SU845083A1 - Ultrasonic flaw detector - Google Patents

Description

(54) ULTRASOUND DEFECT TESTS

one

The invention relates to devices for non-destructive testing by an ultrasonic method and can be used in the development of ultrasonic devices for controlling materials and products of machine-building, aviation and other industries.

According to the main author. St. No. 785742 is known for an ultrasonic flaw detector containing a series-connected synchronizer, probe pulse generator, transducer, amplifier-detector, video amplifier and indicator, sweep generator connected between the indicator input and the synchronizer output, connected between the amplifier-detector and the video amplifier, main cascade of matches, main driver strobe pulses, the input of which is connected to the second output of the detector amplifier, and the output to the second input of the main coincidence stage, the first cad delay connected between the amplifier and detector stage main coincidence serially connected first additional strobe pulse generator having an input coupled to the output of the synchronizer, additional

coincidence stage, the second input of which is connected to the output of the amplifier-detector, and the average noise power meter, the output of which is connected to the second input of the main strobe pulse generator 1.

The disadvantage of it is low control accuracy.

The aim of the invention is to improve the accuracy of the control.

The goal is achieved by the fact that the flaw detector is equipped with a second additional strobe pulse shaper, the input of which is connected to the output of an additional cascade of matches I, an anti-coincidence cascade, the first input of which is connected to the output of the second additional strobe pulse shaper, and the output to the input of the average interference power meter , and the second delay stage, which is included between the anti-coincidence cascade and the additional coincidence cascade.

The drawing shows a block diagram

20 ultrasonic flaw detector.

Ultrasonic flaw detector contains synchronizer 1 connected in series, generator 2 probe pulses. converter 3, amplifier-detector 4, first cascade 5 delays, main cascade 6 connections I, video amplifier 7 and indicator 8. A sweep generator 9 is turned on between the synchronizer and the indicator. Next to the synchronizer output are also connected successively connected to the first additional driver 10 strobe pulses, additional cascade 11 matches, the second input of which is connected to the output of the amplifier-detector, the second cascade 12 delay, anti-coincidence cascade 13, meter 14 average interference power and the main driver 15 strobe pulses, the second input of which is connected to the second output of the amplifier-detector, and the output - to the second input of the main stage 6 matches. Between the cascade of 13 anti-matches and an additional cascade of 11 matches, And the second additional driver 16 strobe pulses is included. Ultrasonic flaw detector works as follows. The synchronizer starts the sweep generator 9 and the probe pulse generator 2. The generator 2 probe pulses excites the transducer 3 emitting a piezoelectric element, which sends pulses of ultrasonic vibrations to the controlled product. The last reflections from defects and the bottom surface of the product fall on the receiving piezoelectric element of the converter 3 and are converted into electrical signals, which are then fed to the input of the amplifier-detector 4 without cut-off. At the detector output, one can observe pulses corresponding to the moments of radiation of vibrations into the material (probing pulses), pulses reflected from defects, and pulses corresponding to the first and second reflections from the bottom surface of the monitored product. Simultaneously with the start of the generator 2, the probe pulses of the synchronizer 1 start an additional / 1 positive shaper-10 strobe pulses with adjustable delay and gating zone duration. The temporal position and duration of the strobe pulse are set so that the condition of equality of the values of the averaged interference power in the zone of additional gating and in the control zone is fulfilled. The additional strobe pulse generated in this way is fed to the first input of the additional cascade 11 coincidence, the second input of which receives amplified and detected probing and echo signals against the background of the noise from the output of the amplifier-detector 4 without a cutoff. At the output of the cascade 11, coincidences may be observed against the background of interferences, for example, signals that, with further averaging of the interference power in a given zone, will introduce an error. To eliminate the influence of these signals using the second additional strobe pulse generator 16, which is a threshold element with an adjustable trigger threshold, strobe pulses are generated, the duration and temporal positions of which correspond to the duration and temporal positions of the reflected signals at the level. The strobe pulses from the output of the second gate driver 16 strobe pulses are supplied to the second input of the anti-coincidence cascade 13, the first input of which is electrically connected to the output of the additional cascade 11 coincidences via the delay 12 cascade. In the anti-coincidence cascade 13, a temporary selection of interference from disturbing signals is performed, and at its output one can observe selected interference signals, the average level of which in zone 1 is equal to the average level of interference in the control zone. Next, the interference thus selected is fed to the input of the average interference power meter 14. The input device 17 of the average interference power meter performs the functions of reducing or amplifying the interference voltage depending on the control conditions. From the output of the meter 14, a voltage proportional to the average interference power is fed to the second input of the main gate driver 15, the first input of which receives amplified and detected probing and echo signals in the background of the noise. The imaging unit 15 produces strobe pulses whose duration and temporal positions correspond to the duration and temporal positions of the output signals of the amplifier-detector 4 without cut-off at a level determined by the output voltage of the average interference power meter 14. The received strobe pulses are fed to one, from the inputs of the main cascade 6 coincidences, to the other input of which amplified and detected sounding and echo signals are fed against the background of interference. With the help of the cascade of coincidence 6, the signals from the noise are temporarily selected and their amplitudes are preserved, and the durations of the signals thus selected at the zero level are equal to the durations of these signals at the threshold level of the gate generator 15, i.e. at the voltage level determined by the average power of the noise. With the help of the first stage 5 of the delay, the delay of the strobe pulses arising in the strobe pulse generator 15 is compensated, and with the help of the second stage of the delay 12, the delay compensation of the strobe pulses,. arising in the former 16.

Claims (1)

Claim Ultrasonic flaw detector according to ed. St. USSR No. 785742, characterized in that in order to increase the accuracy of control, it is equipped with a second additional gate pulse generator, the input of which is connected to the output of an additional coincidence circuit AND, an anti-coincidence cascade, the first input of which is connected to the output of the second additional rob pulse generator, and output - to the input of the average noise power meter, and the second delay stage included between the anti-coincidence stage and the additional coincidence stage I.