SU1147971A1 - Method of measuring ultrasonic wave absorption coefficient - Google Patents

Abstract

A METHOD FOR MEASURING THE ABSORPTION COEFFICIENT OF ULTRASONIC WAVES, which consists in emitting continuous ultrasonic waves at a fixed frequency and analyzing the temperature change of the medium under study, which also produces radiation of continuous ultrasonic waves on two acoustic waves. bases, when the condition of adiabaticity is fulfilled in the medium, measure the frequency change of the received signals; and the absorption coefficient is determined from the ratio bi, t-expt-2oi.X, b {2l-exi) (.- 2otX2l where of, is the absorption coefficient; X, (i2 is the distance of the first (second) base; l, (x121 - the change in the frequency of the received signals in comparison with the emitted signals of the first (second) base.

Description

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The invention relates to a measurement technique and can be used to measure a coefficient: the absorption of ultrasonic waves in substances and products of various materials.

The aim of the invention is to improve the measurement accuracy.

The essence of the method for measuring the absorption coefficient of ultrasonic waves is that they emit ultrasonic waves at two acoustic bases, the change in the velocity of which is & Y () is associated with a change in the temperature hi (tl of the medium examined by the formula

iVCol bbtlt, (1)

where b is the temperature coefficient of the speed of ultrasound propagation. .-.- ,, where 1 (5 is the sound intensity at the starting point; - is the control time; X is the base distance; C is the specific heat capacity; J is the substance density; ot is the absorption coefficient. Phase difference iq) (t) for a fixed moment of time, between the direct and the emitted ultrasonic wave is determined by the formula η-2 "-.i (r1, the frequency of radiation of the body’s radiation; the velocity of the ultrasonic wave at a particular temperature. It is known that the difference phase) and the difference (change) cha

The signals received in relation to the radiated signals are related by

 BUT

tb (l, (l)

  (3)

Then the difference (change) in the frequencies l1, (1 and iljCS) of the received ultrasonic signals as compared to the emitted signals for the two bases under the same experimental conditions (constant power and frequency of the radiation, initial temperature, etc.), taking into account formulas (1) and (2) are determined from the ratios

, (,., -...,) ,, -. ,, ui2 (l Ai-e-2 “) The measurement time C is chosen from the adiabatic condition (the measurement result is not affected by heat transfer along the ultrasonic beam, or radial heat sink from the beam) where R is the radius of ultrasonic radiation; Q - coefficient of thermal diffusivity of the substance. The absorption coefficient is determined from the ratio bi | (,) - itj -exp (-25 (.Xj) where o: is the absorption coefficient; ((Xj) is the distance of the first (second) iijCiijV change in the frequency of received signals in comparison with the emitted signals. Using the method allows you to increase accuracy of measurements.

Claims (1)

METHOD FOR MEASURING THE ABSORPTION COEFFICIENT OF ULTRASONIC WAVES, which consists in emitting continuous ultrasonic waves at a fixed frequency and analyzing the temperature change of the medium under study, distinguished by the fact that, in order to increase the measurement accuracy, the emission of continuous ultrasonic waves is produced at two acoustics - if the adiabatic condition in the medium is satisfied, the change in the frequencies of the received signals is measured, and the absorption coefficient is determined from the relation & £ ₍ I - е хp 1-2 ". X b { ₂ 1-exp (.-2ax ₂ ) ⁵ where ci. is the absorption coefficient; X ₍ (X _g ) .- the distance of the first (second) base; a change in the frequency of the received signals compared to q with the emitted signals of the first (second) base.