Coefficient Of External Friction Research Articles

Comparison of the reliability of strength limit calculation methods for prismatic samples with different spreading of normal contact stresses in their wedge failure shape

This article explores methods for calculating the strength limits of solid objects subjected to compression. Traditionally, two stress distribution patterns are used: the exponential pattern by E.P. Unksov and the linear pattern by L. Prandtl. The authors introduce an enhanced stress distribution method. They compare the accuracy of these methods in calculating strength limits and constructing “normal stress - longitudinal strain” diagrams for wedge-shaped failures in rock samples. Four properties are considered: shear strength, coefficients of internal and external friction, and elasticity modulus. The results show that, with an external friction coefficient up to 0.3, all methods yield similar accuracy in strength limit calculations and ultimate stress-strain curves. Some curves exhibit stress drops, explained by a transition from convex to concave slip lines during failure. Additionally, there are hardening curves in the ultimate curves without theoretical justification. The comparison of calculated strength limits with experimental data confirms the method’s accuracy: 13.7% error for the exponential method, 11.4% for the linear method, and 8.1% for the enhanced distribution, especially for low contact friction values (up to f c=0.3).

Physical and chemical properties of amaranth grain as affected by the varietal characteristics and humidity

Purpose. To establish the peculiarities of the formation of physicochemical properties of amaranth grain under the effect of varietal characteristics and humidity. Methods. Laboratory methods for determination of physicochemical and physicomechanical properties of grain; calculation for determination of volume, area and sphericity of grain; mathematical and statistical methods for the analysis of the experimental data. Results. The research shows that the carbohydrate content of amaranth grain varied from 63.1 to 68.7%. At the same time, the content of carbohydrates in the grain of variety ‘Kharkivskyi-1’ was significantly higher compared to ‘Atstek’ and ‘Helios’. The content of protein in the grain of the studied varieties varied significantly. The highest protein content was in the grain of 'Lera' and ‘Kharkivskyi-1’ varieties (20.2–24.9%). It should be noted that the lysine content in the grain of these varieties was also the highest (0.85–0.91%). Grain moisture content in the studied varieties was low (8.3–11.1%). The highest grain quality was in the ‘Helios’ variety – 819 g/dm3, while in the rest of the studied varieties it ranged from 748 to 775 g/dm3. 1000-kernel weight and 1000-kernel volume were almost equal in the studied amaranth varieties. At the same time, the angle of the natural slope varied reliably. The coefficients of external friction at rest and the coefficient of external friction in motion for the grain of the varieties ‘Kharkivskyi-1’, ‘Lera’ and ‘Atstek’ were significantly higher compared to ‘Helios’. The geometric parameters of grain changed reliably depending on their humidity: as the humidity of the grain increases, its geometric parameters increase. An increase in the moisture content of the grain increases the linear dimensions. At the same time, the volume and surface area of the grain increases, thanks to which the sphericity increases. Conclusions. It was established that the physicochemical properties of amaranth grain reliably change as affected by varietal characteristics and humidity. The grain of amaranth varieties ‘Lera’ and ‘Kharkivskyi-1’ has the highest protein content (20.2–24.9%) and lysine (0.85–0.91%). The carbohydrate content is 65.3–68.7%. ‘Helios’ variety has the highest grain quality – 819 g/dm3. 1000-kernel weight is 0.664–0.710 g, depending on the variety. The grain of varieties ‘Kharkivskyi-1’, ‘Lera’ and ‘Atstek’ is characterized by a higher angle of natural slope, coefficients of external friction at rest and external friction in motion. An increase in grain moisture significantly increases its geometric parameters.

The Dynamic Behavior of Silos with Grain-like Material during Earthquakes

Grain security is an important guarantee for sustainable development. However, the dynamic behavior of silos containing grain-like material is not well understood. The effective mass and dynamic effects are the key parameters for the assessment of the silo–bulk material system during earthquakes. Herein, on the basis of the Janssen continuum model, it is proposed that the seismic energy is entirely dissipated by the interactions between the materials and the silo and the materials themselves. The seismic inertia forces among storage materials were introduced, and dynamic equilibrium equations considering the vibrations of storage materials were established. Theoretical solutions for the horizontal forces exerted and the effective mass of the silo–bulk material system during earthquakes are proposed. It is worth noting that the additional stress on the side wall proposed in this work is related to the depth, silo radius, storage density, internal friction coefficient, lateral pressure coefficient, and seismic acceleration. In addition, the effective mass coefficient is negatively correlated with the external friction coefficient, the lateral pressure coefficient, and horizontal seismic acceleration under a storage vibration state. A narrower silo (i.e., with a larger height–diameter ratio) has a low effective mass coefficient. The results from our method are in good agreement with those attained using experimental data, which demonstrates the accuracy and universality of the proposed formulations.

Determination of engineering properties of selected animal feed and fodder materials

The traditional ways of handling feed and fodder in a commercial dairy farm are labour intensive, tiresome and also leads to huge expenses as labour charges. Therefore, there is a need of mechanised feed and fodder distribution unit in order to reduce the human drudgery and other expenses. Thus, an attempt was made to determine the engineering properties (moisture content, bulk density, angle of repose and coefficient of internal friction) of feed which would be affecting the design of a mechanised feed and fodder unit. Three feed materials viz., oat green, wheat straw and concentrate mixture were selected for study. The angle of repose varied from 24.78±0.34 to 37.79±0.76°,the coefficient of friction from 0.187±0.024 to 2.628±1.612depending on the moisture content and the bulk density of the selected materials. The coefficient of external friction was determined for different fabrication materials including wooden/ply board, galvanized iron, aluminium, mild steel and stainless steel and the maximum coefficient of external friction was offered to the feed materials by ply board followed by mild steel.

Experimental Study of the Compacting Pressure Influence on the Product of the External Friction Coefficient and the Lateral Pressure Coefficient for Powder Materials

Experimental Study of the Compacting Pressure Influence on the Product of the External Friction Coefficient and the Lateral Pressure Coefficient for Powder Materials

Arabica coffee flow properties assessed using different roasts and particle sizes during storage

Abstract Flowability of agricultural products is an important factor to be considered at post-harvest, thus impacting directly on number of operations and the design of machinery. This study aimed to evaluate and determine the K coefficient and flow properties as a function of different levels of roasting, grain size, temperature and storage. Coffee beans were roasted at medium light and moderately dark, then ground at fine, medium and coarse sizes. An additional coffee lot was not ground. Samples were stored at 10 ºC and 30 ºC and analyzed during storage (0, 30, 60, 120 and 180 days), regarding internal and external friction coefficients, angle of internal friction, effective angle of internal friction, wall friction angle (concrete, rough steel and wood) and lateral pressure coefficient (K coefficient). Angle of internal friction varied significantly due to particle size and roast degree. Moderately dark roast with fine particle size led to higher values (about 29.5 º) of wall friction angle. The wood sample was the material with the highest values of wall friction angle, followed by the concrete and steel samples, when compared at the same storage temperature, roast degree and particle size. Whole coffee was classified as free-flowing. Fine particle size leads to cohesive flow characteristic, according to the flow function. Coffee roasted at medium light, kept whole requires storage facilities with higher pressure support, accordingly to the K coefficient values.

Improved model of powder blend compacting in a roll compactor

A new mathematical model of mineral fertilizer compacting using a roll compactor is developed. This model is based on the transition to the values of stress tensor components averaged over the cross-sectional area of the powder mixture flow. To define these stresses, equations of equilibrium of the elementary layer determined in the mixture by two planes perpendicular to the flow direction are composed. To obtain relatively simple analytical relations in the calculations, the hypothesis of a power-law dependence of hydrostatic pressure on mixture density, accepted in the framework of the Johansen model, was used. In order to take into account changes in the mechanical characteristics of the mixture (angle of internal friction, coefficient of external friction, transverse strain coefficient) while compacting, we approximated the known experimental dependencies of the corresponding characteristics on the density. The inter-particle cohesion parameter was taken to be proportional to the hydrostatic pressure. The model allows calculating the gap between the rolls surfaces for a given initial bulk density and the required flake density. With the known gap value, the distribution of the axial average stresses in the powder mixture, the normal and shear stresses on the rolls’ surfaces are determined. The results of the calculations of the rolls surface gap and the normal roll pressure diagram are compared with the experimental data given in the literature for the urea compacting process.

DETERMINATION OF PHYSICAL AND TECHNOLOGICAL PROPERTIES OF QUINO GRAIN - THE MAIN STAGES OF JUSTIFICATION OF STORAGE AND PROCESSING TECHNOLOGY

The work is devoted to determining the physical and technological properties of quinoa grain. Quinoa is an unconventional crop for Ukraine, but experiments on its cultivation have been successfully completed in the Sumy region. Due to its unique chemical composition, quinoa is used in dietary and functional products.Quinoa contains about 20% protein, which makes it an excellent dietary supplement for people who do not eat animal products. The amino acid composition of quinoa proteins is very balanced and is characterized by a high content of such essential amino acids. Feature of the fatty acid composition of quinoa. it has a high content of polyunsaturated fatty acids, including linolenic fatty acid and linoleic, which belongs to the acids ω-3 and ω-6 fatty acids.Due to the growing popularity of quinoa and its suitability for cultivation in our climatic and soil conditions, it is important to develop the technology of its storage and processing. One of the main stages of substantiation of the choice of technology for storage and processing of quinoa grain is to determine its physical and technological properties.Physical and technological properties of grain mass are determined by a large number of indicators.Determination of physical and technological properties of quinoa grain was performed for three types of quinoa: red, black and white. In determining the physical and mechanical properties were used methods approved by the relevant standards, or used in research and recommended in the relevant literature.We have identified the following basic physical and technological properties: geometric characteristics, nature, weight of 1000 grains, duty cycle, packing density, air supply, angle of natural slope, coefficient of internal friction, coefficient of external friction. Numerical values of these indicators for each type of quinoa are determined.Knowledge of the physical and technological properties of the grain mass to solve a large number of applied problems that have practical significance. and play an important role in the processes of moistening, heating and cooling of grain. A thorough study of physical and technological properties can provide optimal conditions for storage of seeds without compromising their quality. The obtained data can be used for selection of modes of cleaning, drying and active ventilation.

A study of moisture dependent changes in engineering properties and debranning characteristics of purple wheat

To assess the efficient storage and processing yields, simultaneously reducing the qualitative and quantitative losses from wheat grains, it is necessary to consider and study their engineering properties. The present study was conducted to determine the moisture-induced changes in the engineering properties and debranning characteristics of colored wheat varieties. Wheat was tempered to three moisture levels (12%, 14%, and 16%), and parameters were recorded using standard techniques and methods. Engineering properties such as bulk density, true density, porosity, and grain hardness decreased; the angle of repose, coefficient of external friction, arithmetic mean diameter, geometric mean diameter increased, while the coloring properties (chroma and hue angle) varied erratically with the increase in moisture content. Debranning characteristics also showed a positive correlation with moisture content. Practical applications The engineering properties and debranning characteristics of cereal grains are essential to design new equipment or to upgrade an existing one for their cleaning, grading, sorting, separation, material handling, storage, and milling. The present research provides a database needed for the design and development of purple wheat storage and processing equipment. It thoroughly discusses the impact of moisture levels on the engineering properties and debranning characteristics; the machinery that can be used by the farmers and processors to extract bran which can further be used to extract color rich in anthocyanins.

Physico-chemical properties of four different varieties of guar seeds (Cyamopsis Tetragonoloba L.)

The objective of the study is to evaluate the four new guar varieties (GAUG13, HG563, RGC986 and HG884) to study their chemical composition and physical properties. Samples were collected from the experimental farm, University of agricultural sciences Raichur. Proximate composition, Thousand seed weight, length, width, thickness, geometrical mean diameter, sphericity, bulk density, true density, co-efficient of external friction, co-efficient of internal friction, angle of repose and terminal velocity were carried out for the guar seeds. Result obtained showed that verity HG-365 had a highest content of Ash (7.26 %), Fat (10.16%), Fiber (16.40) and Protein (51.95). Significantly highest value of moisture content (12.55%) and carbohydrates (20.53%) found in the varieties HG-884 and RGC-986. The verity GAUG13 found highest value of length (3.81 mm), thickness (3.74 mm) and geometrical mean diameter (3.62 mm). HG563 found highest value of width (3.47 mm), sphericity (0.98%) and Terminal velocity (4.81 m/s). RGC986 found highest value of co-efficient of external friction (0.77). HG884 found highest value of thousand seed weight (35.21 g), bulk density (1.24 g/cm3), true density (2.42 g/cm3), co-efficient of internal friction (0.77) and angle of repose (30.37 o).

The method for determining the parameters of the diagrams of a truncated-wedge destruction of cylindrical samples of rocks

Purpose. Development of an analytical method for calculating the parameters of complete diagrams longitudinal tension deformation for the truncated-wedge shape of destruction of cylindrical rock samples to control the stress-strain state of the rock mass and effective destruction of these materials during disintegration. Methodology. Analytically, by developing a mathematical model of the fracture process of cylindrical rock samples with their truncated-wedge form of crack development, an algorithm is created for calculating the full deformation diagram from the acting tension using the experimental values of four indicators of material properties the shear resistance limit, internal and external friction coefficients and elastic modulus. The method is based on the improved Coulomb strength criterion, supplemented by the parameters of contact friction and allowing one, using the theory of slip lines, to calculate the limiting state of the material at the tip of cracks developing from the edges of the sample of the correct geometry, taking into account the release of part of the material from the load and compliance with Hookes law deformation of the sample bearing area and the specific force on it. Findings. The method of mathematical modeling makes it possible to determine the ultimate strength and residual strength of cylindrical rock samples using four property indicators that can be experimentally established by simple methods. Originality. For the first time, analytical modeling of the process of destruction of cylindrical rock samples with their truncated-wedge form of destruction was carried out, taking into account the internal contact friction depending on the properties of the rock material and external contact friction. Practical value. The proposed method of mathematical modeling and the calculation algorithm make it possible to determine the limit and residual strength of rock samples using four property indicators, which can be established experimentally by simple methods under laboratory conditions of enterprises of the mining and metallurgical complex. The calculation results can be quickly used to control the state of the rock mass and effective destruction upon disintegration.

Analytical method for calculating the strength limit of rock specimens of wedge form of destruction at linear distributing of contact normal tensions

Abstract. An analytical method for calculating the parameters of the “stress – deformation” diagrams of prismatic samples with their wedge-shaped destruction is presented based on the distribution of the L. Prandtl contact stresses with using experimental values of four indicators of rock properties: shear resistance limit, internal and external friction coefficients, elastic modulus, which can be determined experimentally by simple methods in mining enterprises, where the calculation results can be promptly used. The method is based on the theory of local destruction of rocks along sliding lines developed by the authors. The theory makes it possible to determine the current values of the normal stresses at the crack tip during its development. As a strength criterion, the Coulomb strength criterion was adopted, supplemented by the authors by taking into account contact friction. The regularities of the distribution of normal stresses from contact friction were previously established by E.P. Unksov and L. Prandtl. The regularity of E.P. Unksov was used by the authors earlier to develop a method for calculating the strength limit of rock samples of the mentioned form of destruction. In this paper, the method is based on the method of L. Prandtl. To determine the strength limit, it was necessary to develop a method for calculating the parameters of “normal stress – longitudinal deformation” diagrams. The fact is confirmed that the stress at which the crack is formed is not the limit strength. The limit strength in the case of wedge-shaped destruction of the samples is the maximum value of the normal stress on the out-of-limit branch of the “stress- deformation” diagram. Some exorbitant curves have stress discharge, which are confirmed by experimental observations. At the moment of discharge, areas appear in the form of a so-called yield tooth, the formation of which we explain by the stresses discharge on the convex part of the slip line. In the middle part, the out-of-limit curves have stress jumps, which indicate the strengthening of the samples, which have not yet received any theoretical justification. We explain this phenomenon by the transition of the destruction process from the convex part of the slip line to the concave one. Comparison of the calculated strength limit of prismatic samples obtained according to the laws of distribution of contact normal stresses, exponential – by E.P. Unksov and linear – by L. Prandtl testifies to their practical identity. Keywords:rock, strength limit, destruction, crack, “stress – deformation” diagram.

Study of the dynamics of the coefficient of external friction of seeds crops with shell

The article is devoted to the study of the coefficients of external friction of grain agricultural products-friction in static and dynamic modes, as the most important physical and mechanical characteristics of bulk materials. The description of carousel laboratory unit, program, methodology and results of studies on the practical determination of the coefficients of external friction for typical agricultural grain products according to the materials typical of the working bodies of the production machines. As a result of the research, it was found that in the range of linear velocities from 0 to 1.75 m/s, there is a change in the friction coefficients, which has a nonlinear character.

Improving the efficiency of equipment and technology of waste briquetting

The present-day problem of the accumulation of carbon waste was considered in connection with the aggravating urgency. General tendencies and approximate rational compositions of unprepared polydisperse fractions of mixtures of potential raw materials during their compaction and subsequent thermolysis have been experimentally determined. It was found that with an increase in moisture or binder content, solid carbon waste becomes more plastic and viscous (from 0.6 to 0.4), the coefficient of internal friction decreases. The effect of moisture on the coefficient of external friction is less noticeable (up to a 25 % reduction). It has been determined that preheating of the charge to 80 °C contributes to a decrease in density of the resulting briquettes (on average by 5–6 %) and leads to an increase in the coefficient of elastic expansion. Briquettes, all other things being equal, are 5–10 % stronger but a 1 % increase in strength accounts for a 2 % increase in energy costs. Upon re-compaction, a noticeable change in compression properties occurs. The briquette density increases by an average of 7 %. With a lower binder content, a 14 % increase in density was obtained. In this case, the increase in strength is directly proportional to energy consumption. An increase in binder content in briquets and their re-compaction were recommended. It has been found that with the optimized operation of the boiler plants that incinerate the briquetted waste, the coefficient of expenditure per year is 32.9 % less than the value of this index when using the equipment for recovery of unprepared waste. At the same time, the coefficient of influence on the environment over a 15-year period was 28.89 % less than the value of this index when operating similar equipment. The results obtained reasonably indicate that the optimized technology of waste briquetting and subsequent incineration is characterized by a significant increase in the environmental and economic efficiency of the waste recovery process

On the processing properties and friction behaviours during compaction of powder mixtures

ABSTRACT Iron-based powder mixtures were prepared by dry and wet mixing method. The friction properties during compaction were tested by measuring the internal and external friction coefficient. The test results showed that the wet mixing process could realise the homogeneity of lubricant and improve the processing properties of the powder mixtures. With 0.6 wt-% lubricants, wet mixing powder mixtures have a flow rate of 29.6 s/50 g, an apparent density of 3.18 g cm–3, a repose angle of 35.5°, and the friction coefficient during the compaction is 0.223. An equation to calculate the total (both internal and external) friction forces during the compaction process is proposed, and then the factors influencing the friction coefficient during compaction were quantitatively analysed.

Engineering Properties of Paddy and Wheat Seeds in Context to Design of Pneumatic Metering Devices

Engineering properties play important role while designing of metering devices of the planter/seed drills. Present investigation was conducted to study the change in engineering properties of paddy (Kranti (PV1) and Pusa1121 (PV2)) and wheat (HI1544 (WV1) and Lokwan (WV2)) seeds due to soaking in water for predetermined duration. Geometric mean diameter of PV1, PV2, WV1 and WV2 was ranged between 3.89 and 4.07 mm, 3.87–4.14 mm, 4.03–4.59 mm and 4.18–4.61 mm, correspondingly due to soaking. Sphericity with aspect ratio of PV1, PV2, WV1 and WV2 seeds were varied as 48.43–49.56 with 0.41–0.42, 32.03–32.07 with 0.2, 60.68–64.12 with 0.51–0.58 and 57.29–60.67 with 0.46–0.52, respectively. Thousand seed weight of PV1, PV2, WV1 and WV2 was increased from 27.80 to 34.88 g, 28.64–35.91 g, 45.68–67.6 g and 48.21–71.13 g, respectively. Bulk and true densities of PV1 and PV2 were increased from 626.49 to 661.98 kg/m3 and 1150.83–1322.45 kg/m3 and 540.35–562.15 kg/m3 and 1376.76–1412.58 kg/m3, respectively, for dry to 2 days soaked seeds. Bulk and true densities were 833.06–676.91 kg/m3 and 1388.09–1258.84 kg/m3 for WV1 while 816.18–669.85 kg/m3 and 1647.7–1485.62 kg/m3 for WV2. Porosity of PV1, PV2, WV1 and WV2 was varied from 45.48–49.87%, 60.61–60.17%, 39.91–48.02% and 50.44–56.55%. Angle of repose of PV1, PV2, WV1 and WV2 was ranged as 30.33–38.13ο, 27.78–34.15ο, 29.22–37.97ο and 32.42–38.51ο, respectively. On wooden platform, static coefficient of external friction was varied as 0.56–0.62, 0.45–0.53, 0.38–0.65 and 0.41–0.69 for PV1, PV2, WV1 and WV2 seeds, while on mild steel corresponding values of coefficient were 0.37–0.56, 0.40–0.51, 0.33–0.68 and 0.37–0.75. Coefficient on plastic platform was varied as 0.34–0.41, 0.36–0.41, 0.34–0.67 and 0.29–0.63 for PV1, PV2, WV1 and WV2 in same order. Terminal velocity values for PV1, PV2, WV1 and WV2 were ranged between 6.5 and 8 m/s, 6.2–7.6 m/s, 7.4–9.10 m/s and 7.5–10.1 m/s, respectively. Statistical models with ANOVA and multiple pair wise comparison also determined change of the seeds behaviour for soaking conditions.

Dynamic friction coefficients of grain crops of bulk agricultural products

The article covers issues related to the study of physical and mechanical characteristics of bulk materials, namely the coefficients of external friction in static and dynamic modes. The program, methodology and results of research on the practical study of external friction coefficients of typical agricultural grain products by the surfaces made of materials typical for the working bodies of production machines, using an innovative carousel-type device, are presented. As a result of research, it was found that in the range of linear speeds from 0 to 1.75 m/s, there is a change in the friction coefficients, which has a nonlinear character.

Studying physical and mechanical characteristics of corn feed

The use of condensed extract in the production of corn feed contributes to the improvement of their nutritional and biological value. The rheological properties of the feed material are of great importance in the mechanical interaction with the working bodies of the machines, in the movement of viscous media along technological conveyors, as well as in the intensification of heat exchange processes. The technique, laboratory equipment and the results of studies of physical and mechanical characteristics of corn feed are presented. The viscosity properties of the corn extract are investigated depending on the temperature. It is shown that when decreasing the temperature, the viscosity of the corn extract increases due to the aggregation of its components, which characterizes the non-Newtonian flow of the extract. The coefficient of external friction of the pulp and extract mixture in the technology of preparing corn feed allows calculating the geometry of the storage tanks and energy costs of the processes. The change in the coefficients of friction of corn feed when interacting with various surfaces, depending on the content of dry substances. The specific heat capacity, thermal conductivity and thermal diffusivity of the extract and corn feed were determined and investigated. It has been revealed that the dependences of the thermo-physical parameters of the extract and corn feed on the solids content are non-linear in nature, monotonously decreasing when increasing the concentration of solids.

Static and dynamic friction coefficients of grain crops and mineral materials

There are many devices for determining the coefficients of external friction, but there are almost no devices for determining the coefficients of internal friction of bulk products. The paper considers the question of physical and mechanical characteristics of bulk materials - the coefficients of external and internal friction. The purpose of this study was to create a device for determining the friction characteristics of bulk materials and its approbation by determining the coefficients of static and dynamic friction of grain materials. The basic parameters of the installation to determine the friction characteristics of bulk materials were defined - static and dynamic, internal and external friction coefficients. The developed installation allows measurements of shear forces inside the bulk material. The relationship between the coefficient of static and dynamic friction in organic and inorganic bulk materials is revealed. Grain crops have a higher value of the dynamic coefficient of friction at a speed up to 0.215 m/s. The difference between the values of static and dynamic friction coefficients was not revealed in the specified speed range of legumes. Dynamics of change in the coefficient of friction for grain crops depending on speed is studied using the example of wheat, and for mineral materials - using the example of table salt. For a speed range of 0-0.215 m/s, the relative change in the coefficient of friction for grain crops has a polynomial regression model, for mineral materials it has a logarithmic.

The study on soils external friction

The molecular-mechanical (adhesion-deformation) theory of friction with respect to a dispersed medium was confirmed in the article on the basis of theoretical and experimental soils external friction studies. At the same time, the soil particles interaction calculated model of a spherical shape with a smooth polymer surface was developed and an expression for determining the area of their actual contact with a solid surface under the action of a load N was obtained. The calculated contact area results‘ comparison for coarse and fine sand showed satisfactory convergence with the experimental data (discrepancy does not exceed 8-10%). The particles behavior analysis of the dispersed medium adjacent to a solid smooth surface under shear, presented in the computational model, was confirmed by the experimentally obtained and fixed plastic deformations of the polymer surface layer. The experimental studies using a soil tribomer allowed to determine the deformation proportion and adhesive components in the external friction force of sandy and clay soils. Using the obtained dependencies for calculating and contacting soil particles with a solid surface, a method for calculating the coefficient of external friction of the soil based on the molecular-mechanical theory of friction is proposed.