SU792577A1 - Pulse selector for apparatus for acoustic investigations - Google Patents

Description

one

The invention relates to devices for non-destructive quality control of materials and can be applied to isolate acoustic emission signals from cracks in brittle failure 5 in sheet materials and shells of structures under stress.

A pulse discriminator of duration is known, which contains two feedback systems, covered by feedback, capacitors and resistors l.

The main disadvantage of the discriminator is the insufficient accuracy of pulse selection. 15

Closest to the invention, the time selector pulses, containing a peak detector, pulse shapers, linear transducer L2J. The time pulse selector provides in aggregate the transmission of the first pulse from the radio pulse bundle, representing an acoustic emission signal and selecting all other pulses, including the reflected ones, 25 if they are adjacent to the main signal. At the end of the radio pulse, the selector is again ready to receive and select the first pulse (half-wave). Thus, the selector provides 3D

The first incoming impVlca, i.e., the half-wave of the longitudinal waves that came first because of the high velocity of propagation.

A disadvantage of the known temporal pulse selector is that the selected half-wave carries insufficient information about the crack, there is no information about distortions in the propagation of waves in a solid and the orientation of the receiving sensor relative to the direction of propagation of the crack. From the experimental data, it was found that if the sensor is installed in the area of the radiation pattern from the crack edges, the acoustic emission signal is significantly different from the waveforms obtained for the same crack when the sensor is oriented to the crack output. The obtained information on the orientation of the crack allows us to more accurately plot the relationship between the acoustic emission signal and the size of the crack.

The selection of the envelope of a radio pulse or the measurement of its peak amplitude, in which only part of the information about the size of the crack is embedded, leads to a decrease in the reliability of non-destructive testing by the method of acoustic emission. In order to increase the information content of the control, acoustic emission signals of the same type of waves should be singled out, while other types of waves and reflected signals should be suppressed. In order to provide acoustic emission signals that carry additional information, for example, on the orientation of opening cracks relative to the receiving sensor, it is necessary to ensure the separation of several waves of the full type, provided that the amplitude of the next half-wave should not exceed the amplitude of the previous half-wave. This leads to the determination of the orientation of the crack, and ultimately to the reliability of the non-destructive control. The purpose of the invention is to improve the accuracy of selection. The goal is achieved by the fact that the pulse selector for acoustic research equipment, containing the first pulse shaper whose input is connected to the input bus and the input of the delay element whose output is connected to the first input of the analog switch, the peak detector with a reset, the second pulse shaper, a logical element And , one input of which is connected to the first output of the first pulse generator, a frequency divider by two is entered, the limiter, the threshold element and the trigger whose output is connected to the second the input of the analog key and the second input of the logic element I, the output of which is connected to the first input trigger, the second input of which is connected to the output of the second pulse former, the information input of the peak detector with reset through the limiter connected to the input bus, the reset input through the frequency divider two with the second output of the first pulse former, and the output with the first input of the threshold element, the second input of which is connected to the input bus and the output to the input of the second pulse former. FIG. 1 is a block diagram of the selector; in fig. 2 — Pulse waveforms for individual selector blocks. Pulse selector contains pulse generator 1, divider 2 hours into two, peak detector 3 with reset, limiter 4, threshold element 5, pulse shaper logical gate And 7, trigger 8, analog switch 9, delay element 10, block 11 further processing information. The pulse selector works as follows. An input to the pulse shaper 1 is an analog acoustic emission signal, which, for example, has the shape shown in FIG. 2, The same signal through limiter 4 is fed to the first input of the peak detector 3 with a drop, to the second input of the threshold element 5 and to the input of delay element 10 and the switching time of the signal in the given pulse selector. From the pulse shaper, through the divider 2, two positive pulses arrive at the second input of the peak detector 3 with a throw, which provides a charge for the subsequent discharge of the memory capacity, detected at the first input from the signal previously limited at the lower MJ / level (Fig. 2 ). From the output of the Peak Detector 3, the voltage level corresponding to the amplitude value of the signal of the first or second half-wave having equal amplitude values is fed to the first input of the threshold element 5, to the second input of which an analog acoustic emission signal is applied. If the amplitude of the signal exceeds the second, third, and so on half-wave threshold value given by the voltage level from the first or second half-wave, a pulse is released at the output of the threshold element 5 (Fig. 2), and a short pulse is formed on the leading edge of the former 6 pulses. From the output of the pulse former 6, the pulse arrives at the second input of the trigger 8. At the same time from the pulse former 1, the first input of the logic element I 7 arrives at the second input, the second input of which supplies the potential to allow or prohibit the trigger 8 output. To the input of the logical element I, one pulse of the leading edge of the first half-wave is shown (Fig. 2), and the trigger 8 with its potential through the logical element AND blocks itself and gives the potential of the resolution to the first input of the analog key 9 (Fig. 2). The resolution signal will be present at the first input of the analog key 9 until a short pulse from the output of the imaging unit 6 pulses generated on the rising edge of the signal exceeding the amplitude of the set threshold value received at the input of the imaging device 6 pulses. A short pulse received at the second input removes the trigger 8 from self-blocking, which at its potential prepares the logic element AND 7 to receive the next signal and prevents the analog switch 9. During the presence of the resolution potential at the first input of the analog switch 9, the analog signal passes through the analog switch to the second input through the delay element 10, the magnitude of which is selected

Claims (1)

Claim A pulse selector, for example, for 1 acoustic research equipment, comprising a first pulse shaper, the input of which is connected to the input bus and the input of the delay element, the output of which is connected to the input of the analog key, a peak detector with reset, the second pulse shaper, a logic gate And, one input which is connected to the first output of the first pulse shaper, characterized in that, in order to increase the accuracy of selection, a frequency divider into two, a limiter, a threshold element and tr a ger whose output is connected to the second input of the analog key and the second input of the logic element AND, the output of which is connected to the first input of the trigger, the second input of which is connected to the output of the second pulse shaper, the information input of the peak detector with a reset through the limiter connected to the input bus, reset the input through the frequency divider into two - with the second output of the first pulse shaper, and the output - with the first input of the threshold element, the second input of which is connected to the input bus, and the output - to the input of second pulse shaper.