DETERMINING LOADING PATTERNS IN THE BEARING STRUCTURE OF A RAILROAD FLATCAR WITH A FLOOR MADE FROM SANDWICH PANELS (р. 6–13

The object of research is the processes of emergence, perception, and redistribution of loads in the supporting structure of a flatcar with a floor made of sandwich panels. To reduce the impact of dynamic loads on the supporting structure of a flatcar, as well as the safety of goods transported in it, it is proposed to manufacture floors from sandwich panels. Within the framework of the study, mathematical modeling of the dynamic load on a flatcar when it runs in a loaded state was carried out. It was found that, taking into account the proposed solu-tion, the accelerations acting on the supporting structure of a flatcar are reduced by 8.4 % compared to the typical one. At the same time, accelerations acting on cargo placed on a flatbed car are reduced by 11.7 %. The results of calculating the strength of sandwich panels, when arranged on a flatcar, proved the feasibility of the proposed improvement. The main indicators of dynamics of the improved flatcar structure operated in an empty state were determined. It was established that the flatcar movement is assessed as “good”. A feature of the results reported here is that the improved supporting structure of a flatcar contributes not only to reducing its dynamic load but also to improving the safety of transported cargoes. The scope of practical application of the results is the engineering industry, in particular, railroad transport. The condition for the practical application of the research results is the use of energy-absorbing material in the structure of sandwich panels. The study could contribute to devising recommendations regarding the design of modern structures of railroad vehicles and increasing the efficiency of the functioning of the transportation industry.

by a prestressed winding.The simulation was carried out for two variants of fixing the upper edge of the tank wall, which correspond to cases of absence or presence of tank coating.The estimation cases for the coefficients of the tension force of the wire relative to its tensile strength were investigated: at k 1 =0.2; k 2 =0.4; k 3 =0.6 and k 4 =0.8.Variation studies were carried out both taking into account the additional loads caused by the action of hydrostatic pressure from the maximum and half poured oil into the tank, and without oil.The magnitude of changes in the vibration frequencies of the tank wall without the influence of the coating varies within 12-27 % and when taking into account the influence of tank coating, 21-62 %, depending on the degree of filling of the tank.The revealed pattern relates to the fact that a decrease in the tension force of the filament in the winding leads to an increase in the frequency of oscillations.Thus, pre-stress can be applied to regulate the oscillation frequency of the tank wall.By decreasing which in the winding, it is possible to increase the natural frequencies of the wall and to lower the frequencies through an increase in the prestress.The research results can be used in the future as anti-seismic measures in the design and construction of steel vertical cylindrical tanks, as well as to improve the strength characteristics of existing cylindrical structures.
Keywords: vertical steel tank, prestress, seismic loads, oscillation frequency.This paper proposes a method that makes it possible to study the patterns of changes in the concrete strength of reinforced concrete crossbars depending on the heating temperature under fire conditions by interpreting the results of their standard fire tests.For the implementation of this method, it is proposed to use similar data obtained using mathematical modeling based on the finite element method and given material properties, including the curve of concrete strength reduction recommended by the guidelines, as data included in the set of measurement results during fire tests depending on temperature.Such data are time dependences of temperature indicators at individual cross-section points and time dependence of the maximum deflection of the crossbar.The article proposes an interpolation method that makes it possible to set the temperature at any point of the section based on the approximation of the isotherms by parabolas with a variable indicator of their power.A method based on the mathematical interpretation of temperature indicators obtained using the proposed interpolation method and the curve of the dependence of the maximum deflection on time using a deformation model for describing the stress-strain state is proposed to identify the dependence of the concrete strength of reinforced concrete crossbars.
The work also shows that the results obtained using the proposed method of identifying concrete strength reduction coefficients This paper presents a finite element analysis of a composite shaft under dynamic variable fatigue loading.The object of this study is the behavior of the fatigue life of a composite shaft under dynamic variable fatigue loading.The fatigue life of the shaft is then determined by analyzing the stress distribution and its effect on the material's fatigue strength.The investigation of fatigue behavior involves evaluating factors such as stress concentrations, fatigue crack initiation and propagation, and the cumulative damage caused by cyclic loading.The study explores the impact of biaxial loading on the shaft's fatigue performance and provides insights into its significance in predicting fatigue life and it is 10e7 cycles.Furthermore, a damage indicator is predicted to assess the accumulated damage and monitor the progression of fatigue-related degradation.This indicator serves as a valuable tool for predicting the remaining useful life of the composite shaft.The equivalent alternative stress is calculated to characterize the combined effect of different loading conditions on the fatigue life of the composite shaft.By quantifying the stress level and variations experienced by the structure, this parameter allows for a comprehensive assessment of the fatigue performance under variable loading scenarios 250 N. The findings of this research contribute to the understanding of fatigue behavior in composite shafts under dynamic variable fatigue loading.The insights gained from the fatigue life investigation, biaxiality indication, damage prediction, and equivalent alternative stress calculation can aid in optimizing design considerations, maintenance planning, and enhancing the reliability and durability of composite shafts in various engineering applications.
Keywords: composite shaft, variable loading, fatigue life, biaxiality indication, damage indicator.are adequate as their relative error is on average no more than 7 %.Based on the results, the possibility of its application to study the regularities of the decrease in the strength of reinforced concrete crossbars under fire conditions has been proven.
The task addressed was the influence of the structural and operational parameters of dual hydrostatic plain bearings on their static and dynamic characteristics.As a static characteristic, the bearing capacities of dual and conventional sleeve hydrostatic bearings were considered.When analyzing the dynamic characteristics, the amplitude-frequency characteristics were determined.They were obtained by calculation and as a result of experimental studies.When calculating the amplitude-frequency characteristics, the trajectory method was used.As external forces in the equations of motion of the rotor, hydrodynamic forces, the weight of the rotor, and its unbalance were considered.
Experimental determination of the trajectories of the rotor was carried out on a special bench.
It has been established that the bearing capacity of a double type bearing is approximately 1.75-1.85times higher than the bearing capacity of a conventional sleeve bearing.The range of stable operation of the rotor on double-type bearings is approximately 1.4 times greater in comparison with the range of stable operation of the rotor on sleeve hydrostatic bearings.The vibration amplitudes in the resonance region for double bearings were approximately 1.5 times less than the rotor vibration amplitudes for sleeve bearings.
The results make it possible to recommend dual-type hydrostatic bearings for rotor bearings of nuclear power plants, in powerful aircraft engines with a gearbox, various types of pumps, and other power plant units.The derived theoretical dependences make it possible to carry out practical calculation of hydrostatic bearings of a double type.
The load-bearing elements of a number of strategic equipment are of limited length and variable cross-section.Most of them are exposed to certain types of heat sources.In order to ensure the reliable operation of this equipment, it is necessary to know the temperature field along the length of the variable cross-section rod.In this paper, a computational algorithm and a method for determining the temperature field along the length of a rod with a limited length and variable cross-section are proposed.They are based on the fundamental laws of conservation of energy.
The nonlinearity of the process is due to nonlinear dependencies of the areas of the variable cross-section on the coordinate.The radius of the cross-section of the rod decreases linearly along the entire length, starting from the left end.The side surface of the first and third discrete elements of the rod is heat-insulated.Convective heat exchange with the environment takes place on the side surface of the second discrete element of the rod.
The cross-sectional area of the left end of the rod is under the heat flow with a constant intensity, and a heat flow with different intensities is supplied to the right end, wherein the heat transfer coefficient is considered constant.For this task, you must first determine the law of temperature distribution along the length of the rod.In addition, if one end is rigidly fixed and the other end is free, the elongation must be calculated depending on the available heat sources, the physical and geometric characteristics of the rod, taking into account the presence of insulation.
In case of pinching of both ends of the investigated rod, the value of axial compressive force is calculated taking into account the addition of real factors.The distribution of all components of the strain, stress, and displacement field is also defined.
Keywords: heat flux intensity, thermal conductivity coefficient, temperature, heat transfer coefficient.
A mathematical model was built based on data visualization for the impact grinding mechanism in a tumbling mill, which is mainly implemented during coarse grinding.
The determination of impulse interaction parameters is problematic due to the difficulty of modeling and the complexity of hardware analysis of the behavior of intramill loading.
Conceptually, it was envisaged to identify the relative dynamic parameters of the impact action as components of the model, which are criteria for the similarity of the loading movement and the grinding process.Impact power was taken as an analog of grinding performance.The initial characteristic of the impact was considered to be the averaged vertical component of the speed of loading movement in the flight zone at the boundary of contact with the shear layer.The formalization of the model revealed the effect on the performance of the mass fraction of the flight zone and the reversibility of loading.
The method of numerical modeling was applied, based on experimental visualization of the behavior of granular loading in the cross section of a rotating chamber.
The influence of the rotation speed on the performance at a chamber filling degree of 0.45 and a relative particle size of a milling load of 0.0104 was estimated by experimental simulation.The maximum productivity value was found at the relative speed of rotation ψ ω =1-1.05.A rational condition for impact grinding at ψ ω =0.75-0.9 has been established.
The test proved the effectiveness of using visualization to evaluate dynamic loading interaction analogs.Verification of modeling results was implemented by comparison with the data of the technical standard.The use of similarity criteria unifies approaches to modeling different mechanisms of destruction.
The model built makes it possible to predict the rational parameters of the grinding processes by impact, crushing, and abrasion.