Transportation systems and technology

The implementation of the magnetically levitated train’s (MLT) levitation force (LF) occurs during the interaction between fields of superconductor train (STC) and short-circuited track contours (SCTC), which are the elements of levitation module (LM).

Purpose. Based on above, the purpose of this study is to obtain a correct description of such interaction. At the present stage, the main and the most universal tool for the analysis and synthesis of processes and systems is their mathematical and, in particular, computer modeling. At the same time, the radical advantages of this tool make even more important the precision of choosing a specific methodology for research conducting.

Methodology. This is particularly relevant in relation to such large and complex systems as MLT. For this reason, the work pays special attention to the reasoned choice of the selective features of the research paradigm. The analysis of existing versions of LF implementation’s models show that each of them, along with the advantages, also has significant drawbacks.

Results. In this regard, one of the main result of the study should be the construction of this force implementation’s mathematical model, which preserves the advantages of the mentioned versions, but would be free from their shortcomings. The rationality of application, for the train’s LF researching, of an integrative holistic paradigm, which assimilates the advantages of the electric circuit and magnetic field theories, is reasonably justified in work.

The scientific novelty of the research. The priority of creation of such a paradigm and the corresponding version of the implementation of LF’s model account for the novelty of the research.

Practical significance of the work. The practical significance consists in the possibility, in case of using its results, of significantly increasing the efficiency of dynamic MLT research while reducing their resource costs.

On the basis of schemes of cargo magnetic levitation stations, developed by the specialists of the Department of "Railway stations and junctions" of Emperor Alexander I St. Petersburg State Transport University, and the technology to transport goods over discrete-continuous principles created a model that allows to perform dynamic experiments to identify significant design parameters and performance of magnetic levitation terminals.

Goal: To identify dependencies of key operating parameters of freight terminals required for their design and choice of rational performance of basic elements and devices.

Method: In order to solve this problem, it is proposed to use a simulation method by means of a programme AnyLogic.

Results: The technological algorithm of a freight station was developed, on the basis of which in the software environment of AnyLogic of the Russian company “the AnyLogic Company” the simulation model was built, and necessary report data were obtained – the required number and capacity of loading and unloading equipment, annual turnover of terminal, the average time spent on the platforms at the station and unproductive downtime of magnetic levitation platforms.

Practical importance: The model verification has shown that the proposed simulation method allows to determine and justify the required parameters of the freight terminal of magnetic levitation lines, which will ensure rational spending of the funds for their construction and required processing ability.

Introduction. With the development of numerical methods and computational complexes, it is quite easy to evaluate the stress state of thin-walled structures in the form of rotation bodies. However, when solving such problems by the finite element method, it is necessary to choose such finite element grid to "grasp" all possible singularities of the stressed state. To correctly take them into account, you must reduce the size of the finite elements. Reducing the size of the elements leads to an increase in the required computing power.

Formulation of the problem. When solving applied problems, even with a sufficiently coarse grid, the number of elements can exceed hundreds of thousands. When solving problems for real constructions in a three-dimensional setting, the amount of computation can be quite large and not every supercomputer can even handle such a solution.

Objective. The purpose of this paper is to use the well-known approach used in shell theory, which allows us to reduce the three-dimensional problem to the solution of a one-dimensional problem, which substantially reduces the requirements for computing power.

Method (methodology). The problem of determining the stress state of shell structures in the form of bodies of revolution is considered. The approach is based on the integration of the equations of the theory of shells and the expansion of functions into Fourier series for separation of variables. The expansion into a discrete Fourier series in cosines and sines is used in this paper, which describes arbitrary asymmetric mechanical loads.

Results. A thin-walled cylindrical structure hinged at the ends is considered. The structure is loaded in three places by a distributed force acting normal to the surface of the shell. After integrating the system of equations for the shell, the found stress-strain state of the shell is determined by the stress components on the outer and inner surfaces of the shell and the displacement components. The paper compares the calculation results with the proposed methodology and the finite element method.

The conclusion. It is shown that the use of methods of shell theory, and the proposed expansion of resolving functions and loads in a Fourier series, allows solving problems using small computing resources. At the same time, the necessary accuracy of calculation for all components of the stress-strain state of the structure is ensured.

High-speed ground maglev transport creates electromagnetic interference of wide frequency spectrum during the movement. Electromagnetic interference spreads both in the surrounding environment and within the transport itself.

Mathematically, electromagnetic interference is a vector (and in some cases tensor) field, where the functions are magnetic and electrical tenseness.

Purpose. The purpose of the work is to ensure electromagnetic safety of high-speed ground maglev transport’s technical means and people (passengers and staff) by means of optimisation synthesis.

Objective. The objective of the works is to optimise the placement of field sources in areas with variable geometric characteristics.

Methodology. The method of the work is to synthesise elements of an energy system whose characteristics depend on the behaviour of electromagnetic interference. The mathematical model of the energy system being designed should take into account technological and constructive constraints, and electromagnetic interference.

Calculation of electromagnetic interference from several sources in the premises, where the energy system is located by means of solving nonlinear tasks of special type mathematical programming. The peculiarities of this type of problems do not allow using known methods of mathematical programming. Finally, methods of formalisation and algorithms for solving optimisation problems of placement.

Practical significance. The search of solution of optimisation tasks became feasible owing to a number of suggestions put forward by the author: introduction of scalar potentials for describing external electromagnetic interference of the electric power plant elements; the introduction of interinfluence taking into account the influence of closely-located sources; development of screening functions in the form of harmonic decompositions; the application of addition theorems which enable describing  solutions of mathematical physics equations  in different coordinate systems.

Conclusion. The suggested method of formation of maglev transport electric energy system may be useful.

The article presents results of monitoring state of railway subgrade using seismic methods in the Far North area.

 Purpose: The purpose of the studies is to find out reasons of subgrade subsidence in turfed soils of Onezhsky District of Arkhangelsk Oblast. 

Methodology: Studying soils in foundations of subgrade, a complex of active and passive methods was used, including: seismic exploration of refracted waves, multi-channel analysis of ground waves, and engineering seismic analysis based upon spectrum analysis of seismic noises. This complex enabled considering and estimating the system “subgrade-soils of foundations”.

Results: A relative high capacity of weak soils, probably containing turf, lying under subgrade. Sections of increased water saturation in subgrade soils were found out. Loads from passing trains and resonant effect in weak soils cause its compression resulting in emergence of subsidence. Resonant effects whereby are not that strong, whereas passing trains have a more significant impact on the state of subgrades.

Practical significance: Elaboration of technology of quick estimation of state of railway subgrade for immediate detection of a dangerous defect at an early stage of its development is a topical and acute challenge.