SU1633292A1 - Device for measuring ultrasound speed - Google Patents

Abstract

The invention relates to the field of non-destructive testing and can be used for ultrasonic testing of metallic structural materials subjected to cyclic burning. The purpose of the invention is to increase the sensitivity and accuracy of measurements. By measuring the propagation time of ultrasound, refer ... i to the first reflected echo signal to estimate the propagation velocity of ultrasound in the monitored material. The introduction of a high-level comparator eliminates false measurements of the propagation time of an eltra in the presence of noise and random noise in the electro-acoustic path, which improves the measurement accuracy. 2 Il. five (/)

Description

The invention relates to the field of non-destructive testing and can be used for ultrasonic testing of metallic structural materials subjected to cyclic loading.

The purpose of the invention is to increase the sensitivity and accuracy of measurements by eliminating spurious measurements of time, the propagation of ultrasound in the presence of structural noise and random noise in the electro-acoustic path.

FIG. 1 is a functional diagram of the device for measuring the speed of ultrasound; in fig. 2 - timing diagrams for the operation of the device.

A device for measuring the speed of ultrasound contains (Fig. 1) a probe pulse generator 1, a piezo transducer 2, an amplifier 3, a high comparator 4

level, low comparator 5, delay blocks 6 and 7, element 3 and 8, commutator 9, counters 10 and 1I pulses, drivers 12 and 13 pulses, source of 14 time intervals, / -trigger 15, integrator 16, adder 17 filter 18, inverter 19, registering unit 20, display unit 21, for example, a Piezo-converter 2 oscilloscope is connected to the first output of the generator I of probe pulses and to the input of the amplifier 3, the output of which is connected to the first input of the display unit 21, to the inputs of the comparators 4 and 5. The second output of the generator 1 probe pulses Inonii adjusting inputs to counters 10 and 11 pulses, a second input of the indication unit 21 to the first control input of switch 9 and to the input of the first delay unit 6, whose output is connected

O5 PA SO GS

SS

yo

with the first input of the element 3 AND 8 and with the input of the second delay unit 7 The output of the second delay unit 7 is connected to the second control input of the switch 9 and to the second input of the element 3 AND 8 connected by the third input to the output of the high level comparator 4 and the input of the switch 9, the first and second outputs of which are connected to the counting inputs of the counters 10 and 1 1 pulses respectively The first driver 12 pulses are connected to the output of the counter 10 pulses by the first input, the second input to the output of the low level comparator 5 and to the second input of the pulse driver 13 and the output to the start input of the source 14 time slots. The second driver 13 of the pulses is connected to the output of the pulse counter 11 of the pulses by the first input and output to the S input / 5 of the trigger 15 connected by / input to the output of the 14 temporary source intervals and output - to the input of the integrator 16, the output of which is connected to the first input of the adder 17 and to the input of the filter 18 The output of the filter 18 is connected to the input of the inverter 19, the output of which is connected to the second input of the adder 17 connected to the input of the register securing unit 20

The device for measuring the speed of ultra sound works as follows

From the first output of the generator 1, the pulses arrive at the piezoelectric transducer 2, which studies ultra sound pulses in the material under study. Ultrasonic echo signals arriving at the piezoelectric transducer 2 are converted into electrical ones and amplified by the amplifier 3, from the output of which (Fig. 2a) are fed to high and low levels of the comparator 4 and 5 inputs The high level comparator 4 (Fig. 2) triggers when the input signal reaches the voltage UOM., which is larger than the amplitude of random noise and the Comparato structural acoustic noise 5 low level triggered when the input signal passes a zero potential. The signal from the output of the comparator 4 high level through the ZI element 8 is fed to the information input of the switch 9. The pulse from the output of the comparator 4 high level to the switch 9 at the moment of passing the probe signal and at the time of passing intermediate echo pulses between the first and -th echo signals are carried out using an element ZI 8 and series-connected delay blocks 6 and 7 (Fig. 2, c and d) Starting the delay unit 6 is effected by a signal from the second output of the probe pulse generator (FIG. 2, e). The delay unit 7 is started by a signal from the output of the delay unit 6 (FIG. 2, d). The switch 9 directs the pulses. from the output of the ZI 8 element (Fig. 2e) in the presence of a signal at the first control input of the switch 9, to the counting input of the counter 10 pulses, and if there is a signal at the second control input of the switch 9 - to the counting input of the counter 11 pulses Counter 10 pulses generates a signal at the output (FIG. 2, g) at the moment of steps of the signal corresponding to the nth period in the first reflected signal. Pulse counter 11 forms

output signal (Fig. 2, h) at the moment of arrival of the signal corresponding to the nth period in the l / th reflection signal. Setting the counters 10 and 11 pulses to the initial state is carried out by a pulse.

from the second output of the generator 1 probe pulses The signals from the outputs of the counters 10 and II, respectively, arrive at the first inputs of drivers 12 and 13, the second inputs of which receive signals from the output of the low level comparator 5 Shaper 12 and 13 produce pulses at the output coincides with the moment of passage of the signal from the output of the amplifier 3 zero potential Signals from the output of the first driver 12

5 (FIG. 2, and) is fed to the input of the 14-slot source start and is triggered by its leading edge. From the 14-slot source output, the signal delayed by the time of the Gdz (Fig. 2, l) goes to the R input / 5-flip-flop 15, 5-entrance

0 which receives a signal from the output of the second generator 13 (Fig. 2, k). As a result, at the output of the 5-flip-flop 15, we have a signal with the duration t (Fig. 2, m).

5 oscillator 1 probe pulses From the output / 5-flip-flop 15 a signal of duration t is fed to the input of integrator 16, which converts this signal into a voltage UBH proportional to t

0iv „1k,

where L / Bfi is the voltage at the output of the integrator 16,

k - coefficient

The propagation time of ultrasound in the material in this case is equal to

,

where / lz -time formed by the source

14 time intervals. Under cyclic uniaxial loading, the value of m is equal to

50

(, + 4-) а0со5 (a) / - г-фХп + Лт.А,

- coefficient of elastic acoustic

connection;

- Punch coefficient, - Young's modulus, - voltage amplitude, MPa, - cyclic loading frequency, - phase, - current time,

/ o is the propagation time of the ultrasound at the initial time of the test, TO-time t at the initial

moment of trial.

Atu - increment of the propagation time of ultrasound as a result of irreversible changes in the material subjected to cyclic loading

The value of At is a slowly varying parameter in comparison with the variable component arising due to the elastic-acoustic effect h due to the change in the length of the acoustic path.

The signal from the output of the integrator 16, proportional to the value of t, is fed to the input of the filter 18, passing the variable component to the output of the frequency w the signal from the integrator 16 output. As a result, the following function is implemented at the output of the adder 17

T3 To-f- / Jalicos (co / + (f) + / g ооС05 (Ои / + (g - (-) / (t,

where k ky + -Ј

The value proportional to teff is recorded by the recording unit 20 during the loading process, and the display unit 21, which uses an oscilloscope, is monitored by the echo signals received from the output of amplifier 3

The material thickness changes due to irreversible processes under cyclic loading in the area of high-cycle fatigue almost does not occur. In this case, when testing for fatigue, most of the material durability is determined by the accumulation of dispersed microdamages

WEF / (,

 V ,, + AIV,

L + At / y

where t,

/ o is the length of the acoustic path, Uuf is the speed of ultrasound propagation in material 22 subjected to cyclic loading, Ko is the speed of ultrasound at,

,

AV / v - change in the speed of ultrasound due to irreversible changes in the material

Choosing one of the periods of the first reflected signal as the base for estimating the propagation time of ultrasound in the material, by passing to relative measurements, we eliminate the errors that occur in the electroacoustic path during measurements, when as a basic signal

five

0

A reference pulse, an excitation probe pulse generator, is taken.

In the known device, the measured time is

G / el + / ksgM,

where / ed - time delays in the electrical path,

/ к.с ..- time delay of the signal in the piezo-converter when it is excited and in the contact layer between the piezotransducer and the material under study,

 - time of propagation of the first reflected ultrasonic echo signal

For the reflected signal we have

// e-Mke-g

Perrho to relative measurements of G - /

we have

/ -

 -I

five

0

five

0

five

0

As a result, the effect of 1e.c and / .c on the measurement results is eliminated. When the material is loaded in an elastic region, the device extracts a signal at the output of integrator 16, the value of which is proportional to the effective elastic stresses, which allows it to be used as a meter. Mechanical stresses The use of the invention improves the sensitivity and accuracy of measurements ia by eliminating false measurements of the propagation time of ultrasound in the presence of structural noise and random interference in the electroacoustic tract

Claims (1)

Invention Formula A device for measuring the speed of ultrasound, containing a series of electro-acoustically connected probe pulse generator, a piezotransducer amplifier and a low level comparator of a series-connected source of time intervals, a / 5 flip-flop, an integrator, an adder and a recording unit, a display unit, an inverter and a filter connected by an input to the integrator output , output - to the input of the inverter, the output of which is connected to the second input of the adder, and the indication unit is connected to the output of the amplifier, the first input It is distinguished by the fact that, in order to increase the sensitivity and accuracy of measurements, it is equipped with two delay units, a ZI element, two pulse counters, a switch, two pulse shapers, and a high level comparator, connected to the output of the amplifier, and output to the first input of the ZI element , the second output of the probe pulse generator is connected to the first control input of the switch, to the second input of the display unit, to the setup inputs of both pulse counters and to the input the first delay unit, the output of which is connected to the second input of the ZI element and to the input of the second delay unit connected by the output to the third input of the ZI element and to the second control input of the switch connected by the information input to the output of the ZI element, the first and second outputs to the counting inputs the first and second pulse counters, respectively, the output of the first pulse counter is connected to the first input of the first pulse shaper connected by the second output to the low level comparator output and to the second input the second pulse shaper, the output to the start input of the time interval source, the output of the second pulse counter is connected to the first input of the second shaper connected by an output to the S input of the trigger. Fi & 1 Probe, sig1eho-sign. Eekho-signal. but / 71 ft Wush tf-echo B to B ± l J.