SU534686A1 - Method for automatic registration of defects - Google Patents

Description

one

The method relates to ultrasonic testing of materials without their destruction and can be used to create automatic installations for controlling products of the metallurgical, machine-building and electrical engineering industries.

There is a known method for automatically registering defects, implemented by the devices fl, 2, 3, which consists in analyzing the presence of signals about a defect in the strobe pulse of the control zone in two or more periods of a probe pulse.

The known method uses the asynchronous occurrence of interference pulses with the frequency of the probing generator pulses or, respectively, the frequency of the gating pulses of the automatic defect detection systems. In this method, a sequence of reflected pulses in the strobe-pulse of the control zone, synchronized with the frequency of the probing messages, is compared with the strobe-pulse, i.e. can be recorded as a defect and interference signals that are not in one place

in the strobe pulse. This leads to a false rejection of products. The larger the control zone, the greater the likelihood of interference in it and the lower the reliability of the control. Therefore, the noise protection in the specified method of automatic registration of defects is carried out according to the number of pulses of significantly more than two.

Since the value of the permissible probe pulse repetition frequency is limited due to the reverberation conditions, this method leads to a significant decrease in the control performance.

There is also known a method for automatically registering defects with ultrasonic echo-pulse monitoring of products, which consists in analyzing the temporal position of signals from a defect in the strobe pulse of the control zone in two and more periods of a probe pulse. This method is based on the coincidence of the echo signals from the defect in two successive periods of the following pulse during the delay of the first echo signal from the defect by the value of the follow-up period. The implementation of this method has difficulty in manufacturing and setting up defectoscopes with an ultrasonic delay line. In addition, difficulties arise in the manufacture of accurate ultrasonic delay lines, which leads to the need to create large-sized equipment. Automatic registration of defects cannot be performed when the frequency of the probing parcels changes, since it is necessary to change the length of the delay line, making it equal to the follow-up period. When the thermal conditions change, there is a significant difference between the length of the probing period and the delay time of the ultrasonic delay line, which makes this method unacceptable, since the reliability of defect registration decreases. In order to increase the reliability of registration by the proposed method, the strobe-impulse of the control zone is divided into parts and, according to the temporal coincidence of the signals on the defect in the first and subsequent periods of the probe pulse, the corresponding parts of the strobe pulse are judged to have a defect . With interference falling into the control zone in several periods of a probe pulse, the probability of coincidence of its temporal position decreases by as many times as the duration of the strobe pulse is longer than the length of the part into which it is divided. When any change in the frequency of the probe pulse does not require any restructuring of the circuit, since the parts into which the strobe pulse is divided are synchronized with the frequency of the zones of the driving pulse. The drawing shows a block diagram of a device that implements the proposed method comprising a strobe pulse generator 1, a clock frequency generator 2, a decoder counter 3, two parallel groups of selectors 4 and 5, and trigger 6 and 7, coincidence circuit 8, actuator 9 and time selector 10, as well as synchronizer 11 and trigger 12 connected in series. The device operates as follows. The clock frequency generator 2 sends pulses to the counter decoder 3 in the presence of a strobe pulse at its input. The period of the clock pulses is chosen so as to provide the necessary immunity, for example, approximately equal to the duration of the echo pulse reflected from the defect. In this case, the temporary position of the defect will be determined with an accuracy equal to the period. The counter-decoder 3 is reset by the falling edge of the strobe pulse. From the counter-decoder 3, for the period between clock pulses, the enabling signals are fed to the corresponding bits of the counter-decoder 3 selectors 4 and 5 of both groups. When the permissive pulses from the output of trigger 12, triggered by synchronizer 11, appear at the second input of these selectors, and the signal from the time selector 10 passes the signal from the selectors of both groups, at the input of which the three signals coincided. The trigger 12 provides the enabling signals equal to the period of the clock pulses from the synchronizer 11 alternately for each group of 4 and 5 selectors. When one of the triggers of the first 6 and second 7 groups of the signal from the selector of the corresponding group 4 or 5 appears at the input, it is thrown and is in such a state until a second pulse arrives at its second input corresponding to the falling edge of the second arm signal of the trigger 12, the appearance of a defect, i.e. immutability of the temporal position of the echo signals from the defect in the two periods of the synchronization pulses from the synchronizer 11 (probe pulse); the respective triggers of both groups apply the enabling signals to the circuit 8 coinciding in time with each other in a certain time interval. This indicates the presence of a defect. The pulses of non-synchronous interference change their temporary position in each period of the probe pulse, even if they fall into the strobe pulse of the control zone. The signal from the output of the coincidence circuit triggers the actuator 9. If there is interference in the control zone gating pulse in two periods of the clock, the probability of coincidence of its temporary position is reduced by as many times as the strobe pulse duration is longer than the clock frequency generator 2. When any change in the clock frequency of the clock (probe) does not require any restructuring of the circuit, since the 2 clock frequency generator works only with a strobe pulse and, therefore, is synchronized with the clock frequency. The splitting of the strobe pulse of the control zone into parts and the judgment of the presence of a defect due to the temporal coincidence of the signals about the defect in the first and subsequent periods of the probe pulse in the corresponding parts of the strobe pulse distinguishes the proposed method from the known method 4, since

To make automatic registration of defects in various frequencies of the probe pulse, the equipment dimensions are reduced and the reliability of defect detection is increased.

Claims (4)

1. Author's certificate of cl. G 01 N 29 / O4. 2. The copyright certificate of cl. G 01 N 29/04. 3. Author's certificate of cl. G, 01 N 29/04. 4. The copyright certificate of cl. G 01 N 29/04