SU754262A1 - Vibration-type meter of rheological characteristics of viscoelastic materials - Google Patents

Description

The invention relates to the field of research of physical and mechanical properties of substances, namely, devices for measuring and recording the processes of changing their dynamic elastic modulus and dynamic viscosity.

A known elastomer comprising a housing, a cuvette with a test substance, a rod with a probe immersed in the ’test substance, a drive, a rod displacement sensor and a gain sensor developed by the test substance, the outputs connected via an elastic modulus signal generator 1

the input of the Executive unit of the channel of the modulus of elasticity, the output of which is connected to the input of the inverse transducer of the modulus of elasticity [1]. The known device allows to measure20 with high accuracy and in a wide frequency range the elastic component of the complex modulus of a substance, however, it does not allow to isolate the viscous component and exclude its influence on the process of measuring the elastic modulus. The elastomer measures the average value of the dynamic elastic modulus in the entire sample volume and does not allow to select the modulus of elasticity of the study 30

2

moss substance and its surface layer.

The closest technical solution is a vibrating elastovis coosimeter, made in the form of a vibration transducer, comprising a housing, a cuvette with a test substance, a rod with a probe in the form of a plate, immersed in the test substance, θ platform, a cuvette drive, a force sensor developed by the test substance during deformation, rod displacement sensor and rod displacement speed meter, inverse modulator of elastic modulus, consisting of a stator and an anchor with a coil rigidly connected with the rod, inverse transducer l viscosity, consisting of a stator with a coil and an anchor with a coil rigidly connected with the rod, registrars of the elastic modulus and viscosity, the measuring unit modulus of elasticity, which includes serially connected signal generator modulus of elasticity, the inputs of which are connected to the outputs force sensors and rod displacement, viscosity measuring unit, including 1 consequently connected form 3

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Viscosity signal finder, filter and viscosity channel actuator, whose inputs are connected to the outputs of force sensors and rod speed meter, and its output is connected to the stator coil of the inverse viscosity converter, while the armature coil of the inverse viscosity converter is connected to the output of the rod speed meter , the elastic modulus inverter armature coil is connected to the output of the elastic modulus measurement unit, and the inverters stators are mounted on the platforms And ·

Vibrational elastoviscoeimeter allows to measure with sufficient accuracy the viscoelastic characteristics of the studied materials in the whole range of their change, including the area of minor changes in their size. The disadvantage of this measuring device is to measure only the averaged values of the dynamic modulus of elasticity and dynamic viscosity in the entire volume of the sample under study, while in practice the sample under investigation always has a surface layer, the magnitude of the components of viscoelastic characteristics of which is always different from the components in its volume. Especially this difference is dependent on the solvent and temperature conditions, however, the analysis of the measurement results is always under the assumption that the viscoelastic properties of the surface layer are insignificant, which obviously reduces the measurement accuracy.

The aim of the invention is to improve the accuracy of measurements and enhanced functionality. This goal is achieved by introducing a second vibration transducer into the vibratory gauge of the rheological characteristics of viscoelastic materials, which has a common drive with the first one, and its probe is made in the form of two plates having the same areas and sides parallel to the probe sides of the first vibration transducer, whose lengths are related by the relation

L <+ ί> ι _ Ь with

where b, b b are the lengths of parallel

the horizontal sides of the plates of the probes of the first and second vibration transducers, respectively /

s, s. , с - lengths of parallel

V ¹ vertical sides

plates of probes of the first and second vibration transducers, respectively /

in each vibration converter, the stators of the inverse transducers of the elastic modulus and viscosity are mounted on the meter body, the stator of the inverse transducer of the elastic modulus is equipped with a coil connected to the output of the elastic modulus measurement unit, and its armature coil is connected to the output of the rod displacement sensor, and the outputs of the elastic modulus measurement blocks the first and second vibration transducers through the respective large-scale amplifiers are connected to the inputs of the respective recorders, and the outputs of the measuring units yazkosti first and second vibration transducers through appropriate scaling amplifier connected to the inputs of the third and fourth comparators, the outputs of which through their scale amplifiers are connected to the inputs of the corresponding registers.

Since the test influences from the common drive side are transferred to the cuvettes with the test substance of both vibration transducers, the probes of which are of different designs, this causes the occurrence of forces acting on the rods from the test substance, the values of which are determined by the complex modules of the test substance, its surface layer and geometrical dimensions of the probes in accordance with the following

Niyami: = ^r o < ⁺ . (ABOUT g = P g 2 01 'N 9. where G is power acting on stock through the plate probe the first Ό vibro

converter

- the force acting on the stock

through the plates of the probe of the second vibrator;

Р _ol = · с-Ь-С§ is the force due to the complex module of the test substance, acting as a plate of the primary transducer probe>

caused by the complex modulus of the surface layer of a substance acting on the plate of the probe of the first in the conversion unit;

= -5- ° = 5 - deformation isl ^l o 'O

blown substance and surface layer;

O ( _O is the strain amplitude;

0 - the size of the gap;

c, b - geometric dimensions

plates of the first vibrator;

five

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^with n *>. ^с * _а ^- complex modules of the surface layer of a substance with different deformation characters?

^g og

strength,

due to the complex module C * · of the test substance acting on the plates of the second vibration transducer;

⁴ · ¹ '> ^s a ~ geometric

the dimensions of the plates of the probe of the second vibrator;

^г п _г = Ч - * - ( ^Ь 4 ^{+ ь} г><<4 ⁺ υ ^ ^Ε θ ^ι) "force due to the complex module of the surface layer of the substance acting on the plates of the second vibration transducer.

To simplify the design of the vibration meter for the rheological characteristics of viscoelastic materials, we impose the following restrictions on the dimensions of the probes:

B h + s 1

c, + c _L

^{with <b} 4

(2)

(3)

"eleven

Taking into account conditions (2) and (3), the relations of forces due to the complex module of the surface layer of a substance acting on the probes of the first and second vibration transducers can be represented as follows?

ten

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thirty

ld

:four)

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and the forces due to the complex ^ modulus C * of the substance acting on the plates of both vibration transducers are equal to

(five)

Let us set the relations between the geometric dimensions of the plates of the probes, taking

: e)

B = sc · s

B _A = d, b _g = o ( _g c ,,,

where and are constant coefficients. Then, taking into account conditions (2) and (3), we can write

C, Οΐ οί-, C

(7)

WITH,

<] with

^g TEST (o *. a ") - s *. ss g ⁺ '

ΛΛ, О <аС__

⁴ WOC Us *. ("* _L - * L) 'H * CHORD OF THE Eyes /

45

50

55

60

O1 with

Using relations (7), we determine the perimeters of the plates of the probes of the first and second vibration transducers

Р ₍ > 2 (б + с) "2с (ok + d '),

p Ην \ | -r Λ | С

^g K ₂ [° H * g <UE " ^{/ 4 ί8)}

Their ratio is equal to the right side of expression (4). Consequently, the ratio of the forces acting on the probes of vibration transducers, due to the complex modulus of the surface layer of a substance, is equal to the ratio of their perimeters.

Thus, equal forces act on the probes of the first and second vibration transducers, due to the complex module of the substance under study, and forces caused by the complex module of the surface layer, the ratio of the magnitudes of which is proportional to the ratio of their perimeters. This allows, changing the perimeters of the probes of both vibration transducers, to select from the complex module of a substance the complex module of its surface layer.

The need to connect the cuvette of both vibration transducers with a single drive leads to the insertion of a coil into the stator of the inverse transducer of the elastic modulus and fixing it on the housing.

This greatly weakens the requirements for the quality of the drive due to its unloading and reduction of inertial forces and improves the accuracy of generation of the frequency of probe oscillations, and hence the accuracy of measurements.

FIG. 1 shows a diagram of a vibration meter for the rheological characteristics of viscoelastic materials; in fig. 2 - the design of the probes of the vibration meter of the rheological characteristics of viscoelastic materials.

The vibration meter for the rheological characteristics of viscoelastic materials, such as polymers, contains rods 1, onto which probes 2 are fixed, the first of them contains plate 3, and the second contains two plates 4 and 5 with equal areas and with sides parallel to the sides of plate 3 and satisfying the above relation immersed in the test substance 6. On the rods 1, connected with the help of elastic stretch marks 7 with the meter body 8, the anchors 9 of elastic moduli inverters with coils 10, anchors 11 inverse transforms ers viscosity with the coils 12, the shutter 13 sensors force developed material upon deformation, the shutter 14 dates tors displacement rod 1, anchors 15

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measuring the speed of the rod 1. On the case 8 of the vibration meter of the rheological characteristics of viscoelastic materials, the stators 16 of the elastic moduli converters with coils 17, the stators 18 of the viscosity converters with coils 19, the force sensor housings 20, which strengthened the photodiodes 21 and the electric bulbs 22, are strengthened. The housings 23 of the rod displacement sensors, where the photodiodes 24 and the electric bulbs 25 are reinforced, through the thrust 26, on which the coils 27 of the stators of the measuring speeds of the moving rod are fixed s, are connected to cam 28 and actuator 29 through bracket 30, where working planes 31 and · are located

32 cuvettes through calibration plates 33 and 34. Using plates 33 and 34, the required gaps 35 and 36 are established with the substance under test. 6. The bracket 30 is pressed against the cam 28 by springs 37 and 38 and, together with the working planes 31 and 32, is located in a thermally stabilized chamber (not shown). The outputs of the force sensor photodiodes 21 are connected to the first inputs of measurement units 39 and 40, the elastic modulus, where the active components of the complex module stand out, and the first inputs of the viscosity measurement units 41 and 42, where the reactive components of the complex module stand out. The second inputs of the modulus of elasticity measurement blocks 39 and 40 are connected to the outputs of the photodiodes 24 of the displacement sensors of the rods 1, which are also connected to the inputs of the coils 10 of the anchors 9 of the elastic moduli inverters, and the second inputs of the viscosity measuring blocks 41 and 42 to the outputs of the displacement coils 27 rods 1, which are also connected to the inputs of the coils 12 of the anchors 11 inverse viscosity converters. The first outputs of the modulus of elasticity measurement blocks 39 and 40 are connected to the inputs of the coils 17 of the stators 16 inverse moduli of the elastic moduli, and the first outputs of the viscosity measurement units 41 and 42 are connected to the inputs of the coils 19 of the inverse viscosity converters 18. The second outputs of the modules 39 and 40 measuring the modulus of elasticity are connected to the inputs of the scale amplifiers 43 and 44, respectively, and the outputs of the scale amplifiers are connected to the inputs of the first comparison unit 45. Moreover, the comparison unit 45 'is connected to the input of the scale amplifier 46, the output of which is connected to the input of the registering device 47 modulus of elasticity of the substance. The second outputs of blocks 39 and 40 through the scale of 8

Amplifiers 48 and 49 are also connected to the inputs of the second comparison unit 50. The output of block 50 is connected via a scale amplifier 51 to the input of the recorder 52 of the elastic modulus of the surface layer of the substance. The second outputs of the blocks 41 and 42 through the large-scale amplifiers 53 and 54 are connected to the inputs of the third comparison unit 55, the output of which is connected to the input of the large-scale amplifier 56, the output connected to the input of the recorder 57 of the substance viscosity. The second outputs of the viscosity measurement units 41 and 42 are connected to the fourth comparison unit 60 via the large-scale amplifiers 58 and 59, and the output of the comparison unit 60 through the large-scale amplifier 61 is connected to the output of the viscosity recorder 62 of the surface layer of the substance.

Vibration meter rheological characteristics of viscoelastic materials works as follows

When turning on the drive 29 through the cam 28, the bracket 30 is transmitted reciprocating motion of a fixed amplitude and frequency. Through the test substance 6, the probes 2 with plates 3,4,5 are affected by forces that cause the reciprocating movement of the rods 1 connected with the probes. Under the action of these forces, the rods 1 of both vibration transducers make a reciprocating movement with the same frequency, but with different amplitudes and phases. In this case, from the first outputs of the photodiodes of the 21 force sensors of both vibration transducers, signals proportional to the total forces C and __ will be taken:

arising from the deformation of the test substance, which arrive at the first inputs of blocks 39 and 40 of the elastic modulus measurement of the first and second vibration transducers, and their second inputs receive signals from the outputs of photodiodes 24 rod displacement sensors 1, whose magnitudes are proportional to the active components of the complex module of the substance and its surface layer. In blocks measurement modulus 39 and 40 signals proportional to the total force F _L detected and corresponding displacement signals are filtered at the frequency of oscillation and drive signals are generated to compensate for the resistive component of the complex modulus of vibration transducers both. Output signals proportional to the magnitude of the elastic modulus of the substance and its surface layer are fed to the first and second outputs of the modules measuring the elastic modulus 39 and 40. The signals from the outputs of the photodiodes 24 are also fed to the inputs of the coils 10 of the anchors 9

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elastic modulus inverters that form variable magnetic moles in their gaps. Thus, in accordance with expression (1), from both outputs of the modulus of elastic modulus measuring block 39 are removed 5

signals whose magnitude can be expressed

and from both outputs of block 40 signals are taken, the magnitude of which is expressed

¹ 4 ^с 1+ ^с г о. l ₄ + about _g

where K * is the coefficient of proportionality, Οθ, C _p ', C _p are the elastic moduli of a substance and its surface layer with different deformation characters. The signals from the first outputs of the elastic modulus measurement units 39 and 40 are fed to the inputs of the coils 17 of the stators 16 of the inverse transducers of the elastic modulus and form constant magnetic fields in their gaps, which are proportional to the values of the signals defined by expressions (10) and (11). Permanent magnetic fields of stators 16 ,. interacting with the variable magnetic fields of the coils 10 of the anchors 9 of the inverters of the modulus of elasticity, cause the occurrence of forces applied to the rods 1 of both vibration transducers, which are equal in magnitude and inverse to the corresponding forces of resistance of the probes 2 with the rod 1, due to the modulus of elasticity of the substance and its surface layer.

When compensating the resistance forces to the movement of the probes 2 by the electromagnetic forces of the inverse transducers of the elastic modulus, the values of the elastic modulus of a substance and the elastic modulus of the surface layer can be determined. From the second outputs of blocks 39 and 40, the signals arrive at the inputs of the scale amplifiers 43 and 44. The output signals of the amplifiers 43 and 44 arrive at the inputs of the first comparison unit 45, where they are subtracted, and from its output the resultant signal is fed to the input of the scale amplifier 46, the output signal of which is recorded in the registrar 4 7 moduli - elasticity of the substance. From the second outputs of blocks 39 and 40, the signals are also fed to the inputs of amplifiers 48 and 49. Their output signals go to the inputs of the second comparison unit 50, where they are subtracted, the result of which goes to the input of amplifier 51, the output of which is connected to the input of the recorder 52, where the magnitude of the elastic modulus of the surface layer is recorded 15

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25

thirty

35

40

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55

60

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properties. From the outputs of the photodiodes 21 of the force sensors of both vibration transducers, signals proportional to the total forces also arrive at the first inputs of the viscosity measurement blocks 41 and 42 of the first and second vibration transducers, and the second inputs receive signals from the outputs of the coils 27 of the stators of the movement speeds of the rod 1 moving, whose values proportional to the reactive components of the complex module of the substance and its surface layer.

In blocks 41 and 42 of viscosity measurement, the output signals of the photodiodes 21 of the force sensors are detected by signals from the outputs of the coils 27 of the stators measuring the speed of movement of the rods 1, shifted by the angle L / 2 relative to the signals of the movement of the rod 1, filtered at the frequency of the drive oscillation and generated signals to compensate reactive component of the integrated module of both vibration transducers. Output signals

proportional to the values of the viscosity of a substance and its surface layer, go to the first and second outputs of blocks 41 and 42. At the same time, signals from the outputs of coils 27 are also fed to the inputs of coils 12 of anchors 11 inverse viscosity converters, which form alternating magnetic fields in their gaps. , in accordance with the expression (1), the signals from the outputs of block 41 are removed, the magnitude of which can be expressed as follows:

% -CaG ⁵ , ^C ' ^s Ch0 ^{+ La} ''< ¹² '

and the values of the signals from both outputs of the block 42 measuring the viscosity of a substance

45

where k ₂ is the proportionality coefficient, η ₀ , Π λ ₄ , Π'ηι ~ dynamic viscosities of the substance and its surface layer with various deformation characters.

The signals from the first outputs of the blocks 41 and 42 are fed to the inputs of the coils 19 of the stators 18 of the inverse viscosity converters of the first and second vibration transducers and form. constant magnetic fields in their gaps, which are proportional to the magnitudes of the signals defined by expressions (12) and (13). The constant magnetic fields of the stators 18, interacting with the variable magnetic fields of the coils 12 of the anchors 11 inverse viscosity converters, cause the occurrence of forces applied to the rods 1 of both vibrators 11

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converters that are equal in magnitude and inverse in sign to the corresponding forces of resistance to the movement of probes 2 with rod 1, due to the viscosity of the substance and its surface layer. When the forces of resistance to the movement of the probes 2 are compensated by the electromagnetic forces of the inverse viscosity converters, the values of viscous, bone matter and the viscosity of its surface layer can be determined.

From the second outputs of the viscosity measurement units 41 and 42, the signals arrive at the inputs of the amplifiers 53 and 54, respectively. The output signals of the amplifiers 53 and 54 are fed to the inputs of the third comparison unit 55, the output signal of which is fed to the input of the scale amplifier 56, and its output signal is recorded in the recorder 57 of the substance viscosity.

From the second outputs of blocks 41 and 42, the signals also go to the inputs of large-scale amplifiers 58 and 59, from the output of which the signals go to the inputs of the fourth comparison unit OO, and from its output to the input of amplifier 61, the output signal of which goes to the input of the recorder 62, where the viscosity of the surface layer of the substance is recorded.

When the viscosity of a substance and its surface layer changes, the amplitude of the second phase of oscillation of rods 1 with probes 2 will change, which will lead to a change in the signals at the output of blocks 41 and 42, compensating for the change in the viscosity of the substance. The change of signals from the second outputs of blocks 41 and 42 will cause a corresponding change in the output signal of the third comparison unit 55, which will be registered in the recorder 57 as a new value of the viscosity of the substance. A change in the signals of viscosity measurement units 41 and 42 will also cause a corresponding change in the output signal of the fourth comparison unit 60, which will be registered in the recorder 62 as a new viscosity of the surface layer of the substance.

A change in the modulus of elasticity of a substance and its surface layer will lead to a change in the amplitude and phase of oscillations of rods 1 with probes 2. This will cause a change in the signals at the output of blocks 39 and 40 of the measurement of the modulus of elasticity up and down the signals from the first outputs of blocks 39 and 40 will not create forces on the rods 1 of both vibration transducers, compensating for the change in the elastic modulus of the substance. Then the change of signals from the second outputs of the modules 39 and 40 of the measurement of the modulus of elasticity will cause the corresponding. output change

the signal of the first comparison unit 45, which will be registered in the registrar 47 as a new value of the modulus of elasticity of the substance. A change in the signals from the outputs of the modulus of elasticity measurement units 39 and 40 will also cause a corresponding change in the output signal of the comparator unit 50, which will be registered in the recorder 52 as a new value of the modulus of elasticity of the surface layer of the substance.

The device allows not only improving the accuracy of measurements of the modulus of elasticity and viscosity of a substance, but also provides the possibility of studying the rheological characteristics of the surface layers, which is especially important when analyzing the influence of various media on the kinetics of polymers. The use of the present invention opens up the possibility of the synthesis of new materials with surface-active properties, the ability to analyze the qualitative and quantitative influence of the external environment on the kinetics of materials and allows to obtain a significant economic effect.

Claims (1)

Claim Vibration meter for the rheological characteristics of viscoelastic materials, including the first vibration transducer, comprising a housing, a cell with a test substance, a rod with a probe, a cell drive, a force sensor, a rod displacement sensor and a rod displacement velocity meter, an inverse viscosity converter, an elastic modulus recorders and viscosity, modulus of elasticity measurement unit, viscosity measurement unit, characterized in that, in order to improve the accuracy and expand the functional capabilities of the meter, a second vibration transducer is inserted in it, which has a common drive with the first one, large-scale amplifiers of signals of measurement units of the modulus of elasticity and viscosity, four comparison units with large-scale amplifiers, while the probe of the second vibration transducer is made in the form of two plates having the same areas and sides parallel the sides of the probe of the first vibration transducer, whose lengths are related by the ratio B a + bd _ b. , ^С 1 ^{+ С} 1 ^с where b, 64, b _g - lengths of parallel horizontal sides of the plates of the probes of the first and second vibroconversion13 754262 14 The lengths of the parallel vertical sides of the plates of the probes of the first and second vibration transducers, respectively, are respectively, c, c, and _2; module elastic- guests, and its armature coil is connected to the output of the rod displacement sensor, the outputs of the modules measuring the modulus of elasticity of the first and second vibration transducers through appropriate, large-scale amplifiers connected to the inputs of the first and second comparison units, the outputs of which through their large-scale amplifiers are connected to the inputs of the respective recorders, and the outputs of the viscosity measurement units of the first and second vibro-transformation; through appropriate scale amplifiers are connected to the inputs of the third and fourth comparison units, the outputs of which through their scale amplifiers are connected to the inputs I appropriate registrars.