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The boiling in a superheated water jet discharged from a short cylindrical nozzle in the presence of a passive swirler has been experimentally investigated. The evolution of the disintegration of the boiling liquid jet with an increase in the degree of superheating has been studied. Characteristic structures and forms of the flow have been identified. The correlation between the jet shape and boiling regimes has been found. Significant fluctuations and flow instability at certain temperatures was noted. The possibility of influencing the flow pattern has been experimentally shown.

A mathematical model is constructed to describe a steady one-dimensional temperature distribution in a hollow circular cylinder made of a polymer dielectric with a constant difference in the electric field potentials on the cylinder surfaces. Based on systematized data on the dependence of the thermal conductivity and electrical conductivity of polymer materials used as dielectrics in engineering on temperature, a qualitative analysis of the model is performed for a prescribed density of the heat flux supplied to the inner surface of the cylinder and intensity of convective heat transfer on the outer surface. The results obtained in the study allow one to determine the area of applicability of polymer dielectrics used in various electrical engineering applications, including electrical insulation of DC high-voltage cables, and to formulate the conditions for the thermal breakdown of the cylindrical layer of the dielectric.

This paper presents the results of an experimental study of the occurrence and control of flaming combustion and thermal decomposition of typical forest combustible materials by creating a fire break in the form of a wetted layer with a fixed width, length, and depth and a given volume of the contained liquid. The ranges of parameter values that ensure stable suppression of the flaming combustion and thermal decomposition of forest combustible material were determined. Experiments were performed for all major types of forest combustible materials: leaves, needles, twigs, and mixtures of the listed materials. Prediction of the required (minimum) water volumes and sizes of the fire break for guaranteed control of the combustion of forest combustible materials of the types studied was made.

Results of a series of firing tests of two model nozzles made of a carbon--carbon composite material are reported. This material can be used to fabricate nozzles for a large-scale liquid-propellant rocket motor. The tests are performed in an experimental setup operating on oxygen and hydrogen. It is shown that the thermochemical loads on the nozzle material in model tests are greater than those under real conditions. The temperature of the outer surface of the nozzle is measured in each experiment by thermocouples and an infrared imager. The level of linear erosion of the wall material during the entire test period is determined. It is demonstrated that the results of firing tests can be used for estimating the operation performance of a large-size motor. A simple analytical dependence is proposed for recalculating the results of model tests on material erosion to full-scale conditions.

This paper deals with the problem of steady-state creep of a rectangular membrane in a rigid matrix with a ratio of the height to width of not less than 0.5 in the case of piecewise constant dependence lateral velocity over time. The creep of the membrane with a single change in the rate of transverse pressure over time is investigated. Two variants of the contact conditions of the membrane and matrix: perfect slip and no-slip are considered. Three stages of creep of the membrane are investigated. The analysis is carried out until the time at which the membrane is in almost complete contact with the walls of the matrix. Time dependences of the variable thickness of the membrane and the stress intensity in the membrane are obtained. It is shown that in this problem, the rule of summation of partial times is not performed.

A problem of compression of an isotropic medium with a periodic system of variable width slits compared with elastic displacements is under consideration. The edges of the slits are under the action of internal pressure. It is assumed that the ends of the slits have zones of plastic deformation. The presence of several zones of contact of the edges of each slit is studied in the assumption that one of the section may have slippage. The problem of equilibrium of the periodic system of slits with partially contacting edges under the action of a compressive load reduces to the problem of linear coupling of analytical functions. Contact stresses and the sizes of contact zones, adhesion zones, and end zones of plastic deformations are determined.

The problem of determining the transversely isotropic tensor closest in Euclidean norm to a given anisotropic elastic modulus tensor is considered. An orthonormal basis in the space of transversely isotropic tensors for any given axis of symmetry was obtained by decomposition of a transversely isotropic tensor in the general coordinate system into an isotropic part, two deviator parts, and a nonoric part. The closest transversely isotropic tensor was obtained by projecting the general anisotropy tensor onto this basis. Equations for five coefficients of the transversely isotropic tensor were derived and solved. Three equations that are stationary conditions were obtained for the direction cosines of the axis of rotation (symmetry). Solving these equations yields the absolute minimum distance from the transversely isotropic tensor to the given anisotropic elastic modulus tensor. The transversely isotropic elastic modulus tensor closest to the cubic symmetry tensor was found.

The Lord-Shulman theory of generalized thermoelasticity based on a memory-dependent derivative is employed to study the propagation of plane harmonic waves in a two-dimensional semi-infinite thermoelastic medium. The numerical solution is analyzed for various values of the time delay parameter.

This paper describes a problem of the theory of elasticity for a three-layer material in which two layers located symmetrically relative to the central layer have identical properties. The central layer has a normal detachment crack whose tops are located in the neighboring layers. The solution of this problem is reduced to solving a system of Fredholm integral equations of the second kind. A stress intensity factor for normal detachment cracks is determined, and its dependence on the problem parameters is investigated.

This paper describes the simplest cases of a rectangular cantilever beam loaded by an concentrated force that is distributed by the load or dead weight. There are five geometric parameters whose optimal values can be calculated on the basis of five requirements: rigidity (or concentrated elastic energy), strength, equal strength, ratio of sectional sizes, and resistance to the shear force (strength condition in interlaminar shear). The parameter range is determined, outside of which the linear beam theory cannot be used to correctly calculate the bending of equal strength beams loaded by distributed forces or dead weight.