# Experimental Studies on the Strength of a Flatar during Shunting Impacts
## 4 Experimental Determination of the Strength of the Flatar  
The strength of the bearing structure of the flatcar during a shunting collision was determined by means of full-scale tests in accordance with the \"Programs and methods for testing the bearing structure of the flatcar\". This document was developed by the authors' team and approved by the Research and Engineering Institute of Railway Transport under JSC Ukrzaliznytsia. The test objects were a model 13-401M flatcar and two containers. It is important to say that the developed \"Program and methodology of testing\" can be used for other versions of flatcars and containers. The flatcar and containers were selected from those available at the station at which the tests were carried out. They were cleaned of dirt, and the remains of the cargo were transported and transferred for a technical inspection in order to prepare the relevant acts of selection and identification. The representatives of the Department of Commercial Work and the authors of the article were attended. During examination, selection, and identification, the flatcar and containers were checked for defects, such as deformations, fractures, wear, bends, deflections, corrosion, breaks, loosening of fastening of nodes and parts, holes, and cracks. The results of examination were used to establish that the flatcar and containers to be tested were fully repaired and in working condition. The collision tests to determine the strength of the structural elements of the flatcar loaded with containers were carried out during daylight on a straight horizontal section of the railway track using a locomotive. Moreover, the following equipment was used:  
* Hammer wagon, the weight of which was more than the weight of the car under study;
* Several freight cars (open wagons), the movement of which was restricted by rail shoes;
* Dynamometric wagon with appropriate equipment (on the adjacent track). At the same time, the difference between the axles of the automatic couplers of the car under study and those of the hammer wagon did not exceed 50 mm. When wagons collided, the largest longitudinal force in the automatic coupler was in the range of the normative force value, i.e., 3.5 MN. Figure 4: Stress state of the flatcar frame. The procedure and technology used to prepare the car for the tests included the condition of the maximum technical compatibility and safety of all operations stipulated by the program. The condition at which the test must be finished was to obtain the complete set of experimental data assigned by the test program or disruption of the integrity of the flatcar structure that might threaten the safety of tests. Only those qualified and certified as required were permitted to the tests. The appropriate requirements regarding all stages of the tests were presented in the normative technical documentation on labor protection, fire and industrial safety, etc. All operations on determining the strength and dynamic indicators of the bearing structure of the flatcar under a typical diagram of interaction between the fixed fittings and container fittings were performed by the authors' team. All operations on shunting were conducted by workers of the station or wagon depot. All those involved in the tests were briefed on labor protection and safety and appropriately registered in the test log before the testing. Only after that did the testing on the flatcar begin. During the tests, the flatcar was loaded with coiled steel (Figure 5). The gross weight of the freight was identical to the gross weight of two containers. The maximum stresses in the flatcar frame were determined with the method of strain gauging. The strain gauges were installed on the flatcar as presented in Figure 6. As far as it was technologically difficult to determine the stresses in the fixed fittings, the strain gauges were installed on the most loaded frame elements of the flatcar. They were found using the stress distribution fields in the flatcar frame by means of the FEM. Their resistance was checked before testing.