Granulated Medium Research Articles

Проектирование технологии обработки в гранулированных средах в условиях цифрового производства

The problem of mechanical technology design for machining parts in granulated media in the conditions of digital produc-tion is viewed. The peculiarities of part process in abrasive media and with steel balls (finish- machining and strengthening treatment techniques) are shown. Dependences for determining the parameters of a single interaction of a medium particle with the surface of a part during processing in granulated media are obtained. Dependences for depth maximizing in cases of particle penetration into the surface of the machined part, the parameters of a single trace, surface roughness, processing time are found. For finish- machining and strengthening treatment techniques for granulated working media, dependences for determining the depth of the hardened layer and the degree of deformation are also obtained. The obtained theoretical dependences have been tested for adequacy through drawing an analogy with the results of experimental studies. During the research, it was found that the developed system of models does not take into account the peculiarities of various processing methods and their dynamics, and shape of the particles of the medium. To account all these parameters, the Rocky DEM ap-plication software package is used. The package allows modeling the processing chamber, the dynamic parameters of the machining process, the number of particles in the working space according to their mass, the shape and dimensions of the particles, the mass and shape of the machined part and its location in the processing chamber, the material of the machined part, the ratio of the mass of the part and the mass of the abrasive medium, some physical properties of the material of the processed part, slip coefficient of the abrasive medium on the part surface, process liquid properties and other parameters. The package made it possible to refine theoretical models and obtain results closer to production conditions. Based on the research carried out and being aimed at their introduction into modern digital production, the design technique of techno-logical processes has been developed and a software product has been proposed allowing to select possible working meth-ods in granulated media (in order of preference) according to the characteristics of the part, and to determine the technolog-ical modes for each of them and characteristics of working environments.

Simulation of Hydrodynamics and Heat Transfer of a Granulated Medium in a Circular Bunker

Numerical simulation of the hydrodynamics and heat transfer of a dense layer of a highly loose high-concentration granulated medium in a circular bunker on the basis of a non-Newtonian medium with application of the ″power-law liquid″ model and boundary slipping conditions on solid walls is presented. The influence of regime and geometric parameters on the dynamics and heat transfer of a high-concentration granulated medium is investigated. The validity of the results obtained is confirmed by comparison of the numerical results with well-known experimental and analytical data. The results of the investigation carried out can be used in powder technology apparatuses in the processes of drying, mixing, homogenization, batching, and transportation of granulated materials.

Optimization of Dynamic Surface Plastic Deformation in Machining

Machining by surface plastic deformation in granulated media is investigated. The process is optimized in terms of fluctuation of the strain rate.

Mathematical model of oil-containing water purification process in the volume of granulated media

A mathematical model of oil-containing water purification process in the volume of granulated media is developed. On the basis of this model, the purifying ability of filtering unit with granulated coalescing media, which regenerates filtering media in the mode of pseudo liquefaction of granule without disassembling and replacement of filtering element, is studied. In the process of theoretical research, the physical model of oil-containing water purification process in the volume of granulated coalescing media is elaborated. The consistent patterns of the analysed process have gained further development. Due to these patterns, the factors which determine the effectiveneness of purification are established. After realization of the experiment plan for the first time, the mathematical model of a ship’s oil-containing water purification process in the volume of granulated media on the basis of the regression equation has been received. This model allows to calculate the rational constructive and operational parameters of the plant with granulated filter elements.

Technological effect of vibroprocessing by flows of organic granular media

The analysis of approaches to modeling of vibrational processing by granulated media is carried out. The vibroprocessing model which provides effective finishing of the surfaces of the parts due to the stone fruit organic media granules is developed. The model is based on the granule flow energy impact on the surface being treated. As the main characteristic of the organic media processing, a specific volumetric metal scrap is used, the physical meaning of which is the increase rate in the thickness of the material removed from the surface at a given velocity and pressure of the medium. It is shown that the metal scrap depends on the medium flow velocity, the height of the loading column of the granular medium, and the conditions for the formation of a medium stationary circulation motion. Based on the analysis of the results of experimental studies of the influence of amplitude-frequency characteristics on the removal of metal in the process of vibroprocessing with abrasive granules, the dependence of the specific volume metal removal is proposed for organic media processing, taking into account the threshold amplitude and frequency of oscillations of the working chamber, at which the effect of surface treatment is observed. The established set of relationships describing the effective conditions for vibroprocessing with stone organic media was obtained using experimental data, which allows us to assume that the model obtained is valid.

Technological effect of processing with the organic granular media flows

There has been carried out the analysis of approaches how to model vibrational processing by granulated media. The vibroprocessing model has been developed, that provides effective parts’ surfaces finishing work with granules of stone organic media initially based on the approach of energy impact of the granule flow on the processed surface. Specific volumetric metal scrap has been used as the main characteristic of processing with organic media its physical aim is increase rate of thickness of the material removed from the surface in the frames of definite velocity and pressure of the media. It is shown that metal scrap depends on media flow velocity, granular media height of the loading column, conditions that form stationary circulation motion of the media. Taking into account the analysis of experimental studies results of amplitude-frequency characteristics influence on the metal scrap during of abrasive granules vibroprocessing, there has been disclosed some certain dependence of the specific volume metal scrap while organic media processing, considering threshold amplitude and frequency of oscillations of the working tank that made it possible to observe the effect of surface treatment is. The established dependence describing the effective vibroprocessing conditions with stone organic media that was achieved due to experimental data which allows to assume validity of the obtained model.

Method for calculating the power of a rotor-screw machines

Features of parts machining in rotor-screw technological systems are presented. It is shown that the mass of the load, consisting of the processed parts and the granulated working medium, is located along the internal perimeter of the screw rotor asymmetrically to the axis of its rotation. In this regard, there are difficulties in designing the rotor-screw machines drive, and in the rationale for its optimal power. A technique is proposed for calculating the drive power of rotor-screw machines, which makes it possible to carry out a techno-economic assessment study of their applicability for finishing-hardening machining of parts in machinebuilding production. The technique is illustrated on the basis of justifying the drive power of a rotor-screw machine for hardening the details of St3 steel in a screw rotor mounted from 9 octahedra, steel balls are used as a working medium.

CALCULATION OF HYDRAULIC PRESSURE LOSS IN FILTERING NOZZLES OF MAGNETIC FILTERS

It was proved that use of magnetic filters with ferromagnetic granular filtering masses for deep purification of technological water of heat power engineering is rational. This allows purification of the technological waters with temperature up to 500oC and velocity of filtration up to 1000 m/h. During operation of filter the granulated medium creates hydraulic resistance when a stream of water passes through it, which is characterized by a loss of hydraulic pressure and hydraulic resistance coefficient. Based on the large amount of experimental data the improved equation for the coefficient of hydraulic resistance for granular filtering mass, in the form of ball pellets, at values of Reynolds coefficient more than 10 and analytical equations to determine the loss of hydraulic pressure ΔP were obtained. The analytical dependence of ΔP value for filtering materials both in the form of balls and mini parallelepipeds (pellets of crushed steel chips 0Х13-40Х13) were determined. Comparative calculations show that the coefficient of hydraulic resistance of chip mass is three times higher than that of the ball mass. Experiments found that for balls mass with diameter d=3,1mm, porosity e=0,4, and velocity V=(0,4-2) m/s the value of pressure loss ΔP is 5-6 times higher compared to granules with d=6 mm , e=0,42, V=(0,3-1,25) m/s, and almost 10 times higher than for the ball granules with d=7,9mm, e=0,43, V=(0,3-0,8) m/s. After analyzing of the ΔP dependence on V for different diameters a conclusion can be drawn that the increase of ΔP at smaller diameters is explained by window geometry (air layer) between granules. The size of window with smaller diameters is less, so velocity of the water flow increases and ΔP value increases too.

On Identification of Flow Regimes in a Polyspherical Medium with the Use of Velocity Dependences for the Losses of Head

It is shown that the “universal” expressions usually obtainable for the coefficient of hydraulic resistance Δp of a bed of granulated (granular) medium and for the magnitude of this resistance in a wide range of Reynolds numbers do not allow one to identify flow regimes and critical (transitional) values of Re = [Re] of the changes of regimes. With the use of substantiated approaches to the generalization of data on Δp in a bed of spheres, “piecewise-linear” (in logarithmic coordinates) dependences of Δp on Re and the values of [Re] = 60–80 have been obtained. Expressions are given for Δp that are valid for laminar (Δp ~ Re) and postlaminar (Δp ~ Re1.75) regimes of fl ow. The question as to the role of porosity of the medium in the form of an alternatively considered strong power function (Δp ~ 1/ω4.2) is discussed as the one deserving attention.

Gibbs sampler optimization for analysis of a granulated medium

A new variant of the method of probability density distribution recovery for solving topical modeling problems is described. Disadvantages of the Gibbs sampling algorithm are considered, and a modified variant, called the “granulated sampling method,” is proposed. Based on the results of statistical modeling, it is shown that the proposed algorithm is characterized by higher stability as compared to other variants of Gibbs sampling.

Analysis of Magnetization Properties of the Ferromagnetic Granular Beds

Magnetization properties of the packed beds that are constructed from ferromagnetic balls and metal chips have been examined. The average magnetic permeability and magnetization curves of the non-homogeneous ferromagnetic granulated medium (different size polyballs and chips) have been determined using the channel-by-channel magnetization model. From the magnetic properties of the single chain of the different sized balls as an element of the chain bundle in the polyball medium, application conditions of the model to the polyball medium were estimated. A new correlation for the influence of the packing density factor or the bed porosity change on the average magnetization curve has been evaluated. A new correlation between the packing density factor and the size of the bed elements, and also a relationship between the relative magnetic permeability of the bed elements and the external magnetic field intensity were obtained. The obtained theoretical results were compared with statistical data and an agreement was observed.

Research highlights: improved understanding of ecological impacts resulting from nanomaterial-based in situ remediation.

Nanomaterials are currently being used for in situ remediation of soils and groundwater. However, the continued use of currently implemented nanomaterials and the systematic development of more effective and ecologically benign materials require a more complete understanding of their ecological impact, which should include the transport through the subsurface, acute, chronic and long term effects of exposure, and the role of nanomaterial characteristics (e.g., composition, surface coating). In the current highlight, three articles that examine different aspects of nanoscale zero-valent iron (nZVI) transport, reactivity or exposure to model organisms are summarily reported, which advance the development of more sustainable remediation approaches. The first study examines the role of a model biofilm on the transport of different Pd-doped nZVI species through granulated media, and also the associated nanomaterial toxicity to the forming and sessile bacteria. The second study examines the multigenerational reproductive impacts of C. elegans resulting from nZVI exposure. Lastly, the resulting products of nZVI reactivity with U(vi) species at environmentally relevant molar ratios are examined, and a thorough analysis of the resulting products are reported, which provide valuable data for predicting the consequential role nZVI remediation will have on the ecosystem at and near contaminated sites.

Adsorption immobilization of sulfide-oxidizing bacteria in the mass of the support medium made of phosphogypsum

The basic patterns and mechanisms of adsorption immobilization of sulfide-oxidizing bacteria in the mass of mineral support medium made of phosphogypsum were determined for gas purification system. The advantage of the adsorption method on the granulated support medium of phosphogypsum is that it allows to bind the bacteria in the granules with the bioactive layer formation. Granules based on phosphogypsum are characterized by permeability to Thiobacillus sp. and contain useful minerals for bacteria growth such as calcium, magnesium, phosphorus, etc. Bacterial matrix is closely associated with the support medium matrix. Therefore, its use helps minimize the removal of the sulfide-oxidizing bacteria active mass from biofilter during the process of washing and bio-sulfur removing from the surface granules of phosphogypsum.

Riedel megashears R' and the trend to gravitational equilibrium as main factors of tsunamigenic earthquakes

Riedel megashears R' and the trend to gravitational equilibrium as main factors of tsunamigenic earthquakes

Mathematical Simulation of Kinematics of Vibrating Boiling Granular Medium at Treatment in the Oscillating Reservoir

The results of mathematic simulation of directed motion of the circulating flow of granulated working medium in the oscillating reservoir of finishing-grinding vibration machine are given. The model is based on the physical phenomenon, at which the granulated medium changes into vibro-boiling state clue to the action of vibrations. The solutions of Navier-Stokes implicated equations give the expressions of Bessel functions and their integral transformations. The model solutions ground the complex cycloid-trochoid nature of working medium kinematics on the vibration treatment operations and allow to determine the velocities of displacements of medium flows in any point of the reservoir. It is necessary for determination of the technological parameters and required equipment as well as their complex influence on the vibration treatment effectiveness. The zones of reservoir with increased impulse loading at combining the schemes of energetic action into the working medium and processed products are observed.

Influence of static and dynamic internal actions on elastic nonlinear properties of a granulated unconsolidated medium

We have studied the influence of external static (pressure) and dynamic (caused by an elastic wave with a finite amplitude) actions on the linear and nonlinear elastic properties of a granulated unconsolidated medium, which was simulated by steel spheres with diameters of 2 and 4 mm. We have analyzed the equation of state for such a medium taking into account the presence of weakly and strongly deformed contacts between individual spheres. We have obtained expressions for the elasticity coefficient and second- and third-order nonlinear elastic parameters, and we have experimentally studied the influence of external static pressure on their values. We have measured the dependence of the velocity of elastic waves on external static pressure and the probing signal amplitude. In the studied medium, a number of structural phase transitions were observed, related to rearrangement of the packing of spheres, which were caused by both static and dynamic actions. The structural phase transition was accompanied by an anomalous change in the nonlinear elastic parameters of the medium and the velocity of elastic waves. We have analyzed the results based on the Hertz theory of contact interaction.

Impact response of layered steel–alumina targets

The efficacy of a ceramic in protecting against penetration by high velocity projectiles depends not only on its hardness but also on its resistance to flow after comminution. Here we investigate experimentally the response of a model armor system comprising an alumina tile and two steel face sheets subject to impact by steel spherical projectiles. Complementary experiments are performed on the face sheet materials and the ceramic alone in order to gain insights into the inelastic responses of the constituent materials. A parallel numerical modeling study is performed of the system response with emphasis on the shape of the back face following impact. To this end, we employ the ceramic deformation model developed by Deshpande and Evans and modified here to account for dilatational softening following full comminution. Comparisons between model predictions and experimental measurements demonstrate the important role of granular flow. Preliminary parametric studies further suggest that additional effort is required to understand the transition in mechanical response of a ceramic as it transforms from a monolithic solid to a densely-packed granulated medium.

Aqueous Photocatalytic Oxidation of Doxycycline

AbstractThe experimental research into the aqueous photocatalytic oxidation of doxycycline, a tetracycline family antibiotic, was undertaken. The objective of the study was to ensure the feasibility of doxycycline photocatalytic degradation by UVA irradiated titania coatings on granulated media to be used in fluidised bed photocatalytic reactor and by slurries of P25, Evonik, as well as by visible light-sensitive sol-gel synthesized carbon-containing titania. The parameters influencing doxycycline oxidation, like catalyst concentration, initial doxycycline concentration and pH with P25 TiO

Nonlinear model of a granulated medium containing viscous fluid layers and gas cavities

We analyze nonlinear oscillations and waves in a simple model of a granular medium containing inclusions in the form of fluid layers and gas cavities. We show that in such a medium, the velocity of one of the wave modes is low; therefore, the nonlinearity is high and the effects of interaction are more strongly expressed than usual.

Modeling the hydrodynamics and the process of averaging a highly concentrated granulated medium in powder technology apparatuses

Investigation of the hydrodynamics and of the process of averaging a highly concentrated granulated loose medium in a vertical rectangular channel with a sudden contraction has been carried out on the basis of the model of a viscous nonlinear fluid. The characteristic features of the model of motion of such a medium consists in taking the slipping of particles on solid surfaces into account by introducing an independent empirical coefficient. The validity of numerical results was checked by comparing with the well-known experimental data. Based on the hydrodynamics obtained, the modeling of the process of averaging a granulated medium is presented, the intensity of which was analyzed depending on the regime parameters of flow.