A pipe with protective lagging and thermal insulation is modeled by a multi-layered structure. Sinusoidal or sed eddy current are induced by a circular coil held above the structure to measure the thickness of the pipe 11. Analytical solutions of both sinusoidal and pulsed eddy c urrent measurements are deduced. Parameters ecting the measurement are studied using the analytical solutions. Measurement conditions are di scussed ed on the analytical results. Keywords: wall thinning, muti-layered structure, ed...
英字タイトル:
Simulation for the Assessment of Wall Thinning using Eddy Current Method

A transient eddy current measurement method is presented to determine the thickness and conductivity of a conductive plate. The conductive plate is induced by an air-cored coil, the magnetic flux density along the axial is measured and the various signals corresponding to plates with dif ferent thickness and conductivity are calculated using a 3D transient eddy current simulator. Characteristic features are obtained from the tran sient response. A similarity-based modeling method is utilized in this study ...
英字タイトル:
Simulation of the Transient Eddy Current Measurement for the Characterization of Depth and Conductivity of a Plate

In the low-frequency electromagnetic nondestructive testing of cracks in ferromagnetic structures, both the magnetic flux leakage and eddy current perturbation coexist and the pickup signal is the combination of the two effects: signals arise from flux leakage effects when the crack orients transversal to the flux, and signals arise from eddy current perturbation when the crack orients transversal to the eddy currents. Numerical simulations are carried out to analyze the signals and the phase angles of...
英字タイトル:
Low-Frequency Electromagnetic Testing of Cracks in Ferromagnetic Structures

Swept-frequency eddy current testing is applied to measure a metal plate’s thickness. The swept-frequency eddy current testing signals are normalized and spectral analysis was conducted on the normalized impedances. Theoretical and experimental studies show that the extreme value of the normalized impedance is correlated with the plate thickness. The thickness of a non-magnetic plate can be measured by SFECT and spectral analysis on the normalized impedance even without knowing the conductivity of the t...
英字タイトル:
Thickness Measurement of Metal Plates Using Swept-Frequency Eddy Current Testing and Spectral Analysis

The distribution of eddy current is disturbed in the presence of cracks. An equivalent solenoid model and a loop current model were proposed respectively to model the bypasses of eddy currents to the underside and longitudinal end of a crack. Eddy current testing signals were qualitatively analyzed by using the equivalent current models. Simulation showed that the signal due to the bypass of eddy current to the under side of a crack was appropriate for the evaluation of crack depth, and the signal due ...
英字タイトル:
Enhancement of Defect Sizing Ability by ECT Data Fusion

This study proposes new signal processing methods to restore surface shapes of flaws from eddy current testing（ECT）signals. A linear discriminant analysis method is applied to ECT signals embedded in multi-dimensional state space to identify flaw signals form background noises in prior. A new concept of equivalent point spread function is introduced, and the real flaw shape is restored by utilizing a deconvolution filter based on Richardson-Lucy algorithm. An EDM notch covered by large welding noises...
英字タイトル:
New Signal Processing Methods for Surface Shape Restoration in Eddy Current

It is well-known that Cr depletion in Inconel 600 changes its magnetic properties, and there is a possibility that electromagnetic nondestructive evaluation has capability of evaluating sensitization of Inconel 600 quantitatively. In this study, we discuss application of eddy current method to the evaluation. For the purpose, magnetic proper ties of Inconel 600 with different aging times were evaluated by B-H loop analyzer. Results show that some magnetic parameters correlate well with Cr depletion. Focus...
英字タイトル:
Evaluation of Sensitization of Inconel 600 Using Eddy Current Method

A partial-contact stress corrosion crack (SCC) is electrically modeled as a crack region with non-zero conductivity in eddy current testing (ECT). This partial-contact effect is excluded by an optimally designed crack-conductivity-insensitive depth sizing index, and consequently the master curves obtained from electric-discharge machining (EDM) notches can be utilized directly in the depth sizing of SCCs. This approach is numerically validated and applied to the characterization of SCCs in SUS304 from...
英字タイトル:
A New Depth Sizing Method for Partial-Contact Stress Corrosion Cracks from ECT Signals