SU794492A1 - Concrete strength determining device - Google Patents

Description

one

The invention relates to non-destructive testing of materials and products and can be used, in particular, to control the quality of products of precast concrete plants and large-panel housing construction, as well as on construction sites.

The invention is based on measuring the propagation time of oscillations (UT) in a material.

The closest to the technical essence of the invention is a device for determining the strength of concrete, containing sequentially connected synchronizer, probe pulse generator, radiating and receiving electroacoustic transducers, amplifier, difference trigger, connected to the synchronizer delay circuit and digital indication unit, made in series pulse counter and counting pulse generator 1. In this device, the counting pulse generator is tunable L R A decision algorithm (B-t), where R-strength concrete, A - frequency generator countable pulses B - delay time in the delay circuit, t- propagation time of ultrasonic testing in

the material measured by the device, which converts the time of ultrasonic testing to strength, measured by the device, with digital indication of the result directly in units of concrete strength. This eliminates the manual operation of processing the result of the tables and graphs.

However, the known device has a significant drawback - the measurement accuracy is low due, firstly, to the fact that there is no parasitic time delay compensation scheme in the device circuit and electroacoustic transducers, which leads to a systematic error in measuring the strength of concrete, especially for small acoustic bases, where this error can reach significant relative values. In addition, the coefficient B set by the indicator (pulse width meter, for example, frequency meter 43-30) does not include a time interval equal to the compensation time for setting the pool, which in the measurement mode

strength leads to a systematic error, reaching 1.5-3 μs.

In addition, the block diagram of the device does not contain elements of periodic monitoring of the correct installation of the coefficients A and B, and the set and verification of the algorithm require connecting an external oscillator and frequency meter, which cannot be done during long-term operation of the device away from the AC power sources.

At that time, due to the temporal and temperature drift of the frequency of the counting pulse generator, a systematic measurement error may occur, the greater the rarer the verification of the installation of the algorithm and the greater the change in external conditions.

The aim of the invention is to improve the measurement accuracy by eliminating the systematic measurement error.

The goal is achieved by the fact that the device is equipped with a compensation unit connected between the delay circuit and the Stop Difference Trigger input, the trigger former, the zero setting circuit, the type of operation switch, the control interval driver and the frequency divider; trigger-shaper time interval input “Stop connected to the output of the amplifier, input“ Start through the zero setting circuit - to the synchronizer, one output - to the input “Trigger trigger of the difference, the other output through the switch of the type of work - to the digital display unit, to which also the switch is connected to the output of the difference trigger and the control interval imager, which is connected via a frequency divider to the counting pulse generator of the digital display unit, and the output of the delay circuit is additionally connected ene through the selector switch to the block digital display.

FIG. 1 is a block diagram of the device; in fig. 2 - voltage diagrams for device operation.

A device for determining the strength of concrete contains a synchronizer 1, a generator 2 of probe pulses connected in series with it, radiating and receiving electroacoustic transducers 3 and 4, an amplifier 5 connected to the input of the Stop Trigger-Former 6 of the time interval, the input of which is started through the installation circuit 7 the zero is connected to the synchronizer 1, and the output is connected to the input “Trigger trigger 8 of the difference” and through the switch 9 of the kind of work - to the digital display unit 10. The synchronizer 1 through the circuit 11 of the delay and the circuit 12 compensation connected to the input of the Stop trigger 8 difference. The outputs of the circuit 11 of the delay and the trigger 8 of the difference through the switch 9 kind of work connected to the unit 10 of the digital display.

The digital display unit 10 consists of a counter of 13 pulses and a generator of 14 counting pulses. The output of the latter is connected to the counter 13 pulses and through the frequency divider 15 is connected to the input of the imaging unit 16 of the control interval, the output of which is connected to the digital display unit 10 through the switch 9 of the type of work. The converters 3 and 4 are placed opposite on opposite sides of the controlled plate 17. The device operates as follows.

The synchronizer 1 determines the frequency of the pulses of the generator 2 of the probe pulses and synchronizes the operation of all the other units of the device (plot 18, Fig. 2). Ultrasonic oscillations 19 of the probe pulse generator 2 through the radiating electroacoustic transducer 3 are introduced into the monitored product 17 and, having passed through time t, are picked up by the receiving electroacoustic transducer 4 and amplified by an amplifier 5 (20). At the input of the Trigger Trigger-Former 6 time interval with the frequency of the parcels, synchronizer pulses 1 are received, delayed by time 4 (21) with respect to

by the time the generator triggers 2 probe pulses in order to compensate for parasitic delays in the electronic unit and electroacoustic transducers. To the input of the Stop Trigger-Former 6 of the time interval, the front pulses of the received ultrasonic signal (20) come from the output of the amplifier 5. Thus, the output of the Trigger-Former 6 forms a rectangular

impulse (22), equal to the time of UT propagation in the plate. These pulses in the mode of measuring the propagation time of the UST (position I of the switch 9 of the type of operation - Fig. 1) are fed to the counter 13 of the pulses of the digital display unit 10 and serve to compensate for parasitic delays tf, when adjusting the zero setting circuit 7. After compensation, the duration of the pulse (22) of the trigger generator 6 becomes equal to (), i.e. the true time of the UST propagation in the plate 17. This time at position I of the switch 9 of the type of operation enters the digital display unit 10 (23) and is indicated by a counter 13 pulses when filling the quartz frequency from the generator 14 counting pulses.

Simultaneously with the adjustment of the zero setting circuit 7, an adjustment is made

compensation circuit 12, on which the delay time is also set to t. On the generator 14 of the counting pulses of the digital display unit 10, a predetermined value of the coefficient A of the algorithm is established. The frequency A (24) in position II of the switch 9 of the type of operation fills the interval T (25) formed by the shaper 16 of the control interval, and is fed to the display in digital form on the counter 13 pulses (26).

The synchronizer 1 starts the circuit AND the delay, which regulates by the counter 13 pulses in position III of the switch 9, the work type is set to the value of the coefficient B of the algorithm (27). Period B is digitally indicated by a counter of 13 pulses when the oscillating frequency from the generator of 14 counting pulses is filled (28).

The delay circuit 11 by the falling edge of pulse B (27) starts the compensation circuit 12, which, as already noted above, produces a compensating pulse of duration tu (29).

The falling edge of the pulse (29) of the trigger of the time interval 6 triggers the difference trigger 8, and the falling edge of the pulse (29) of the compensation circuit 12 returns the trigger 8 to the initial state. Thus, at the output of the difference trigger 8, a rectangular pulse (30) is formed, the duration of which is equal to the difference

(B + t,) - (,} (B-f).

This pulse at position IV of the switch 9 of the kind of work enters the counter 13 pulses of the digital display unit 10, where it is filled with pulses of frequency A (24) generated by the generator 14 of counting pulses (31). In this case, an algorithm is indicated in the digital form on the counter of 13 pulses.

R AlB-tl,

which is an approximation obtained experimentally in accordance with GOST 17624-72 of the correlation curve associating the propagation time t of the UT in the material with the value of the compressive strength of concrete R.

Thus, a direct measurement of the quality of the material is carried out with indication of the result in units of concrete strength without the need for additional mathematical processing of the measurement result. Using the invention allows ultrasonic monitoring of the quality of concrete with indication of the measurement result in units of concrete strength. In this case, the measurement is carried out with high accuracy, since the systematic measurement error, equal to and, is eliminated in the displayed result. In addition, when measuring, the operator has the ability to systematically check the correctness of the coefficients A and B of the algorithm, i.e., periodically eliminate the additional systematic error resulting from the inevitable change in the value of the time delay B in the delay circuit and the frequency A of the counting pulse generator temperature change during the working day.

Claims (2)

1. A device for determining the strength of concrete, containing a series-connected synchronizer, probe pulse generator, radiating and receiving electroacoustic transducers, amplifier, difference trigger connected to synchronizer delay circuit and digital display unit, made in the form of serially connected pulse counter and counting pulse generator, characterized in that, in order to improve measurement accuracy by eliminating systematic measurement error, it is equipped with a compensation unit connected between the delay circuit and the Stop Trigger input differences, trigger former, zero setting circuit, type of work switch, control interval driver and frequency divider, trigger driver time “Stop connected to the amplifier output, input“ Start through the zero setting circuit to the synchronizer, one output to the input Start the difference trigger, other output through the type of work switch to the digital display unit to which are also connected the output of the difference trigger and the former of the control interval, which through a frequency divider is connected to the generator of counting pulses of the digital display unit. 2. The device according to claim 1, characterized in that the output of the delay circuit is additionally connected via a work type switch to the digital display unit. Information sources, taken into account during the examination 1. USSR author's certificate No. 442422, cl. G 01N 33/38, 1972 (prototype).