The analytical models for calculating the performance of vehicles used to transport fertilizers have been developed. The durability of undercarriages elements is estimated with consideration of kinetic equations for determining the periods of nucleation and propagation of cracks. The formulas for determining the durability of П-shaped thin-walled sections as the sum of the periods of nucleation and subcritical growth of corrosion-fatigue cracks in metal structures of vehicles, depending on the conditions of operation, are applied as well.

Purpose: Development of a computational model of stress-strain state bearing elements of trailer frames for preliminary assessment and identification of areas with increased risk of failure. Design/methodology/approach: The object of the study is the processes of loading the load-bearing metal structures of trailers - fertilizer spreaders. The stress-strain state of the spreader bearing system is investigated for the established three typical cases of external load. To refine the values obtained as a result of modelling, they were determined in SOLIDWORKS. Findings: Computational models of load have been compiled by improving the method of minimum potential deformation energy for its effective correct use in analytical studies of a similar type of metal structures. It is proved that for a flat closed frame structure made of thin-walled profiles, loaded with forces perpendicular to the plane of the frame, the levelling of compression and shear energies, as well as axial and transverse forces and bending moments in the horizontal plane does not significantly affect the calculation results. Research limitations/implications: Horizontal components of the shear forces as well as the normal forces and as a consequence the corresponding potential deformation energy are neglected, which has some effect on the accuracy of the calculations. Practical implications: An effective tool for strength analysis with preliminary assessment and diagnostics of load-bearing metal structures based on the constructed calculation models of stress strain state load-bearing frames of typical geometry with an arbitrarily given distribution of external load. Originality/value: A universal algorithm for recording additive functions of bending and torques, as well as the potential deformation energy of welded frames of trailers.

Purpose: To investigate the strength of tees with regard to their erosion wear, it is necessary to consider the complex three-dimensional geometric shape of the erosion worn inner surface of the tee. In addition, the study of the strength of the erosion worn tees of the main gas pipelines is complicated by the occurrence of additional stresses caused by changes in the direction of movement of the gas stream, resulting in an uneven pressure distribution in the inner cavity of the tee, and the temperature difference in its walls. Design/methodology/approach: Methodology for complex numerical three-dimensional simulation of the stressed state of tees of the main gas pipelines, taking into account the gas-dynamic processes that occur in the places of these defects, erosion wear of the tee wall, temperature difference in the tee walls. Findings: The acceptable parameters of erosion defects of tees of gas pipelines, and residual life of tees with erosion defects of the wall should be determined. Research limitations/implications: The developed model does not take into account internal corrosion and corrosion products as an additional erosion factor. Further studies plan to develop a model of corrosion-erosion wear of pipeline elements. Practical implications: The developed technique allows determining the location of erosion defects, estimating the strength and determining the residual life of tees with erosion wear of the wall in order to ensure their reliability, to rank such defects according to the degree of danger, to determine which of them are critical and need an immediate repair. Originality/value: Based on the gas-dynamic processes occurring in the internal cavity of the main gas pipelines’ tees, the complex three-dimensional geometric form of wall erosion defects, and temperature difference, the technique of three-dimensional simulation of stress state of the main gas pipelines’ tees is developed.

The approach for determining the residual life of the vehicles’ thin-walled metal elements with cracks under the action of cyclic loads and corrosive environment is developed based on the first law of thermodynamics and the fracture mechanics principles. Based on the results of the mathematical description of electrochemical reactions and separate data of fracture mechanics, the equation describing the kinetics of the corrosion-fatigue cracks propagation is deduced. This equation and the initial and final conditions are a mathematical model for determining the residual life of structural elements. The correctness of the developed analytical models is confirmed by the experimental data known in the literature. The performance of this model is demonstrated on the example of determining the residual life of a plate made of 17G1S steel. The plate was diluted by a crack in a 3% NaCl solution and subjected to cyclic loading. An increase in the initial size of corrosion-fatigue cracks is significant to reduce the period of their subcritical growth.

In bearing structures of automobile dump truck semi-trailers engaged in the transport of agricultural goods, mineral fertilizers, a large part of metal structures is under the direct influence of aggressive environments in combination with dynamic loads that arise when driving on roads. The peculiarities of corrosion processes when contacting steel surfaces of dump semi-trailers with mineral fertilizers, as well as their aqueous solutions, are insufficiently studied. Also studied mechanisms of electrochemical corrosion of materials of metal structures of agricultural vehicles to ensure their performance in conditions of prolonged aggressive environments. The authors determined that the mineral fertilizer medium is the most aggressive material used in cargo transportation in the agrarian sector mineral fertilizer and ammonium sulphate cause intense corrosion damage of typical materials of metal structures of automobile dump-carriers, which adversely affects reliability. The obtained results allow a better understanding of the causes of agricultural machines corrosion and can be used in assessing their residual resource.

The processes of corrosion-fatigue failure of materials in contact with mineral fertilizers are insufficiently studied. As a result of joint influence of atmospheric corrosion and mechanical loads, about 70 to 80 % of machine parts get out of order, 20 to 25 % of which are failures caused by operating overload due to the strength loss because of atmospheric corrosion. A large part of metal structures of agricultural vehicles used to transport mineral fertilizers is under the direct influence of aggressive environments and dynamic loads that occur during the motion by field roads. Saturated solutions of the most aggressive working environments used in agricultural production, in particular ammonium sulphate and nitrophosphate are investigated to reduce fatigue resistance of ordinary steels groups – St3 and St5 and quality steels – 10 Steel, 15 Steel, 20 Steel, 25 Steel when loaded at all levels. The fatigue endurance limit decreases in comparison with air up to 2.02 times in a solution of ammonium sulphate, and to 2.32 times in a solution of nitrophosphate. In organic fertilizer environments, compared to distilled water, the conditional fatigue endurance limit increased to 9 %. The properties of the given materials as an inhibitor of corrosion-fatigue failure were discovered and proved.

Jo ou ur rn na al l o of f S Su us st ta ai in na ab bl le e D De ev ve el lo op pm me en nt t o of f T Tr ra an ns sp po or rt t a an nd d L Lo og gi is st ti ic cs s

The article analysed and established the current trends in the logistics environment in Ukraine. There was grounded the necessity of implementing the principles of customer management to the systems of logistic service. There was formulated conceptual mechanism of choosing the optimal carrier based on the methodology of time deviations control in the provision of transport services.