smart monitoring'.

Высокопроизводительный вихретоковый контроль твердости труб с гладкостным покрытием

Высокопроизводительный вихретоковый контроль твердости труб с гладкостным покрытием

The influence of a bobbin probe's radial offset on eddy current testing of tubes

The influence of a bobbin probe's radial offset on eddy current testing of tubes

Virtual positioning and shaping of source fields for ECT of tubes

PurposeThe purpose of this paper is to present a new approach to drive the excitation field sources in the eddy current testing (ECT) of tubular conductive structures.Design/methodology/approachThe magnetic field used for ECT is generated by pairs of counter‐series connected coils, driven by AC currents. The phase and amplitude of the currents is electronically controlled in order to shape the primary field map, allowing circumferential sweeps until the presence of defects is detected, and then “focusing” the field on the defective section of the tube, increasing in this way the sensibility of the ECT probes in the targeted area, in order to determine with higher precision, the position, and the shape of the defect.FindingsIf suitably designed, the field measurement system allows to enable/disable a number of probes to enhance the resolution in the defect area while keeping low the number of required data channels.Research limitations/implicationsThe analyzed geometry is limited to circular‐shaped tubes, of infinite extent. Future work should be on the extension of the methodology to general shapes, and to finite length cylinders.Practical implicationsThe proposed method allows to enhance resolution in ECT of tubes at the end of production lines, guaranteeing a first, simple yet effective quality assessment of tubes in industrial environments.Originality/valueThe paper presents a new technique to test conductive tubes using fixed excitation system, but allowing to focus magnetic field in defective regions. The method could be helpful for industrial diagnostics.

End effect modelling in eddy current tube testing with bobbin coils

A semi-analytical method for modelling electromagnetic fields is applied to eddy current nondestructive evaluation (NDE) to simulate the end effect in tube testing with bobbin coils. The boundary value problem is formulated in terms of the magnetic vector potential and is solved using orthogonal eigenfunctions, the eigenvalues of which are computed as roots of a transcendent complex equation. Closed-form expressions are derived for the impedance change of the coil and the induced eddy currents. The results are in excellent agreement with those obtained by a 2D-finite element package.

Analytical Modeling of Wobble in Eddy Current Tube Testing with Bobbin Coils

By utilizing the second-order vector potential formulation we solve the eddy current problem of a coil inside a conductive tube and in an offset position to it. The study focuses on the derivation of a closed-form expression for the impedance change of the coil, which is used to calculate the signal produced by wobble in eddy current testing of tubes with bobbin coils.

Analytical Modeling of Wobble in Eddy Current Tube Testing with Bobbin Coils

By utilizing the second-order vector potential formulation we solve the eddy current problem of a coil inside a conductive tube and in an offset position to it. The study focuses on the derivation of a closed-form expression for the impedance change of the coil, which is used to calculate the signal produced by wobble in eddy current testing of tubes with bobbin coils.

Analytical Modeling of Wobble in Eddy Current Tube Testing with Bobbin Coils

Analytical Modeling of Wobble in Eddy Current Tube Testing with Bobbin Coils

A novel signal processing technique for eddy-current testing of steam generator tubes

In eddy-current testing of steam generator tubes of nuclear power plants, the signals of defects may be corrupted by noise and other nondefect signals arising from the probe lift-off and the structures attached to the tubes, resulting in unreliable detection and inaccurate characterization of defects. In this paper, a novel signal processing technique is presented to reduce the noise and nondefect signals by the use of a wavelet transform. The noise and nondefect signals are reduced by first decomposing testing signals into wavelet components and then modifying the wavelet coefficients. The defect signals embedded in noise and nondefect signals are reconstructed through the inverse wavelet transform of the modified wavelet coefficients. The results of processing the one-dimensional and two-dimensional signals from eddy-current testing of tube test pieces show that this signal processing technique is effective for extracting defect signals embedded in noise and nondefect signals.

Inverse magnetostrictive effect and electromagnetic non-destructive testing methods

The influences of mechanical stresses on magnetic properties are investigated. A qualitative and quantitative description of the reversible and irreversible components of the magnetostrictive effect in iron and carbon steels is presented. Applications of the effect in a new method for analysis of stress waves in mechanically stressed ferromagnetic metals, and also in an alternative strategy for enhancement of the signal-to-noise ratio of eddy current testing of tubes, wires and rods in mechanized lines are described, as is a non-destructive method for evaluation of the martensite content in the structure of wire rod.

Choice of frequency for eddy-current tube testing

Eddy-current testing can be used to detect faults in metal tubes by passing the tube through a pair of short solenoidal coils which are energized by an alternating current. The decrease in density of the induced eddy-currents from the outer surface is determined by the frequency of the energizing current and by the electrical properties and dimensions of the tube. Since the eddy-currents flow in a circumferential direction, their distribution is not, as often assumed in the past, the same as when current flows in the direction of the axis. The distribution of eddy-currents flowing circumferentially is given in general terms for non-magnetic tubes and the results can be used in conjunction with a nomogram to determine suitable frequencies for many practical applications.