Abstract
Reliable traction between wheel and rail is an important issue in the railway industry. To reduce variations in the coefficient of friction, so-called “friction modifiers” (carrier with particles) are used. Twin-disk tests were done with three commercial friction modifiers, based on different compositions of carrier and particles, to characterize their friction and wear behavior. It is shown experimentally that the influence of the carrier cannot be neglected just after application and very low (0.01-0.05) frictional values are observed in a fully flooded situation. However, starvation occurs quickly and friction values will become relatively stable at an intermediate level around μ=0.2 until the friction modifier is consumed and a new dose is required. After the carrier is pushed out of the running track the particles in the contact dominate the tribological performance. The level of friction is a function of total rolling distance, effective sliding length and sum velocity. The most dominant factor depends on the friction modifier and the working mechanism for friction stabilization. It is also shown that the wear rates during tests do not depend significantly on slip, which makes it possible to predict wear behavior. Wear rates are dependent on the type of friction modifier used.
Highlights
In the railway industry, friction between the wheel and rail is an important topic
Friction Modifier characterization To understand the working principle behind the different FMs the first step is to investigate their components in more detail
Graphite is present in FM C, this can not be identified by X-Ray Fluorescence (XRF) measurements as it is included in the general organic residue
Summary
The main working mechanism of these FMs is to dominate the interfacial layers present at the wheel-rail interface, sometimes indicated as the third body (Gallardo-Hernandez & Lewis, 2008; Godet, 1984; Lu, Cotter, & Eadie, 2005; Popovici, 2010). They are applied onto the rail or wheel surface and are subsequently spread out by passing trains. After a considerable amount of passages, the friction gradually increases
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