# Measurement Repeatability of Rail Wheel Loads Caused by Rolling Surface Damages
## 6 Conclusions  
Rolling stock wheelsets oscillate on the rail track, so the wheel-rail contact points are never on the same circle of the wheel rolling (contacting) surface. As a result of these processes, the wheel damage contacts the rail at different surface points at each moment, and the vertical impact force changes. During rolling-stock operation, it is impossible to determine which of the measured values of the impact force is the most accurate. The scattering field of the values is obtained during the measurements, and a methodology is required to process it. The investigation reveals that the box and whisker method is well-suited for analysing the scattering field of force measurement results.  
The ratio of the total width of the two middle quartiles and the median is proven as the suitable indicator for assessing the effect of the car wheel clearance on the repeatability of vertical force measurements.  
The authors reveal that of all the various factors that affect the repeatability of the measurement of wheel vertical force, speed is the only factor that has an obvious correlation. For other factors (e.g., type of measuring system, nature of wheel damage), no clear correlation is observed during the study.  
The other disclosed aspect is that decreasing the running speed from 80 km/h to 50-60 km/h does not strengthen the correlation between the wheel damage nature and the repeatability of vertical force measurement. Greater reducing levels of train speed were applied to improve the quality of wagon wheel damage nature impact identification. Reduction in the train speed from 80 km/h to 30-40 km/h reduces the value of the indicator \(Q_{M}\) proposed by the authors by 1.5-2 times.  
When operating the rolling stock and knowing the conditions under which the values of \(Q_{M}\) are the lowest, the repeatability of measurement of wheel/rail vertical forces is the highest.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**The First Iteration of Force Testing**} & \multicolumn{4}{c}{**The Second Iteration of Force Testing**} \\ \cline{2-10}
**Speed,** & \multicolumn{2}{c}{**Max Forces**} & \multicolumn{2}{c}{**Mean Forces**} & \multicolumn{2}{c}{**Max Forces**} & \multicolumn{2}{c}{**Mean Forces**} \\ \cline{2-10}
**km/h** & **Loaded** & **Unloaded** & **Loaded** & **Unloaded** & **Loaded** & **Unloaded** & **Loaded** & **Unloaded** \\  & **Wagon** & **Wagon** & **Wagon** & **Wagon** & **Wagon** & **Wagon** & **Wagon** & **Wagon** \\ \hline
30 & 0.045 & 0.244 & 0.040 & 0.034 & 0.110 & 0.207 & 0.021 & 0.043 \\
40 & 0.192 & 0.166 & 0.030 & 0.100 & 0.376 & 0.117 & 0.063 & 0.040 \\
50 & 0.122 & 0.124 & 0.043 & 0.172 & 0.629 & 0.217 & 0.080 & 0.035 \\
60 & 0.224 & 00.13 & 0.026 & 0.126 & 0.411 & 0.124 & 0.041 & 0.016 \\
70 & 0.147 & 0.362 & 0.101 & 0.114 & 0.432 & 0.156 & 0.087 & 0.048 \\
80 & 0.109 & 0.118 & 0.108 & 0.110 & 0.606 & 0.132 & 0.110 & 0.176 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Summarized \(Q_{M}\) values.  
Figure 28: Normalized \(Q_{M}\) values according to the running speed.  
In the future, the authors plan to study the repeatability of measurement results of systems operating on other principles. Furthermore, a limitation of this research is the incompatibility of the measuring systems ATLAS-LG and IC VEIP with other diagnostic systems used in railways. This devise incompatibility causes the low reproducibility of the results of the present study.  
Methodology, conceptualization and writing, G.V.; supervision, G.B.; investigation and formal analysis, S.S. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
For commercial reasons, more detailed research data is not disclosed.  
The authors declare no conflict of interest.