Volume 48, Nº 1 (2019)

The motion of a liquid column in a vertical tube caused by a moving piston that contacts its lower boundary is considered. The law of the piston’s motion is defined based on experimental data. The acceleration of the piston exceeds the acceleration due to gravity. The separation of the liquid from the piston and the change in the volume of the cavitation pocket are accepted. The simplest model of the phenomenon is proposed. A qualitative analytical solution of the one-dimensional problem is presented; the results are compared with experimental data. The pressure upon the collapse of the pocket, the subsequent elastic oscillations of the tube bottom, and the resulting stresses are assessed.

Arguments are made in favor of the use of transporters intended for transporting large-sized indivisible heavy objects, which are composed of separate self-propelled modules. The basic principles of operating such a loosely coupled vehicle using modern information technologies are given in the context of steering control. Some versions of transporters are presented as are schemes of taxi patterns they can perform. The operation of a three-level movement control system of a loosely coupled transporter is considered including its functional arrangement.

This article presents a development of the method of analysis of crack resistance of an oil trunk pipeline in the zone of the transverse welded joint during operation. The nonlinear nonstationary heat conductivity problem was solved by the finite difference method using the boundary conditions of third kind. Modeling of the kinetics of conversion of austenite to ferrite and bainite under non-isothermal conditions during welding was carried out based on the theory of isokinetic reactions. The calculation of the residual welding stress is performed by solving the problem of thermoelastic plasticity using the finite element method for material with a nonstationary structure. The calculation of the crack resistance is based on Irwin’s force failure criterion, and the dependence of the failure viscosity on the structural composition is considered.

A mathematical model of the basic stress-strain state of a circular plate with thickness varying asymmetrically under axisymmetric loading is developed. The method of direct asymptotic integration of differential equations of the 3D theory of elasticity is used. A boundary value problem, which is a system of two second- and fourth-order displacement differential equations with variable coefficients and corresponding boundary conditions, is formulated. An example of plate calculation on the Matlab-14 system using the finite difference method is given.

The results of studies on a monocrystalline carbon coating for tribological uses doped with molybdenum are presented. For comparison, an unalloyed monocrystalline carbon coating, as well as uncoated steel, have been investigated. The studies involved an assessment of the physicomechanical characteristics of the compared materials, as well as of the composition and structure of the coatings, and their influence on the antifriction properties of three model lubricating medias under friction in a boundary lubrication mode. It is established that it is possible to improve the antifriction properties of model lubricating media by applying carbon coatings doped by molybdenum onto the working surfaces of rubbing elements.

A method for computing the level of values of product design by summation of the coefficients based on taking into account the degree of their influence on the laboriousness of the product is stated.

This paper considers a method of forming the inner element (coupling) contour, which makes it possible to obtain relief elements of various sizes from shape memory alloys due to the stresses generated by thermomechanical recovery and specified shaping that meets the requirements for the finished element.

A methodological approach to study the defective structure of metal by the ultrasonic sounding method was proposed. It was shown that the presentation of the processes determining the influence of the material conditions on the parameters of the sound impulse by the static model in the form of the Dirichlet distribution allows us to characterize qualitatively the change in the sounding impulse with account of the change in the metal defective structure and to improve our understanding of the integration phenomena of the sound wave with the environment.