RU2661455C1 - Method for determining the viscoelastic properties of liquid and solid media and the device for its implementation - Google Patents

Abstract

FIELD: measurement technology.

SUBSTANCE: usage for measuring the viscoelastic properties of liquid and solid media. Summary of the Invention is that the excitation of torsional oscillations in the measuring device is carried out by the transducers that are located on its surface, where the excitation of the torsional oscillations is performed by means of applying a pulse signal to the emitting transducers, which are located on the surface of the measuring device, whose geometric parameters allow to excite torsional vibrations in it, record the signal using the receiving transducers, determine the attenuation coefficient of a series of echo pulses of multiple reflections of torsional oscillations in the unloaded measuring device and in the measuring device that is loaded with the studied medium, the attenuation coefficient of a series of echo pulses of multiple reflections of torsional oscillations is calculated taking into account the reflection coefficient at the "converter-pipe" boundary, and the viscosity and shear modulus, taking into account the known density of the studied medium, the calculated attenuation coefficient of the torsional oscillations and the fundamental frequency in the signal spectrum are determined according to the nomograms.

EFFECT: expanded functionality in terms of measuring the viscosity of liquid media, as well as the shear modulus and velocity of propagation of transverse waves in solid media, increased accuracy of measuring the viscoelastic properties of liquid and solid media at the relative simplicity of the device manufacturing.

13 cl, 6 dwg

Description

The invention relates to the field of ultrasonic non-destructive testing and can be used to measure shear viscosity, shear modulus, density of liquid, solid, granular and soil media.

The prior art method and device for measuring the viscosity of liquids based on measuring the propagation time of a longitudinal and transverse waves, calculating their velocities and reflection coefficient at the boundary "solid body - liquid" [Patent US 5365778 A]. Also known is a comprehensive device for measuring the flow rate, density and viscosity of petroleum products, based on measuring the transit time of an acoustic wave pulse in one and the opposite direction and calculating the wave propagation velocity. Using a known speed, the attenuation and viscosity of the test medium are calculated [RF Patent PM No. 66029].

The disadvantages of the known methods and devices are:

- measuring the viscosity of only liquid media;

- low measurement accuracy due to the calculation of the speed of propagation of an ultrasonic wave on a single passage through the measured medium and its excitation in a medium with unknown parameters.

A known ultrasonic device for measuring the shear viscosity and density of liquids, based on measuring the amplitude and time of arrival of the echo signals of an acoustic wave along two flat waveguides, to which are inclined piezoelectric transducers, exciting Lamb waves in the plates [RF Patent PM No. 143319]. The device has several modifications, the purpose of which is to increase the reliability and accuracy of measuring the viscosity and density of liquids during continuous automatic measurements for a long time [RF Patent PM No. 153458, RF Patent PM No. 153622].

The disadvantages of the known devices are:

- measuring the viscosity of only liquid media;

- the dependence of the measurement results through the use of dispersion modes of the longitudinal and flexural Lamb waves;

- the effect of changes in plate thickness on the measurement result.

A known method and device for measuring the viscosity of liquids based on a resonant acoustic method, implemented by calculating the difference between the first resonant frequency obtained in the reference medium and the second resonant frequency obtained in the measured medium, as well as comparing the width of their spectral components [Patent US 4862384] .

The disadvantages of the known method and device are:

- measurement of the viscosity and the real part of the shear modulus of only liquid media;

- the influence of the geometric parameters of piezoceramics, a vessel with a liquid and a resonating device on the measurement result;

- the possibility of the appearance of interfering resonances affecting the accuracy of measurements. Closest to the claimed is a method and device for measuring the parameters of viscoelastic liquid media, based on a comparison of the amplitude-frequency characteristics of a hollow resonant device with axial symmetry and filled with the test medium, calculation of changes in attenuation and viscosity [RF Patent FR No. 2411500].

The prototype device has the disadvantages of the previous technical solution.

The technical result and the problem to be solved is the expansion of functionality in terms of measuring the viscosity of liquid media, as well as shear modulus and shear wave propagation velocity in solid media.

An additional technical result is to increase the accuracy of measuring the viscoelastic properties of liquid and solid media with the relative ease of manufacture of the device.

The specified technical result is achieved due to the excitation of torsional vibrations in the measuring device located on its surface by transducers, while the excitation of torsional vibrations is produced by applying a pulse signal to radiating transducers located on the surface of the measuring device. Next, the signal is recorded using the receiving transducers and processed with a multi-channel analog-to-digital converter. Accepted echograms determine the attenuation coefficient of a series of echo pulses of multiple reflections of torsional vibrations in a measuring device that is not loaded and loaded with the medium being studied. Then, the attenuation coefficient of a series of echo pulses of multiple reflections of torsional vibrations is calculated taking into account the reflection coefficient at the “transducer-pipe” interface, and the viscosity and shear modulus, taking into account the known density of the medium under study, the calculated damping coefficient of torsional vibrations and the fundamental frequency in the signal pulse, determined by nomograms. Using the calculated shear modulus, the propagation velocity of transverse waves in the medium under study is found.

The specified technical result is also achieved by loading the measured medium on any area of the measuring device, as well as the possibility of loading from both the external and internal sides of the measuring device. In this case, one transducer can be used as a radiating and receiving one, and a pipe of any diameter with any wall thickness can be used as a measuring device. Emitting and receiving transducers can be evenly distributed on the surface of the measuring device, while receiving transducers to increase the amplitude connected to a multi-channel analog-to-digital Converter through a signal amplifier.

An additional technical result aimed at improving the accuracy of measurements is realized by exciting torsional vibrations by applying a pulsed signal with a different fundamental frequency in the signal spectrum, thereby the viscosity and shear modulus are calculated at different frequencies, which makes the result more reliable.

The claimed technical result is also achieved through the implementation of a device for measuring the viscoelastic properties of liquid and solid media, containing emitting and receiving transducers located on the outer surface of the measuring device, a computing device and a multi-channel analog-to-digital converter, the inputs of which are connected to the receiving transducers, the generator unit and amplifier, a block of electro-acoustic transducers, consisting of emitting and receiving transducers, moreover, from uchayuschie inverters connected to the generator output and the computing device is associated with the generator unit and multi-channel amplifier and analog-to-digital converter, and a measuring device, the geometrical parameters which allow to excite the torsional vibrations in it and record a series of pulse-echo multiple reflections.

In the claimed device, as a measuring device, a pipe of any diameter with any wall thickness can be used.

The receiving converter may be connected to the analog-to-digital converter through a signal amplifier.

The same transmitter can be used as the transmitter and receiver.

Converters can be evenly distributed around the perimeter of the pipe. When a pipe is immersed in a medium, its internal cavity can be filled with a measured medium or air, in the latter case, the ends of the pipe are sealed. The claimed invention is illustrated by the following drawings.

FIG. 1 - Block diagram of a device for determining the viscoelastic properties of liquid and solid media,

FIG. 2 - Scheme of electro-acoustic transducers and the propagation of ultrasonic waves in a pipe,

FIG. 3 - Echogram of multiple torsion wave reflections from the ends of an unloaded pipe with a diameter of 32 mm, a wall thickness of 4.3 mm and a length of 950 mm,

FIG. 4 - An echogram of multiple torsional wave reflections from the ends of a pipe loaded with sand, 32 mm in diameter, 4.3 mm in wall thickness and 950 mm in length,

FIG. 5 - Nomogram for determining the shear modulus using a steel pipe with a diameter of 32 mm and a wall thickness of 4.3 mm,

FIG. 6 - Nomogram for determining viscosity using a steel tube with a diameter of 2 mm and a wall thickness of 0.2 mm.

Most methods and devices are based on the Maxwell theoretical model based on liquid relaxation time, the Voigt model, the Zener model, or the power-law model, the theoretical approaches of which use the Navier equation with the Stokes-Kirchhoff theory to describe the viscoelastic properties of liquids based on shear viscosity and complex shear modulus. In the general case, the model reduces to finding a solution to the effect on the attenuation of acoustic waves of Newtonian fluids with only a viscous component [I.G. Mikhailov, S.B. Gurevich. Absorption of ultrasonic waves in liquids. Advances in Physical Sciences].

The developed method relates to one of the varieties of the pulsed viscosity measurement method and is based on measuring the attenuation of a series of echo pulses of a torsion wave repeatedly reflected from the ends of the pipe.

The calculation of viscosity is carried out according to the model described in [O.V. Muravyova, S.V. Lenkov, Yu.V. Myshkin. Factors affecting the attenuation of torsional waves in pipes under loading on contact viscoelastic media // Defectoscopy. - No. 9. - 2016. - S. 3-10], where displacements in a torsion wave propagating along an infinite tube are calculated. Displacements are found by the formula:

where r, z, ω are the coordinates in a cylindrical coordinate system,

k is the transformation parameter, J ₁ (rβ ₁ ) is the first-order first-order Bessel function, Y ₁ (rβ ₁ ) is the second-order first-order Bessel function,

, а - внешний радиус трубы, b - внутренний радиус трубы, μ_n - модуль сдвига, η_n - динамическая вязкость, ρ_n - плотность среды, n=1, 2, 3 - индекс, относящиеся к трубе, внешней и внутренней средам соответственно, J₂(rβ_n) - функция Бесселя первого рода второго порядка, Y₂(rβ_n) - функция Бесселя второго рода второго порядка, K₁(rβ_n) - модифицированная функция Бесселя второго рода первого порядка, K₂(rβ_n) - модифицированная функция Бесселя второго рода второго порядка, ω -круговая частота,i is an imaginary unit, Ф ₁ * (k) is the Fourier transform in z of the function ƒ ₁ (z), ƒ ₁ (z) is a continuous function describing the stress distribution along the z axis, defined for - ∞ <z <∞, such what

, a is the outer radius of the pipe, b is the inner radius of the pipe, μ _n is the shear modulus, η _n is the dynamic viscosity, ρ _n is the density of the medium, n = 1, 2, 3 is the index related to the pipe, external and internal environments, respectively , J ₂ (rβ _n ) is the second-order Bessel function of the second order, Y ₂ (rβ _n ) is the second-order Bessel function of the second order, K ₁ (rβ _n ) is the modified second-order Bessel function of the first order, K ₂ (rβ _n ) is the modified second-order second-order Bessel function, ω is the circular frequency,

α ₁₂ and α ₁₃ - slip coefficients at the boundaries of the pipe with the external and internal environment, respectively.

The slip coefficient allows one to describe the “nonrigid” gluing of two bodies and evaluate the deviation from the conditions of “hard” contact (α _12.13 = 1), or of a “sliding” joint (α _12.13 = 0), which leads to a violation of the transmission of elastic components of displacements and stresses across the interface [Abbakumov KE, Konovalov RS Effect of disturbance of acoustic contact on the propagation of Stoneley waves near the boundary of solid half-spaces // Defectoscopy. - 2008. - No. 3. - S. 52-58]. For liquid inviscid and gaseous media in cases with a torsion wave, this coefficient is very small and is usually taken equal to zero, since the torsion wave has only transverse horizontally polarized displacements. For viscous, loose, and ground media, the values of the slip coefficient can vary from 0 to 0.05 (for example, for sandy loam - 0.018, clay - 0.032). For solid media, this coefficient varies widely from 0 to 1 (for example, for bitumen insulation - 0.066, concrete - 0.203). When calculating the dependences for nomograms, it is assumed that the slip coefficient is equal to the ratio of the acoustic impedances of the contact medium material and the pipe material, and the contact area is described by the weight coefficient at the slip coefficient.

To implement the proposed method for measuring viscosity, an experimental setup was used.

The device (Fig. 1) for measuring the viscoelastic properties of liquid and solid media 1 contains a pipe 2, a block 3 of electro-acoustic transducers installed near the end of the pipe 2, a block 4 of a generator and an amplifier, a system unit of a personal computer 5 with an analog-to-digital conversion board 6 for input acoustic signals to computer 5. As an example, in FIG. 2 shows the block of electro-acoustic transducers 3 used in the experiment and consisting of two emitting transducers 7 and one receiving transducer 8, which are installed on the cylindrical surface of the pipe 2 near its end. A larger number of transducers provide the excitation and reception of torsional vibrations with a smaller number and amplitude of extraneous interfering types of vibrations. Moreover, the design with one transducer provides simplicity in the manufacture of the device with a decrease in its cost.

The proposed device operates as follows. On the cylindrical surface near the end of the pipe 2, a block of electro-acoustic transducers 3 is installed (Fig. 1). An electric pulse from the generator 4 is fed to the block 3 of electro-acoustic transducers, where the emitting transducers 7 (Fig. 2) excite torsional vibrations that create a torsional wave propagating along the pipe 2. Repeatedly reflected from the ends of the pipe 2, recorded by at least one receiving transducer 8 and the electrical signal converted from the acoustic signal is amplified in block 3 and fed to the analog-to-digital conversion board 6 (Fig. 1), where personnel are processed and displayed computer 5. Radiation of a torsional wave is provided due to the orientation of the transducers 7 on the surface of the pipe 2, creating shear stresses across the axis of the pipe 2 in the azimuthal direction.

The measurement result is an oscillogram of a series of echo pulses of multiple reflections of an acoustic wave along the length of the pipe (Fig. 3). Each pulse on the waveform is formed as a result of a superposition of waves emitted by each point of contact of the emitting transducers with the cylindrical surface of the pipe, reflected from opposite ends of the pipe and received by the same points or contact points of the receiving transducers and then repeatedly reflected. The position of the nth pulse on the time axis corresponds to the distance traveled by the wave n times along the length of the pipe. In the case of loading the pipe with a viscoelastic medium (Fig. 4), the attenuation of a series of echo pulses of multiple reflections increases and the amplitude of the acoustic noise decreases.

Using the obtained oscillograms, the attenuation of the wave is calculated using well-known formulas taking into account the energy losses of the acoustic wave due to reflections from the ends of the pipe and the boundary of contact with the transducer [Muravyova OV, Zlobin DV The acoustic path of the multiple reflection method for defectoscopy of linearly extended objects // Defectoscopy. - 2013. - No. 2. - S. 43-51]:

where U _n is the amplitude of the echo pulse from the end face of the test object at the nth reflection, U ₀ is the amplitude of the probe pulse, R _e is the reflection coefficient at the “tube – transducer” interface, δ is the acoustic wave attenuation coefficient, x _n = 2⋅ L⋅n + х ₀ - position of the nth reflection on the scale by distance, 2⋅L⋅n - distance traveled by the acoustic wave on the nth reflection, x ₀ - position of the probe pulse on the scale by distance, L = C⋅t is the length of the control object, C is the propagation velocity of the acoustic wave, t is the acoustic wave propagation time of a distance equal to the length of the pipe.

From the formula (6) the attenuation coefficient is expressed:

where U _m is the amplitude of the echo pulse from the end face of the test object at the mth reflection, m is the serial number of the reflection such that m> n.

Next, the main frequency of the echo pulses of the torsion wave, repeatedly reflected from the ends of the pipe, is determined using software tools, or by decomposing the signal into a spectrum. Knowing the wave attenuation, the density of the medium and the pulse frequency determine the viscosity of liquid media or the shear modulus of solid media. According to the known shear modulus, the shear wave velocity is calculated by the formula:

where μ is the shear modulus, ρ is the density of the medium under study.

The determination of the measured values (viscosity or shear modulus) is made from nomograms, a typical view of which is presented in FIG. 5, 6. For example, in a pipe with a diameter of 32 mm and a wall thickness of 4.3 mm and a length of 950 mm when loading it with sand at 80% of the surface area and a density of 1500 kg / m ³ (Fig. 5) weakening the torsion wave at a frequency of 25 kHz is 2 dB / m, which corresponds to a shear modulus of 1.3 GPa, while the shear wave velocity will be 930 m / s. When placing a pipe with a diameter of 2 mm with a wall thickness of 0.2 mm and a length of 250 mm in dextrin with a density of 890 kg / m ³ for 80% of the surface area (Fig. 6), the attenuation of the torsion wave at a frequency of 100 kHz will be 20 dB / m, which corresponds to a viscosity value of 1.3 Pa · s.

The proposed measurement method can be used to measure the viscoelastic properties of liquid, bulk, soil and solid media in the construction, oil and gas, food and transport industries.

Claims (13)

1. The method of measuring the viscoelastic properties of liquid and solid media, including the excitation of torsional vibrations in the measuring device by transducers located on its surface, characterized in that the excitation of torsional vibrations is performed by applying a pulse signal to radiating transducers located on the surface of the measuring device, the geometric parameters of which allow excite torsional vibrations in it, register the signal with receiving transducers, determine the coefficient the attenuation of a series of echo pulses of multiple reflections of torsional vibrations in a measuring device not loaded and loaded with the medium studied, the attenuation coefficient of a series of echo pulses of multiple reflections of torsional vibrations is calculated taking into account the reflection coefficient at the "transducer - pipe" interface, and the viscosity and shear modulus taking into account the known density the medium under study, the calculated damping coefficient of torsional vibrations and the fundamental frequency in the spectrum of the signal is determined by nomograms. 2. The method according to p. 1, characterized in that as the emitting and receiving use the same Converter. 3. The method according to p. 1, characterized in that as a measuring device using a pipe of arbitrary diameter with an arbitrary wall thickness. 4. The method according to p. 1, characterized in that the loading of the measured medium is carried out on any area of the measuring device. 5. The method according to p. 1, characterized in that the loading of the measured medium is carried out from the external and internal sides of the measuring device. 6. The method according to p. 1, characterized in that the transducers are installed near the end of the cylindrical measuring device. 7. The method according to p. 1, characterized in that the excitation of torsional vibrations is produced by applying a pulse signal with a different fundamental frequency in the spectrum of the signal. 8. A device for measuring the viscoelastic properties of liquid and solid media, containing emitting and receiving transducers located on the outer surface of the measuring device, a computing device and a multi-channel analog-to-digital converter, the inputs of which are connected to the receiving transducers, characterized in that the device is equipped with a generator unit and amplifier, a block of electro-acoustic transducers, consisting of radiating and receiving transducers, moreover, radiating transducers and connected to the generator output, and a computing device connected to the generator unit and multi-channel amplifier and analog-to-digital converter and a measuring device, which allow the geometrical parameters excite torsional oscillations therein and record a series of pulse-echo multiple reflections. 9. The device according to p. 8, characterized in that as a measuring device using a pipe of arbitrary diameter with an arbitrary wall thickness. 10. The device according to p. 8, characterized in that the receiving Converter is connected to an analog-to-digital Converter through a signal amplifier. 11. The device according to p. 8, characterized in that the same transducer is used as the emitting and receiving transducer. 12. The device according to p. 8, characterized in that the transducers are evenly distributed around the perimeter of the pipe. 13. The device according to p. 8, characterized in that the transducers are located near the end of the cylindrical measuring device.

Images