# Enhancing Railway Network Safety by Reproducing Wheel-Rail Electrical Contact on a Laboratory Scale
## 1 Introduction  
The accurate localization of trains on railway tracks is crucial for ensuring the safety of railways. This is achieved through a technical device called the \"track circuit\", which provides real-time information about the presence of the train within a specific track section. When a train enters this zone, its wheels and axle create a short circuit between the two rails, indicating the occupancy of the zone. The signaling systems can be activated accordingly. Maintaining a high-quality wheel-rail contact is therefore a major issue for ensuring the reliability of the track circuit system and hence track safety. If this contact is affected by a third body of natural or artificial origin present in the interface, train detection can be jeopardized for a certain period, leading to the phenomenon known as \"deshunting\" where the train's presence is no longer detected. Despite the implementation of various devices to prevent [1] or reduce the occurrence of deshunting, many instances are still being detected every year. The significant impact that deshunting events can have on railway management and on the occurrence of potentially dangerous situations, such as level crossing failures and rail accidents, has forced researchers to focus their attention on studying the behavior of the wheel-rail electrical contact interface. The wheel-rail contact is a very complex and multiphysical subject. In [2, 3], the detection and impact of the mechanical deterioration ofthe wheel rail was studied. The composition of the third body present at the wheel-rail interface may be complex, since it can include both external contaminants (dead leaves, frost, sand, oil...) and oxides formed naturally on surfaces [4]. Regarding oxides, composition was investigated using in situ X-ray diffraction. On the rail head, iron oxide, particularly in the form of FeOOH and Fe\({}_{3}\)O\({}_{4}\), is the most dominant species [5]. Furthermore, [PERSON] et al. provide a surface analysis by examining the concentration of oxide near the contact surface and the composition of both oxide and hydroxide [6]. In [7], the mechanical and electrical aspects of the third body (oxide layer) formed in the wheel-rail contact interface are examined through tribological, morphological and microscopic analyses. The study investigates the electrical conductivity, heterogeneity, continuity and compactness of the third body under both good and poor shunting conditions. Additionally, [PERSON] et al. establish that several factors, including normal load, current intensity, oxide layer thickness and traffic frequency, can jointly influence the contact resistance [8]. A better understanding of wheel-rail electrical contact was also obtained through studies that were carried out on a 1/4 -scale test rig and on-site using an instrumented regional train [9; 10]. These studies highlighted the non-linear \(U-I\) characteristics, which are strongly dependent on the presence of oxide at the contact interface. These results show that scaled-down tests are in fact significantly representative compared to full-scale tests, demonstrating the relevance of performing such experiments. However, conducting tests at full-scale or even 1/4 -scale can be both cumbersome and costly, becoming an obstacle to rapid progress in this area of research. The aim of this work is to develop a laboratory-scale rolling contact test bench that reduces the complexity and cost associated with conducting these experiments while faithfully reproducing wheel-rail electrical contact on a reduced scale. By analyzing various aspects of contact under reproducible conditions (controlled speed, load and oxidation state), we seek to improve our knowledge of the deshunting phenomenon. This paper focuses on the study of the influence of oxidation since it is one of the major causes of deshunting. The first performed tests to validate the bench consisted of investigating the resistance behavior in relation to different parameters such as load, current and time.