Journal of Applied Mechanics and Technical Physics

The technological regimes of welding that promote uniform distribution of the properties over the length of a welded joint are studied by numerically modeling the formation of a weld seam by a nonmelting electrode.

The well-posedness of the problem of linear thermoelasticity in the Ginzburg–Landau theory of phase transitions is proved.

A mechanism for boiling of a fluidized bed was examined in [1]. Due to hydrodynamic instability the solid particles acquire random motion, and as a result of collisions between particles part of the energy of random motion is converted to rotation of the particles. A rotating particle experiences a Magnus force which considerably increases the random motion and leads to spontaneous boiling of the layer. For this mechanism there is typically a minimum boiling time τγ, defined basically as the time to develop a hydrodynamic instability. It is shown in this study that besides the spontaneous mechanism there is an induced mechanism for boiling of the bed arising from the generation of random motion in one particle layer. Particles in that layer boil, transmitting a perturbation to the energy of the next layer, and leading to layer boiling in a manner analogous to the propagation of a detonation wave in solids.

Direct shadowgraphy is used to study the generation of Mach waves and jet noise in a wide range of frequencies by single supersonic jets and by groups of jets in the Mach number range M = 1–4.

Effect of nanosized silicon on mechanical properties, texture, and structure of a polymer paint-and-varnish coating made of gray KhV-16 enamel based on perchlorovinyl and glyphthalic resins is studied. It is established that the abrasion strength, hardness, and elastic modulus are larger than in the case of the original coating. Various methods are used to analyze the structure of the resulting samples of paint-and-varnish coatings. It is established that the structure changes and the mechanical properties of the coatings improve because of the formation of new structure-forming centers in the composite coating due to the addition of nanosized silica.

An analytical solution is obtained for the problem of acceleration of a body in a closed tube filled with a detonating mixture of gases. It is assumed that the body enters the tube with a certain initial velocity sufficient for burning initiation in an annular space between the body and tube surfaces. The effect of the mixture parameters, the shape and mass of the body, and the integral dissipation of the total momentum and enthalpy of the flow on the finite values of the velocity and the acceleration length is analyzed.

The multiple scale expansion method is used to derive amplitude equations for a system with thermohaline convection in the neighborhood of Hopf and Taylor bifurcation points and at the double zero point of the dispersion relation. A complex Ginzburg-Landau equation, a Newell-Whitehead-type equation, and an equation of the ϕ4 type, respectively, were obtained. Analytic expressions for the coefficients of these equations and their various asymptotic forms are presented. In the case of Hopf bifurcation for low and high frequencies, the amplitude equation reduces to a perturbed nonlinear Shroedinger equation. In the high-frequency limit, structures of the type of “dark” solitons are characteristic of the examined physical system.