Vol 48, No 1 (2019)
- Year: 2019
- Articles: 13
- URL: https://journals.rcsi.science/1052-6188/issue/view/12186
Mechanics of Machines
The Dynamics of a Cavitation Pocket and Cavitation Damage
Abstract
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.
Comparative Study of Hybrid Vehicle Powertrains with Respect to Energy Efficiency
Abstract
This paper describes a study of hybrid powertrains that was conducted by means of mathematical modeling. In this study, the comparison of powertrains was undertaken considering the most frequently mentioned hybrid transmission topologies: series, parallel, and series parallel (power-split). The powertrains were equipped with traction batteries having the electric grid charging feature.
Control of Movement of a Loosely Coupled Self-Propelled Modular Transporter
Abstract
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.
Field of a Multilayer and Multiturn Coil with Analytically Set Laws of Variations in the Distances between Layers and Turns
Abstract
Design formulas for three-dimensional magnetic fields generated with a complex system of circular currents, which compose a multilayer and multiturn coil are derived. The distribution of a vector field in any spatial domain can be obtained by setting the analytic function that establishes the distances between turns and/or layers. It is revealed that under uniform winding and equal densities of surface currents, the magnetic fluxes of a single-layer coil and equidimensional axial magnetized cylinder are identical. The magnetic flux of the cylinder is calculated by the demagnetizing factor.
Reliability, Strength, and Wear Resistance of Machines and Structures
Analysis of Crack Resistance of an Oil Trunk Pipeline Considering the Varying Failure Viscosity in the Neighborhood of a Welded Joint
Abstract
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 Technique of Synthesizing Control Actions to Ensure a Preset Level of Reliability
Abstract
The proposed procedure allows considering active control actions in the form of design, technology, and operation parameters when creating engineering systems. It helps control the product improvement process, including the targeted perfection of product output characteristics. The object of research is a special-purpose mobile installation. The control actions are estimated using the set of mathematical tools of matrix calculation and mathematical statistics techniques. The control action equations are derived for the Weibull distribution law and the exponential law without taking into account the restrictions imposed. An example of finding control actions is provided.
The Basic Stress—Strain State of a Circular Plate of Variable Thickness Based on a Nonclassical Theory
Abstract
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.
Thrust Slip Bearings in a Turbulent Friction Mode with the Rheological Properties of a Viscoelastic Lubricant
Abstract
Based on the concept of the turbulent flow of a viscoelastic lubricant, a two-component lubrication system consisting of mineral oil and a viscoelastic lubricant that represents a melt of fusible metals is considered. The results of studies on the tribological characteristics such as friction forces and the bearing capacity of friction assemblies are presented taking into account the viscosity and shear modulus of the molten layer depending on the temperature. Ways to improve the properties of lubricants through the introduction of additives and fillers therein are considered.
A Molybdenum-Containing Carbon Coating for Tribotechnical Use and Antifriction Properties of Oils under Boundary Lubrication
Abstract
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.
Study of the Impact of Wear of Movable Interfaces on Failures of an Immersible Electrically Operated Vane Pump for Oil Extraction
Abstract
This article considers the conditions for wear-induced operating and parametric failure of electrically operated vane pump installations for oil extraction. It is shown that the wear of radial interfaces intensifies the vibration of the installation body by 10 to 15 times. It is found that the amount of leakage through radial seals of different radial stages hardly depends on the capacity of these stages. It is recommended to use wearproof bearings and reduce axial interface gaps.
New Technologies in Mechanical Engineering
Improving the Reliability of Permanent Pipeline Connections by Using the Shape Memory Effect in Thermomechanical Couplings
Abstract
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.
Experimental Mechanics, Diagnostics, and Testing
Study of the Defective Structure of Metal by the Method of Ultrasonic Sounding
Abstract
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.