SU1523998A1 - Apparatus for determining modulus of elasticity of materials - Google Patents

Abstract

The invention relates to the study of the physical properties of materials using ultrasonic vibrations and can be used to determine the elastic modulus of solids. The purpose of the invention is to improve the accuracy of determining the elastic modulus of materials due to changes in the internal structure of the material under external influences. The device measures the ultrasound velocity in a sample of a material from which its elastic modulus is calculated. At the same time, the specific electrical conductivity of the sample is measured and taken into account when calculating the modulus of elasticity, which provides an increase in the accuracy of its determination. 2 Il.

Description

The invention relates to the study of the physical properties of materials using ultrasonic vibrations and can be used to determine the elastic modulus of solids,

The aim of the invention is to improve the accuracy of determining the modulus of elasticity of materials by accounting for changes in the internal structure of the material under external influences.

Figure 1 is a block diagram of a device for determining the elastic modulus of materials; on - signal plots, which explain the operation of the device.

The device contains a probe pulse generator 1, a probe pulse amplifier 2, a piezo transducer 3 and an acoustic communication line 4, an amplifier-limiter 5 reflected pulses, an input connected to a piezo transducer 3, a delay element 6, the input of which is combined with the input of the probe 2 amplifier pulses, meter 7 intervals, detector 8, first 9, second 10 and third 11 D-flip-flops with dynamic control on the pulse front, element I 12, differentiator 13, meter 14 specific elec- the conductivity of the sample material, the modulus of elasticity calculating unit 15 and the bipolar switch to the switch 16, the output of the detector 8 are connected to the C-sync input of the first D-flip-flop 9, and the information D input of which is connected to the output of the And 12 element, and the inverse Q- the output is connected to the C-sync input of the second D-flip-flop 10 and to the first input of the And 12 element, the second input of which is connected to the inverse Q-output

and combined with the information D-input of the second D-flip-flop 10, the separate R-inputs of the zero-setting of the first 9 and second 10 D-flip-flops are connected to the forward Q-output of the third D-flip-flop 11 is connected to its information D-input, and the C-sync input is connected to the output of delay element 6, whose input is connected to the separate R-input of setting the third D-flip-flop 11 to the zero state, the first Q-output of the first D-Trigger 9 is through the differentiator 13 is connected to the input of the meter 7 time intervals, the outputs of The 7 time intervals and the conductivity meter 1A are connected respectively to the first and second inputs of the elastic modulus calculation unit 15, the movable contact of the two-pole push-button switch 16 is connected to the generator output 1 of the probe pulses, the normally closed fixed contact is connected to the amplifier 2 input of the probe pulses, and An open fixed contact is connected to a separate S-input of the installation in a single state of the third L-flip-flop I1.

In addition, FIG. 1 shows sample 17 of the material under study. The inputs of the specific electrical conductivity meter 14 are connected to opposite ends of the sample of material under study 17, which is mounted on the free end surface of the acoustic line 4 CONNECTED

The device works as follows.

Before starting the measurements, to eliminate the uncertain state of the flip-flops 9, 10 and P, pressing the Reset button 16 sets the flip-flops 9-11 and element 12 to reset them. In this case, an electrical impulse of positive polarity (fng.2a) from the output of the generator 1 is sent to a separate input of the unit into a single state of the third trigger 11 and, with its front, sets the voltage of a high level on the direct Q-output, i.e. (Fig. 2e), and at the inverse Q output, a low voltage, i.e. O (fig.2zh). The signal 1 from the direct Q-output of the third trigger 11 is fed to the separate R-inputs of the installation in the zero state

the first 9 and second 10 flip-flops, resulting in the direct Q-output of the first flip-flop 9, 0 (fig.2b, l), and the inverse q-outputs of the first 9 (figo2k) and second 10 (figo2z) flip-flops l Since both the inputs of the And 12 element arrive at 1, then at its output and at the informational D-input of the first trigger 9 also (Fig. 2i).

set to

R

five

0

five

0

five

0

five

five

0

When releasing the button 16 (Measurement position), a short-term electrical probe pulse (Fig 26) from generator 1 is amplified by an amplifier and fed to a piezoelectric transducer 3, where it is converted into an acoustic signal, which via an acoustic link 4 arrives at sample 17, Part of this acoustic signal reflects from the beginning of the sample 17 and via the acoustic line 4 the connection is fed back to the piezoelectric transform 3, where it is converted into an electrical signal and fed to the input of the amplifier - limiting 5 Another part of the acoustic The signal passes through pattern 17, is reflected from its end, passes through it again, to its beginning where it separates again — one part through link 4 and the piezoelectric transducer 3 enters the input of limiting amplifier 5, and the other returns to The body of sample 17. Thus, a series of reflected pulses (A, B N and P) appears at the output of the amplifier-limiter 5 (FIG. 2b) and detector 8 (FIG. 2 g), with the first reflected pulse A appearing after a time interval 2 oe (where tf is the acoustic transmission time through the acoustic line 4 and; t is the delay time of the signal in the electronic circuits of the device) from the beginning of the probe pulse, and the subsequent pulses B, N, and P appear at time intervals 2 (where c, is the time taken for the acoustic signal to follow the pattern). pulse, at the output of amplifier 5 and detector 8, there appears a direct pulse M (fig. 2d) with a piezoelectric transducer 3, coinciding in time with the probe pulse of geyator 1.

From this sequence of pulses, it is necessary to divide the first A and

BTOpoti B ((bf, 2d) reflected pulses and measure the time interval between them, equal to the time of double passage of the acoustic signal on the sample 17, equal to Z LJ, taking into account which the speed of propagation of ultrasonic vibrations in the sample material is determined j For this purpose 6 delays, the first 9, the second 10 and the third 11 P-triggers with dynamic control over the pulse front, element I 13, as well as differentiator 13 and meter 7 time intervals

The measurement of the time interval between the first A and the second B (FIG. 2d) reflected pulses is carried out as follows.

The probe pulse generator 1 (Fig.2b) is fed to the input of the delay element 6 and to the separate R-input of the installation in the zero state of the third trigger 11, as a result of which on its direct Q-output it is set to (fGs2g, e), and on the inverse Q - output and informational D-input 1 (FIG. 2g) “The zero potential from the direct Q-output of the third trigger 11 is transmitted to the separate R-inputs of the first 9 and second 10 triggers. Thus, the trigger 9 is closed by a zero potential at the R input and the impulse M (FIG. 2d) arriving at its C synchronization input cannot change its state, i.e. the potentials of direct Q (Figo 2) and inverse Q () outputs do not change.

The probe pulse delayed in the delay element 6 for the time tj (FIG. 2d), longer than the pulse duration M (FIG. 2d), arrives

on the C input of the synchronization of the third trigger 11, as a result of which, on its direct Q input, it is set to 1 (FGs2e), which is transmitted to the R input of the setting to the zero state of the first o and second 10 triggers. Since the first trigger 9 is already in the zero state (O at the direct output), its state (FIG. 2) does not change. The second trigger 10, having after the first measuring cycle at the inverse output O (FIG. 2h), changes its connection and 1 appears at its inverse output (FIG. 2h). As a result, 12 (fig 2 and on the informational D-input of the first

trigger 9 is set to 1, the circuit is ready to receive the first reflected pulse A (FIG. 2d).

The first reflected pulse A, which arrives at the C-sync input of the first trigger 9, changes its state with its front, i.e. at the direct Q output, 1 is set (FIG. 2L),

and on the inverse Q-output O (FIG. 2k). In this case, the state of the second flip-flop 10 does not change (fig 2), and at the output of the element 12 (fig 2i) and at the 1-format D input of the first trigger 9

a second reflected pulse B is installed (Fig. 2), arriving at the C input of the synchronization of the first trigger 9, changes its state with its front, i.e.

The Q-output is set to O (Fig.2l), and on the inverse Q-output 1 (Fig.2k). In this state, the second trigger 10 is changed,, on its inverse Q-terminal is established (FIG. 2h),

and on the input of the element And 12 the zero potential does not change (Fig. 2i), therefore the Third reflected impulse N is kept at the information input of the first trigger.

(fig2g) and all subsequent ones (in fig. 2d, only one more PV pulse is shown arriving at the synchronization input dc from the first trigger 9 cannot change its state, since at its information D input

stably maintained zero potential (Fig.2), which is repeated at the direct Q-output (Fig2) about

Thus, on the forward Q-rate

the first trigger 9 is formed by a single pulse with a duration of 2 to (fig. 2l) equal to twice the transit time of the acoustic signal in the sample 17. This pulse enters the differentiator 13, where it is converted into two short pulses (fig2m), the time interval between which is also 2 & p, is measured with a 7 time interval meter.

The results of measurements of the transit time of the acoustic signal in the sample are received in block 15 of the calculation of the modulus of elasticity E, which is calculated by the formula

K pji-). (one)

Where

p is the theoretical density of the material;

1 - the length of the acoustic path in the sample 17;

Y is the theoretical and experimental value of the specific conductivity of the material under study.

The value of Y is measured by the conductivity meter 14 and is fed to the second input of the elastic modulus calculation unit 15.

This completes the measuring cycle. With the arrival of the next probe pulse of the generator 1 (FIG. 2b), the next measuring cycle begins. The period T of the following pulses is chosen large enough so that B the test specimen has repeated multiple reflections of the previous pulse completely by the time the next pulse arrives.

The proposed device for determining the elastic modulus of materials, as compared with the known, improves the accuracy of determining the elastic modulus of materials that change the internal structure under external influence, for example, under mechanical loading or temperature variation.

Improving the accuracy of determining the modulus of elasticity is achieved by the fact that in this device, simultaneously with measuring the velocity of propagation of ultrasonic waves in the sample material, the electrical conductivity of the sample material is additionally measured, and the actual value of the elastic modulus is determined by formula (1). This makes it possible to eliminate the methodological error of determining the elastic modulus, due to the influence of changes in the internal structure of the material on the velocity of propagation of ultrasonic waves in it, which can be 1% or more.

Claims (1)

Invention Formula A device for determining the modulus of elasticity of materials, containing a generator of probe pulses, serially connected amplifier of probe pulses, piezo-transform Q 5 o with Q 0 five tel and acoustic lines), an amplifier-limiter of reflected pulses, an input connected to a piezoelectric transducer, a delay element whose input is combined with an input of an amplifier of probe pulses, and a time interval meter, characterized in that, in order to improve the accuracy of determining the elastic modulus materials that change the internal structure under external influence, it is equipped with a detector, first, second, and third D-flip-flops with dynamic control over the front of the pulse, an And element, a differentiator, the conductivity material of the sample material by the module for calculating the modulus of elasticity and a bipolar pushbutton switch, the detector output is connected to the synchronization input of the first D-flip-flop, whose information D input is connected to the output of the And element, and the inverse output is connected to the synchronization input of the second D-flip-flop and to the first the input element And, the second input of which is connected to the inverse output and combined with the information input of the second D-flip-flop, separate inputs of the installation in the zero state of the first and second D-trigger g The sensors are connected to the forward output of the third D-flip-flop, the inverse output of which is connected to its information input, and the synchronization input is connected to the output of the delay element, the input of which is connected to the separate input of the installation to the zero state of the third D-flip-flop, the forward output of the first D the trigger through the differentiator is connected to the input of the time interval meter, the outputs of the time interval meter and the conductivity meter are connected respectively to the first and second inputs of the elastic modulus calculator, odvizhny bipolar contact pushbutton switch is connected to the output of the sounding pulse, the normally closed fixed contact connected to the input of the amplifier probe pulses, and the normally open fixed contact - to the separate installation of a single entry state of the third D-triggerao