SU1283641A1 - Probe-type magnetic-field flaw detector - Google Patents

Abstract

The invention relates to non-destructive testing of articles made of ferromagnetic materials and can be used in the inspection of weld generators weld seams. The invention solves the problem of increasing the reliability of the control. The flaw detector contains a generator of excitation of a flux-gate converter 2 and connected to the latter in series-connected selective amplifier 3, detector 4, pulse shaper 5, pulse delays block 6 key 7, defect recorder 8, as well as series-connected electromagnet 9, converter 10 current - voltage detector 11, the threshold unit 12, the pulse shaper 13 and the second recorder 14. The winding of the electromagnet 9 is connected in series with the converter 10 current - voltage. The output driver 13 is also connected to the control input of the key 7. When an unacceptable defect appears under the converter 2 and the allowable gap between the poles of the electromagnet 9 and the surface of the product at the input of the selective amplifier 3, the voltage that will be supplied from the output of the selective amplifier 3 through the detector to the input of the imaging unit 5 pulses, from the output of which the pulse through the delay unit 6 will go to the input of the key 7, the output of the key 7 will detect the presence of a defect. 1 il. (L ISD 00

Description

The invention relates to the means of non-destructive testing of products made of ferromagnetic materials and can be used in various fields of mechanical engineering, for example, in power engineering during defectoscopy of steam generator welds.

The goal of the invention is to increase the reliability by eliminating false testimony in the separation of an electromagnet from the surface of products.

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

The flaw detector contains sequentially connected oscillator 1 for the fluxgate transducer, fluxgate for converter 2, selective amplifier 3, second detector 4, first pulse shaper 5, for example, square, pulse delay block 6, key 7 and recorder 8. The flaw detector also contains series-connected electromagnet 9, converter 10 current - voltage, first detector 11, threshold unit 12, second shaper 13 pulses, capturing rectangular, and recorder 14. Shaper 13 output connected n to the control, entry key 7.

The first driver 5 may be made, for example, in the form of a trigger. The second driver 13 may be

performed, for example, in the form of a single-shot with a restart. Fluxgate transducer 2 is included according to the scheme of a gradiometer.

The flaw detector works as follows.

The electromagnet 9 with flux-gate transducer 2 is installed on the defect-free surface area of the controlled product (not shown). Between the poles and the surface there is a defined gap for the free movement of the electromagnet over the surface during the control. The flaw detector is pre-configured with a test specimen for the minimum allowable defect.

Include the generator of excitation of the flux-gate converter 2. Adjustment of the threshold voltage

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Since the fluxgate transducer 2 is connected according to the gradiometer scheme, there is no voltage at the input of the selective amplifier 3 (if the gap between the poles and the surface of the product is acceptable) in the absence of defects. The defect recorder 8 does not work.

As the gap increases or the poles detach from the test surface, the flux-gate converter 2 is affected by the scattering field of the electromagnet 9, and the magnetizing current increases. At the output of the selective amplifier 3, a voltage appears from which the second harmonic of the excitation current is released. Through the detector 4, the voltage reaches the input of the driver 5 pulses. Formed

square impulses are fed to the input of the impulse delay unit 6, and then to the input of the key 7 at a time determined by the delay time of the 6 block. The delay is necessary because when the poles are removed or the gap changes, the output of the fluxgate converter enters the key 7 faster The current from the transducer 10 is voltage, and causes the detector to read. An increase in the magnetizing current causes an increase in the voltage at the output of the converter 10, the current — the voltage that is fed through the detector 11 to the input of the threshold unit 12. In the case of exceeding the specified threshold (when the allowable gap between the poles and the surface is exceeded), the output voltage the threshold unit 12, the imaging unit 13 (one-shot with restarting) generates a square pulse. Restarting and selecting the appropriate pulse duration excludes opening the key / and passing a false signal to the recorder 8 at a periodically varying magnetization current. The pulse duration of the driver 13 must be not less than the duration of the half-period of the magnetizing current, starting from the moment of the last start of the driver. Forming voltage

block 12, the lock key 7 is achieved. The lock 13 is fed to the control

and turning off the recorder 8 defects when exceeding the allowable gap between the poles of the electromagnet 9 and the surface of the product.

the key 7 is entered. The key 7 is closed. The pulse received from the key 7 input from the output of block 6 does not pass to the recorder's input 8 defects.

the key 7 is entered. The key 7 is closed. The pulse received from the key 7 input from the output of block 6 does not pass to the input of the recorder 8 defects.

With the appearance of an unacceptable defect under converter 2 and an acceptable gap between the poles and the surface, a voltage appears from the input of the selective amplifier 3 from which, for example, the second harmonic of the drive current of the converter is extracted. The voltage from the output of the selective amplifier 3 through the detector is fed to the input of the driver 5 pulses, from which the pulse passes through the delay unit 6 to the input of the switch 7. Since the key 7 is open, since there is no voltage j on the output of the driver 13 then the switch 7 a voltage appears, and recorder 7 notes the presence of a defect. I

The proposed implementation of the flaw detector allows you to automatically turn off the defect recorder when the gap between the poles of the electromagnet and the surface of the product is exceeded and signaled.

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Claims (1)

Invention Formula , -. - i i A fluxgate flaw detector containing a series-connected excitation generator of a flux-gate converter and a flux-gate converter, a series-connected electromagnet, a current-voltage converter, and a detector, a selective amplifier, and a recorder, characterized in that it is equipped with the output of the selective amplifier by the second detector, the first pulse driver, the delay unit, and the key, the output of which is connected to the Topy register, are connected to the output of the first detector are connected in series by a threshold unit, a second pulse shaper, the output of which is connected to the control input of the key, and a second recorder, and the input of the selective amplifier is connected to the output of the fluxgate converter.