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Natural vibrations of supports comprised of three cylindrical panels supported by ring elements and soil are under study. A system of equations describing the problem is constructed using Hamilton's least-action principle. A dependence between the frequency characteristics and the geometric parameters of the support is investigated.

Changes in temperature and pressure conditions during the development of an oil reservoir with a high paraffin content in a limiting saturated state causes an in-situ phase transition to a solid state, and the filtering of a mixture of oil with solid paraffin particles at a temperature below the flocculation temperature causes clogging in the pore space of the reservoir in narrow places and bottle necks of pores. Thus, laboratory studies are carried out to determine the critical points and parameters of an oil - gas - paraffin mixture under various thermobaric conditions. A mathematical model is developed that describes wax deposition in the pore space of a low-temperature oil reservoir and makes it possible to calculate its permeability during development. The model parameters are adapted to their experimental values. Numerical calculations are used to determine the values of the main parameters that affect the reservoir permeability.

A method for the quantitative evaluation of the matrix and fracture permeabilities was developed and algorithmically implemented within the framework of the dual-porosity continuum model describing mass transfer in a fractured porous reservoir. The method involves the solution of the inverse coefficient problem whose input data are the well flow rate characteristics measured in the stop-start operation mode. The algorithm is based on the obtained analytical solution of the direct problem of the evolution of hydrodynamic fields in the near-wellbore space. The results of numerical experiments show that the inverse problem has a unique solution with a moderate level of noise in the input data.

Based on the applied theory of shells, an energetically consistent resolving system of equations has been formulated and a complex numerical method using an explicit variational-difference schemes has been developed to solve both quasi-static and dynamic problems of nonlinear nonaxisymmetric deformation and buckling of composite cylindrical shells. The reliability of the developed method is verified by comparing calculation results and experimental data. For various of reinforcement structures, an analysis of critical loads and characteristic forms of buckling of composite cylindrical shells previously subjected to quasi-static loading internal pressure followed by dynamic loading by axial compression.

A heterogeneous material obtained by means of cold gas dynamic spraying with subsequent laser processing is studied. The reasons for reduction of the particle size of boron carbide B₄C under the action of a laser beam and the chemical composition of the material containing the "lost" material of B₄C particles are examined. A mathematical model, which takes into account the dissolution of B₄C particles and the presence of a chemical reaction, is developed. The elastic properties of the deposited heterogeneous material are analyzed with the use of continuum approaches that describe heterogeneous media and are based on averaging of the original stochastic equations.

The fragmentation of projectiles penetrating into thin discrete bumpers is accompanied by ejections of material from the front part of the projectile in the direction of its movement. Material ejection from the front part of the projectile and fragments of the rear part of the projectile form two groups of fragments. The distribution of craters formed by these groups of fragments was analyzed, and the intensity and nature of the damage they caused and the effect of projectile velocity on the kinetic energy distribution between these groups were determined. Fragments were recorded using witness plates of great thicknesses placed at a certain distance behind the steel mesh bumper on the path of movement of fragments. It was found that with an increase in velocity, the proportion of specific kinetic energy of the front ejections increased and the fraction of the kinetic energy of the fragments of the rear of the projectile decreased. The kinetic energy distribution was determined in the case of fragmentation of a projectile of an aluminum alloy of 9 mm diameter on a tungsten mesh (wire diameter 0.5 mm, aperture 3.2 mm). The diameter of the projectile to the cell size of the tungsten mesh was the same as for steel mesh. Significant difference shown The kinetic energy distributions for the tungsten and steel mesh were found to be significantly different, probably due to the strength characteristics of the projectile material and the smaller wire diameter in experiments with the tungsten mesh. The features of damage to the witness plate by a group of small fragments were analyzed.

The effects of the most important process-adjusting variables (welding current and welding speed) and the percentage of the combination of TiO₂ and SiO₂ activating fluxes on the most important quality characteristics (weld bead width, depth of penetration, and aspect ratio of these parameters) in welding of AISI316L austenite stainless steel parts are considered. Artificial neural networks (ANN) are used to determine the relations between the input variables and output responses of the activated tungsten inert gas (A-TIG) welding process. To determine the proper ANN architecture (the proper number of hidden layers and their corresponding neurons/nodes), the particle swarm optimization (PSO) method is used. Experimental tests are conducted to evaluate the proposed procedure performance. Based on the results, the proposed method is found to be efficient in modeling and optimization of the A-TIG welding process.

This paper presents a thermophysical model of laser beam scanning of the surface of a two-layer plate, whose top layer melts and shrinks due to changes in porosity, and whose bottom layer (substrate) does not melt. The dependences of the heat capacity, thermal conductivity, and reflection coefficient on porosity are taken into account. Heat loss is due to both radiation and convection. Results are presented showing that the process is nonstationary throughout the scan. It is shown that the complex thermal cycles and inhomogeneous temperature field are directly related to inhomogeneous shrinkage, leading to the surface topography typical of selective laser melting processes.

This paper describes a study of buckling and supercritical behavior of inhomogeneous coatings. On the basis of the variational interpretation of the problem and the Ritz method, the change in the first critical value of the load at which buckling occurs, depending on the problem parameters. Calculations are carried out for inhomogeneous coating of two types: coatings with piecewise constant stiffness and coatings with a continuously changing maximum inside and outside the detachment zone. The supercritical behavior of the coating is studied.

This paper presents an analysis of the experimentally observed evolution of the unstable plastic flow obtained by laser welding of samples of aluminum-lithium alloys of the Al-6Mg-2Li, Al-1,6Cu-1,1Mg-1,8Li, Al-3,4Cu-0,66Mg-1,5Li systems, under various heat treatment conditions after welding. Comparison of the discontinuous yield of alloys with different concentrations of magnesium, copper, and lithium was performed. The effect of copper on the spatial consistency of the localized shear bands formed in aluminum-lithium alloys under unstable plastic flow.