SU789734A1

SU789734A1 - Method of determining longitudinal acoustic wave attenuation factor

Info

Publication number: SU789734A1
Application number: SU782562990A
Authority: SU
Inventors: Евгений Исаевич Серегин; Борис Львович Зайцев
Original assignee: Белорусский Республиканский Центр Стандартизации И Метрологии
Priority date: 1978-01-03
Filing date: 1978-01-03
Publication date: 1980-12-23

Description

Изобретение относится к контрольноизмерительной технике и может найти применение при исследовании структуры материалов.The invention relates to measuring technique and may find application in the study of the structure of materials.

Известен · способ определения коэффициента продольных акустических волн, ⁵заключающийся в том, что в сосуде, содержащем образцовую и испытываемую жидкости с одинаковыми скоростями акустических волн, разделенные тонкой эвукопрозрачной пленкой, перемещают жест- ¹⁰ко связанные между собой, но расположенные по разные стороны пленки излучаетль и приемник.There is a known · method for determining the coefficient of longitudinal acoustic waves, ⁵ which consists in the fact that in a vessel containing a sample and test fluid with the same velocity of acoustic waves, separated by a thin euco-transparent film, they move rigidly ¹⁰ connected to each other, but located on opposite sides of the film and receiver.

Известен способ измерения затухания акустических волн в бетонных конструкциях, заключающийся в том* что измеряют амплитуды двух импульсов, полученных ‘от гранигг. , исследуемого участка при прозвучиваний исследуемого профиля продольными акустическими волнами поочередно во встречных направлениях, и по отношению этих амплитуд определяют затухание [1].A known method of measuring the attenuation of acoustic waves in concrete structures, which consists in * measuring the amplitudes of two pulses received, from granigig. , of the studied area during soundings of the studied profile by longitudinal acoustic waves alternately in opposite directions, and the attenuation is determined by the ratio of these amplitudes [1].

Наиболее близким по технической сущности к изобретению является способ определения коэффициента затухания продольных волн в образце, заключающийся в том, что в иммерсионной жидкости в направлении образца возбуждают акустическую волну, измеряют амплитуды волн, прошедших два различных расстояния в образце, по соотношению которых Ьпределяют коэффициент затухания (2].The closest in technical essence to the invention is a method for determining the attenuation coefficient of longitudinal waves in a sample, which consists in the fact that an acoustic wave is excited in an immersion liquid in the direction of the sample, the amplitudes of waves that have passed two different distances in the sample are measured, the ratio of which determines the attenuation coefficient ( 2].

Недостатком известных способов является низкая точность, обусловленная различным влиянием дифракционных эффектов на амплитуды регистрируемых вели.A disadvantage of the known methods is the low accuracy due to the different influence of diffraction effects on the amplitudes of the recorded leads.

Цель изобретения - повышение точноети способа путем обеспечения равенства влияний дифракционных эффектов.The purpose of the invention is to increase the accuracy of the method by ensuring equal effects of diffraction effects.

Поставленная цель достигается тем. что перед вторым измерением амплитуды изменяют путь волны _;в иммерсионной жидкости согласно критериюThe goal is achieved by that. that before the second measurement of the amplitude, the wave path is changed _; in immersion fluid according to the criterion

-ζ., _ ./ζ|+4<£-ζ_Α * ^C1 где Z4,Z<2 - расстояния, проходимые волной в иммерсионной жидкости и образце соответственно;-ζ., _ ./ζ|+4<$-ζ _Α * ^C 1 where Z4, Z <2 are the distances traveled by the wave in the immersion fluid and the sample, respectively;

Сд, Са - скорости распространения акустической волны в иммерсионной жидкости и образце соответственно;Сд, Са - acoustic wave propagation velocity in immersion liquid and sample, respectively;

О, - радиус пьезопластины излучателя и приемника.Oh, is the radius of the piezoelectric plate of the emitter and receiver.

На фиг.1 представлена схема реализации способа определения коэффициента затухания продольных акустических волн; на фиг. 2 - схема для расчета нового расстояния между пьезопреобразователем и образцом’ на основании критерия (1).Figure 1 presents a diagram of the implementation of the method for determining the attenuation coefficient of longitudinal acoustic waves; in FIG. 2 is a diagram for calculating a new distance between a piezoelectric transducer and a sample ’based on criterion (1).

Устройство для осуществления способа содержит прибор 1 УС-11И, совмещенный пьезопреобразователь 2, ванну 3 с иммерсионной жидкостью и исследуемый образец.A device for implementing the method comprises a device 1 US-11I, a combined piezoelectric transducer 2, a bath 3 with an immersion liquid, and a test sample.

Способ заключается в том, что пьезопреобразователем 2, возбуждаемым генератором прибора 1, излучают иммерсионную жидкость (воду) в ванне 3 акустическую волну в направлении образца 4, измеряют прибором 1 амплитуду волны, прошедшей в образце одно расстояние, перемещают пьезопреобразователь в новое положение согласно критерию (1),.возбуждают акустическую волну в направлений образца 4, измеряют амплитуду волны, прошедшей другое расстояние в образце , и по соотношению измеренных амплитуд определяют коэффициент затухания в образце по формуле ^Αο_Βρ·- Μ ¹(&The method consists in the fact that the piezoelectric transducer 2, excited by the generator of the device 1, emits an immersion liquid (water) in the bath 3 an acoustic wave in the direction of the sample 4, measure the amplitude of the wave that has passed one distance in the sample, and move the piezoelectric transducer to a new position according to the criterion ( 1) ,. excite an acoustic wave in the directions of sample 4 was measured amplitude wave passing another distance in the sample, and the ratio of the amplitudes of the measured attenuation coefficient is determined in a sample by the formula ^Α ο ρ · - Μ ¹ (&

^<г> . где cl d толщина образца; коэффициент затухания акустических волн в воде; коэффициент прохождения акус— · тическпх ‘волн через границу раздела сред; амплитуда импульса, отраженного и? передней грани образца; ^<r> . where cl d is the thickness of the sample; attenuation coefficient of acoustic waves in water; coefficient of transmission of acoustic waves through the interface; amplitude of the pulse reflected and? front face of the sample;

амплитуда первого данного .импульса;amplitude of the first given .pulse;

расстояние между пьезоэлектрическим преобразователем и образцом, при котором измерялась амплитуда Ад;the distance between the piezoelectric transducer and the sample at which the amplitude of Hell was measured;

$2 - расстояние между пьезоэлектоиКпр“ .Aq50$ 2 - the distance between the piezoelectric and Kpr “.Aq50

Si55 ческим преобразователем и образцом при котором измерялась амплитуда Ис.A Si55 transducer and a sample in which the amplitude of Is.

Формула (2) получена для простейшего случая, когда одна из амплитуд А_ъизмеряется при расстоянии, пройденном волной в образце, равном нулю.Formula (2) was obtained for the simplest case when one of the amplitudes A _b is measured at a distance traveled by the wave in the sample equal to zero.

Предлагаемый способ основан на том, что с использованием выражения для среднего давления на приемном преобразователе для значительных расстояний между соосно расположенными излучателем и приемником, работающими в импульсном режиме, теоретически показана возможность достижения равенства суммарных дифракционных поправок,воздействующих на первый и второй принимаемые ι импульсы для двух различных однородных сред при выполнении критерия (1).The proposed method is based on the fact that using the expression for the average pressure at the receiving transducer for significant distances between the coaxially located emitter and the receiver operating in a pulsed mode, it is theoretically shown that it is possible to achieve the equality of the total diffraction corrections affecting the first and second received ι pulses for two various homogeneous media when fulfilling criterion (1).

Выражение (1) означает, что если' систему излучатель - приемник из образ-, цовой среды со скоростью С., при расстоянии между излучаетелем и приемником и радиусами преобразователей а, перенести в другую однородную среду . со скоростью при прежнем расстоянии между излучателем и приемником, то дифракционные воздействия на сигнал в первом и втором случаях не будут равI ны. Для уравнивания дифракционных воздействий необходимо изменить расстояние между преобразователями при измерении в новой среде.Expression (1) means that if the system is an emitter - receiver from a reference medium at a speed of C., at a distance between the emitter and receiver and the radii of the transducers a, transfer to another homogeneous medium. at the same distance between the emitter and the receiver, the diffraction effects on the signal in the first and second cases will not be equal. To equalize the diffraction effects, it is necessary to change the distance between the transducers when measuring in a new environment.

Из критерия (1) получаем а²- к² (z 2с?-ζ,/ζ* * +4 а ² )From criterion (1) we obtain a ² - k ² (z 2s? -Ζ, / ζ * * +4 a ² )

К Vz* ♦ 4α¹ К-- — гдеK Vz * ♦ 4α ¹ K-- - where

При определении нового положения для • случая, когда в акустический тракт входят две или больше количество сред (иммерсионная жидкость и твердый обра * зец), следует использовать следующий прием.When determining a new position for • the case when two or more media (immersion liquid and solid sample) enter the acoustic path, the following technique should be used.

Мысленно сведем расстояние, проходимое акустическим импульсом в иммерсионной жидкости, к расстоянию в материале образца (см. фиг. 2). Используя выражение (3), получаемMentally reduce the distance traveled by the acoustic pulse in the immersion liquid to the distance in the sample material (see Fig. 2). Using expression (3), we obtain

-^4* V f Je4.TZ«· _ ч---- '4) кUsJmqi - S,)- ^ 4 * V f Je4.TZ “· _ h ---- '4) to UsJmqi - S,)

Излучатель смещается на некоторое расстояние и занимает мнимое положение в точке 5 ' , но среда распростране5 ния акустических импульсов между ним и образцом соответствует среде образца. С этого мнимого расстояния акустические импульсы распространяются в среде, соответствующей образцу, входят в образец, отражаются от его задней грани и приходят в точку 7. Имеем распространение волн в однородной среде, к которому применим критерий (1). Так как далее акустические колебания выходят из образца и распространяются в иммерсионной жидкости, необходимо расстояние S” ~ 5^ ♦ 2d свести к эквивалентному расстоянию по жидкости. Это делается по формуле (3)The emitter is displaced by a certain distance and occupies an imaginary position at point 5 ', but the medium of propagation of acoustic pulses between it and the sample corresponds to the medium of the sample. From this imaginary distance, acoustic pulses propagate in a medium corresponding to the sample, enter the sample, reflect from its back face and arrive at point 7. We have wave propagation in a homogeneous medium, to which criterion (1) applies. Since further acoustic vibrations come out of the sample and propagate in the immersion liquid, it is necessary to reduce the distance S ”~ 5 ^ ♦ 2d to the equivalent liquid distance. This is done according to the formula (3)

-s;l-s; l

Таким образом, путь импульса от точки 5 до точки 7 сводится к расстоянию, проходимому импульсом в однородной иммерсионной жидкости S-t · Однако остается еще участок от точки 7 до точки 8..Thus, the path of the pulse from point 5 to point 7 reduces to the distance traveled by the pulse in a homogeneous immersion fluid S-t · However, there is still a section from point 7 to point 8 ..

_ · ___ с <11_ · ___ s <11

Его надо суммировать к расстоянию . ИмеемIt must be summed to the distance. We have

2S₂=S7*S.,O (6) ·2S ₂ = S7 * S., O (6)

Окончательное выражение (6) дает соотношение между расстоянием и первоначальными параметрами 5^4,0 ,С^, сводя систему иммерсионная жидкость— твердый образец к системе образцовая жидкость - отражатель.The final expression (6) gives the relationship between the distance and the initial parameters 5 ^ 4.0, C ^, reducing the immersion liquid-solid system to the model liquid-reflector system.

Выражение (6) приобретаем вид ^X -q] где «=-----sj ~^>2а;Expression (6) we get the form ^X- q] where «= ----- sj ~ ^>2a;

к^К С-ι >to ^K C-ι>

2ύ2ύ

ЭДг скорости распространения акустической волны в иммерсионной жидкости и образце соответственно.The EDg of the velocity of propagation of an acoustic wave in an immersion liquid and a sample, respectively.

Использование изобретения позволяет повысить точность определения коэффициента затухания продольных акустических волн и позволяет определять коэффициент затухания как в жидкостях,так и в твер1/ дых телах.Using the invention allows to increase the accuracy of determining the attenuation coefficient of longitudinal acoustic waves and allows to determine the attenuation coefficient in liquids and in solids / breathing bodies.

Claims

The invention relates to the xz technology and can be used in the study of the structure of materials. The known method for determining the longitudinal acoustic wave coefficient is that in a vessel containing exemplary and testable liquids with identical acoustic wave velocities separated by a torsion of a translucent film, they are rigidly interconnected but disposed along different stresses of the film and receiver. There is a known method for measuring the attenuation of acoustic waves in beta structures, consisting in Toiyi, that the amplitudes of two pulses received from the pulses are measured. t of the area under study when the U1) of the studied area is sounded by longitudinal acoustic waves alternately directed in direction I51X, and the attenuation l is determined from the fire of these amplitudes. The closest to the essence of the invention is a method for determining the attenuation coefficient of the longitudinal waves in a sample, which implies that an acoustic wave is excited in the immersion liquid in the direction of the sample, the amplitudes of the waves passed through two different distances. sample, according to which they determine the coefficient of attenuation. A disadvantage of the known methods is low accuracy, but the effect of different effects is: differential effects on the amplitudes of various screams. The goal of the inventor is to improve the accuracy of the method by ensuring equal effects of the diffraction effect. The goal is achieved by those. that before a change {amplitudes change the path of the WAVE; and the immersion-like fluid with the cosio criterion c. - cr; where z, Zi are the distances traveled by wave B of the immersion liquid and the sample are in accordance with the instructions; Ci, Ca are the propagation speeds of the acoustic wave in the immersion liquid and the sample, respectively; 01 - radius of the piezoplate of the radiator and the receiver. Figure 1 shows a scheme for implementing a method for determining the attenuation coefficient of longitudinal acoustic will; in fig. 2 is a scheme for calculating a new distance between a piezo transducer and a sample based on criteria (1). A device for carrying out the method contains a Prymr 1 US-11I, a combined Piezo transducer 2, a bath 3 with an immersion liquid, and a sample under study. The method consists in that the piezoelectric transducer 2, excited by the generator of the device 1, emits an immersion liquid (water) in the bath 3, the acoustic wave in the direction of the sample 4, is measured by the device 1 the amplitude of the wave passing in the sample one distance, move the piezoelectric transducer to a new position according to the criterion (1), the excitation gives an acoustic wave in the directions |. sample 4, the amplitude of the wave passing the other distance in the sample is measured, and the ratio of the measured amplitudes is used to determine the attenuation coefficient in the sample by the formula. pH / AoV-OBR 2d lAj Mvy qa-d C1 - sample thickness; otg - attenuation coefficient of acoustic waves in water; K ,, p is the transmission coefficient of acoustic waves through the interface between the media Dd-ampldude of a pulse reflected by the 5f front face about-. the difference D is the amplitude of the first δ impulse; the distance between the piezoelectric transducer and the sample, at which the amplitude Ai 52 was measured - the Vastostane between the piezo-electric transducer and the sample at which the amplitude was measured 4c. Formula (2) is obtained for the simplest case, when one of the amplitudes is measured at the distance traveled by the wave in the sample, equal to zero. The proposed method is based on the fact that using the expression for the average pressure on the receiving transducer for significant distances between coaxially arranged emitter and receiver operating in a pulsed mode, it is theoretically possible to achieve equality of the total diffraction corrections acting on the first and second received pulses different homogeneous media when fulfilling the criteria (1). The expression (1) means that if the emitter-receiver system from the sample medium with the speed C., with the distance between the emitter and receiver 2 and the radii of the transducers C, is transferred to another homogeneous medium. with the speed at the same distance between the emitter and the receiver, the diffraction effects on the signal in the first and second cases will not be equal. To equalize the diffraction effects, it is necessary to change the distance between the transducers when measuring in a new environment. From the criterion (1) we obtain .2 ,, 2 / -t4 D -40). When determining Delenin of a new position, in the case when two or more media (immersion liquid and solid sample) are in the acoustic path, the following reception Mentally, we will reduce the distance traveled by an acoustic pulse in an immersion liquid to the distance in the sample material (see Fig. 2). Using the expression (3), we obtain.-5, -S,) The emitter is displaced by some distance and takes an imaginary position at point 5, but the propagation of acoustic pulses between it and the sample corresponds to the sample medium. From this imaginary distance S, the acoustic pulses propagate in the medium corresponding to the sample, enter the sample, are reflected from its rear face and arrive at point 7. We have a wave propagation in a homogeneous medium to which criterion (1) applies. Since the pvpee acoustic oscillations emerge from the sample and propagate in the immersion liquid, it is necessary to reduce the distance of 5-5 to 2d to the equivalent distance of the liquid. This is done by the formula (3). "-Ms; fi - vsi- °, tG-U (5) - S Thus, the path of the impulse from point 5 to point 7 is reduced to the distance traveled by the pulse in the uniform mercury fluid S-t. However, there is still a segment from point 7 to point 8. It must be summed to distance S. (We have 2S, (6) The final display (6) gives the ratio between the distance Sa and the primary parameters 5 (3.0, С, Cji , the vault system is an immersion liquid solid sample to the system of a sample liquid - reflector. The evaporation (6) takes the form & a Q -Q-G-44. Ji. -l,% 4С1 -ic s} 4ai -5, J. Cg. Ci C is the propagation velocity of the acoustic wave in the immersion liquid and the sample, respectively. Using the invention improves the accuracy of determining the coefficient attenuation of longitudinal acoustic waves and allows determination of the attenuation coefficient in both liquids and solids. Formula for determining the attenuation coefficient of longitudinal acoustic waves in a sample, which implies an acoustic wave is excited in the sample direction. The amplitudes of the waves passing through the distances in the sample are determined by the ratio of the attenuation coefficient, characterized in that, in order to improve the accuracy of the method by ensuring equality of effects Nij diffraction effects, before the second measurement izmeyyyut amplitude wave path in the immersion fluid to pulley criterion -1ch ss - / Z | t4ci -2a. C, - c, where 2. ,, 22 is the distance, 1 О сод сод сод имые волн волн волн в in the immersion liquid and sample co. oTBercTB fflo; OtsSa.- speeds: the growth of acoustic warriors in the immersion liquid and the sample, respectively; e - the radius of the piezoolastine emitter “receiver. Information sources . taken into account during the examination 1. USSR author's certificate No. 169908, class, GiOl N29 / OO, 1963.

2. Acoustic, 1971, T.17, p. 317-319 ((photogkp).