Static Friction Coefficient Research Articles

Determination of Ellipsoidal Seed–Soil Interaction Parameters for DEM Simulation

During precision sowing, the contact process between the soil and seeds cannot be ignored. The constitutive relationship of soil is relatively complex, with characteristics such as high nonlinearity, while the contact mechanism between the soil and seeds is unclear. To better understand the contact between seeds and soil, it is necessary to establish a reasonable contact model. Ellipsoidal seeds, such as soybean, red bean, and kidney bean seeds, were adopted as research objects. In this paper, we used the discrete element method to establish an ellipsoidal seed–soil contact model. The JKR + bonding model was adopted for describing the adhesion between soil particles, and the Hertz–Mindlin new restitution (HMNS) model was used for ellipsoidal seed particles to eliminate the multiple contact point issue when modeling with the multi-sphere filling method. Moreover, both simulations and experiments were conducted to calibrate the interaction parameters between soil and seeds. The path of steepest ascent test and Box‒Behnken design (BBD) tests were also used, as well as direct shear tests. Thus, certain soil parameter values were obtained, namely the JKR surface energy was 4.436 J/m2, the normal stiffness per unit area was 2.86 × 106 N/m3, the shear stiffness per unit area was 5.54 × 105 N/m3, the critical normal stress was 1833 Pa, and the critical shear stress was 3332 Pa. In addition, the simulation parameters for ellipsoidal seeds were obtained from previous works. Moreover, to obtain more accurate ellipsoidal seed–soil interaction parameters, collision tests, static friction tests, and rolling friction tests were adopted. A single-factor test was used to calibrate the ellipsoidal seed–soil interaction parameters. The calibration results were as follows: the collision restitution coefficients of ellipsoidal seeds with soil were all 0.25. The static friction coefficient of soybeans with soil was 0.6, that of red beans with soil was 0.65, and that of kidney beans with soil was 0.5. The rolling friction coefficient of soybeans with soil was 0.1, that of red beans with soil was 0.14, and that of kidney beans with soil was 0.14. Finally, the rationality of parameter selection was verified through piling tests between ellipsoidal seeds and soil. The relative error of the angle of repose of soybean/soil was 2.99%, that of red bean/soil was 0.60%, and that of kidney bean/soil was 0.55%. Thus, the feasibility and rationality of the contact models between the ellipsoidal seeds and soil established in this paper, as well as the parameter selection, were verified.

Modulation of Physical and Thermal Properties in Wild Banana (Musa balbisiana Colla) Seed Powder by Moisture Variations.

Engineering and flow properties of banana seed powder as a function of moisture content are important for processing, handling, packaging, and transport processes. The bulk density, tapped density, and porosity increased from 377.37 to 427.36 kg m-3, 622.08 to 746.33 kg m-3, and 38.99-43.74%, respectively, within the increasing moisture content range. The Hausner ratio (Hr) and Carr's compressibility index (CI) significantly (p < 0.05) increased with an increase in moisture content (6.16-19.56% db) of banana seed powder, whereas HR fell in the range of 1.4-2.0, indicating cohesive characteristics of banana seed powder. The angle of repose, angle of spatula, and angle of fall exhibited a linear increase, ranging from 40.6° to 49°, 33.4° to 39.4°, and 35.6° to 42.6°, respectively, with increasing moisture content. The static coefficient of friction was found to be highest for aluminium and glass surfaces and least for stainless steel. The water activity and swelling power of banana seed powder showed a significant increase, while the solubility and oil absorption capacity exhibited a significant decrease within the range of increasing moisture content. The thermal characteristics of wild banana seed powder, such as thermal conductivity (0.16 to 0.20 Wm-1 K-1) and volumetric specific heat (0.58 to 0.99 MJm-3 K-1), demonstrated an increasing trend as the moisture content increased. However, the thermal diffusivity showed a decrease from 0.31 to 0.19 (×10-6 m2s-1) with the increase in moisture content.

Impact of faults on the remote stress state

Abstract. The impact of faults on the contemporary stress field in the upper crust has been discussed in various studies. Data and models clearly show that there is an effect, but so far, a systematic study quantifying the impact as a function of distance from the fault is lacking. In the absence of data, here we use a series of generic 3-D models to investigate which component of the stress tensor is affected at which distance from the fault. Our study concentrates on the far field, located hundreds of metres from the fault zone. The models assess various techniques to represent faults, different material properties, different boundary conditions, variable orientation, and the fault's size. The study findings indicate that most of the factors tested do not have an influence on either the stress tensor orientation or principal stress magnitudes in the far field beyond 1000 m from the fault. Only in the case of oblique faults with a low static friction coefficient of μ=0.1 can noteworthy stress perturbations be seen up to 2000 m from the fault. However, the changes that we detected are generally small and of the order of lateral stress variability due to rock property variability. Furthermore, only in the first hundreds of metres to the fault are variations large enough to be theoretically detected by borehole-based stress data when considering their inherent uncertainties. This finding agrees with robust stress magnitude measurements and stress orientation data. Thus, in areas where high-quality and high-resolution data show gradual and continuous stress tensor rotations of &gt;20∘ observed over lateral spatial scales of 10 km or more, we infer that these rotations cannot be attributed to faults. We hypothesize that most stress orientation changes attributed to faults may originate from different sources such as density and strength contrasts.

An Investigation of Garlic’s Physical Properties Prior to Collection for the Development of a Garlic Collector

In this study, the physical properties of garlic just before collection were investigated, and garlic-collecting conditions are presented as basic data of design factors that can be utilized during the development of garlic collectors. The physical properties were subdivided into geometrical properties and mechanical properties, and the ecotype of garlic was divided into CSG (cold-season garlic) and WSG (warm-season garlic). Geometrical properties were compared between CSG and WSG by measuring the average weight, length, width, number of kernels, volume, and density of each cultivar, and WSG showed higher geometrical properties in all geometrical properties. In addition, there was garlic on the incomplete side of WSG, and shape non-uniformity was higher than that of CSG. There was no significant difference in the average Poisson’s ratio of mechanical properties. In the case of the modulus of elasticity, Namdo cultivars showed the lowest value at 15.52 MPa. The average allowable compressive stress measured using Hooke’s law was the lowest in the Uiseong cultivar (204.33 kPa) and the highest in the Danyang cultivar (376.42 kPa). The static friction coefficients among the four different materials by cultivar exhibited a commonality of being highest in aluminum and generally lowest in plastic. It is expected that the design of the garlic collector will be carried out in consideration of garlic when developing it using up-to-date physical properties of garlic just before collection.

Diffusion transitions induced by shear-thinning viscosity: application to laser-cooled atomic gases

We study the diffusive dynamics of a system in a nonlinear velocity-dependent frictional environment within a continuous time random walk model. In this model, the motion is governed by a shear-thinning frictional force, −γ0v/[1+(v2/vc2)]μ ( 0<μ⩽1 ), where γ 0 represents the coefficient of static friction and µ is the scaling index. Through analytical and numerical results, we construct a diffusion phase diagram that encompasses different regimes upon variations in parameters γ 0 and µ: normal diffusion; superdiffusion; and hyperdiffusion. These transitions occur because the induced weaker friction enhances the diffusion. With a decrease in the scaling index, we find that the γ 0-dependent exponent of diffusion converges towards the experimental findings for ultracold 87Rb atoms because the strong effective friction arises. The discrepancies between the fractional Lévy kinetics and the experimental findings may be potentially reconciled. We believe that these findings are helpful for analyzing experimental observations of cold atoms diffusing in optical lattices.

Study of mechanical and technological properties of seed fruits of vegetable and melon crops

The analysis of literature sources shows that the production of seed material for vegetable and melon crops is one of the most important problems that exists in the field of agricultural processing. The production of cucumber and melon seeds is an urgent issue in view of the volume of their cultivation in Ukraine. To study the processes of fruit grinding and seed production in agriculture, the key parameters are the dynamic friction coefficient, the volume deformation coefficient and the static load coefficient, but existing methods and equipment are limited to determining the limit values of the indicators, not allowing a full study of the dynamics of changes in properties at different stages of the technological process. To solve this, it is proposed to develop new methods, in particular, the use of computer modelling, which will allow a more detailed study and optimisation of physical and mechanical properties and their changes. The aim of the article was to study the physical and mechanical properties of vegetable fruits, which have the greatest impact on the quality of the technological process of fruit seed grinding and preliminary seed extraction. The study was conducted in the problematic research laboratory of the Faculty of Engineering and Energy of Mykolaiv National Agrarian University. Experimental setups were used to determine the dynamic coefficient of friction of melon and cucumber seeds, a device for determining the initial density of seed fruits, and a device for determining the dependence of seed deformation on compressive load. Experimental data show that the most optimal values of the static coefficient of friction, depending on the type of surface, for cucumber and melon seeds are perforated sieves, the values of which are 0.75 and 0.85, respectively. Optimal values of dynamic friction coefficients for cucumber have a surface made of perforated sieve – 0.69 and for melon made of aluminium – 0.88. The dependence of the linear deformation of seed fruits on the specific pressure increases from 0.9 to 3.6. The values of fruit deformation from compressive load vary from 4.1 to 24.6. The research presented in the article is of practical importance and can be used in the field of agricultural production and in the development of new engineering solutions

Parameter Calibration for Discrete Element Simulation of the Interaction between Loose Soil and Thrown Components after Ginseng Land Tillage

Given the lack of accurate and reliable discrete element simulation parameters to study the interactions between soft soil and soil casting components after ginseng land cultivation in Northeast China and the design of ginseng land-specific borders, this paper calibrates the relevant model parameters of ginseng soil using the Hertz–Mindlin with JKR contact model in EDEM to standardize the contact parameters between soil particles and between soil and Q235 steel in soft soil after cultivation in ginseng land. Taking the soil particle accumulation angle as the response value, a Box–Behnken design (BBD) was introduced to establish a regression model for the soil accumulation angle; the surface energy, static friction coefficient, rolling friction coefficient, and coefficient of restoration parameters were obtained, respectively, through the optimization of the model, at which time, the simulated value of the soil accumulation angle was 37°, which is a 4% relative error to the actual measured accumulation angle of 35.5°. Taking the sliding friction angle of the soil on the Q235 steel plate as the response value, the regression model of the soil sliding friction angle was obtained based on the BBD. The static friction factor, rolling friction factor, and coefficient of restitution between the soil particles and the Q235 steel were obtained, respectively. Based on the combination of these parameters, the simulated value of the sliding friction angle was 32.2°, which is a 2% relative error to the measured accumulation angle of 31.5°. To verify the accuracy of the optimized simulation parameters, field and simulation tests of soil-throwing components were conducted. The results show that the maximum relative error between the measured value and the simulation value is 5.6% and 3.4%. The error is within an acceptable range, and the simulation test and field test soil-throwing effects are the same, which verifies the accuracy and reliability of the reference soil parameter calibration. The results of the study can be used for discrete element simulation analysis of the interaction between ginseng loam and touchdown components and their structural optimization.

Quantitative assessment and optimization of parallel contact model for flexible paddy straw: a definitive screening and central composite design approach using discrete element method

To simulate the bending behaviour of paddy straw at varied moisture contents after crop harvesting, we created a flexible paddy straw specimen model based on the Hertz–Mindlin with parallel contact bonding model using the discrete element model (DEM) approach. The research presented in this study aims to investigate a new approach called Definitive Screening Design (DSD) for parameterizing and screening the most significant parameters of the DEM model. This investigation will specifically focus on the three-point bending test as a means of parameterization, and the shear plate test will be used for validation purposes. In addition, the most influential DEM parameters were optimized using another Design of Experiments approach called Central Composite Design. The findings from the DSD indicated that parameters such as bonded disk scale, normal stiffness, and shear stiffness have the highest impact on the bending force, while the coefficient of static friction (Straw-Steel) has the least effect. The three bonding parameters were respectively calibrated with the loading rate (0.42, 0.5, and 0.58 mm s−1) and a good agreement between actual and simulated shear force at moisture content M1—35 ± 3.4%, M2—24 ± 2.2% and M3—17 ± 2.6%. Modelled stem helps simulate the straw with low error and increases the accuracy of the simulation. The validated model, with an average relative error of 5.43, 7.63, and 8.86 per cent, produced reasonable agreement between measured and simulated shear force value and loading rate.

Calibration of Simulation Parameters for Fresh Tea Leaves Based on the Discrete Element Method

To address the problem of a lack of accurate parameters in the discrete element simulation study of the machine-picked fresh tea leaf mechanized-sorting process, this study used machine-picked fresh tea leaves as the research object, established discrete element models of different fresh tea leaf components in EDEM software version 7.0.0. based on the bonded particle model using three-dimensional scanning inverse-modeling technology, and calibrated the simulation parameters through physical tests and virtual simulation tests. Firstly, the intrinsic parameters of machine-picked tea leaves were measured using physical tests; the physical-stacking tea leaf test was conducted using the cylinder lifting method, the tea leaf repose angle being 32.62° as measured from the stacking images using CAD. With the physical repose angle as the target value, the Plackeet–Burman test, the steepest-ascent test and the Box–Behnken optimization test were conducted in turn, and the results showed that the static friction coefficient between tea leaves, the rolling friction coefficient between tea leaves and the static friction coefficient between tea leaves and PVC have a major effect on the repose angle, and the optimal combination of the three significant parameters was determined. Finally, five simulations were conducted using the optimal combination of parameters, the relative error between the repose angle measured by the simulation test and the physical repose angle being just 0.28%. Moreover, the t-test obtained p &gt; 0.05, indicating that there was no significant difference between the simulation test results and the physical test results. The results showed that the calibrated discrete element simulation parameters obtained could provide a reference for the discrete element simulation study of fresh tea leaves.

Is water a lubricant?: Inquiring about a dilemmatic statement in physics education

We designed an inquiry activity to investigate the question, ‘Is water a lubricant?’ Placing the same object on surfaces of three different materials, we observed the effect of adding a small amount of water on the coefficient of static friction, μs . Up to 1 ml of water was added. The results of each surface were graphed and compared with one another. In general, our findings show that the addition of water serves to increase μs up to a certain point, before decreasing it. The experiment can be easily replicated in a secondary school science lab. It presents two seemingly opposing phenomena, but they both hold because they occur within their respective boundary conditions.

Control of Static Friction by Designing Grooves on Friction Surface

This study numerically investigated the friction of viscoelastic objects with grooves. A 3D viscoelastic block with grooves on a rigid substrate is slowly pushed from the lateral side under uniform pressure on the top surface. The local friction force at the interface between the block and the substrate obeys Amontons’ law. Numerical results obtained using the finite element method reveal that the static friction coefficient decreases with increasing groove width and depth. The propagation of the precursor slip is observed before bulk sliding. Furthermore, bulk sliding occurs when the area of slow precursor slip reaches a critical value, which decreases with increasing groove size. A theoretical analysis based on a simplified model reveals that the static friction coefficient is related to the critical area of the precursor, which is determined by the instability of the precursor. A scaling law for the critical area is theoretically predicted, and it indicates that the decrease in the effective viscosity due to the formation of the grooves leads to a decrease in the static friction coefficient. The validity of the theoretical prediction is numerically confirmed.Graphical

Triaxial experimental study of mechanical behavior of non-persistent jointed granite subjected to slight cyclic dynamic disturbances

A slight disturbance can induce fault-slip burst failure in deep rock masses. In this paper, a series of triaxial tests were conducted to investigate the strength, deformation characteristics, and failure behavior of non-persistent jointed granite specimens subjected to slight cyclic loading. A representative stress–strain curve for non-persistent jointed rock was generated and used to study the crack evolution process (initiation → propagation → coalescence). The effects of varying the joint angle and frequency and amplitude of the disturbance were then analyzed. A theoretical (fracture mechanics) model for a non-persistent joint subject to triaxial cyclic loading was also established and used to investigate the combined effects of static confining stress and slight disturbances. Finally, the mechanical mechanism by which a slight dynamic disturbance induces fault-slip burst was discussed. Our results show that the failure mode of a non-persistent jointed rock mass depends more on the joint angle than the amplitude and frequency of the slight disturbance. The disturbance induces the initiation and extension of cracks. It can also induce fracture-slip bursting once the disturbance exceeds a certain threshold. The value of this threshold depends on the initial stress state, joint angle, length, dynamic and static friction coefficients, and fracture toughness of the rock. The study thus enriches our mechanistic understanding of the crucial ingredients involved in the triggering of fault-slip rock bursts in deep rock masses by slight disturbances.

Vickers Hardness Mechanical Models and Thermoplastic Polymer Injection-Molded Products’ Static Friction Coefficients

The surface mechanical properties of thermoplastics are crucially important for evaluating molded products’ vulnerability to scratching. Because surface mechanical properties reflect material performance directly in terms of durability and frictional behavior, understanding and modeling them is important for industry and research. This emphasizes the surface mechanical properties of Vickers hardness and the static friction coefficient, with attempts to model them as functions of stress at yield initiation. Vickers hardness can be related to the compressive stress at yield initiation. The static friction coefficient can be modeled as a function of the surface shear strength and Vickers hardness. This research has improved our understanding of thermoplastics’ surface mechanical properties and has enabled the prediction of the scratch performance of molded products and the provision of effective indicators for material design.

Impact of multiple coating layers on finished floor slip resistance

Abstract: Slip, trip and fall (ST&amp;F) events are a cause of significant mortality, hospitalisations and financial expense. Floor conditions are a factor in some portion of ST&amp;F events and thus important to monitor. In commercial buildings, flooring surfaces are often coated with a removable floor finish to protect the floor and provide a consistent walking surface. The relationship between the number of coating layers of a floor finish and the slip resistance, i.e. coefficient of friction, is poorly reported in the literature. In this study, vinyl composite floor tiles were coated with four different floor finishes, varying from 2 to 10 coating layers. The static coefficient of friction (SCOF) was tested using the James Machine and ASTM D2047 to determine whether there was a change in the SCOF/slip resistance and thus the ST&amp;F risk, associated with different numbers of coating layers of finish. The number of coating layers of floor finish did not negatively impact the SCOF/slip resistance of the tiles. This study suggests that maintaining an appropriate layer of floor finish, typically recommended by manufacturers to be four coating layers, provides a slip-resistant walking surface that is not negatively affected by additional coating layers of finish.

Calibration and test of contact parameters for alfalfa stalk at primary florescence based on discrete element method.

In view of the lack of accurate models for discrete element simulation in the current research and development process of forage harvesting and crushing machinery, the contact parameters were calibrated based on Hertz-Mindlin (no slip) contact model by EDEM simulation software with alfalfa stalk at primary florescence as the research object. Based on the angle of repose, the restitution coefficient, static friction coefficient, rolling friction coefficient of alfalfa stalks were determined through the Placket-Burman test, steepest ascent test and Box-Behnken test. The simulation test of the repose angle was carried out with the determined contact parameters. The results showed that the relative error between the simulated repose angle and the physical test repose angle was 0.48%, which indicated that the calibrated contact parameters could truly reflect the physical characteristics of alfalfa stalks at the primary florescence. It provided a reliable model and parameter calibration method for the discrete element simulation in the research and development process of forage machinery, and also provided a reference for the research and optimization design of forage harvesting, crushing and processing machinery.

ОПРЕДЕЛЕНИЕ ФИЗИКО-МЕХАНИЧЕСКИХ СВОЙСТВ ПРОРОЩЕННОГО ЗЕРНА

One of the most common types of raw feed in farming is grain. It is used as the main component in combined feeds. Sprouted grain is a feed additive natural that vitamins containing. It is known that stronger animals food first eating. In order for the sprouted grain had reached the livestock entire proportion for feed consumption, the first evenly in the feed must be distributed. To do this, the sprouted grain must be dried, crushed, and then mixed with combined feed. The sprouts and sprouted grain’s strength properties differ from ordinary (non sprouted) grain, therefore, at crushing them in conventional hammer crushers, the energy intensity process will increase. To reduce the sprouted grain grinding’s energy consumption, it is necessary that cause destruction’s loads knowing. It is known that the grain by crushing is crushed, and the sprout is cut. To design the grinding machines’ working bodies, it is necessary the grain and sprouted grain’s germ strength properties knowing. At sprouted grain preparing, it is moving along the processing line and pouring itself repeatedly. To avoid sprouted grain’s on the gravity flows’ surface sticking, it is necessary the static friction coefficients taking into account. The stands for loads’ determination causing the grains and germinated grain sprouts’ destruction are presented. On one stand, due to the applied effort, the grain is split by a rod using, and by the rod with a knife replacing the sprout is cut. During the experiments, the force is recorded. On another stand, the static friction coefficients of sprouted and unsprouted grain on galvanized steel, plastic, rubber, plywood surfaces are determined. The experimental studies’ results are presented. It has been established that the Young modul’s of sprouted grain average value is lesser than for unsprouted one. The unsprouted wheat had the lowest the friction coefficient value on plywood, it’s 0.31...0.33, on rubber this coefficient took the highest value - 0.4...0.47.

ON THE THEORY OF FRICTION SYSTEMS WITH HEREDITARY TYPE FRICTION

The work is devoted to the study of the nonlinear dynamics of frictional vibration systems, which take into account, when developing mathematical models of vibration systems, an essentially nonlinear function that describes the work of friction forces with memory. The problem considered in the work combines two well-known Painleve? problems and the problem of studying the friction forces of hereditary friction. In both cases, we are talking about the idealization of real elastic bodies and flexible bonds with ideal absolutely hard and rigid ones. Using the well-known experimentally proven hypothesis of A.Yu. Ishlinsky and I.V. Kragelsky about the hereditary dependence of the coefficient of friction of relative rest at low speeds of movement of bodies, the dynamic system under study is transformed from autonomous to non-autonomous, in which new types of movements that have not previously been observed in the study of vibration systems appear. In particular, taking into account the Painleve? paradox entails the previously unexpected possibility of the occurrence of instability and self-oscillations, and taking into account the heredity of the friction coefficient leads to the appearance of chaotic movements of bodies. A numerical and analytical method has been developed for studying the behavior of the dynamic characteristics of friction vibration systems depending on the chosen model of the relative static friction coefficient. Based on the main parameters, the new bifurcation diagrams presented in this work demonstrate the presence of arbitrarily complex periodic regimes of body motion, including chaotic ones. It has been established that the transition to chaotic modes of motion occurs according to the well-known period doubling scenario. Analytical relations are given for point mappings of Poincare? surfaces, which made it possible to obtain succession functions illustrating arbitrarily complex modes of body motion, including chaotic ones. It is noted that such body movements were not found during the study of such vibration systems.

Procena nekih fizičko-mehaničkih karakteristika pšeničnog zrna kod određenog sadržaja vlage

Physical properties and mechanical properties of grains have importance in design of farm machinery, processing equipment's, handling equipment's, and processing of food and agricultural products. The physical properties must be known to an engineer to design a machine for handling, cleaning, conveying, storing and milling. There are some of important physical properties such as shape, size, volume, density and mechanical properties like angle of repose, static friction coefficient of different grains is necessary for the design of seed drill cum fertilizer, harvester, thresher etc. and food processing units such as separating, handling, storing, drying systems etc. Physical and mechanical properties of grain were estimated at Food Research Lab, Food and Processing Engineering, Vaugh Institute of Agricultural Engineering and Technology, Sam Higginbottom University of Agriculture, Technology and Sciences, Prayagraj, (Uttar Pradesh). Therefore, The objective of present study was to determine some physical and mechanical properties of wheat grain at 9.2 % moisture content such as dimensions (length, width and thickness); equivalent, geometric and arithmetic mean diameter; sphericity; surface area; area of flat and transverse surface; volume; mass of one grain; and then other properties under effect of moisture content variation such as density, thousand kernel mass, coefficient of friction against deferent materials and angle of repose. The average length, width and thickness of wheat seed were measured 6.25, 4.48 and 3.73 mm at a moisture content of 9.7 % (wet basis) respectively. Equivalent diameter and sphericity were calculated at moisture content of 9.7 % were 4.63 mm and 74 %. The bulk density and particle density was estimated 623 and 1215 kg/m3 at same moisture content while mechanical properties such as angle of repose and static friction were determined 24.60 and 0.352 respectively at same moisture level. Therefore, these estimated physical and mechanical properties can be used to design and development of combine tillage and sowing assembly.

基于离散元模拟的白米仿真参数标定

Aiming at the lack of discrete element simulation models and parameters for rice polishing, grading, color sorting and other technologies and equipment, and the difficulty of guiding equipment design and optimization through simulation, this paper calibrates the simulation parameters of white rice based on angle of repose (AOR) test and simulation methods. Huanghuazhan and Dongnong 429 white rice were selected as research object. Numerical model of white rice was established by multi-sphere filling. According to physical test and references, the simulation parameter range of white rice particles was determined. Plackett-Burman test was used to screen parameters, and it was found that the particle-particle static friction coefficient and particle-particle rolling friction coefficient had significant effects on the AOR of white rice. The regression model between the AOR and the significance parameter was established according to the central composite design method. The simulation parameter combination that has significant influence on the physical AOR was determined through the optimization design, and verified by the simulation test. The simulation AOR was compared with the physical AOR, and the relative error of the two kinds of white rice was less than 3%. The results show that the calibration method proposed in this study can accurately simulate the physical AOR test, which can provide reference for discrete element simulation of white rice processing.

EFFICIENCY OF POLYMER MATERIALS IN HIGHLY LOADED SYSTEMS IN THE AVIATION INDUSTRY

The static coefficient of friction was calculated on an inclined plane tribological stand. Different specimens and masses loading the system were used during the experiment. Surface-to-surface contact was tested in a pin-on-plate setup. The tested polymer pairs were POM on POM, PA6 on PA6 and PET on PET. The variables in the experiment were different pressures acting on the friction pair, and dry and lubricated friction was tested. Static coefficients of friction for each case was calculated and the surface quality of the pin and plate was measured by profilometer and optical microscope. The coefficient of static friction was higher for lubrication friction than the dry friction. It was also observed that the coefficient of friction decreases with increased load. POM – POM pair had the lowest coefficient of friction under dry conditions, while for lubricated friction, PA6 – PA6 had the most stable increase of friction coefficient.