SU1493941A1 - Method and apparatus for eddy-current test - Google Patents

Abstract

The invention relates to instrumentation technology and can be used in the control of non-magnetic electrically conductive products for the presence of surface and subsurface defects. The aim of the invention is to improve the accuracy of flaw detection by creating an electromagnetic field that varies in time according to the law Ξ _{I = 1} A _I COSΩT. The device implementing the eddy current flaw detection method contains a transformer eddy current transducer 1, four adders 2,3,4,5, amplifier 6, indicator 7, a multiphase pulse former made in the form of serially connected multivibrator 8, counter 9 and a decoder 10 connected the outputs of the decoder are three formers 11, 12, 13 amplitudes and polarities of pulses, the outputs of which are connected to the corresponding inputs of adders 2, 3, 4, the voltage converter 14 is the current connected between the output of the first adder a 2 and an eddy current transducer 1, a multiplying device 15 and an integrator 16. 2 s. and 1 z.p. f-ly, 1 ill.

Description

co oo co

four;:

HLiJCL

The invention relates to instrumentation technology and can be used in the control of non-magnetic electrically conductive products for the presence of surface and subsurface defects.

The aim of the invention is to improve the accuracy of the flaw detection by creating an electromagnetic field that varies over time.

The drawing shows a diagram of a device that implements the method of eddy current testing.

The eddy current defectoscopy device contains a transformer eddy current converter 1 VTP, four adders 2-5, amplifier 6, indicator 7, a multiphase pulse former (FS), made in the form of serially connected multivibrator 8, counter 9 and decoder 10 connected to the decoder outputs of three formers 11-13 amplitudes and polarities of pulses, the outputs of which are connected to the corresponding inputs of the adders. 2-4, a voltage-current converter 14 connected between the output of the first adder 2 and the eddy-current converter 1, a multiplying device 15 and an integrator 16.

The eddy current flaw detection method consists in the fact that in the control zone an electromagnetic field is created that varies in time according to the law.

00

 And cos iw t,

where w 2 1Г / Т; T - period;

A, -1.776 Ad -0.43; AZ 0.583 A4 0.883; A5 0.583; -0.033

A −0.64i; , A8 -0.954. I

as a reference signal, a sequence of rectangular pulses with a period T equal to the period of the alternating magnetic field is used, the synchronization of the alternating field and the reference signal is performed by combining the midpoint of the pulse from the reference signal with the beginning of the period of the alternating magnetic field, and the period T is chosen from the condition

, а-6 „23. ..30,

where R is the average radius of the eddy current transducer}

d

5 0 5 0

five

0

five

0

five

6 - the maximum value of the specific electrical conductivity of the product material in the control zone;

fjg - absolute magnetic permeability of air. A device implementing the eddy current flaw detection method works as follows.

Multivibrator 8 generates clock pulses, which are fed to a binary counter 9, which controls the operation of the decoder 10. The output signal (digital code) is taken from counter 9. Blocks 8-10 form a multiphase pulse former (PMF). From the output of the PMI, n-consecutive pulses go to the three units of amplitude and polarity formation of the pulses of the FAPI 11-13. Next, the pulses from the first FAPI arrive at the first adder 2, the output of which receives a signal of the required form, coming through block 14 to the exciting winding of the VTP, then to the fourth adder 5, which also receives the compensating signal formed by blocks 12 and 3.

In the adder 5, the transformer EMF is compensated, the output signal of the adder 5, due to the eddy current field of the product, is fed to the multiplier 15, to the second input of which the reference signal formed by the blocks 13, 4 is fed. The compensating and reference signals are formed in a manner similar to the signal that feeds the exciting winding of the ECP.

Claims (3)

1. A method of eddy current flaw detection of a product made of non-magnetic materials, which consists in creating an electromagnetic field in the control zone, generating a signal proportional to the reaction field, compensating the reaction signal at the nominal values of monitored parameters and detecting a synchronously compensated signal To improve the accuracy of the flaw detection, the electromagnetic field is created by varying in time according to the law BUT . cos i w t, n where tu 2 G / t; T - period; A, -1.776, Ag -0.43,, 583 A4 +0.883; Aj + 0.583; Aj - 0.033, AI -0,641; Afl -0,954. as a reference signal, a sequence of rectangular pulses with a period T equal to the period of the alternating magnetic field is used, the pulse duration of the reference signal is chosen equal to 1/8 T, the synchronization of the alternating magnetic field and the reference signal is performed by combining the midpoint of the pulse of the reference signal with the beginning of the alternating magnetic field period, and the period T is selected from the condition 23 ... 30, where R is the average radius of the eddy current transducer J 6 dd, the maximum value of the specific electrical conductivity of the product material in the zone control} pp - absolute magnetic permeability of air. 2. Device for eddy current testing of products from non-magnetic materials, comprising a transformer eddy current converter, four adders, an amplifier and an indicator, characterized in that it is equipped with a driver ten phase pulses, made in the form of serially connected multivibrator, counter, decoder, connected to the outputs of the decoder, three formers of amplitudes and polarities of pulses, the outputs of which are connected to the corresponding inputs of three adders, a voltage-current converter connected between the output of the first adder and their - with a current converter, the output of the eddy current converter through an amplifier is connected to the input of the fourth fifth adder, the second input of which is connected to the output of the second totalizer pa multiplier perpp and second inputs to which podklkocheny You are a: third and fourth passages su1.mato- pit, and an integrator connected between the output of the multiplier and an indicator. 3. The device according to claim 2, that is, so that the block of the driver of amplitudes and polarities of pulses is made in the form of n identical voltage converters, each of which consists of two series-connected inverters, the outputs which are interconnected by means of extreme outputs of a preemptive resistor, and n capacitors, one output of each of which is connected to the slider of the corresponding variable resistor, and the second output is the output of the block. 0 five 0