Journal of Applied Mechanics and Technical Physics最新文献

Mechanical properties of acrylonitrile butadiene styrene (ABS) plastic have been studied by loading finite-thickness (1–5 mm) plates of this material using a spherical lead particle weighing 0.45 g. We have carried out a series of experiments whose results have been taken as a basis for mathematical simulation with the Reactor3D software package. Comparison of the results indicates that a spherical particle weighing 0.45 g makes a through hole in a 3.5-mm-thick ABS plastic barrier at interaction speeds of at least 230 m/s. The interaction speed required for penetration through ABS plastic barriers 1 to 5 mm in thickness lies in the range 140–300 m/s. The parameters obtained in this study have been shown to be capable of describing the behavior of finite-thickness plates during loading with an accuracy of 5% or better.

This paper presents a review of studies concerned with hydrophobic and anti-icing coatings produced by the cold spray method. We consider approaches to the preparation of polymer-, metal-, and ceramic-based coatings with good hydro- and icephobic properties by this method. An important advantage of the cold spray method is that it ensures the formation of structured coatings, which allows good hydro- and icephobic properties to be ensured without additional treatment. We consider the main theoretical models of wetting and factors determining the anti-icing properties of surfaces.

In this paper, we describe the CCDS2000 detonation system and demonstrate its capabilities for producing insulating and wear-resistant alumina coatings. The dielectric strength of such coatings is above 25 kV/mm at thicknesses in the range 50–300 μm. The resistivity of the coatings at a temperature of 20°C and relative humidity below 59% is ρ_e > 2.67 × 10¹³ Ω cm. As humidity increases, ρ_e drops sharply, by two to three orders of magnitude. The adhesion of the coatings to a steel substrate is up to 60–70 MPa, their microhardness is HV_0.1 = 1522–1655, and their porosity ranges from 0.35 to 1.00%. Our results demonstrate that, to obtain electrical insulation coatings, it is reasonable to use a C₂H₂ + 2O₂ detonating mixture, and that optimal wear resistance parameters can be obtained with a 0.69C₂H₂ + 0.53C₃H₆ + 2.51O₂ mixture. Switching to the dual-fuel mixture ensures a fourfold increase in abrasion resistance and a 34% increase in erosion resistance.

The dynamic loading of VT20 titanium alloy widely used in aviation is compared with that of a metal matrix composite consisting of 316L steel and A356 aluminum to assess the possibility of replacing expensive alloys with new metal matrix composites consisting of more affordable materials.

The viscosity and rheology of benzene and benzene-based nanofluids containing carbon nanotubes having various lengths and two diameters have been studied using nonequilibrium molecular dynamics simulation. The results demonstrate that, with increasing shear rate, these fluids become pseudoplastic. Correlations have been obtained describing the corresponding critical shear rates as functions of carbon nanotube concentration and length. The difference in viscosity between the base fluid and the nanofluids differing in nanotube length has been shown to decrease steadily at high shear rates, which is caused by a change in mechanisms of momentum dissipation in the system at nonzero shear rate.

This study describes the creation of permanent joints in a high-strength aluminum alloy using friction stir welding. The strength of the welded joint was achieved at the level of the base metal strength by using an active liquid cooling system and subsequent aging of the alloy. The influence of liquid cooling intensity on the structure and mechanical properties of the joints was also revealed. Welding parameters were developed to form full strength weld.

The paper presents an overview of SUNSHYNE software system, designed for the numerical simulation of compressible gas flows on modern multiprocessor computational systems with high-performance graphical processing units. The software has a graphical user interface and allows computations in domains with complex geometries for industrial applications owing to a variety of implemented boundary conditions, support of unstructured and block structured grids, as well as integration with computer-aided design systems. Physical models, numerical methods, and functional capabilities of the system are described; examples of computations are presented, including computations of nonequilibrium flows, direct numerical simulation of the transition to turbulence, and modeling of heterogeneous detonation.

This paper presents the results of an experimental and numerical investigation of the interaction between shock waves and highly porous, gas-permeable barriers having both homogeneous and heterogeneous spatial structures. The experiments are performed in a shock tube over a range of shock wave Mach numbers M = 1.2–1.8. The barriers used in the experiments consist of mesh stacks with triangular cells and layers of cellular-porous nickel. The shock wave interaction with the barriers is numerically simulated on the basis of the solution to the Reynolds-averaged Navier–Stokes equations, employing a toroidal skeletal model of the porous material. The study demonstrates that minimal shock wave reflection is achieved using combined barriers. These barriers comprise a series of mesh stacks with successively decreasing cell sizes, closed by a layer of cellular-porous material with minimal pore size.

The effect of quasi-two-dimensional protruding relief elements (strips) inclined to the flow direction on the position of laminar-turbulent transition on a wing model with a sweep angle of 45° is studied using quantitative thermography under various experimental conditions. The robustness of the sweeping surface relief method for laminar flow control in the presence of enhanced freestream turbulence and increased wing surface roughness is investigated and discussed. It is shown that this laminar flow control method is also robust to moderate variations in freestream velocity.

This paper presents the results of an experimental study of the effect of heat input through homogeneous condensation in a supersonic expanding flow on the density distribution and shock-wave structure of underexpanded rarefied gas jets. This effect is shown to be significant in modeling the force and thermal effects of control and orientation thruster plumes on adjacent spacecraft structural elements.