SU1589197A1 - Apparatus for measuring acoustic resistance of materials - Google Patents

Abstract

This invention relates to non-destructive testing using ultrasonic signals. The aim of the invention is to increase the sensitivity of measurements in the study of materials with high acoustic impedance due to the increased response of the device to the relative change in the measured value of acoustic impedance. The operation of the device is based on the reflection of ultrasonic signals from the interface between two media with known and measurable acoustic impedances. The reflected signals are received by ultrasonic transducers, converted by them into electrical signals, processed by the device blocks, and at the output of the latter, a signal is generated that is proportional to the acoustic resistance of the material under study. 1 il.

Description

The invention relates to non-destructive testing using ultrasonic signals and can be used to measure the acoustic resistance of solids and liquids.

The aim of the invention is to increase the sensitivity of measurements in the study of materials with high acoustic impedance.

The drawing shows a block diagram of the proposed device for measuring acoustic resistance of materials.

The device contains the first 1 and second 2 ultrasound transducers intended for contact through the reference medium 3 with the test material C and the control medium 5, respectively. The device also contains an ultrasonic generator 6, the outputs of which are connected to the first 1 and second 2 ultrasonic transducers, respectively, and connected in series, dividing the cascade 7, divider 8 and block 9 of the functional transducer realizing the dependence

and .... 1 (.1)

where and

bh

vmh

and

and

Bh

yyh

input and output levels of the block, respectively, j

constant coefficient equal to the acoustic resistance of the known reference medium 3 in the chosen physical measurement system.

ate

00

with so

h |

The first input of the summing cascade 7 of the device is connected to the first ultrasound transducer 1, and the second input together with the second input of the de- litel 8 is connected to the second ultra-Sonic transducer 2. The output of block 9 of the function transducer is the output of the device.

To ensure acoustic contact of ultrasonic transducers 1 and 2 with the test material I and the control medium S, the latter (should be placed on the iO surface of the reference medium 3 located in the immersion bath 11, at the bottom of which the ultrasonic surfaces are fixed at the same depth and parallel to the surface. transducers. Any immersion fluid with a known acoustic impedance can be used as a coupon medium 3. Air is used as a control medium. If this medium is a liquid, then zuyut solid sound- wires bonded to the transducers.

A device for measuring the acoustic resistance of materials operates as follows.

Ultrasonic generator 6 generates electrically-developed ultrasonic signals of the same amplitude at its first and second outputs, which are converted by the first 1 and second 2 ultrasonic transducers into acoustic signals. Spreading in the reference medium 3, the acoustic signals are reflected from the contact boundary of the reference medium with the test material 4 and with the control medium 5, reach the first and second ultrasound transducer 1 and 2 and are converted. them into electrical signals. In this case, the amplitudes A and Ap of the signals reflected from the contact boundary of the reference medium 3 with the test material 4 and with the test medium 5, received by the first 1 and second 2 converters respectively, will be determined by the difference in the acoustic impedance values of the indicated media and the material under study. Electric signals from the outputs of the ultrasonic transducers are fed to the inputs of the summing stage 7 and the signals from the second ultrasonic transducer 2 also go to the second

input divider .8, the output of which sets a voltage proportional to the value

„- Dx + AO

R l

The value of P is associated with the values of 7. IQ and ZP of the acoustic resistance of the material under study C and the control medium 3 by dependence

R

2Z,

Z. + Z.

X o

The signal P from the output of the divider 8 is fed to the input of the functional conversion unit 9, at the output of which the voltage U is set,

and il about P

-) z

X

proportional to the measured acoustic impedance of the material under study. The magnitude of the differential sensitivity D of the device when measuring the signal p is determined from the ratio.

Thus, when studying materials with acoustic impedance, much larger than in the reference environment, the device provides a high differential sensitivity to changes in the acoustic impedance of the material under study, which increases the sensitivity of measurements.

Claims (1)

Invention Formula A device for measuring the acoustic impedance of materials, comprising first and second ultrasonic transducers for contacting through the reference medium with the test material and the test medium, respectively, an ultrasonic generator, the outputs of which are connected to the first and second ultrasonic transducers, divider and a functional conversion unit, the input of the latter is connected to the output of a divider, the second input of which is connected to the second ultrasonic converter, characterized in that, in order to increase the sensitivity of measurements in the study of materials with high acoustic impedance, it contains a summing cascade, the first input of which connected to the first ultrasound transducer, the second input to the second ultrasound transducer to the consumer, the output is connected to the first input of the divider, and the Functional Transformation block implements the dependence , 2 and in (1x 0% It: where and and vx mx and, - t), - levels of input and output signals of the block, respectively constant coefficient. one / BUT.. x: fi