Classification of raw materials. Basic physical quantities. Ideal laws of rheology

The study of the deformation behavior and the flow of real liquid media led to the discovery of a number of phenomena not inherent in Newtonian fluids.

For Nenyutonovsky liquids, a change in viscosity with a change in the shear rate (the effect of viscosity anomaly), the phenomenon of thixotropy, relaxation, reiochection, highly elastic and elastic types of deformation, the occurrence of normal stresses, the existence of limit stresses of shift, etc.

Manifestation of certain abnormal phenomena when app
The fluid of external forces, first of all, depends on its physical nature, its structure, as well as from external factors.

It should be noted that the Newtonian liquid corresponds only to a narrow special case.

In nature and in the industry there are mainly Nengeton liquids (rheological media). For example, pharmaceutical, food, paints and paper industry products; petroleum products and drilling solutions; Polymer materials obtained and processed in the chemical industry; high-temperature coolants based on polymers and suspensions; Highly concentrated filled rocket fuels and fuel mixes in power engineering, etc.

Rheological environments in their mechanical properties occupy an intermediate position between ideally viscous (Newtonian) liquids and perfectly elastic lean bodies. In material
Under the action of external forces, in the general case, reversible develops
and irreversible deformations:

Here - elastic deformation, - viscoelastic deformation, is the deformation of the flow. Elastic and highly elastic deformations are reversible, flows are irreversible.

Elastic deformation develops at the initial time of the load application, its speed of propagation is equal to the speed of sound in this environment. After removal of the load, it disappears at the same speed. Highly elastic deformation develops in time, and the speed of this development is significantly dependent on the temperature of the medium. The value is in dozens and hundreds of times more. High-elastic deformation has a relaxation. Depending on the type and aggregate state of the material, the quantitative ratio between the types of deformation may be different.

Unlike solid bodies, the liquid does not have the ability to maintain its shape, it is mobile and flows under the action of gravity.

In the fluid hydraulics are treated as solid media filled with mass continuously.

Below is a classification of liquids:

The section of hydraulics studying the deformation behavior of Nengeton fluids is part of the rheology. Rheology is studying the mechanical behavior of the media - from Newtonian liquids to solid bodies subject to the law of the throat.

Gaseous liquids. Gaseous fluids under the action of gravity occupy the entire volume of the vessel, without having the surface of the section; compressibles, while heated are very hot, low. Despite this, with small changes in pressure and temperature (with small changes in volume), the gases are subject to the same laws of movement as drip fluids. Significant changes in the volume of gas are occurring at speeds close to the speed of sound. Unlike hydraulics, the aerodynamics studies the movement of the gas at low speeds, taking into account its compressibility, and gas dynamics - at speeds close to the speed of sound and supersonic.

Drip fluids.Drip fluids, almost incompressible, under the action of gravity occupy the volume of the vessel, having a partition surface. Under certain conditions, in contrast to gases, drops are formed on a solid surface. Drip fluids do not resist to tensile loads, do not perceive concentrated loads: the forces (load) should be dispersed over the surface. The behavior of drip fluids is studied in the hydraulics.

Ideal fluids. Perfect liquids absolutely
incompressibles, the molecules of this fluid possess unlimited freedom of movement, therefore - there are no forces of internal friction, i.e. Viscosity is zero.

Real liquids.

Newtonian liquid. For the case of one-dimensional flow, the molecular transfer of the pulse can be represented as:

where T is the shift voltage, M is the coefficient dynamic viscosity of the fluid, is a speed gradient (shift rate). The dependence (2.2) is the mathematical formulation of the law of viscous friction of Newton: "The tangential internal friction stress is proportional to the speed gradient in the direction perpendicular to the movement." The liquids submitted to Newton's law are called Newtonian.
Depending on the choice of reference direction according to the normal, the speed gradient can be positive and negative. The sign in (2.2) is assumed so that the tangent stress is positive. For Newtonian fluids, viscosity is a constant value,
It does not depend on the hydrodynamic situation. Changing viscosity value can be achieved by changing fluid temperature.

Newton's law obey, mainly low molecular weight fluids.

Abnormal viscous liquids. Liquids whose viscosity depends on the hydrodynamic situation is called abnormal-viscous. Experimental studies show that dependence for many real liquids is nonlinear, showing a change in viscosity from the shift rate and from the prehistory of the fluid.

As established for pseudoplastic fluids (Fig. 2.1
and fig. 2.2, Curve 2 ) With small values \u200b\u200bof the speed gradient, viscosity has a constant value, the dependence M occurs with increasing.

Fig. 2.1. Real fluid flow curves:

1 - Newtonian; 2 - pseudoplastic; 3 - dilatant
and 4 - visco-plastic medium

Fig. 2.2. Viscosity Change Curves (designations in Fig. 2.1)

The value of M with increasing decreases to a certain critical value, after which it has a permanent value. Hence,
You can install 3 zones:

- the greatest Newtonian viscosity;

- variable (efficient) viscosity;

- The smallest Newtonian viscosity.

It has been established that the ratio can achieve large values \u200b\u200b- .

To describe the flow curve of pseudoplastic fluids, numerous dependencies are proposed. The highest distribution was the empirical dependence in the form of a power law:

(2.3)

where and the rheological constants of the liquid. Usually, using a power law, only an effective viscosity zone is described.
Then we have:

(2.4)

In this case . Despite the limitations, the power law due to its simplicity was widely used in engineering practice.

The dependences describing all the zones of the flow curve give more complex equations of the impulse conservation law, the use of which causes large mathematical difficulties.

Anomaly of viscosity for suspensions containing asymmetric particles is explained by orientational effects. Viscosity decrease
As long as the possibility of further orientation of particles is preserved. With the limit orientation of the particles, the viscosity does not change. Initially, the disorienting effect of the thermal motion of one order
With orientation effects, therefore viscosity does not change. The orientation effects explain the viscosity anomaly for melts and solutions of polymers, as well as emulsions.

Anomaly of viscosity for polymers is also explained by relaxation processes.

For dilatant liquids (Fig. 2.1 and Fig. 2.2, curve 3 ) Viscosity increases with an increase in speed gradient. To describe the deformation behavior of dilatancy fluids, dependence (2.3) can be used. But in this case.

Dilatated liquids are concentrated suspensions and solutions of some polymers.

An increase in viscosity is associated with an increase in volume (swelling) occupied by the dispersed phase, while the volume of liquid sucks increases. For the new structure of the two-phase medium, the fluid is not enough for lubrication of the particles of rubbing. This effect externally manifests itself as an increase in the viscosity of the suspension.

Anomalistic viscous fluids, the rheological characteristics of which depend on time.Many real liquids cannot be described by equations of type (2.2) and (2.3). There are materials for which communication depends on time. For these materials, an efficient viscosity depends not only on the speed gradient, but also on the length of the shift. These fluids increase or decreases the value of effective viscosity in time (when), are divided into thixotropic and reopectic.

Thixotropy is associated with the destruction of the internal bonds of the structure of the fluid. The rate of destruction depends on the number of connections before the start of the destruction of the structure. Over time, the number of connections decreases (decreases). At some point there comes a dynamic equilibrium - The rate of destruction and structure formation will be equal. Thixotropy is a reversible process.

In the reopectic fluids, structure formation occurs when shear. For example, a 42% aqueous solution of plaster. After shaking, this material hardens at rest in 40 minutes, and with slow shaking in 20 seconds.

It should be said that the viscosity anomaly, as well as all the other features of the mechanical behavior of rheological media, is a consequence of the relaxation mechanism of deformation and that all the deformation characteristics of the medium can be calculated if the main relaxation characteristic of the medium is known - its relaxation spectrum.

Visco plastic medium. Visco-plastic medium (Fig. 2.1, line 4 ) It is characterized by the limit shift voltage. The visco-plastic medium to stresses behaves like a solid.
With further tall t begins viscous (Newtonian) current.

Such behavior of liquids is explained by the fact that they are capable
to the formation of spatial structures; To stresses, the structure is preserved, in the future it is destroyed. After removing the load
In static position, the spatial structure of the medium is restored. The rheological equation of visco-plastic medium has the form:

(2.5)

where M is a plastic viscosity coefficient.

Comparing dependencies (2.2) and (2.5), we introduce the concept of apparent viscosity:

(2.6)

By the nature of the flow to visco-plastic fluids include drilling muddles, sludge, oil paints, consistant lubricants, pastes, etc.

There are cases when the flow process is characterized by
with viscosity anomaly (Fig. 2.1, position indicated by the dotted line). For such media, the rheological equation has the form:

(2.7)

In visco-plastic media, two types of deformation are being implemented - elastic and viscous flow.

Visco-elastic fluid. Visco-elastic fluid exhibits
Both elastic form restoration and viscous flow. Vyazko-elastic from viscous liquids is also distinguished by the presence of reversible deformation, they have a memory.

Current page: 18 (In total, a book of 19 pages) [Available excerpt for reading: 13 pages]

111. Rheological properties of free-dispersed systems

The main factors defining the structure and rheological properties of the dispersed system are the concentration of particles φ (volume fraction) and paired particle interaction potential. Diluted aggregative-stable dispersed systems, where particles retain complete freedom of mutual displacement or a certain structure are missing, they are newtones, their viscosity is calculated by einstein equation:

η = η 0 (1 + αφ ).

where η 0 - environment viscosity; α - A coefficient equal to 2.5 for spherical particles during their free rotation in the stream.

Rheological properties Free-part systems: viscosity, elasticity, plasticity.

Created by outer force F tangent t. It is entirely on overcoming friction between layers of liquid and proportional to the shift speed - This is the law of Newton:

t. = ηγ

Value η \u003d T / Γ (viscosity) Fully characterizes the rheological properties of fluid in laminar flow mode.

Viscous bodies differ from plastic in what flows for any voltages. The flow of perfectly viscous bodies is described. newton's equation:

where f.- the power of viscous resistance; h.- coefficient of friction; u. - linear flow rate; h.- coordinate, normal to flow.

More general is the expression of this law through the deformation of the shift. In an elastic body, the work of the external force t. Foresting in the form of potential energy of elastic deformation, and in a viscous medium it turns entirely into heat. Part of the energy is dissipated, i.e. the material also creates a viscous deformation resistance. Such materials are called viscoelastic. An important rheological characteristic of the viscoelastic medium is the relaxation time of elastic deformations (form recovery time). In addition to the forces of viscous and elastic resistance to deformation, a number of materials inherent in the ability to resist the strength of external (static) friction. In dispersed and polymeric materials, such force arises simultaneously with viscous resistance, the overall resistance is described by the equation:

t. = T. C +. ηγ .

Value η * = (t - T. from) / γ It is called plastic viscosity, and the material is plastic. It is fully characterized by two rheological constants: t. with I. η * Magnitude t. C is called the limit stress of the shift (yield strength). The behavior of the plastic material can be described by Newton's law, where η - Variable value, or Swedov-Bingama law with two permanent ( t. with I. η *). Viscosity, on Newton, takes into account all resistance depending on the rate of deformation. Plastic viscosity takes into account only part of the resistance.

Liquids and plastic viscous bodies whose friction force is not subject to Newton's law, called Nengetonovsky (abnormal) liquids. Some of them are called bingami liquids. Plasticity is the simplest (in mathematical terms) manifestation of Nengeton properties. The transition from creep to plastic and then Newtonian flow occurs gradually. Most often the largest range of shear rates (from γ 1 BE γ 2) falls on a plot of plastic flow. This determines the practical importance of the Swedov-Bingama and Rheological Consanties η * I. t. from.

112. Rheological properties of connected systems. Bingama equation

The main method of rheology is the consideration of mechanical substances on certain models whose behavior can be described by a small number of parameters, in the simplest cases, rheology can be determined by only one parameter.

Elastic behavior - a process that can be characterized by the proportionality of stresses and deformations, i.e., as if linear addiction between τ and γ . This dependence is expressed law of Guka. :

τ \u003d gγ.,

where G. - elastic modulus cabin boy.

If you depict graphically, according to the leg, the dependence between the shear voltage and the displacement can be expressed by the linear dependence of the tilt the angle of inclination to this straight will be a Jung's elastic module.

When the load is removed, the immediate restoration of the initial body parameters occurs, the energy dissipation occurs during the processes of loading and unloading the body. The process of elastic behavior may be peculiar only by solid bodies.

The nature of this phenomenon may be in contact with small deformations. The elastic module may depend on the nature of the interaction in the solid and is a very large amount. The body can strive for recovery with thermal motion, which violates this orientation.

The elastic module also depends on the temperature and may have a small amount. Elastic deformation for solid bodies can be determined, it can occur to a certain value, above which is the destruction of the body. This type of voltage for fragile bodies characterizes strength.

Viscous behavior (or viscous flow), which can be characterized by the proportionality of stresses and the rate of deformation processes, is called Newton's law:

t. = ηγ 1 ,

where t. - shift voltage; h.- Viscosity.

After stopping the impact of the shear stress, the former form of the body can no longer recover. Such a viscous course may be accompanied by dispersion of energy, i.e., the energy that is dissipated in the volume of the body. A viscous flow is associated with the transfer of mass when exchanging places between atoms or molecules with their thermal motion.

The applied potential voltage can reduce the energy barrier of the particle movement in one direction and increase or decrease in the other. It can be assumed that the viscous flow process is a temperature activated process and viscosity will depend on the temperature exponentially.

Plastic May be non-linear behavior. With such a phenomenon, there is no dependence and proportionality between different impacts, many types of deformation. Plasticity is a combination of both dislocation processes and a break and restructuring of bonds between atoms. The plastic body after the removal of the voltage saves any shape that it was given in the process.

Bingama equation:

The deformation rate, which is described by the Bingam equation, should be proportional to the difference and acting voltage, and the limit shift voltage. Moreover, the equation is based on a combination of the two simplest elements of rheology - a parallel connection of a viscous element and a pendan element of dry friction.

113. Real method of study of dispersed systems. Basic concepts and ideal laws of rheology

Riology - a complex of knowledge and concepts, formulating laws and rules to determine the behavior of solid and liquid-shaped bodies. The main method that the rheology uses is the consideration of the mechanical properties of materials on certain models, which are described by a small number of parameters.

Elastic deformation Described by the Dungal Law:

τ \u003d gγ.,

where t. - shift voltage; G. - shift module (N / m 2); γ - relative shift deformation.

The nature of the elasticity of each body consists in reversibility of small deformations, connections between atoms. The elastic module can be determined by the nature of the interactions in the solid and practically does not depend on the increase in temperature. The elastic module can be considered as a certain double-dwarf value of elastic energy, which is intensified by a unit of volume with a single deformation. Elastic deformation of the body may occur to a certain limit, after which the destruction of more fragile bodies occurs.

Strength - The property of the material is resist by external influences under the action of external stresses.

Viscosity Describes Newton's law:

t. = ηγ ,

where h.- Viscosity (N / m 2) - a parameter that is characterized by proportional voltage and deformation rate may also depend on the shift rate.

The viscosity of polymer materials may be accompanied by dissipation of energy, i.e., the state when all the energies secreted can go to heat. Viscosity is a process that is thermally activated, and viscosity has an exponential dependence on temperature.

Plastic It is a nonlinear element, there is an absence between impacts and various deformations. The plasticity of the material will be determined by the processes of gap and the restructuring of interatomic bonds for which the dislocation is possible.

Internal tension - parallel combination of the elastic element and friction of dry.

Deformation - the relative displacement in the time of some points of the system of the system, at which there is no change in the continuity of the material.

Plastic deformation - Deformation at which the material destruction does not occur.

Elastic deformation - The deformation at which there is a complete restoration of the body after removing a certain load.

Modeling must be carried out using real different models of tel. When using a model approach, the full load falls on each element, and, accordingly, the complete deformation of the system or the rate of deformation will be folded from all types of deformations acting on the body, and the rates of all elements forcing the system. If we consider the parallel connection of the deformation and speed elements, they will be the same for all elements, and the entire remaining system load will be folded from the loads of all combined elements. If you use the rules of successive and parallel deformation, you can simply use various rheological models. If you expand the capabilities of the characteristics of quantitative properties for real bodies, you can use several ideal models. It was accepted that there is no difference between the rheological properties of real liquids, as well as solid bodies. This can be explained by the fact that these systems are condensed states of the substance.

114. Rheological models

There are three main cases of mechanical behavior:

1) elasticity;

2) viscosity;

3) Plasticity.

Combining these processes and rheological models of processes, you can get more complex models that will describe the rheological properties of various systems.

In all cases, each combination will be considered in a certain mode of deformation characteristic of this phenomenon in which the properties of models will appear compared to the properties of its elements.

1. Maxwell model - Sequential compound of elasticity and viscosity. The sequential connection of such elements may mean by the third law of Newton, which the same forces will act on the two components of the model (shift voltage τ ), and deformations of elasticity ( γ G) and viscosity ( γ η ) can be folded:

γ = γ G. + γ ?,

where g.- General deformation.

In this model, quick deformation is possible to a certain value and maintain it at a constant level. At high time values, this type of system can be close to the property to the liquid, but when the shift voltage is applied, the system can behave as an elastic solid.

2. Model Kelvin - parallel compound of elasticity and viscosity. In such a model of deformation of both elements, it may be the same, and the shift voltage will be summed up. With constant exposure to the voltage, the Kelvin model behaves differently. The viscous element cannot afford to be implemented immediately deforming the elastic element. Then the general deformation can gradually develop in time:

This equation corresponds to the gradually slowing deformation. The removal of general voltage occurs due to the energy accumulated by the elastic element, the process of deformation of the elastic body occurs, and the dispersion of the energy occurs on a viscous element. An example of such models: attenuation of oscillations, primarily mechanical in rubber.

3. Entering the system of nonlinear item. A model is obtained that describes the occurrence of internal stresses with a parallel combination of an elastic element and dry friction. If the system applied voltage exceeds the yield strength, then deformation arises, which may be due to the accumulation of energy of the elastic element.

4. Model Bingama - Parallel connection of a viscous Newtonian element and a dry pendant friction element. Since the elements are the same, then their deformations will also be the same, and the voltages will be folded. Moreover, the voltage on the Coulomb element cannot exceed the limit value of the shift voltage.

From this it follows that the deformation rate, which is described by a viscous element, should be proportional to the difference in the active voltage and the limit stress of the shift.

In case of complication of rheological models, the mathematical apparatus of deformation descriptions is complicated, so all types of stresses are trying to reduce easier models. One of the methods of facilitating such tasks is the use of so-called. Electromechanical analogies, i.e., obtaining rheological models with electrical circuits.

115. Classification of dispersed systems. Newtonian and Nengeton liquids. Pseudoplastic, dilatantum liquids and solid-shaped bodies

It is known that there are many types of structural and mechanical properties that can reflect all the variety of both natural and synthetic bodies. Many systems are dispersed phases, which, in turn, have many different combinations of phases differing in both nature, and an aggregate state, and particle size. The structural and mechanical properties of many dispersed systems are continuous and infinite rows that include both old and new ones when considering the system. Studies in the field of structural and mechanical properties conducted P. A. Rebelder which suggested dividing substances to condensation and crystallized and coagulation structures. The condensation-crystallized formation of the structure can occur with direct chemical interaction both between the particles and when they are excluded before the formation of a rigid structure having a large volume. If the particles participating in the process are amorphous, then the structures that are formed in the dispersed systems are customary to be called condensation if crystals are involved, the resulting structures are crystalized. The structure of the condensation-crystalized type can be characteristic of dispersed systems of the associated type, i.e. systems having a solid dispersed medium. The use of such structures gives products strength, fragility, but they are not restored after destruction. Coagulation can be those structures that are capable of forming only during coagulation. In the formation of such structures, the interaction between the structures can be carried out through all layers of the dispersion phase, and are Vanderwals forces, the use of such structures cannot lead to stability of the structure. The mechanical properties of such structures are determined not only by the properties of the particles, of which the system consists, but also depend on the nature of the links and the interlayers between the media. The structure of coagulation type has a liquid environment, for such systems it is important to restore the system after its destruction. In practical use, both alone and other materials are characteristic of both the composition and uniformity of the material, and in the process of the technology, the formation processes are regulated.

Liquid-shaped systems are divided into two types:

1) Newtonian;

2) Nenyutonovsky.

Newtonian Systems are called, the viscosity in which does not depend on the voltage arising from the shift, and may be a constant value. These liquids are divided into two types: stationary (for such systems, rheological properties do not change over time) nonstationary, the rheological characteristics of which are determined by the temporary framework.

Nengetonovsky They are called systems that do not have the law of Newton, and viscosity in such systems depends on the stress of the shift.

Dilatant liquids - Systems that are found a large amount of solid phase, in them the chaotic movement of molecules leads to a decrease in viscosity due to non-ordering. With an increase in the load on such systems, the dense packaging of particles may be impaired, the volume of the system may increase, which will lead to an increase in viscosity in the system.

Pseudooplastic liquids - Systems for which a decrease in Newtonian viscosity is characterized by increasing the deformation rate of the entire shift.

116. Viscosity of liquid aggregative-stable dispersed systems

The foundations of this theory were laid by A. Einstein, who was engaged in the study of dilute suspensions. A. Einstein studied hydrodynamic equations for all solid particles having a spherical shape that can acquire additional rotational motion. Scattering, which occurred, was the cause of viscosity ascending. A. Einstein removed the equation that binds the viscosity of the system η and the volume fraction of the dispersed phase φ :

η = η 0 (1+ 2,5φ ).

In the output of the equation, it was assumed that the system may not shrink, there is no slip between particles and liquid. The experiments that A. Einstein spent many times confirmed his assumptions, it found that the coefficient that is under the parameter of the fraction of the dispersed phase depends only on the shape of the particles.

From the theory of A. Einstein, it is possible to draw conclusions that dilute and stable systems are newtonic liquids, their viscosity linearly depends on the bulk fraction of the dispersed phase and does not depend on the dispersion. Parameter 2.5, as a rule, more for some particles. This is explained by the fact that the rotation of the non-confering particle exceeds the volume of the particle itself. This particle has a large resistance that can increase the viscosity of the system. If significant deviations from the spherical shape occur, the system can turn into a non-migon fluid, the viscosity of which depends on the stress of the shift.

Einstein equation does not take into account the presence of surface layers (adsorption, solvate) in particles. An increase in viscosity may occur due to the presence of such layers. Surface layers do not change the shape of the particles, their influence is taken into account with an increase in the volumetric fraction of the phase. Further, this theory was supplemented by the city of Staudinger, which used it to describe the viscosity of dilute polymers solutions. Staudinger equation:

η UD \u003d. KMC.,

where TO - constant characterizing the polymer; M. - polymer mass; from - Mass concentration of polymer.

Staudinger suggested that when lengthening the polymer chain increases its rotation volume and increases the viscosity of the solution at the same concentration. The viscosity of the equation does not depend on the concentration of the polymer solution and can be proportional to its molecular weight. The equation derived by the city of Staudinger is used to determine the molecular weight of the polymer. This equation can only be true for solutions of polymers in both short and hard chains, while preserving their form. But the most frequently used equation for determining the mass of the polymer is equation Marka Kuna-Hauvinka:

{η } = KM. α ,

where α It is a characteristic that is capable of reflecting the shape and density of the macromolecule, the values \u200b\u200bof this value do not exceed the units.

It follows from the equation that the higher the voltage in the system, the greater extent there is an unfolding of the polymers molecules and the less their viscosity becomes. This is due to an increase in the degree of dissociation of polymeric materials when diluted, which increases the increase in the charge of the molecule and increases its volume. In solutions of any polymers, the intermolecular interaction can lead to a sharp increase in the viscosity of the system, at the same time, viscosity can be determined by the effective particle volume, which is per unit mass of the polymer. This is true for all polymeric materials for which you can define the viscosity of the system.

117. Full rheological curve of dispersed systems with coagulative structure

The viscosity changes sharply for connected systems that have a coagulation structure. With this examination, use a whole range of values \u200b\u200bbetween two extreme states of the system: with an indestructible or completely destroyed system. When considering the applied shift voltage, the rheological properties of such systems are changed in very wide ranges up to Newtonian liquids. Such a dependence of rheological properties from coagulation can be represented as a rheological curve.

Rheological curve It is the dependence of the limiting deformation from the shift voltage.

In the study of relaxation properties, it was found that at low shear stresses, an elastic impact occurs, which is associated with the mutual orientation of the particles, for them is characterized by thermal motion. High viscosity values \u200b\u200bmay be due to the flow of the dispersion medium from cells, which are reduced in size, into neighboring cells through narrow passes and with a slide of particles relative to each other.

When a certain value of the limit stress of the shift may appear the area of \u200b\u200bslow, but viscooplastic flow or, as they call, creep.

1. In this area, a shift occurs, which is carried out during fluctuations and is destroyed, but can be recovered under the action of voltages applied from outside. At the same time, all particles are combined into a single coagulation structure, which is experiencing fluctuations on their position in contacts.

2. In this area, a creep system occurs, which can be described by the rheological model of the viscoplastic flow with a small limit stress of the shear and a sufficiently high viscosity.

3. In the third section of the curve, the area of \u200b\u200bthe flow of a vigorously destroyed structure is formed. This site can be described when using the Bingama model.

4. At this stage, the properties of the Newtonian fluid occurs, the viscosity of which is increased. With a further increase in voltage, a deviation may occur on the Newton equation, which is associated with the phenomenon of turbulence.

Rheological properties of the system may vary when exposed to vibration. When analyzing a rheological curve, it can be concluded that even a very complex mechanical behavior of the system can be divided into several simple sections that will be determined by a simple model.

To achieve an equilibrium between the processes of destruction and restoring contacts, it is necessary enough long deformation of the system at a constant speed, which is not always possible when conducting practical work.

But at the same time, different phenomenon on the molecular mechanism, such as creep and viscosetic flow, can be described by the same model, but with different parameters. The rheological characteristics of dispersed systems can be strongly changed when the vibration field is exposed.

Vibration can lead to the destruction of contacts between particles, which leads to the dilution of the system at very low shear stresses. The rheological curve in modern technique when using vibration effects allows you to see how you can control the different properties of dispersed systems, such as suspensions, various pastes or powders.

Consider the simplest rheological properties - elasticity, plasticity and viscosity of the three so-called ideal bodies. In rheology, ideal bodies are customary called the names of scientists who introduced them for the first time)