## 7 Conclusions  
1. The authors have proposed the FLAT RACK removable module structure and determined the optimal profile for the removable module in terms of the minimal material capacity; this profile is the rectangular tube. In this case, the parameters of the profile are determined by the resistance moment of the cross-sections of the module components. With this profile, the mass of the module is about 0.88 tons. The loading on the removable module at the operational modes can be decreased by means of viscoelastic bonds in the fittings.
2. The research included the determination of the dynamic loading on the removable module structure. The results of the calculation demonstrate that if the rigidity of an elastic element is 20 kN/m and the viscous resistance coefficient is 30 kN\(\cdot\)s/m, the accelerations to the removable module placed on the flat car during a shunting impact are about 34.1 m/s\({}^{2}\) (0.34 g). The acceleration value obtained is 15% lower than that on the removable module under the typical diagram of interaction between fittings and fitting stops, provided that it is stationary.
3. The numerical values of the accelerations to the removable module and their distribution fields are determined by means of computer modelling. The maximum accelerations are recorded in the middle part of the flat wagon and on the areas with the removable modules located behind the middle part; they amount to 30.5 m/s\({}^{2}\). The models of the dynamic loading of the removable module are verified with an F-test. It is found that the hypothesis on adequacy is not rejected.  
4. The removable module is calculated for strength. The maximum equivalent stresses are recorded in the contact areas between the side beams and fittings; they amount to 282.2 MPa and do not exceed the allowable values. In the middle parts of the longitudinal beams, the maximum stresses are about 180 MPa.
5. The research conducted can be used by those concerned about designing modern module structures for rail vehicles and enhancing the operational efficiency of rail transportation.  
Conceptualization, J.G. and A.L.; methodology, G.V., S.P. and A.L.; software, A.L.; validation, S.P., A.L. and M.P.; investigation, A.L., M.P. and K.K.; resources, S.P., A.L. and K.K.; writing--original draft preparation, A.L., M.P. and K.K.; writing--review and editing S.P. and J.G.; visualization, G.V., A.L. and K.K.; supervision, S.P. and J.G. All authors have read and agreed to the published version of the manuscript.  
This publication was issued thanks to support from the Cultural and Educational Grant Agency of the Ministry of Education of the Slovakia in the project \"Implementation of modern methods of computer and experimental analysis of properties of vehicle components in the education of future vehicle designers\" (Project No. KEGA 036 ZU-4/2021). This research was also supported by the Slovakia Research and Development Agency of the Ministry of Education, Science, Research and Sport of the Slovakia in Educational Grant Agency of the Ministry of Education of the Slovakia in the project and VEGA 1/0513/22 \"Investigation of the properties of railway brake components in simulated operating conditions on a flywheel brake stand\". The authors also gratefully acknowledge funding from the specific research on \"Innovative principles for creating resource-saving structures of railroad cars based on the refined dynamic loads and functionally adaptive flash-concepts\", which was funded from the state budget of Ukraine in 2020.  
Not applicable.  
The authors declare no conflict of interest.