SU794459A1 - Electromagnetic flaw detector - Google Patents

Description

cathode ray tube cloning plates.

The drawing shows a block diagram of the electromagnetic defectoskon.

It contains a generator 1, a rotating transformer 2, connected to two electromagnetic converters 3 and 4, measuring rotating transformers 5 and 6, an amplifier amplifier automatic adjustment unit 7 connected in series, one input of which is connected to the output of a measuring transformer 5, detector 8, unit 9 modulation signal processing and cathode ray tube 10 of the indicator.

The measuring rotating transformer 6 is connected in series with an amplifier 11, a phase detector 12 and a block 13 of modulation signal processing connected to a cathode ray tube 10.

Electromagnetic flaw detector works as follows.

The sinusoidal current produced by the generator 1 through the rotating transformer 2 feeds the current windings of two electromagnetic transducers 3 and 4, of which the transducer 3 is made differential in the form of two identical semi-sensors connected in opposite directions. From its output, the difference signal that occurs when one of the half-sensors passes over the defect goes through measuring rotating transformer 5 to automatic gain control unit 7 and then to detector 8. After detection, the low-frequency envelope signal is fed to block 9 of modulation processing of the signal associated cathode ray tube 10 indicator. The signal from converter 4, carrying information about the size of the gap between the sensors and the product and the presence of surface defects, through a rotating transformer b goes through the amplifier 11 to the control input of the automatic gain control unit 7 to automatically control the differential signal transmission from the converter 3 when the gap changes between converters and controlled surface. Thus, at the output of block 7, changes in the difference signal of the differential converter are compensated for by changing the gap, which allows detection of defects at different gaps with the same sensitivity.

Simultaneously with the amplifier 11, the signal of the converter 4 is fed to the phase detector 12. Since the signal of the converter 4 is formed so that its phase does not depend on the change in the gap (within certain limits), a signal proportional to changes in the phase of the emf is produced at the output of phase detector 12 caused only by cracked defects.

Next, the signal from the phase detector 12 enters the modulation signal processing unit 13, and from the output of both modulation processing units 9 and 13, the positive polarity signals are fed to the vertical deflection plates of the cathode ray tube, the horizontal beam sweep of which is sawtooth pulses from the position sensor of the scanning head of the transducer (not shown) synchronously rotating with the transducers 3 and 4. The transducers 3 and 4 are separated by kruzhnosti rotation a predetermined distance, and therefore the pulses of both channels on the screen the cathode ray tube observed separately.

The nature of the detected defects (cracks or pores) on the flaw detector screen is determined by the following features. If the defect is a narrow crack, then signals will appear from it in both channels of the flaw detector, and two-linear pulses will be observed on the screen of the cathode-ray tube. If the defect is a pore, non-metallic

switching on or a sink, then the screen receives only pulses from the channel of the difference signal, and unipolar pulses will be observed. To make signals

one flaw detector circuit can be equipped with an adder, to the inputs of which signals are supplied from both channels, and its output is connected to the vertical-deflecting plates of the cathode-ray tube directly or through an amplifier of vertical deflection.

Thus, the invention makes it possible to simultaneously detect defects of various types, as well as to determine their nature, which increases the reliability of the control.

Claims (2)

1. Directory. Instruments for non-destructive testing of materials and products. M., Mashinostroenie, t. 2, p. 141. 2. Reference book. Instruments for non-destructive testing of materials and products. M., Mashinostroenie, t. 2, p. 139-140 (prototype).