# Measurement Repeatability of Rail Wheel Loads Caused by Rolling Surface Damages
## 1 Introduction  
Track failures or rail vehicle derailments represent approximately 50% of overall accidents in railway transport [1]. The majority of the track integrity problems are related to the track geometry or gauge distortion. Other factors that harmfully impact on properness of wheel-rail contact are badly repaired running gear, discrepancy of rails, and critical dynamical impacts (such as high tractive and braking forces of trains). Furthermore, some railway traffic accidents happen due to the diminishing of reliable wheel/rail contact and due to the unsatisfactory stability of rolling-stock running [2]. The parameters and shape of the rolling surface of the rail wheel mainly influence the technical condition of rolling stock running gear. The \"wheel-rail\" contact transfers high vertical static and dynamic loads to the vehicle and the track [3]. As the wheel rolls, high-impact loads are created by track irregularities and rail junctions [4]. During rolling-stock exploitation, the interaction between the wheel and the rail may cause damage to the rolling surface of the rail wheel [5]. They can also be caused by manufacturing inaccuracies [6] or poor machining [7]. It should be noted that the occurrence of damage is most affected by braking and track surface irregularities [8]. The damage of the wheel rolling surface is very destructive to the upper track structure. It can also cause wheel cracks and derailment of the wagons [9]. Polish scientists [PERSON] et al. defined the dynamical properties of the driving train and evaluated the technical state of the rail track by using proprietary measurement software and a mobile device. Authors proposed useful metrics to describe the dynamical properties of the driving train [10]. Strikes of damaged wheels produce high noise and vibrations that impair passengers' comfort [11]. Vertical interactions of the wheel with the rail acquire an impact character when the wheel is damaged. These studies require unique methods since the processes under investigation have a higher frequency [12]. Polish scientists [PERSON] et al. defined the dynamical properties of the driving train and the evaluated the technical state of the rail track by using proprietary measurement softwareand a mobile device [13]. Furthermore, authors proposed useful metrics to describe the dynamical properties of the driving train. [PERSON] et al. considered the impact of rail damage on vibration waveforms and vibroacoustic spectrum images of vibrations. The major source of railway vibration is the structural vibration of the wheel and rail, which is generated by the combination of small-scale undulations on the wheel and rail contact surfaces. The inevitable vibration transmitted by running rail vehicles through the rails and wheels causes and propagates various cracks in the metal of running gear elements. The authors revealed the amplification of the signal from the Ai3 sensor located near the damaged place where the frequency oscillated around 4000 Hz, while the spectral analysis of the signal for the Ai2 sensor located 5.4 m away to the damage indicated oscillating values in the range from 50 to 500 Hz [14]. Depending on the train's speed, the maximum duration of the force is in the order of several milliseconds. The ATLAS-LG subsystem of wayside equipment is used by Lithuanian Railways (LTG) to detect and prevent damage due to their impact. ATLAS-LG type systems are used by Lithuanian and Swiss Railways and are designed to avoid traffic accidents. These systems detect passing wagon running gear that causes vertical impact loads on the rail track, which can be caused by damage to the wheel rolling surface (e.g., flat, crack, uneven wear, and \"out-of-roundness\"). Worldwide rigorous research activities are targeting not only security. A high level of safety and reliability of infrastructure systems also aims to diminish the problems associated with the degradation of performance in terms of train-ride quality and stability, passenger comfort, etc.