Eddy-current testing

About: Eddy-current testing is a research topic. Over the lifetime, 3010 publications have been published within this topic receiving 28472 citations.

Defect Characterization of a Multifrequency Eddy Current System

Abstract: The important steps in eddy current testing for defects in test objects are: detection, classification and sizing. This paper concentrates especially on the last two items.

Accuracy Evaluation of an Electromagnetic Method for Conductive Tube Inspection

Abstract: Eddy-current nondestructive testing of metallic tubes, includes measurement of tube inner diameter and electromagnetic properties - magnetic permeability and electrical conductivity. In our previous work we have developed a procedure for simultaneous measurement of inner diameter and permeability-to-conductivity ratio by minimizing difference between measured impedance of a coil excited at only one frequency and prediction of a two-parameter impedance model. In this paper we evaluate the errors that rise from the usage of the two-parameter model and requirements for accuracy of the coil impedance measurement. Our findings show that the errors and required coil impedance accuracy are within limits acceptable for practical implementation of the procedure

Electrical resistivity eddy current testing method of solar silicon chip

Abstract: The invention relates to an electrical resistivity eddy current testing method of a solar silicon chip. The electrical resistivity eddy current testing method of the solar silicon chip is suitable for non-contact tests of a mono-crystal solar silicon chip and/or a poly-crystal solar silicon chip. An eddy current exciter f1 stimulates the solar silicon chip and forms an eddy on the surface of the solar silicon chip, an eddy sensor senses the eddy to generate a current signal and a voltage signal, transmission, frequency beating, intermediate-frequency amplification, detection and low-pass filtering, direct-current amplification and analog-digital conversion are sequentially conducted on the current signal and the voltage signal, finally, the voltage analog quantity and the current analog quantity are obtained, and the electrical resistivity of the solar silicon chip is worked out according to a formula. Compared with the prior art, the electrical resistivity eddy current testing method is clear in structure, simple in circuit structure, adjustable in system and convenient and rapid to use, involves few instruments and meters, and has the advantages of being stable in work, good in repeatability, long in service life and low in cost.

Estimation of Mutual Induction Eddy Current Testing Method Using Horizontal Exciting Coil and Spiral Search Coil

Abstract: The mutual induction type eddy current testing using a spiral type search coil is one of the eddy current testing (ECT). In this type ECT probe, since the thickness of a spiral search coil is very thin, the distance (lift-off: L o) between the ECT probe and the specimen is able to set small. Therefore, the high detection sensitivity is obtained. However, since the wire is coiled in the shape of spiral, the evaluation of the flux density inside the spiral search coil is made difficult by experiment. Moreover, the phenomenon elucidation of inspection using this ECT probe is not carried out. In this paper, the inspection characteristic of a surface defect on an aluminum plate using this probe was investigated by 3-D alternating electromagnetic finite element method (FEM). Moreover, the evaluation in consideration of the characteristic of the spiral search coil in this ECT probe is also investigated by (1 + 1) evolution strategy. It is shown that high detection sensitivity is obtained using the spiral search coil.

Development of an Unsaturated Differential Magnetic Probe for the Visualization of Back-side Slits with Different Directions on Carbon Steel Plate

Abstract: Magnetic Flux Leakage (MFL) and Eddy Current Testing (ECT) in Nondestructive Testing (NDT) are considered as commonly used techniques in the detection of cracks within metallic materials. MFL relies on the analysis of the flux leakages, while ECT relies on the analysis of eddy currents that resides within a metallic sample. The conventional MFL system, however, requires a strong magnetic field to be applied to a sample to achieve magnetic saturation so that strong flux leakages can be produced. In this work, an unsaturated differential magnetic probe that utilizes the highly sensitive AMR sensors is developed, which aims to eliminate the need for the sample saturation. Besides that, the ECT is rarely applied to ferromagnetic materials due to the large distribution of the magnetization signals compared to the eddy current signal. Thus, the phase-sensitive detection technique is proposed using a digital lock-in amplifier, which will allow the separation of both MFL and ECT signals. Besides that, a 2-mm carbon steel plate is used as the sample for this work. The surface of the plate is engraved with artificial slits with different directions, which are 0° (horizontal), 45°, and 90° (vertical). Then, a 2-D map measurement is conducted from the backside of the sample. From the results, the slits with the direction of 45° and 90° can be clearly observed for both real and imaginary components. However, the 0° slits are nowhere to be seen within the backside 2-D map for both real and imaginary components. Furthermore, the optimum frequency for the 2-D map measurement is concluded to be at 110 Hz for both MFL and ECT. Finally, by observing the intensity of the blue color region (for the real component) and red and blue region (for the imaginary component), the depth of the slits can be further estimated.