SU1682914A1 - Device for quality control of materials by integral acoustic emission signal - Google Patents

Abstract

This invention relates to non-destructive testing by an acoustic emission method. The purpose of the invention is to improve the measurement accuracy of emission pulses with a large interval by simplifying the device and improving the quality of digital-to-analog conversion. The pulses from the electroacoustic converter 1 are fed to the meter 3 of the signal maximum (peak detector) and then compared in the comparator 4 with the value of the smoothed analog signal carrying information about the amplitude of the largest pulse for the period of study, determined by timer 6. 2 Il.

Description

figure 1

The invention relates to the field of non-destructive testing by the method of acoustic emission (AE) and can be applied to control the quality of materials and products in mechanical engineering, nuclear energy and other areas of technology.

The aim of the invention is to improve the accuracy with A3 pulses with a large spacing interval by simplifying the device and improving the quality of converting digital signals to analog signals.

Figure 1 shows the structural diagram of the device for quality control of materials according to the total value of the AE signals; Fig. 2 shows diagrams of electrical voltages at some points.

The device contains a series-connected electroacoustic transducer 1, amplifier 2, meter 3 of maximum pulse amplitude, comparator 4, RS flip-flop 5, in which the S input is connected to the output of comparator 4, the R input to the output of timer 6, direct output through the driver 7 reset pulses - to the bus Reset of the meter 3, inverse output - to the first input of the coincidence element 8, whose second input is connected to the generator output of 9 counting pulses, and the output to the input of the digital-to-analog converter 10, the transitional integrating RC-chain KU connecting the output of a digital-to-analog converter (DAC) 10 with a second input of the comparator 4, in which a diode connected by an anode with a common bus is connected parallel to the resistance R.

The device works as follows.

Before starting the manual reset button (not shown), the meter 3 is reset to zero, and the trigger 5 is set to one. At its inverse output is set low, therefore, the pulses from the generator 9 of the counting pulses do not pass through the element 8 to the input of the DAC 10.

The AE pulses (Fig. 2a) come from the output of the electroacoustic converter 1 through the amplifier 2 to the input of the meter 3, at the output of which (Fig. 26) the amplitude value of the largest AE pulse is recorded during the time interval ti -12 determined by the strobe pulses of timer 6 figv).

When a pulse of timer b arrives at the R input of the trigger 5 at time t2, the latter is set to the zero state, a high level appears at its inverse output, and the pulses from the generator 9 of counting pulses (Fig. 2d) arrive at the input

DAC 10. The voltage at its output begins to increase and, in the interval t2-13, has a corresponding appearance (Figure 2d). This step voltage through the RC junction circuit arrives at the reference input of the comparator 4. At time 1c, when the voltage at its direct voltage equals the voltage at its inverse output, the comparator 4 is triggered, the trigger 5 is set to one state, and the pulses from the generator 9 ceases to pass through the element 8. At this moment the pulse shaper 7 generates a pulse, dropping the 3 amplitude meter to zero. As a result, at the output of the D / A converter, the amplitude value of the largest pulse for the intervals ti - t3 is remembered. Upon receipt of the next timer pulse at the described time

the process is repeated.

Thus, the RC transition circuit transmits only the variable component of the voltage from the output of the DAC 10 to the input of the comparator 4, not skipping its constant

component.

With the passage of a stepped voltage through an RC circuit, the capacitor C is slightly charged with polarity (Fig. 1). Diode D is for

accelerating its discharge in time intervals between timer pulses.

The invention differs from the known device in that it uses only one D / A converter. This, along with the simplification of the design, makes it possible to increase the accuracy of the summation of AE pulses, since the output of the DAC in the summation process stores exactly that value between each pulse of the timer.

analog value, which is directly equal to the maximum value of the analog value of AE pulses, coming from the electro-acoustic converter to the input of the comparator for

comparison at a given time.

Claims (1)

The claims of the device for quality control of materials on the total value of the signals an acoustic mission containing a series-connected electroacoustic transducer, an amplifier, a pulse amplitude maximum meter, a comparator, an RS flip-flop and a reset pulse shaper, the output of which is connected to the control input of the pulse amplitude maximum meter, a timer connected to the R-trigger RS-trigger, a series connected counting pulse generator; a matching element. the second input of which is connected to the inverse output of the trigger, and a digital-to-analog converter, characterized in that, in order to increase accuracy, it is equipped with an integrating RC-circuit connected between the output of the digital-analog converter and the reference input of the comparator, and a diode connected in parallel with the resistance of the RC-chain by an anode to a common bus.  Llaldlllll ll 1 t l / I /  . 1 M. 11 I b but tl l Jl / B c FIG. 2 t, ts t