SU1714486A1 - Method for determining acoustic resistance of homogeneous media - Google Patents

Abstract

The invention relates to non-destructive testing. The aim of the invention is to increase the sensitivity and accuracy of measurements. Ultrasonic vibrations are emitted in the direction of the acoustic contact between the reference and the media under study, and they receive reflected signals. The magnitudes of the amplitudes of the emitted and reflected signals are measured, r ^ rHaVe 9a ^ this level, selected from the ratio UcH AO t Z - Zo / Z * Zo д АО de AO ^ amplitude of the emitted oscillations; Zo is the acoustic impedance of the reference medium: Z-: measuring the value of the acoustic impedance of the medium under study, which take into account the desired acoustic resistance. The invention relates to the area of non-destructive testing and can be used for ultrasonic testing. is an increase in sensitivity and accuracy. The method for determining the acoustic impedance of homogeneous media is as follows. • h. "'..."'. • Acoustic contact is created between the test and reference media, emitting ultrasound vibrations in the direction of this contact, receive signals reflected from the contact surface, amplitudes of the incident and reflected signals are limited from the bottom to the same level UQ, oCr these values are increased by a factor of k , measure the value of the AO and A 'amplitudes of the amplified signals of the incident and reflected ultrasonic oscillations and determine the Z value of the acoustic resistance of the medium under study by the formula Z = Zo2kU-f-Ao - "- Af' (1) AO-AERED = 1 if Z ^ Zo. or / 3 "-1. if 2 <Zo; Zo is the acoustic impedance of the horizontal medium; Maximum sensitivity is reached when the Up level is selected> gt; & When ultrasonic oscillations with an amplitude of AO are incident on the surface of an acoustic contact, the amplitude of the reflected oscillations is A = AoZ-Zo Z + Zo (3)

Description

Thus, when directly measuring the amplitudes A and AO and determining the acoustic impedance Z of the test medium from their values, the sensitivity N is

2ZoZ

(4) 72 72

I-f-Q When the values of AO and A are limited from below on the level Uo, amplifying the remaining values by a factor of k, measuring them and determining the desired parameter with regard to the measured values of Ab and A, the sensitivity is. - .. :; V. . : l. . .; ((- .- .., 22 (AB + Sho)) 2o (z / Zo-4-1) AO (z / Zo - 1) - 2kUo) ;; - / l; .-- :. .- :; W for: Z.Zo. ; - ;;;, d.;,:., -...,; ; , , From expressions (4) and (5) it can be seen that the increase in sensitivity is large ..., ::: ... : -. N-: ../,:. ., -. AO (Z / Zo-1) () (Z / Zo-1) where it is taken into account that (Ao-Uo}. A similar expression also takes place in the case of Z Zo Metii more difference in acoustic resistance of the investigated and

reference media, the higher the increase in sensitivity.

Maximum sensitivity is achieved when the denominator (6) is zero, i.e. at such a ratio between Uo and AO, when

-Z-Zo

Zf-Zo Formula and 3 obre and The method for determining the acoustic impedance of homogeneous media, which consists in emitting ultrasonic vibrations through the reference medium in the direction of its acoustic contact with the medium, measure the values of the incident and reflected signals and take them into account when determining the desired parameter, with tl and h C) n and s, 4TOv in order to increase the sensitivity and accuracy, the desired parameter is determined taking into account the magnitudes of the amplitudes of the measured signals exceeding the specified the second level Uo, chosen from the relation Z + Zo where AO is the amplitude of the emitted oscillations; Zo is the acoustic resistance of the reference medium (b; 2-measured value of the acoustic / resistance of the medium under study.

Claims (1)

Claim A method for determining the acoustic impedance of homogeneous media, which consists in the fact that ultrasonic vibrations are emitted through the reference medium in the direction of its acoustic contact with and the consumed medium, receive reflected signals, measure the magnitude of the incident and reflected signals and take them into account when determining the desired parameter, In order to increase sensitivity and accuracy. the desired parameter is determined taking into account the magnitudes of the amplitudes of the measured signals exceeding a given level Uo. selected from the ratio Uo-Ao Ι-ξ-, I, ίτίο. where Ao is the amplitude of the radiated oscillations: Zo is the acoustic impedance of the reference medium; Z is the measured value of the acoustic impedance of the test medium.