Journal of Applied Mechanics and Technical Physics最新文献

In this paper, the modified polyaryletherketone (PAEK) was used as a toughening agent to prepare the PAEK/epoxy blends. Effect of PAEK on the erosive wear behaviors of blends was also investigated by the water jet technology. The surface morphologies of the wear scars were examined. With the increased of the PAEK content, the hardness and the impact toughness showed the phenomenon of first increased and then decreased. The erosive wear resistance of the epoxy resin blends was improved significantly, especially when PAEK content increases up to 35 phr. The erosion wear rate of the specimen shows 9.1% reduction than that of unmodified epoxy resin sample. The material removal occurred on the eroded surfaces of the epoxy blends due to the micro-plowing, cracks, micro-cutting and plastic distortion. All these results suggested that the addition of PAEK could optimize the structural strength, indicating that the PAEK/epoxy blends are suitable for erosive environments.

The main objective of this study is to investigate the mechanism of forced transition to turbulence in a swept-wing laminar boundary layer with dominant cross-flow instability using spanwise-periodic rows of cylindrical turbulators (trip devices). Measurements using hot-wire anemometry were performed on a 25-degree swept wing model at low subsonic freestream velocities in a low-turbulence wind tunnel at the Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk. The investigated range of trip-height Reynolds numbers was between 565 and 3613. The main boundary-layer characteristics required to construct transfer functions for jumps in boundary-layer integral parameters important for numerical simulation of swept-wing flows in the presence of trip devices were obtained. The turbulence spectra are shown to agree with Kolmogorov’s and Heisenberg’s laws. Faulkner’s and Hama’s empirical formulas were verified and refined for the evolution of integral parameters in a three-dimensional boundary layer. This paper is Part 2 of the study.

This paper presents a review of theoretical and experimental results obtained by Russian and international researchers in recent decades. An ice sheet is simulated using an elastic plate. The focus of the study is forced hydroelastic waves caused by dynamic loads on a floating elastic plate or disturbances generated by sources submerged in the fluid.

The vector potential of the magnetic field in a region between the induction coil, upper part of the floating zone, liquid film, feed rod, and protective shield has been determined in an axisymmetric problem of floating zone melting of a silicon cylinder 5–10 cm in radius. The boundary condition at infinity has been brought to some semicircle connecting the feed rod and protective shield and located at a sufficiently large distance from the coil, which has made it possible the problem to be treated in a finite region. This region has been conformally mapped onto a rectangle, in which the problem of determining the magnetic field vector potential has been solved. The problem reduces to solving Laplace’s equation for the only nonzero component of the vector potential ({A_varphi }), where (varphi ) is the azimuthal angle, with first- or second-order boundary conditions on the rectangle sides. The proposed method can be used to evaluate the variable thickness and shape of the liquid film adjacent to the lower part of the feed rod and the hydrodynamic flow in the film.

This study delves into the impact of low-velocity loading and thermal effects on functionally graded material (FGM) circular plates crucial in aeronautical and space engineering. Examining varied conditions, the focus lies on radial displacement and transverse deformations in hot, ambient, and cold environments. Notably, findings highlight an increased likelihood of damage in hotter scenarios, emphasizing the imperative need to design FGM plates with enhanced resistance against impact loads and thermal stresses in extreme conditions. These results bear crucial implications for aerospace applications, guiding the development of FGM plates that can effectively withstand challenges in diverse environments.

This paper touches upon the propagation of a step-pressure wave and a finite-duration pulse from a liquid into a porous medium saturated with a bubbly or a “pure” liquid. The effect of these waves on a solid wall with a layer of a saturated porous medium located in front of it is studied. It is shown that the calculation results are in good qualitative agreement with known experimental data.

The paper deals with the diffusion-wave solutions to a system of two degenerate nonlinear parabolic equations. The problem of diffusion wave initiation is considered for arbitrary nonlinearity in the equations of the system and for arbitrary directions of motion of the zero fronts of two unknown functions. For this problem, a theorem on the existence for four different (depending on the directions of motion of the zero fronts) analytical solutions is proved. A new numerical method is proposed which allows the problem to be solved for the first time for the case of oppositely moving zero fronts. A new exact solution is constructed explicitly and used to verify the calculation results. A computational experiment is performed showing the convergence of the numerical method and its effectiveness for various problem parameters.

The deformation of an elastic body containing two thin anisotropic inclusions intersecting at a right angle is studied using a mathematical model with unilateral boundary conditions. The inclusions intersect at an interior point of one of them to form a T-shaped structure in the elastic body. One of the inclusions delaminates from the matrix to form a crack. Inequality type boundary conditions are specified on the faces of the cut. Numerical solution of the problem in the domain with the cut is performed by a domain decomposition method using a Uzawa type algorithm. A method based on space decomposition into a direct sum of subspaces is used to determine the displacement functions of the semirigid inclusion.

This paper presents some aspects of the use of physics-informed neural networks to solve a two-dimensional stationary problem of flow around an obstacle using the Navier–Stokes equations. The influence of the activation function, quantitative parameters of the training set, adaptive regularization, and adaptive grids on the quality and accuracy of solutions is studied for a fixed neural network architecture. The relationship between these factors and modeling quality is analyzed to identify optimal conditions for increasing the accuracy and stability of solutions.

We have demonstrated for the first time different scenarios of the collapse of a hemispherical low-density cavity formed as a result of gas heating by a pulsed submillimeter electric discharge near a dielectric surface: a scenario due to cavity boundary stability loss in the zone where the cavity is in contact with the surface and a scenario involving stability loss in the zone farthest from the surface. Both “bubble” collapse scenarios occur stochastically under invariant experimental conditions. Using particle image velocimetry, we obtained distributions of velocity fields in the region of a cavity at various instants of time. High-speed filming data lead us to assume that which scenario will occur depends on the shape of the conducting channel at the instant of electric breakdown.