SU1337755A1 - Probe-type magnetic-field flaw detector - Google Patents

Abstract

This invention relates to non-destructive testing. The invention makes it possible to increase the reliability of control by eliminating the effect on the result of the state of the surface of the test item. The flaw detector contains a generator 1 connected in series, a fluxgate converter 2, a selective amplifier 3, an amplitude detector 4, a key 5, a peak detector 6, a key 7, an analog memory block 8, an integrator 9, a threshold element 10, a recorder 11, a divider 12, a block 15 subtracting signals, a logic element 13, a second recorder 14, and a control unit 16. When the flaw detector is in operation, the signals coming from the output of the amplitude detector 4 and the output of the integrator 9 are divided and subtracted by divider I2 and block 15. When defects appear, signals from the outputs of divider 12 and block 15 are fed to the inputs of the logic element 13 and the recorder 14 will fix the presence of unacceptable defects. With a rough control surface, the signal level from the integrator 9 rises, threshold element 10 is triggered, the recorder 11 detects the presence of a bad surface, which is not a defect registered in the recorder 14. 1. (L - 00 00 D1 O1

Description

The invention relates to instrumentation technology and can be used for non-destructive testing of hardware defects and welds using the fluxgate method.

The purpose of the invention is to increase the reliability of control due to detuning from the influence on the result of monitoring the state of the surface of the product.

The drawing shows a block diagram of the fluxgate flaw detector.

The flaw detector contains a series-connected generator 1, a ferro-probe converter 2, a selective amplifier 3, an amplitude detector 4, a first switch 5, a peak detector 6, a second switch 7, an analog memory block 8, an integrator 9, a threshold element 10, a recorder 11, serially connected divider 12, logic element 13 and second recorder 14 connected to the output of the amplitude detector 4, subtraction unit 15 connected between the output of the detector 4 and the second input of the logic element 13, control block 16 connected to the control inputs audio keys respectively 5 and 7, the peak detector 6 and the block 8, an analog memory, the integrator output is also connected to second inputs of the divider 12 and subtractor block 15. Control unit 16 can be implemented, for example, in the form of interconnected several square pulse drivers, in the form of a set of keys, operating keys 5 and 7, a peak detector 6 and an analog memory block 8.

The flaw detector works as follows.

In the initial state, the voltage at the output of the divider 12 signals is zero, if the ratio of the voltages

and

and more than zero (sufficient to trigger the logic element 13) when

-t.

Where

and, step 50, the step during which the key 5 is opened. The voltage from the output of the peak detector 6 is recorded when the key 7 is released in block 8 of the analog memory, remains unchanged in magnitude at the output of the amplitude detector 4; U- is the voltage at the integrator output; K is the ratio of the signal from the defect to the noise level, corresponding to the next step and is fed to the given preset sensitivity level — the input of the integrator 9. The output of the block is 8 ti. The voltage at the output of block 15 is obtained by stepwise varying readings of signals greater than zero, if the voltage, the magnitude of which is of varying and, - and and, and is equal to zero, the house step corresponds to the maximum

where and - exceeded and, - Uj 5 the signal from the defect above the noise level for a given sensitivity level.

The flux-bridging transducer 2, excited by the generator 1, together with a magnetizing device (not shown) moves at a constant speed over the surface of the test object (not shown). The magnetization can be performed by both a variable and a constant magnetic field. In the absence of defects on

5, the transducer 2 is affected by the magnetic fields of the magnetizing device scattering and the field of the scattering associated with the presence of an uneven surface, scratches, scratches, structural

0 inhomogeneities, which causes some level of noise signals. The selective amplifier 3 is allocated

second harmonic excitation current

I

An amplitude detector 4 is detected. The voltage U, from the output of the detector 4, is fed to the input of the key 5, to the input of the divider 12 signals and the input of the block 15 of the signal subtraction. To the input of the control unit 16 is supplied the reference

0 voltage, for example, from the magnetizing device winding (not shown) or from the output of the amplitude detector 4 when magnetized by an alternating magnetic field, or from a source of periodically varying voltage (not shown) when magnetized by a constant field. The control unit 16 generates a series of rectangular signals, which in the following

0, the order of operation is controlled: resetting the contents of block 8 of the analog memory, opening the key 7, resetting the voltage of the peak detector 6, unlocking the key 5, resetting the contents of block 8 and

5 so on in the same sequence. Peak detector 6 extracts the maximum value of the envelope of the signal at the output of amplitude detector 4 for a certain period of time 0 step during which key 5 is opened. The voltage output from peak detector 6 is recorded when key 7 is unlocked in block 8 of analog memory, remains unchanged the magnitude of the next step and is fed to the input of the integrator 9. At the output of block 8, a variable voltage is obtained, the value of which at each step corresponds to the maximum

the envelope value of the signal at the output of the amplitude detector A in the previous step. Since the steps are the same length, the voltage at the output of integrator 9 corresponds to the average value of the amplitudes of the signals for a certain period of time, determined by the integrator's constant time 9 (this time is much longer than the duration of the conversion step and the duration of the signal from the defect).

If there are no defects at the output of the integrator 9, there is a constant voltage equal to the voltage at the output of the amplitude detector 4. At the outputs of the divider 12 and the signal subtraction unit 15 there is no voltage, and the recorder 14 does not work.

When a defect appears, there is a sharp increase in voltage at the output of the amplitude detector 4, which is fed to the inputs of the divider 12 and

thirty

signal subtraction unit 15, and a significant 25 integrator, the threshold threshold exceeds the voltage at the second inputs connected to the input of the integrator 9. The inputs of the logic element 13 are energized, and the recorder 14 notes the presence of a defect. The voltage at the output of block 8 of the analog memory increases abruptly. But since the duration of the signal from the defect is small compared to the time constant of the integrator 9, the voltage at the output of the integrator 9 increases slightly, and the sensitivity of the control remains almost unchanged.

In the case when the surface of the product is very coarse and cannot be controlled with the required sensitivity, the recorder 11 is triggered. At the same time, the level of noise and voltage with inactivity increases significantly.

40

A detector and recorder, a serially connected divider, a logic element and a second recorder, connected to the output of the amplitude detector, and a subtraction unit connected between the output of the amplitude detector and the second input of the logic element, the second inputs of the divider and the subtractor are connected to the output of the generator, Advantageously, in order to increase the reliability of the control, it is equipped with a serially connected first key, a peak detector, a second key and an analogue memory unit connected between the amplitude detector set and the integrator, and a control unit connected to inputs are grappling with the first and second keys, the peak detector and an analog memory unit.

Or E.Kopcha 4122/40

Compiled by V.Filinov Tehred M.Hodanich

Corr Pod

Circulation 776 VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

0

five

0

Tegrator 9 exceeds the threshold of threshold element 10.

Thus, comparing the amplitude of each signal with the average value of the amplitudes of the signals for a certain period of time allows you to automatically automatically change the sensitivity of the flaw detector, depending on the amplitudes of the interference signals, determined by the state of the surface. The rejection of suitable products is excluded and the reliability of control is increased, and the sensitivity of the flaw detector when using different fluxgate transducers is almost the same.

Claims (1)

Invention Formula A fluxgate flaw detector containing a series-connected generator, a flux-gate transducer, a selective amplifier and an amplitude detector, successively single integrator, threshold element a cop and recorder, a serially connected divider, a logic element and a second recorder connected to the output of the amplitude detector, and a subtraction unit connected between the output of the amplitude detector and the second input of the logic element, the second inputs of the divider and subtractor connected to the output of the generator, In order to increase the reliability of the control, it is equipped with a serially connected first key, a peak detector, a second key and an analog memory block connected between the amplitude detector a torus and an integrator, and a control unit connected to the control inputs of the first and second keys, the peak detector and the analog memory block, respectively. Proofreader S.Shekmar Subscription