Eddy Current Flaw Detection Research Articles

Research on Bearing Eddy Current Testing Based on ANSYS

In order to quantitatively analyze the eddy current flaw detection of bearing parts, the eddy current testing model is established by ANSYS finite element simulation software. The simulation analysis object selects a self-inductance eddy current probe. There is only one coil in the probe, which is both an excitation coil and a detection coil, and the detection signal is reflected by the change of the impedance of the coil. Through the simulation experiment, the influence of the structure size of the probe coil and the lift-off distance excitation signal of the probe on the detection effect when using the eddy current detection method for non-destructive testing of the bearing parts is explored. Study and analyze the influence of the change of the defect size on the detected object on the detection signal in the eddy current simulation.

RESEARCH OF MEASUREMENT SIGNAL PARAMETERS DEFINITION ERRORS IN CASE OF IRREGULAR SAMPLING

Reviewed influence of an irregular sampling of informative cyclic signals in measuring testing computerized systems on an example of eddy current robotized testing system.It was found that in case of ADC clock signal forming in processor block, there is an irregular sampling of informative signals. Vibrations of sampling period appears because of interrupt processing in a computerized system and asynchrony of a clock frequency of internal bus and signal sampling frequency. Irregular sampling of a cyclic informative signals makes additional fault of signals characteristics measurement to appear. In testing-measuring systems such fault can cause decrease of testing reliability.In this article real signals of robotized eddy current testing system were analyzed. The distribution of sampling intervals for computerized eddy current flaw detector was obtained. Was performed evaluation of mean squared error of amplitude and phase harmonic test signal characteristics determination in case when signal is set on irregular time grid. Was obtained graphs of the mean squared error of harmonic signal phase and amplitude characteristics dependences with its irregular sampling. Experimental proved that in computerized eddy current testing systems with average reliability in purpose of costs minimization it is permissive to use informative signals irregular sampling, which have place in test signals generation in process block of the system. Although, in case of creation of precise systems with increased reliability level it is necessary to build system with different blocks for data collecting with regular signal sampling, which allows to collect some amount of data in autonomous mode and transmit it to computerized system for its further processing and visualization of flaw detection process results.

Application of Neural Networks for Recognizing Rail Structural Elements in Magnetic and Eddy Current Defectograms

To ensure traffic safety of railway transport, non-destructive test of rails is regularly carried out by using various approaches and methods, including magnetic and eddy current flaw detection methods. An automatic analysis of large data sets (defectgrams) that come from the corresponding equipment is an actual problem. The analysis means a process of determining the presence of defective sections along with identifying structural elements of railway tracks on defectograms. This article is devoted to the problem of recognition of rail structural element images in magnetic and eddy current defectograms. Three classes of rail track structural elements are considered: 1) a bolted joint with straight or beveled connection of rails, 2) a butt weld of rails, and 3) an aluminothermic weld of rails. Images that cannot be assigned to these three classes are conditionally considered as defects and are placed in a separate fourth class. For image recognition of structural elements in defectograms a neural network is applied. The neural network is implemented by using the open library TensorFlow. To this purpose each selected (picked out) area of a defectogram is converted into a graphic image in a grayscale with size of 20 x 39 pixels.

Finding the Level of Useful Signals on Interpretation of Magnetic and Eddy-Current Defectograms

Nondestructive testing of rails using various approaches and methods, including methods of magnetic and eddy-current flaw detection, is regularly carried out to ensure traffic safety on railway transport. This article is devoted to the problem of automatic determination of the threshold level of the amplitudes of useful signals (from the flaws and structural elements of the track) when interpreting defectograms of magnetic and eddy-current flaw detectors. A signal is considered useful (and is subject to further analysis), if the deviation of its value from the average value of all signals is, at least, twice more than the threshold noise level of rails. The probability of appearance of a signal with some amplitude in flawless rails in a section without structural elements, i.e. being a rail noise, is characterized by the normal distribution law. Thus, the three-sigma rule can be used to calculate the threshold noise level, and doubling the noise threshold gives a level that, if it exceeds the amplitude deviation from the sample mean, means that the signal is useful. This article proposes an algorithm to find the threshold noise level of rails and gives its theoretical justification, as well as examines examples of its operation in several fragments of real magnetic and eddy-current defectograms.

Epitaxial films of garnet ferrite with anisotropy “easy plane” for magneto-optical eddy current flaw detection

The possibilities of magnetooptical sensors based on ferrite garnet films with various types of magnetic anisotropy are studied in the visualization of eddy current images of linear defects in the test object from aluminum alloys. Potentially high efficiency of sensors based on an easy-plane anisotropy films is shown.

An Efficient Algorithm for Finding a Threshold of Useful Signals in the Analysis of Magnetic and Eddy Current Defectograms

To ensure traffic safety of railway transport, non-destructive testing of rails is regularly carried out by using various approaches and methods, including magnetic and eddy current flaw detection methods. An automatic analysis of large data sets (defectgrams) that come from the corresponding equipment is still an actual problem. The analysis means a process of determining the presence of defective sections along with identifying structural elements of railway tracks on defectograms. At the same time, under the conditions of significant volumes of incoming information, fast and efficient algorithms of data analysis are of most interest. This article is an addition to the previous article devoted to the problem of automatic determination of a threshold level of amplitudes of useful signals (from defects and structural elements of a railway track) during the analysis of defectograms (records) of magnetic and eddy current flaw detectors, which contains an algorithm for finding the threshold level of a rail noise and its theoretical justification with examples of its operation on several fragments of real magnetic and eddy current defectograms. The article presents a simple and effective implementation of the algorithm, which is successfully used in practice for the automatic analysis of magnetic and eddy current defectograms.

Investigation of welds by the method of the magneto-optical eddy current flaw detection

The paper deals with the magneto-optical eddy current method of flaw detection of conducting materials, in which epitaxial films of ferrite garnet are used as sensors. In particular, the possibilities of visualization of welded seams in magnetic and non-magnetic samples, as well as the defectoscopy of the seams themselves, are considered. The second part of the work is devoted to mathematical modeling of the distribution of the magnetic fields of eddy currents near similar defects.

Development of the eddy-current flaw detector from u-type magnetic circuit with the purpose of compensation of external interferences

Development of the eddy-current flaw detector from u-type magnetic circuit with the purpose of compensation of external interferences

On Finding a Threshold of Useful Signals in the Analysis of Magnetic and Eddy Current Defectograms

To ensure traffic safety of railway transport, non-destructive testing of rails is regularly carried out by using various approaches and methods, including magnetic and eddy current flaw detection methods. The paper is devoted to the problem of automatic determination of a threshold level of amplitudes of useful signals (from defects and structural elements of a railway track) during the analysis of defectograms (records) of magnetic and eddy current flaw detectors. A signal is considered useful (and is subject to further analysis) if a deviation of its value from an average of all signals is at least twice the threshold noise level of rails. The probability of obtaining a signal from a section without structural elements (a rail noise signal) is characterized by the normal distribution law. Thus, the rule of three sigma can be used to calculate the threshold noise level. And a signal is useful if its amplitude deviation from a sample mean exceeds twice the threshold noise level. The paper proposes an algorithm for finding the threshold level of a rail noise and gives its theoretical justification, and it also examines examples of its operation on several fragments of real magnetic and eddy current defectograms.

Analysis of Eddy-Current Measurement System for Residual Stress Assessment in Stainless Steel Grade 304

The objective of this paper is an analysis of statistical discreteness and measurement capability of an eddy-current measurement system for residual stress assessment in stainless steel Grade 304 (SS304). Cylindrical specimens with 50 mm in diameter and 12 mm thickness were prepared to generate residual stress by Resistance Spot Welding at which the welding currents were set at 12, 14, and 16 kA. The eddy-current measurement system was including a probe with frequency range of 0.1 to 3 MHz and an eddy current flaw detector. They were performed by contacting the probe on the specimen. The measurements were performed particularly in the vicinity of heat affected zone (HAZ). In order to determine the results of the residual stress measurement, the calibration curves between static tensile stress and eddy current impedance at various frequencies were accomplished. The Measurement System Analysis (MSA) was utilized to evaluate the changed eddy-current probe impedance from residual stress. The results showed that using eddy current technique at 1 MHz for residual stress measurement was the most efficient. It can be achieved the Gauge Repeatability & Reproducibility %GR&R at 16.61479 and Number of Distinct Categories (NDC) at 8. As applied on actual butt welded joint, it could yield the uncertainty of ± 58 MPa at 95 % (UISO).

Surface Crack Detection for Carbon Fiber Reinforced Plastic Materials Using Pulsed Eddy Current Based on Rectangular Differential Probe

Aiming at the surface defect inspection of carbon fiber reinforced composite, the differential and the direct measurement finite element simulation models of pulsed eddy current flaw detection were built. The principle of differential pulsed eddy current detection was analyzed and the sensitivity of defect detection was compared through two kinds of measurements. The validity of simulation results was demonstrated by experiments. The simulation and experimental results show that the pulsed eddy current detection method based on rectangular differential probe can effectively improve the sensitivity of surface defect detection of carbon fiber reinforced composite material.

Computational transformation of signals of a measuring information system for eddy-current flaw detection

The features of a computational-transformation algorithm that is used for engineering implementation of an eddy-current nondestructive testing method using a combined multisector transducer with a magnetic field at different frequencies are described.

On complex permeability in eddy-current flaw detection

This paper critically considers attempts to prove the frequency dependences of the electrical conductivity and magnetic permeability of metals at frequencies lower than 1 MHz. Such attempts were made by certain authors when studying the operation of eddy-current transducers. It is shown that the complex character of the output voltage of an eddy-current transducer is determined by the vector summation of the magnetic fluxes of the primary magnetizing alternating field and the field of eddy currents, which are induced by the primary field, in a tested article. The frequency dependence of the results of this summation is quite sufficient for a physically correct description of the operation of an eddy-current transducer without involving a hypothesis on the frequency dependence of the physical constants of the material of the tested article.

A method of eddy-current flaw detection of bars and tubes based on the use of a combined eddy-current transducer with excitation of spatial magnetic-field components at different frequencies

The possibility of using the method of eddy-current testing using a combined multisectional transducer with a heterofrequency magnetic field is described. The technological implementation of this method for detecting flaws in bars and tubes under the conditions of significant transverse displacements is described.

G030014 渦電流法によるオーステナイト系ステンレス鋼のひずみ検出([G03001]材料力学部門一般セッション(1):非破壊検査)

This study examined a method on non-destructive detection of the strain of SUS304 and SUS316, which are austenite stainless steel. Eddy current method was employed to detect strain. Four specimens were prepared for SUS304 and SUS316 respectively. The plastic strain of 1, 5, 10, and 16% were applied to the specimens by using a tensile testing equipment. The eddy current signals on the center of the specimens were measured with an eddy current flaw detector. The eddy current signals were determined by difference on the detector output of the specimen without strain and the strain applied specimen. Specimen without strain and the strain applied specimen. Specimen with larger plastic strain showed larger eddy current signals. SUS316 indicated smaller value on the eddy current signal than that of SUS304. Eddy current signals and plastic strain of the specimens showed a linear relation. The relation can be used to estimate the plastic strain by eddy current signal.

Phasec 3 Series eddy current flaw detectors

Phasec 3 Series eddy current flaw detectors

Portable BΔ-12HΦM and BΔ-12HΦΠ eddy-current flaw detectors

The scope of application, specific features of design and operation, and the main technical characteristics of portable BΔ-12HΦM and BΔ-12HΦΠ eddy-current flaw detectors are considered.

Use of the Compton scatter spectrometry technique in non-destructive evaluation of engineering components

Non-destructive testing of engineering components is a prime requirement of a quality control programme before putting them into service. Several techniques are available for non-destructive inspection, such as radiography, ultrasonic testing, eddy current testing and magnetic flaw detection. In all the techniques, scanning energy, in different forms such as electromagnetic waves, ultrasound waves, electrical energy, polarised light, is applied to the component under test and their interaction with a flaw is recorded and later this signal is analysed to extract information. It is known that each technique has its limitations. For example, magnetic particle inspection is limited to ferromagnetic material, eddy current testing is applicable to electrically conducting materials, radiography is less sensitive in detecting planar flaws. Therefore, newer methods are emerging in the field of non-destructive inspection technology for specific requirements. Infrared thermography, holography, neutron radiography, Compton scatter spectrometry are all such techniques. In the Compton scatter technique, material is scanned with a photon beam. It is known when an X-ray or gamma-ray impinges on a target material that some of the photons are scattered and deviate from their initial path. This Compton scattered radiation provides useful information. In this paper, the use of Compton scatter radiation for the non-destructive evaluation of materials has been explored.

Eddy-current flaw detection in structural elements

We describe promising directions in the development of the eddy-current method for the flaw detection of structural elements. We show the possibilities of subsurface flaw location based on the use of low working frequencies and quantitative control with the identification and evaluation of parameters of the found defects. The possibilities of applying high working frequencies for the control of thin surface layers of an article and low-conducting materials are described. We present also the possibilities of new eddy-current converters and flaw detectors as well as testing technologies developed on the basis of their application. Finally, we describe new methods of information processing, in particular, the two-dimensional visualization of testing results.

Nondestructive Testing of Drilling Equipment Components

We consider the principal methods of nondestructive testing of drilling and blowout preventer equipment: the capillary (penetrant) method, ultrasonic flaw detection, magnetic particle flaw detection, eddy-current flaw detection, the acoustic emission method, and hardness and strength testing.We also consider the equipment required for such testing.