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The authors offer an analysis of the main parameters of vibration-wave stress concentrators for eliminating flash in the course of molding and pressing powder materials. They give calculations of the main parameters of flashes acting as concentrators for various types of waves.Recently, the technology of producing ceramic preforms from powder by compaction has become extensively used. The main advantages of this technology include a shorter time required per product unit and the possibility of automatization and mechanization of different operations. One of the most complicated operations in the production process is the removal of flash formed when excessive batch flows out of the mold. In some cases, up to 38% of workers are engaged in this work [1].The purpose of the present study is to determine the main parameters of vibration-wave stress concentrators for flash removal in molding and pressing powder materials (PM). The main ideas consist of regarding a flash fin as a vibration-wave concentrator receiving vibrations of a certain frequency from a vibrator, which generates vibrations and waves of a certain type (longitudinal, torsional, bending) in the flash and thus destroy it due to a large vibration amplitude both at the vertex and at the base of the flash fin where it is fixed to the preform. Schemes for calculating such concentrators exist in vibration-cutting machines [2].It should be noted that using a particular method for flash removal from a finished product depends on the physicomechanical properties of the PM, its weight, and the product structure and size. To facilitate compaction of complex-configuration items, the moisture of the molding powder is raised to 14%. The molded preform in this case has low compressive strength (ó comp = 10 MPa [1]) and high density. Such "moist" perform is hard to trim because of its high plasticity and possible sticking of the flash in trimming.The compressive strength of molded ceramic preforms can be raised (to 250 MPa) by additional heat treatment (drying) to moisture 1 -2%. Such preforms are trimmed on various machines for partial and volumetric treatment [1, 3 -7]. The disadvantages of these methods are the need to use high-power drying plants taking a large amount of production space, complicated trimming units, and, frequently, the use of manual labor.Removal of flashes without predrying immediately after firing is rarely used and only for simple "bead-like" articles of size up to 10 mm [1]. Trimming of fired products (without predrying) is less energy-consuming; however, in this case the high mechanical strength of flash may cause the product to break in trimming or impair its exterior appearance and service parameters. The rejection rate may reach 30%.A new approach to developing new trimming methods for molded ceramic preforms consists of combining partial heat treatment (drying) of the flash with its volumetric trimming. After the preform leaves the mold, it is transferred to a low-power air-heater. Considering that the flash thickness is not more than 1....

Creation of conditions for optimal flow of Bingham media, such as ready-mixed concrete and mortar mixes, in the circular pipeline during delivery by various types of transporting equipment has not been sufficiently studied so far. Purpose: finding patterns of flow of concrete and mortar mixes in different sections of the pipeline, based on the variability of the viscosity coefficient when the medium is flowing through long circular pipes. In calculations of the flow capacity of mortar and concrete pipelines and the required power of the pumping equipment, the properties of concrete and mortar as Bingham media should be taken into account. Dependences for description of the operation process of flow of concrete and mortar mixes through circular pipelines have been found on the basis of the Buckingham equation in the laminar flow mode.Dependences of determination of flow rate and required power with continuous delivery of concrete and mortar mixes in the pipeline, as well in case of alternate inlet pressure variation are presented. Law of variation of μр can be obtained only experimentally, which also results in errors in the computation model.

Reasonable development and creation of any device in which there is an interaction between the fluid flow and the elements of the flow parts (for example, heat exchangers, transport and power machines, main pipelines), is impossible without detailed information about the characteristics of the flow, about the forces on the surfaces that are around, about vibroacoustic phenomena, etc. Among the various methods of obtaining information about the characteristics of the flow, about the forces on surfaces that are flown around, about vibroacoustic phenomena, an important role is played by theoretical methods that rely on the equation of hydrodynamics and numerous ways to solve them. In this case, the main efforts are aimed at solving the system of Navier-Stokes equations. In this paper, a general method is described for the numerical solution of the problem of unsteady flow of a viscous incompressible fluid in flat channels of an arbitrary shape of heat exchangers. An effective solution to the problem is achieved by using adaptive networks. The mathematical model of the flow is based on the two-dimensional Navier-Stokes equations in the variables "flow function - vortex" and the Poissonequation for pressure, which are solved on the basis of the finite-difference method. A numerical simulation of the fluid flow in a flat curvilinear elbow is carried out at the Reynolds number Re = 1000. This form reflects the most characteristic features of the flow paths of various hydraulic machines, heat exchangers, hydraulic and pipeline systems. The presentation of the numerical results was carried out on the basis of the VISSIM graphic processing package. One of the main problems (difficulties) in the numerical solution of problems of mathematical physics is the representation of boundary conditions for regions of arbitrary shape. The implementation of various artificial methods that are now used in the approximation of both the curvilinear boundaries themselves and the boundary conditions on them can lead to significant losses in the accuracy of the solution. This is especially evident in problems in which solutions in the boundary region have maximum gradients. An effective method for solving this problem is the use of adapted grids for the computational domain. The essence of this method lies in the fact that such a coordinate system, not necessarily orthogonal, is found in which the boundary lines (surfaces) of the region coincide with the coordinate lines (surfaces). In the flat case, the computational domain is transformed into a rectangular one, and the limit curve is displayed on the sides of the rectangle. In practice, the problem of constructing an adapted mesh is reduced to finding functions that describe the mappings of the canonical (rectangular) region onto the region for which the problem was originally formulated, that is, for the two-dimensional case, the functions x (ξ, η), y (ξ, η) are determined.

The process of restoration of museum exhibits is associated with the forming of various structural media, for example, drying of paints layers, varnishes and hardening of gypsum and concrete solutions during the restoration of statues, elements of room decor. The mechanics of such media is characterized by spectra of viscous, plastic and elastic properties in their various combinations. The forming of these substances is influenced by the microclimatic conditions of the premises, in which these processes take place. In technological operations, as a rule, large shear deformations take place, which greatly exceed the elastic limit. Thus, the most significant for technological calculations are viscoplastic properties, which reflect the relationship between the existing shear stresses and the rate of irreversible shear deformation. For a qualitative description of this relationship, it is customary to use consistency curves that relate shear stresses to the rate of irreversible shear deformation or the dependence of the effective viscosity on the rate of irreversible shear deformation. Structure formation is one of the main processes in the technology of processing solidifying paste-like and liquid-like media when their characteristics approach those inherent in the corresponding capillary-porous bodies. The properties of such media depend on the type and nature of the structure. The study and control of the process of structure formation to obtain a medium with desired properties is an important technological task, which can be solved, in particular, by microclimate systems. The change in the structural state of the solidifying medium can be estimated from the corresponding changes in plastic and conventional mechanical strength, degree of hydration, heat release, elastic modulus, etc. In this work, structure formation is understood as a process, as a result of which the characteristics of the material approach the characteristics of the corresponding capillary-porous body (CPB). The main parameter that determines this approximation is the degree of completeness of structure formation. Analysis of the hardening process of the considered pasty and liquid-like media on the basis of the moisture state diagram makes it possible to fix the structural state of the capillary-porous structure of these media and to evaluate the interaction of chemical reactions and the process of structure formation. And the resulting changes in the rate of structure formation allows to identify and evaluate the destructive processes that occur during solidification of the substance.