Rolling–Sliding Laboratory Tests of Friction Modifiers in Leaf Contaminated Wheel–Rail Contacts

Abstract

Leaf-related adhesion problems have been present in many railway networks all over the world in the last few decades. Since the early 1970s many measures have been undertaken in order to mitigate the problem. One of the measures adopted by many railway networks is the use of friction modifiers. However, the low adhesion problem still persists. Furthermore, the effectiveness of these friction modifiers has not well proven yet due to the lack of research in controlled conditions. Consequently, the rolling stock operators and infrastructure managers do not clearly understand the performance and side effects of the friction modifiers used on their networks. In this paper, an investigation of the performance of two existent friction modifiers in controlled laboratory conditions is presented. These friction modifiers have been used or tested in several railway networks. A twin-disk roller rig has been used to study their performance in leaf contaminated contacts. The adhesion characteristics of both friction modifiers are examined for different slip ratios. The constituents of the friction modifiers are identified and the solid components are analyzed. In addition, damage that these friction modifiers may cause to wheel and rail is also discussed.

Wheel-rail creep force model for predicting water induced low adhesion phenomena

“…In Great Britain during the autumn period (from October to November) numerous incidents, such as "station overruns" and signals passed at danger (SPADS) occur every year which are related to low adhesion conditions [RSSB T1042]. For about half of the incidents an autumn leaf contamination has been reported [RSSB T1042] which is known to cause low adhesion [Cann 2006, Oloffson 2004, Arias-Cuevas 2010, Li 2009, GallardoHernandez 2008. A proportion of the other half were related to small amounts of water on the rail head caused by prevailing environmental conditions.…”

Influence of Different Application of Lubricants on Wear and Pre-existing Rolling Contact Fatigue Cracks of Rail Materials

“…If oil and water are present together (regardless of amount), oil has the dominating effect and adhesion coefficient remains at low levels similar to having oil alone [21]. At present, many friction modifiers (FM) have been used to improve the friction level of the wheel/ rail interface [22,23]. The wheel/rail interfacial friction coefficient is strongly dependent on the rheological properties of third-body layer from different FMs.…”

Tribology of the wheel–rail contact – aspects of wear, particle emission and adhesion

“…Leaf fall can also cause a lot disturbance to traffic on the network [45]. Research into leaf contamination and low adhesion has been carried out using various methods including actual trains [67], pin-on-disc [58,68], twin-disc [69,70] and ball-on-disc [71] test rigs. A comparison of these tests was discussed in [72], and is shown in Table 4.…”

“…It was pointed out that with increased thickness of the oxide layer on the railhead surface the friction coefficient reduces [72] although no definitive relationship was found between leaf contamination thickness and the friction levels [64]. [68] GallardoHernandez and Lewis [70] Li et al [69] Cann [71] Arias-Cuevas and Li [67] Test apparatus Pin-on-disc …”