SU888024A1

SU888024A1 - Eddy-current flaw detection method

Info

Publication number: SU888024A1
Application number: SU802904865A
Authority: SU
Inventors: Валентин Николаевич Учанин; Анатолий Яковлевич Тетерко
Original assignee: Специальное Конструкторско-Технологическое Бюро Физико-Механического Института Ан Усср
Priority date: 1980-04-02
Filing date: 1980-04-02
Publication date: 1981-12-07

Description

(54) СПОСОБ ВИХРЕТОКОВОЙ ДЕФЕКТОСКОПИИ(54) VORTEX-CURRENT DEFECT-COPY METHOD

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Изобретение относитс к н еразрушающему контролю и может быть использовано дл обнаружени несплошностей по толщине металлических изделий.The invention relates to non-destructive testing and can be used to detect discontinuities in the thickness of metal products.

Известны способы вихретоковой дефектоскопии , заключающиес в амплитудно-фазовой обработке сигнала датчика, сканирующего по контролируемой поверхности 1.Eddy current flaw detection methods are known, which consist in amplitude-phase processing of a sensor signal scanning a controlled surface 1.

Сдвиг по фазе на 90° опорного напр жени по отношению к сигналу помехи позвол ет подавить ее вли ние на результаты контрол .A 90 ° phase shift of the reference voltage relative to the interference signal suppresses its effect on the control results.

Недостатком известного способа вл етс сложность реализации при выделении полезного сигнала.The disadvantage of this method is the complexity of the implementation of the selection of the useful signal.

Наиболее близким по технической сущности к изобретению вл етс способ вихретоковой дефектоскопии, заключающийс в том, что в контролируемом изделии возбуждают вихревые токи, выдел ют составл ющую магнитного пол дефекта, мен ющую знак в процессе сканировани датчиком, и по сигналу с фазового детектора определ ют искомые параметры 2.The closest to the technical essence of the invention is a method of eddy current flaw detection, which implies that eddy currents are excited in a controlled product, the component of the magnetic field of the defect, the sign changing during the scanning process is extracted, and the desired options 2.

Недостатком известного способа вл етс низка точность контрол .The disadvantage of this method is low control accuracy.

Целью изобретени вл етс повыщение точности контрол .The aim of the invention is to increase the accuracy of the control.

Поставленна цель достигаетс тем, что по линии сканировани выбирают п нечетных равноотсто щих друг от друга точек контрол , определ ют сумму сигналов равного числа измерений до и после выбранной точки контрол , вычитают их и полученную величину относ т к выбранной точке , по полученной зависимости .дл всех выбранных точек по линии сканировани опреto дел ют наличие дефекта и по ее максимуму - координату дефекта, а рассто ние между крайними точками контрол определ ют из соотношени :The goal is achieved by choosing n odd equidistant points of control from each other along the scanning line, determining the sum of signals of an equal number of measurements before and after the selected control point, subtracting them and the resulting value is related to the selected point, according to the resulting dependence. all selected points determine the presence of a defect by the scanning line and, by its maximum, the coordinate of the defect, and the distance between the extreme points of the control is determined from the relation:

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где4 - рассто ние между точками контрол ;where 4 is the distance between control points;

OJ - кругова рабоча частота контрол ;OJ - circular operating frequency control;

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б - электропроводность материала контролируемого издели ;b - electrical conductivity of the material of the controlled product;

Claims

Ug is the magnetic permeability of the vacuum material of the controlled product. FIG. 1 shows the output signal characteristic of a phase detector for p 3; in fig. 2 - transformed according to the proposed method for p. 3. The eddy current flaw detection method is carried out as follows. In a controlled product, eddy currents are excited. The control zone is determined from the relation: VcJ6ji (taking into account that this distance should not be longer than the abnormal field. The orthogonal component or non-orthogonal gradient of the defect field is selected. The output signal of the phase detector for p 3 has the form shown in Fig. 1. During the scanning process, the signals at the points x - + and x - 1 are measured and their difference is related to the point x; the signal from the defect takes the form shown in Fig. 2. The maximum signal from the defect is positive and double exceeds the initial level. It is known that the sum or difference of two random variables obeying the normal distribution law with the bo dispersion is also normal with the bo dispersion 2bo. The root mean square error of the booster W6o, while increasing times. Thus, the transformation doubled the useful signal and increased the root-mean-square error only by V2 times. In general, if you measure the signal values at an odd number of points and perform the conversion according to the scheme (U. + ... U p-L-f UjT ± i + ..) about h V7 then the ratio of the useful signal to interference will increase by UI-1 times. The proposed eddy current flaw detection method allows to increase the reliability,. control and accuracy by eliminating the rejection of monitored products due to interference. Claims 1. The eddy current flaw detection method, which consists in exciting eddy currents in a controlled product, isolates the component of the magnetic field of the defect, which changes the sign of c. the scanning process by the sensor, and the signal from the phase detector determine the desired parameters, characterized in that, in order to increase the control accuracy, along the scanning line, n odd equidistant points of control are determined, the sum of signals of an equal number of measurements before and after selected control points, subtract them and the resulting value is related to the selected point, according to the obtained iiyvjiJivyv ./jiiY UU1 kVLyciiJu jiri. jj I y .n „dependencies for all selected points for a long scan determine the tension of the defect, and by its maximum - the coordinate of the defect. 2. The eddy current flaw detection method according to claim 1, characterized in that the distance between the extreme points of the control is determined from the relation:,. $ ....: where is the spacing between control points; o-round working frequency control; 6 - electrical conductivity of the material of the controlled product; l, the magnetic permeability of the vacuum material controlled product. Sources of information taken into account in the examination 1. Instruments for non-destructive quality control of materials and products, handbook UND. V. V. Klyueva, M., “Mechanical Engineering, 1976.

2. A. Ya. Teterko and others. Features of the design of flaw detectors with gradient-type sensors, collection “Industrial Application of Electromagnetic Control Methods, M., TP im. F.E. Dzerzhinsky, 1974 (prototype).

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