Advances in Mechanical Engineering

The paper considers the organization of distance learning in higher mathematics during the period of quarantine measures. It is told about the means already available and their further development. The issue of the possibilities of intermediate certification in the remote mode is discussed, as well as the experience of conducting a colloquium with proctoring elements is highlighted. Interim students’ results on studying higher mathematics of one of the streams are given. The results showed that remote learning, which, of course, cannot completely replace personal communication with lecturers, can and should be used not only during the period of self-isolation, but also in the normal educational process.

This work discusses issues and approaches to organizing training for specialists in the field of engineering of industrial cyber-physical systems (ICPS) at technical universities. An overview of the current state of research in the field of competence models of a future specialist, expectations of industrial enterprises is presented. This work proposes a novel educational approach T-CHAT and its application in education of engineers in the field of ICPS. Additionally, a comprehensive organization and provision of students are examined connecting the competency model, the architectural model of the “smart factory”, the formation of curricula, and individual educational trajectories of students. Furthermore, this work formulates recommendations for the use of the indicated practices and approaches in the training of specialists in the framework of consideration of the educational aspect of the engineering of industrial cyber-physical systems.

The paper presents the results of a system analysis of the process of cold axial rotary forging of parts from thin-walled tube blanks with a conical roll. The technology is designed for manufacturing axisymmetric hollow parts of various shapes. A feature of the process is the possible loss of stability of the shape of the tube blanks, which does not allow getting the parts of the required geometry. On the basis of experiments and computer simulation of the process, six types of metal flow of the tube blank during rotary forging are determined, three of which are associated with the loss of stability of the tube blank. The main ten parameters that affect the technological process, including the kinematic characteristics of the machine and the geometric parameters of the tube blanks are systematized. Only three parameters can actually be used to control the metal flow. Recommendations are offered to reduce the time of adequate computer simulation of metal flow when forming tube blanks in the Deform 3D complex, which is used to determine the rational values of the parameters of a stable rotary forging process.

The goal of this work is the mathematical modeling of the electrical line stretched and supported by two isolators while a robot inspector moves with a constant speed along with it. The model, involving the flexural rigidity of the conductor, solved by the expansion method and Galerkin method. As shown in results, the difference between model including flexural rigidity and not including flexural rigidity is negligible, and results obtained by the Galerkin method are in a good match with results obtained by expansion methods. Also, one can see from the results that the fluctuations occur although the speed of the robot is constant and stable. These vibrations may affect the performance of the robot inspector or even cause failure.

When developing the theoretical basis for the design of technological equipment and its individual units that perform reciprocating movements, the development of a fundamentally new type of drive for rod depth pumps is particularly promising in terms of reducing energy consumption, which will also reduce the weight, dimensions and cost of foundations for their installation. The development of theoretical foundations for designing equipment with minimal energy costs will allow us to develop both design algorithms and evaluation of technological equipment in terms of energy costs. The relevance of the task of reducing energy consumption by technological equipment is that there is currently no systematic approach to identifying and evaluating the components of energy costs. Reducing energy costs, for example, by three times, will reduce the required drive power by nine times. This applies primarily to oil production and loading and unloading operations.

The paper is devoted to the problem of decomposition of an orthogonal polyhedron of arbitrary dimension into a set of large orthogonal objects. To solve this problem, an algorithm has been developed based on the application of the model of potential containers which is used in solving of orthogonal packing problems of arbitrary dimension. Examples of decomposition of two-dimensional and three-dimensional orthogonal polyhedrons are given.

The paper is devoted to the synthesis of the load characteristics of pulse shapers with shock test stands. For reproduction of shock acceleration spectra, shapers (gaskets) of different sizes and shapes made of a variety of materials are used. With new requirements to shock spectra, there is a need for quick calculation of shaping gaskets. It would be very convenient to have analytical expressions that link the spectrum parameters to the gasket parameters. There are already some good analytical dependencies in the literature which link the static load characteristics of a shaper with its geometrical and physical parameters. There are also very simple expressions to calculate the shock spectrum on the basis of the time function of acceleration. The problem of obtaining acceleration depending on the nonlinear characteristic of the shaper remains unsolved. This paper is devoted to the solution of this particular problem.

The authors consider the kinetostatic calculation of flat-faced linkage mechanisms with allowance for friction in kinematic pairs exemplified by an Assur group with three rotational pairs (RRR). The paper provides examples. In order to determine reactions in hinge joints, the authors propose the algorithm of searching for a structural group with replacement ideal kinematic pairs.

In the paper the oscillations of a circular cylindrical shell of the Kirchhoff – Love type with additional inertia in the form of a “mass belt” of zero width is considered. The dispersion equation is obtained and the nature of the dispersion curves in the vicinity of singular points is investigated. Additionally, a modal analysis of the system was carried out in ANSYS program by the finite element method.

The article discusses a dynamic model of a transmission containing a dual-clutch gearbox. The absence of a torque converter in such gearboxes with taking into account the short duration of gear shifting (0.2–0.5 s) allows to present the gear shifting process as an impact. Gear shifting excites the output shaft of the gearbox. Thus, the transmission of the vehicle can be considered as a vibro-impact self-oscillating system.

This work dedicated to the electrolytic-plasma polishing technology development for elongated foramen internal surface finishing and apparatus design for implementation the proposed technology.

Determined main technological interdependence factors, such as flow speed, electric field tension, electrolyte concentration for internal elongated surface quality received by electrolytic-plasma polishing process.

Developed local forced electrolytic-plasma polishing technology and obtained rational processing parameters allows to reaching desired internal surfaces quality for copper tubular workpieces.

In this work the local buckling issues of curved on radius plates, compressed by axial force are considered. Were investigated instability modes, influence of geometrical parameters and boundary conditions of unloaded sides on local buckling and buckling stresses. Buckling stress dependencies are obtained depending on the boundary conditions and the geometrical parameters of the plate.

The paper considers the problem of accuracy assurance during part manufacturing. Ensuring the required accuracy is one of the aspects of achieving the level of quality, implied during product design. It should start even before the actual manufacturing process, during process planning, which is one of the main stages in product life-cycle. In digital manufacturing, while using automatic and semi-automatic equipment, including CNC machines, a multi-operational technological process must be reliable in the context of ensuring its accuracy parameters, i.e. must guarantee in advance the compliance with requirements of dimensional accuracy and surfaces location and orientation which is specified in a part drawing. This can be achieved by carrying out a dimensional accuracy analysis of a technological process at its design stage, which will reduce time and material costs when introduced in production, due to a significant decrease in the probability of obtaining defects, related to precision parameters. When conducting a dimensional accuracy analysis of a technological process, it is necessary to preliminarily create diagrams of linear dimensions and circular runouts. Creating these diagrams and performing the required calculations manually is a rather time-consuming process. This fact as well as the lack of necessary software packages (even though there exist several programs for calculating linear and diametric dimensions and machining allowances, developed by authors of the present paper) today at industrial enterprises engineers do not conduct dimensional accuracy analysis when designing multi-operational manufacturing processes and rely solely on their own experience and the experience of adjusters and CNC machine operators. And this, in turn, holds back the process of manufacturing process automation, which is unacceptable during the transition to digital manufacturing. As a solution to this problem, it is proposed to introduce into the practice of technological process design developed calculation programs and a software tool in development, based on methods of interactive synthesis of linear dimensional and runout diagrams, described in the paper.

The construction of equilibrium systems of two-layer shells of revolution (cylindrical, conical, toroidal) with respect to the calculation of the corrugations of lens compensators for pipelines of hydropower and nuclear energy is given. The solution of boundary value problems for corrugations of lens compensators is based on the application of a modified method of successive approximations. To accelerate the convergence of the solution, the method of telescopic shift of the Lanczos power series is used, in which the original Mac-Loren series are represented through shifted Chebyshev polynomials.

The issues of thermoelasticity of bends of bimetallic pipelines of nuclear energy are considered taking into account ovalization of the cross section. The dependence of the physicomechanical characteristics of the material of pipelines on temperature and on exposure to radiation is taken into account. An algorithm for the analytical solution of the Karman boundary value problem for elastic bending based on the modified method of successive approximations is presented.

The authors consider some issues of machine dynamics, taking into account the elasticity of the transmission mechanism links. Such mechanisms are based on gear drives, which even under the constant external load have variable forces acting on their teeth, i.e. they are a source of vibration activity of the machine. The paper analyzes the causes of internal vibration activity of a spur gear train: variable gearing stiffness, kinematic errors of gears.

The authors present an analysis of the work of the cylinder-piston group parts and a method for determining the clearance values in the parts of the cylinder-piston group (CPG) of a diesel engine.

The method is developed on the basis of calculating the power of mechanical losses in the cylinder-piston group of a diesel engine while maintaining the oil burning loss within the permissible limits for operation without scuffing of the cylinder-piston group. This ensures a guaranteed clearance in the loaded zone of the “piston-cylinder sleeve” friction pair, taking into account the heat-stressed and deformed state of the piston and engine cylinder over the entire range of operating power conditions of the engine.

This paper considers the dynamics of a double mathematical pendulum whose cylindrical joints axes are not collinear to each other and form a certain acute angle between them. Such system is the simplest scheme of spatial two-link manipulator and can also be a component of various multi-link robotic devices. Basic geometric and kinematic characteristics of a double pendulum are given, which are necessary for deriving the equations of its motion. Small oscillations of the system near the lower equilibrium position are studied. As a result, formulas for the natural frequencies and modes of small oscillations are obtained. The dependence of frequencies and modes on the angle between the pendulum joints is revealed using a qualitative and graphical analysis of found expressions. The obtained results are both of theoretical interest and important practical value.

The paper deals with the organization of transportation of dangerous goods. Difficulties in ensuring the safety conditions for the transport of dangerous goods were noted, including due to the lack of appropriate controls and methods for determining the dangerous zones of the transport route. The article presents the existing methods for determining risks in the transport of dangerous goods. In this paper, a new method has been developed and proposed for determining the risks of transporting not only dangerous goods, but also other types of cargo transportation.

We consider a system of differential equations in the Cauchy form, containing homogeneous linear and cubic forms with respect to phase variables and small perturbing functions. We consider the system as a polynomial dynamical system under constant disturbances. We propose a method for constructing a nonlinear exponential differential inequality for a quadratic Lyapunov function and a square inequality. By integrating the exponential differential inequality, we obtain an estimate of the Lyapunov function from a function of time and initial conditions and an estimate of the phase variables.

The article considers the issues of increasing the efficiency of cryogenic vacuum pumps to create a deep vacuum used in production processes during chemical and physical experiments. It is noted that the use of zeolites as a sorbent material, in comparison with activated carbons, provides a more efficient absorption of hydrogen and helium. It is proposed to increase the heat sink using compositions of zeolite and metal powders with high thermal conductivity, pressed onto the surface of the tubes. It is shown that the best results are achieved when using the composition of zeolite - copper powder. It is proposed to use the process of elastostatic pressing for the manufacture of coaxial-cylindrical samples. The original design of the pump with coaxial-cylindrical samples with the pressing of the sorbent composite layer is presented. The results of practical tests of the pump are presented. The prospects of using the developed adsorption cryogenic-vacuum pumps with sorbent elements based on zeolite and copper powders are considered. This research work was supported by the Academic Excellence Project 5–100 proposed by Peter the Great St. Petersburg Polytechnic University.

The mathematical and computer models of the shock testing machine air suspension are considered. Estimates are obtained for the influence of the main characteristics and parameters of the suspension elements: pressure, piston area and the stroke of pneumatic cylinders, the properties of shock absorbers and the inertia block mass on the parameters of reproducible shock pulses and the dynamic load onto the foundation.

It analyzes a number of ways to reduce the excitation of vibrations when crossing the resonance zones of cyclic machines with constant and variable positions of the center of mass. For parametric resonances, in order to maintain dynamic stability, methods are proposed for determining threshold values of dissipative characteristics and the duration of the intersection zone. The results can be used to increase the productivity of machines, the accuracy of reproduction of the programmed movement of the working bodies, the implementation of technological requirements, as well as the ergonomic working conditions of the human operator.