applied sciences Article Calculation of Loads on Carrying Structures of Articulated Circular-Tube Wagons Equipped with New Draft Gear Concepts Alyona Lovska 1, Oleksij Fomin 2 , Pavel Kuˇcera 3,* and Václav Píštˇek 3 1 Department of Wagons, Ukrainian State University of Railway Transport, Feuerbach sq., 7, 61050 Kharkiv, Ukraine; [email protected] 2 Department of Cars and Carriage Facilities, State University of Infrastructure and Technologies, Kyrylivska str., 9, 04071 Kyiv, Ukraine; [email protected] 3 Institute of Automotive Engineering, Brno University of Technology, Technická 2896/2, 616-69 Brno, Czech Republic; [email protected] * Correspondence: [email protected]; Tel.: +420-541-142-274 Received: 23 September 2020; Accepted: 18 October 2020; Published: 23 October 2020 Featured Application: The research results will inspire technicians to design modern railway vehicles with higher operational efficiency. Abstract: This article deals with the dynamic load and strength of the carrying structures of articulated circular-tube wagons. The study was conducted on the carrying structures of wagons equipped with new draft gear concepts. The accelerations on the carrying structures of wagons were determined using mathematical modeling. The results of modeling show that implementation of the draft gear concept can decrease the dynamic load of wagons by about 10% in comparison with that of a typical SA-3 coupler. Using the created computational models, the service life of the structure of the proposed articulated wagons was also determined. This research will encourage engineers to design modern structures of railway vehicles of higher operational efficiency. Keywords: wagon; articulated wagon; carrying structure; draft gear; dynamic load; strength; transport mechanics 1. Introduction Higher operational efficiency, as a precondition for maintaining the leading position in the global transportation market, can be achieved through the introduction of articulated wagons on railways. A special feature of such wagons is the two-section carrying structure resting on three bogies. The sections interact through a joint assembly. The lower material capacity of the carrying structure of a wagon, under observance of the conditions of strength and operational reliability, can be achieved with the use of circular tubes in the carrying structure elements. Previous research enabled us to conclude that such implementation could decrease the tare weight of a wagon by 3–5% in comparison with that of a prototype wagon. However, the problem of determining the fatigue strength under operation remains unsolved. It is known that one of the most considerable loads on a wagon in operation is the dynamic load, and the main devices absorbing the kinetic energy that affects the carrying structure of a wagon are automatic couplers or buffer devices. However, they cannot fully absorb the kinetic energy under increased normative values of dynamic loads. It causes damage to the carrying structures of wagons in operation and requires off-schedule repairs. Therefore, there is a need to develop and implement new draft gear concepts for rail vehicles. Appl. Sci. 2020, 10, 7441; doi:10.3390/app10217441 www.mdpi.com/journal/applsci Appl. Sci. 2020, 10, 7441 2 of 11 Appl. Sci. 2020, 10, x FOR PEER REVIEW 2 of 12 The structural and design features of a universal long-base wagon for intermodal transportation in EuropeThe are structural presented and indesign [1], whichfeatures provides of a universal the results long-base of strengthwagon for calculations intermodal transportation for the carrying in Europe are presented in [1], which provides the results of strength calculations for the carrying structure of a wagon. However, the study does not propose any measures to decrease the dynamic structure of a wagon. However, the study does not propose any measures to decrease the dynamic load under operation at the design stage. load under operation at the design stage. The Department for Mechanics and Applied Information of the Military University of Technology The Department for Mechanics and Applied Information of the Military University of (Poland) has developed a specialized wagon with a low rotary loading platform [2]. 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The results of the structural finite element analysis of a freight wagon using the finite element The results of the structural finite element analysis of a freight wagon using the finite element method are presented in [7]. The research was conducted using the BOXN25 open wagon used by method are presented in [7]. The research was conducted using the BOXN25 open wagon used by IndianIndian Railways. Railways. TheThe objective objective of of this this study study was was to to demonstratedemonstrate some peculiarities peculiarities in in computation computation of ofthe the dynamic dynamic loadload and and strength strength of of the the carrying carrying structure structure ofof anan articulatedarticulated wagon wagon of of circular circular tubes. tubes. To To achieve achieve the the objective,objective, the the following following tasks tasks were were set: set: ToTo propose propose techniques techniques for for lowering lowering the the dynamic dynamic loadload on articulated wagons wagons in in operation, operation, • ToTo conduct conduct mathematic mathematic modeling modeling of of dynamicdynamic loads on on the the carrying carrying structure structure of ofa circular-tube a circular-tube • articulatedarticulated wagon, wagon, and and To determine the basic strength parameters of the carrying structure of an articulated circular- To determine the basic strength parameters of the carrying structure of an articulated • tube wagon. circular-tube wagon. 2. Improvement of the Draft Gear for Articulated Circular-Tube Wagons 2. Improvement of the Draft Gear for Articulated Circular-Tube Wagons The absorber of the autocoupling device of the wagon is designed to mitigate the longitudinal The absorber of the autocoupling device of the wagon is designed to mitigate the longitudinal (tensile and compressive) forces arising in the train during operation and transfer them to the (tensile and compressive) forces arising in the train during operation and transfer them to the supporting supporting structure of the car. Sh-2-V-90 draft gears are used on wide-gauge freight wagons (Figure structure1). of the car. Sh-2-V-90 draft gears are used on wide-gauge freight wagons (Figure1). FigureFigure 1. Sh-2-B-901. Sh-2-B-90 absorbing absorbing mechanism: mechanism: 1, 1, body; body; 2,2, frictionfriction wedge;wedge; 3, pressure cone; cone; 4, 4, nut; nut; 5, 5, bolt; bolt; 6, external6, external spring; spring; 7, internal 7, internal spring. spring. Appl. Sci. 2020, 10, 7441 3 of 11 Appl. Sci. 2020, 10, x FOR PEER REVIEW 3 of 12 Appl. Sci. 2020, 10, x FOR PEER REVIEW 3 of 12 TheThe acting acting forces forces are are decreased decreased duedue toto transformationtransformation of of the the kinetic kinetic energy energy of ofthe the masses masses of the of the