## 2 Analysis of Recent Research and Publications  
An improvement in the hopper wagon model 19-9862 bearing structure to ensure strength was carried out in a work [4]. At the same time, strengthening the junction of the end-wall last vertical and middle columns with the transverse angle fitting of the inclined end wall was proposed. The grounds for extending the service life of hopper wagons were provided in the paper [5]. The research was carried out on the example of a hopper wagon model 19-6930. However, the authors did not pay attention to the modernization of the hopper-wagon-supporting structure to increase the efficiency of its operation. Features of the innovative hopper wagon design, developed by \"The Greenbrier Companies\", were presented in the paper [6]. Unloading of the proposed wagon body was carried out in 30 s by using an automatic system. It was possible to adjust the flow rate of the cargo. However, this wagon was not adapted to the transportation of high-temperature goods by rail. The works [7; 8] were devoted to the creation of perspective freight wagon designs. The authors presented the spatial models of the wagons and the results of their strength analysis. At the same time, these wagon designs were adapted to the transportation of the assigned cargo nomenclature, which reduced their demand on the transportation market. Features of the construction of the freight wagon made from composite panels were presented in the publication [9]. To reduce the corrosion wear of the wagon body components, it was suggested to cover them with anti-corrosion materials. At the same time, it was interesting to apply the proposed modernization to the hopper wagon for transporting hot pellets. To improve the hopper wagon body, using circular pipes as the main structural elements was proposed in the paper [10]. The results of strength analysis were given. However, the proposed hopper wagon design did not allow the simultaneous transportation of various types of cargo in it. That is, the wagon was highly specialized and was designed to transport a specific type of cargo, which reduced its demand in operation. The grounds of the introduction into operation of an articulated-type hopper wagon with bearing elements in the form of circular pipes were put forth in the paper [11]. The results of determining the bearing structure of the hopper wagon confirmed the reasonability of the decisions made during its designing. However, the proposed wagon design also did not allow the simultaneous transportation of various types of cargo in one section. In the work [12], the development and optimization of the technological process of vacuum infusion for the manufacture of hopper wagons using polymer composite materials were considered. The research was carried out in relation to the hopper wagon model 19-5167. The use of polymer composite materials in body and roof components was substantiated. The issue of optimizing the hopper wagon design using functional honeycomb sandwich panels was considered in the publication [13]. It was established that the proposed methodology allowed reducing the material capacity of the hopper wagon by more than 16% compared to the prototype. However, the proposed hopper wagon designs did not allow the simultaneous transportation of various types of cargo in them, which reduced their operational efficiency. Features of the use of promising materials in railway car building were presented in the paper [14]. Extruded elements that make up the wagon body were developed using an optimization algorithm. The results of numerical modeling were presented. The design of the railway wagon body made of aluminum panels was considered in the publication [15]. When carrying this out, structural optimization was applied. The proposed body design helped to reduce its weight. However, these wagon designs did not provide the possibility of the simultaneous transportation of various cargo types.