Fast Procedures of Crack Localization in Tested Objects Using Pulse Envelopes of Arbitrary Shapes

With a view to improving the efficiency of flaw detection based on various geometric parameters and aimed at cracks of various configurations, we suggest a modified version of the Fibonacci strategy for fast detection of maximal amplitudes of pulse envelopes from an eddy-current transducer (ECT) scanning the surface of a tested object. The suggested algorithm prescribes a unified procedure in the cases of the unimodal, bimodal, and local-bimodal shapes of ECT pulse envelopes and allows a considerable reduction in the number of steps in the search process.     

A two-step algorithm for finite-element solution of electromagnetic-testing problems: Eddy-current testing

An algorithm for finite-element simulation of eddy-current testing problems is described. This algorithm allows calculation of transducer signals from any 3D flaw in a metallic item. In practice, the studied flaws are often characterized by small dimensions. Therefore, the measured increment of the voltage induced in the transducer’s output winding owing to the presence of such a flaw is only several percent of the voltage’s average value. If a standard calculation scheme based on the finite-element method is applied, significant computational resources are needed to solve this problem. The two-step algorithm allows a significant reduction in the required resources. The essence of the algorithm is that the source of the field of a flaw’s effect is determined from the distribution of eddy currents in metal free of flaws. Such an approach allows the calculations of the “unperturbed field” to be simplified significantly through consideration of the geometric symmetry of the problem solved and thus, through reduction of its dimensionality. The efficiency of the two-step algorithm is demonstrated during the solution of a typical problem: the use of a through differential transducer for eddy-current testing of a segment of a heat-exchange pipe in the steam generator of a nuclear power plant.     

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.     

A neural-network classifier of flaws for multifrequency Eddy-current tests of heat-exchange pipes

A neural-network classifier has been developed that evaluates the geometric characteristics of a detected flaw on the basis of the parameters of the corresponding multifrequency signals obtained via scheduled eddy-current tests conducted with a through-type probe. The classifier is intended for testing heat-exchange pipes in steam generators of a nuclear power plant with a water-moderated water-cooled power reactor. The representative library of signals required for the design was formed on the basis of theoretical and experimental data. The theoretical data were obtained in a numerical physical and mathematical model of the electromagnetic testing procedure implemented with the MagNum3D program for finite-element analysis. The experimental data were obtained through measurement of multifrequency eddy-current signals from test specimens with artificial flaws.     

Flaw detection of alloys using the eddy-current method

A subminiature transformer eddy-current transducer (ECT) that is intended for the study of different nonuniform materials, alloys, miniature parts, printed-circuit boards, and microscopic defects has been designed. A block diagram of the transducer is given and its basic technical characteristics ensuring localization of the magnetic field on areas of approximately 50 × 50 μm are stated. A scheme that uses a computer as a generator and receiver of signals from windings is proposed. It is capable of automatically changing the filtering cutoff frequency and operating frequency of the device. The designed measuring system eliminates the main drawback of eddy-current transducers (the small area of the electromagnetic field), simultaneously significantly reducing the noise level due to the use of high-quality amplifiers and filters, and searches for defects in printed circuit boards, metal–dielectric–metal-junctions, and alloys of different metals. A measurement procedure that allows one to perform high-accuracy monitoring of flaws in different alloys is described. The eddy-current transducer was successfully tested on several objects, e.g., a 5.5-μm thick Al–Mg alloy and welded seams of 5-mm thick titanium plates, as well as other objects. The dependences of the ECT signal on the flaws in these structures are given.     

Eddy-current nondestructive testing of long cylindrical components using spatial magnetic field components of different frequencies

The feasibility of the eddy-current nondestructive testing using two orthogonal harmonic components of the driving magnetic field has been studied. The paper describes the practical implementation of the method in a flaw detector testing ferromagnetic rods and pipes and designed for detecting elongated flaws with small gradients of longitudinal parameters.     

Signals from an attachable anaxial-type eddy-current transducer positioned above a conducting half-space

An exact analytical expression that describes the introduced voltage of an attachable anaxial-type eddy-current transducer (ECT) with displaced axes of the exciting and measuring coils, which is positioned above a conducting nonmagnetic half-space, was obtained. The loci of the introduced voltage in a complex plane, which were constructed on the basis of the results of a numerical analysis of this expression, are presented. It was established that in contrast to axial ECTs, anaxial transducers are characterized by a higher phase sensitivity of the introduced voltage to changes in the generalized testing parameter β and also by the fact that, as the value of this parameter increases, the loci for anaxial ECTs shift to the fourth quadrant of the complex plane to the third and second quadrants. The influence of the design parameters of an anaxial transducer on the shape of its introduced-voltage loci was investigated.     

On the development of national standards for magnetic and eddy-current nondestructive inspection of steel pipes

Comparative analysis of the technical level of different nondestructive-testing methods (ultrasonic, magnetic, and eddy-current) used in the production of seamless and HFC welded pipes is performed. To increase the quality of pipes produced for operation under elevated pressure and to unify nondestructive-testing methods and facilities used, standards for magnetic and eddy-current inspection are developed in accordance with the stated foreign acceptance levels.     

Eddy-current quality control of soldering of current-carrying joints in electrical machines. II. Experiment

The possibilities of the eddy-current method for quality control of soldering of joints of stator copper windings in electrical machines are studied. The contribution of closed eddy currents, which are induced in inspected joints by an eddy-current transducer and differ in perimeters and location depths of joints, to the signal of the eddy-current transducer is considered experimentally. The information content of eddy-current transducer signals is shown to be sufficient for estimating the soldering quality of joints of this type. The effect of various technological factors on the reliability of the inspection was determined.     

一种电容层析成像系统结构的优化方法

介绍了电容层析成像的基本原理,针对现有电容层析成像系统存在的问题,提出了一种总线型、模块化的微弱电容测量电路新结构,对电容层析成像系统的结构进行了优化,以使该技术更适应工业现场应用。     

An eddy-current gauge for measuring the wall thickness of light-alloy drill pipes

The operating principle and design of an eddy-current transducer intended for in-service measurement of the wall thickness of light-alloy drill pipes are described. The block diagram and algorithm of conversion are provided for measurement-data signals from the eddy-current thickness gauge. The main technical specs are listed for a thickness gauge prototype.     

The ways of reliable detection of metal inclusions by an eddy-current device

The ways of processing signals of an eddy-current probe in the reception channel of an induction metal detector are considered. It has been shown that the reliable detection of a metal article is possible only if both orthogonal signal components on the phase plane from the article are detected. The ways of complex indication of the orthogonal signal components and elimination of noise caused by unbalance of the eddy-current probe are described.     

Robust dynamic inversion algorithm for the visualization in electrical capacitance tomography

Electrical capacitance tomography (ECT) is considered as a promising visualization measurement technique, in which reconstructing high-quality images is crucial for real applications. In this paper, a robust dynamic reconstruction model, which incorporates the ECT measurement information and the dynamic evolution information of a dynamic object, is presented. Under the considerations of the low rank property of an ECT image and the inaccuracies on the sensitivity matrix, the reconstruction model and the measurement data, an objective functional that fuses the ECT measurement information, the dynamic evolution information of a dynamic object, the spatial constraint, the temporal constraint and the low rank constraint is proposed. An iteration scheme that integrates the advantages of the fast composite splitting (FCS) algorithm is developed for solving the proposed objective functional. Numerical simulations are implemented to validate the feasibility of the proposed algorithm.     

Eddy-current quality control of soldering of current-carrying joints in electrical machines. I. General principles

The possibility of testing the electrical conductivity of soldered joints using and eddy-current transducer has been studied. The simplest model calculations allowing evaluation of the relative value of a signal from an inhomogeneity depending on its location inside a specimen are presented. It is shown that signals yielded by an eddy-current transducer are quite informative for determining the quality of soldering of current-carrying joints.     

电容层析成象系统中微小电容测量法

电容层析成象技术（ＥＣＴ）是一种最早发展起来的过程成象技术。由于为重建图象所需测量的电容变化量相对于ＥＣＴ传感器的固有电容非常小,总的杂散电容值又远大于待测电容,因此ＥＣＴ对电容检测提出了极为严格地要求。本文介绍了ＥＣＴ系统中最常用的３种微小电容检测电路—充电／放电电路、带反馈补偿的交流测量电路以及自平衡电容测量电路,并指出了它们的优缺点。     

The influence of a combined strain-heat treatment on the features of electromagnetic testing of fatigue degradation of quenched constructional steel

The possibilities of the magnetic and eddy-current methods for testing fatigue degradation during low-cycle loading of quenched steel 50 (0.51% C) that was subjected to a combined strain-heat treatment according to an optimal regime that included friction treatment with subsequent tempering at T = 350°C, were investigated. It is shown that for steel that was subjected to a combined nanostructuring treatment, the accumulation of a plastic strain under “hard” cyclic loading can be tested using the coercimetric method and values of the residual magnetic induction on the major and minor magnetic-hysteresis loops, values of the maximum and initial magnetic permeabilities, and readings of an eddy-current instrument at a low excitation frequency of the eddy-current transducer. The appearance of surface fatigue cracks can be tested via eddy-current measurements at high frequencies, when the contribution of the crack formation in the hardened layer to the eddy-current characteristics is considerable.     

双层电容层析成像传感器及应用

电容层析成像在气力输送过程中具有十分重要的应用地位，可进行固相浓度分布测量，流型判断。利用双层电容层析成像传感器不仅可以进行浓度测量还可以进行相关测速。基于这种思想，设计了一种双层电容传感器，与电容测量系统结合，用于气力输送过程固相浓度和速度的测量。     

Solution of reciprocal problem of magnetic flaw detection through calculation of multipole moments of an elliptic flaw

An algorithm has been developed for calculating parameters of an effective elliptic flaw (EEF) on the base of changes in the magnetic field intensity in the air. EEF is defined as a flaw with an elliptic cross section whose magnetic moments (dipole, quadrupole, and octupole), hence the field at a large distance, are the same as those of a given flaw with an arbitrary shape. The relation between the parameters of EEF and real flaws has been established by solving Grinberg’s integral equation for internal and surface flaws of the two-dimensional configuration in a half-space filled with a linear (μ=const) ferromagnetic material. This relation was used in drawing up the solution of the reciprocal problem of magnetic flaw detection.     

Split Bregman iteration based image reconstruction algorithm for electrical capacitance tomography

Practical applications of the electrical capacitance tomography (ECT) rely mainly on the effectiveness of reconstruction algorithms. In this paper the solution of the inverse problem with the focus on the ECT imaging is reformulated to be an optimization problem by introducing a new loss function with regularizes encoding multiple features of solution. An iterative scheme that decomposes a complex optimization problem into several simpler sub-problems is developed to solve the proposed loss function, in which the linearization approximation and the acceleration strategy are introduced to improve numerical performances. Numerical experiments validate the effectiveness of the proposed imaging method in tackling the ECT inverse problem.     

VE-26NP Eddy-Current Structuroscope

The destination and technical characteristics of a VE-26NP eddy-current structuroscope are described. The domains of application and characteristics of the VE-26NP eddy-current structuroscope are presented. The question of the necessity for presorting on the basis of the specific electrical conductivity is considered. The possibilities of using the VE-26NP eddy-current structuroscope for nondestructive testing of the quality of heat treatment of products from nonmagnetic alloys are analyzed. Examples of testing the specific electrical conductivity of thin-wall objects are given.