## 6 Results and Discussion  
The authors of the article propose using the removable module design in order to increase the efficiency of rail transportation. The peculiarity of the removable module is its rectangular-pipe components and elastic-viscous fittings, which will help to reduce the loading of the removable module in operation. The profile of the removable module is chosen through its calculating as a rod system on hinged fixed supports. The results of the calculation have made it possible to determine the resistance moments of the module cross-sections. With this in mind, a rectangular pipe is selected as the profile of the removable module (Figure 7). Such an intersection is chosen due to the fact that it has a better resistance moment compared to the typical profiles of vehicles: I-beam, channel, lane, etc. For example, in comparison with an I-beam profile of the same height as a rectangular pipe, the resistance moment of the rectangular pipe is almost 20% greater. To determine the dynamic loads on the removable module, the authors have proposed mathematical model (3). The model's limitation is the absence of vertical movements of the flat car with removable modules in the vertical plane, that is, jumping oscillations. In addition, the model does not include possible movements of the freight relative to the removable module. This assumption will be taken into account in subsequent studies by the author's team. The results of the solution to the mathematical model have made it possible to determine the accelerations to the removable module and include them as a component of the  
Figure 14: Stress–strain state of the removable module. Figure 15: Distribution of the stresses along the side beam of the removable module (I is the length of the removable module). dynamic loading when calculating the structural strength. The acceleration value obtained is 15% lower than that on the removable module, if one takes into account the typical diagram of interaction between fittings and fitting stops and if it is stationary. It should be noted that the model is verified by the F-criterion. The results of the calculations for the removable module strength have showed that the maximum stresses in the structure are 282.2 MPa and they do not exceed the permissible values (Figure 14). These stresses occur in the areas of interaction between the side beams and the fittings. Additionally, the stress concentration in the corner parts of the module is avoided due to the fact that the fitting is solid, and the longitudinal beam is made of a pipe with a smaller moment of resistance than that of the fitting. Therefore, maximum stresses occur precisely in these areas. The advantage of this study, in comparison with [8, 9], is that the design of the removable module can reduce the dynamic loading on it due to the elastic-viscous bonds in the fittings. Unlike works [10, 11, 12, 13, 14], the introduction of flexible bonds is implemented not in the design of traction vehicles, but in a modular-type vehicle intended for transportation by various modes of transport, including international transport. In contrast to work [15], the reduction of the dynamic loading on the removable module is achieved by introducing elastic-viscous bonds in the fittings, rather than elastic-friction ones. In addition, the main load-bearing frame elements of the removable module are made of rectangular pipes, and not of U-shaped profiles with resilient elements inside overlapped by horizontal sheets, which significantly complicates the design, and, accordingly, its maintenance and repair. If compared to [16], the vehicle strength is improved not by introducing materials with improved strength characteristics, but by reducing dynamic loads. A further area of this study is to determine the feasibility of using lightweight fillers in the removable module components to further reduce its load in operation. In addition, the issues of experimental determination of the strength of the removable module require attention.