SU998943A1 - Ultrasonic flaw detector - Google Patents

Description

(54) ULTRASOUND DEFECT TESTS

The invention relates to non-destructive testing by ultrasound and can be used to automatically control products. five

A ultrasonic flaw detector is known, which contains a series-connected continuous oscillator, an emitting and receiving transducer, a receiving device with a filter for selecting a homepler frequency shift, a detector and an indicator 1.

A disadvantage of the known flaw detector is the low noise immunity of the flaw detector, since with a significant change in the speed of movement of the filter, the release filter of the domplerov shift is. Frequency ha must have a wide bandwidth.

The closest to the invention according to

The technical essence and the achieved result is an ultrasonic flaw detector containing a series-connected probe generator, shlpuls, transducer, amplifier, tunable filter, detector and recorder, as well as a filter control unit connected between the transducer and the tunable filter rom 12.

The disadvantage of the known flaw detector is low noise immunity if the flaw detector is interfered with at a frequency equal to or close to the frequency of the signals reflected from the defect.

The purpose of the invention is to increase the noise immunity and control performance at a variable scanning speed.

The goal is achieved by the fact that the ultrasonic flaw detector is equipped with series-connected pulse shapers, the input of which is connected to the detector output, and a threshold counter, the second input of which is connected to the output of the tunable filter, and the output to the recorder.

FIG. 1 shows a block diagram of an ultrasonic flaw detector; in fig. 2 - time diagrams showing the work of the scheme.

Claims (2)

The ultrasonic flaw detector contains a series of probe pulses, a transducer 2, an amplifier 3, a tunable filter 4, a detector 5 and a recorder b, and a filter control unit 7 connected between the transducer 2 and tunable filter 4 and sequentially connected pulse former 8, the input of which is connected to the output of the detector 5 and the threshold counter 9, the second input of which is connected to the output of the Loaded filter 4, and the output with the recorder 6. The ultrasonic flaw detector ta em as follows. The transducer 2, continuous ultrasonic oscillations of the ultrasonic frequency, received from the generator. 1, converts to acoustic and sends to the controlled article 10 at a certain angle. Reflected from. defects, a part of the emitted ultrasonic oscillations and possible signals from noise. The converter 2 enters, where the inverse transformation of acoustic oscillations into electrical ones occurs. Amplifier 3 suppresses generator signal 1 and amplifies signals that have a Doppler frequency shift. From the output of amplifier 3, signals are sent to a tunable filter 4, where frequency selection is made by screening interference, whose frequency is different from the frequency of the useful signal. the scanning speed of the filter control unit 7 changes the parameters of the filter 4 so that the filter bandwidth and its average frequency remain optimal for extracting the signals reflected from the defect. Pulses 11 (Fig. 2) from the output of the filter 4 are fed to the input of the detector 5 and the threshold counter -9. The threshold counter 9 counts the number of Doppler frequency periods in the echo signal and sends a signal 12 to the recorder b only when the number of Doppler frequency periods exceeds a predetermined value of p then Detector 5 selects the echo envelope 13 and feeds it to the driver 8 pulses, where a pulse 14 is formed with a duration equal to the duration of the input signal at a certain level. The falling edge of this pulse is the reset of the threshold counter 9, and the circuit is reset. FIG. 2, two pulses 11 are shown, selected by a tunable filter 4 and consisting of 12 and 5 periods of oscillation of the Doppler frequency, respectively. Accepting that the threshold of counter 9 is set equal to nine periods (n then 9). Therefore, when a signal containing 12 periods of oscillations at the Doppler frequency (n and then) is received, the threshold counter 9 generates a pulse 12, which starts the automatic recorder 6 From the second pulse with five periods of oscillations (pores), the automatic recorder 6 does not trigger. The invention makes it possible to increase the noise immunity of an ultrasonic flaw detector through the use of selection based on the spatial and temporal characteristics of signals from defects at their expected duration, since the number of Doppler frequency periods in the echo signal from the same defect at different scanning speeds is constant. The use of a threshold counter makes the flaw detector insensitive to interference, the duration of which is less than a certain value, consistent with the duration of the signal reflected from the defect. Ultrasonic flaw detector containing a series-connected probe pulse generator, transducer, amplifier, tunable filter, detector and recorder, as well as a filter control unit connected between the transducer and tunable filtrament, characterized in that, in order to improve noise immunity and monitoring performance, variable scanning speed, it is equipped with a pulse generator connected in series, the input of which is connected to the detector output , and a threshold counter, the second input of which is connected to the output of a tunable filter, and the output - with the recorder. Sources of information taken into account in the examination 1.Patent СЫА № 3321959, cl. 73 - 67.7, 1974. 2. USSR author's certificate for application number 2840524/28, class G 01 N 29/04-, 1979.