Judicious selection of available rail steels to reduce life-cycle costs

Abstract

The rate of rail degradation and hence its expected life is not uniform throughout any railway network and is governed by a combination of track, traffic and operating characteristics in addition to the metallurgical attributes of the rail steel. Consequently, it is suggested that any route or network is not a single linear asset but is a compilation of individual segments with different track characteristics, degradation rates and expected life spans. Thus, the choice of rail steel grade to maximise life (and minimise life-cycle costs) needs to combine knowledge of the metallurgical attributes of the available rail steels with the conditions prevailing at the wheel–rail and vehicle–track interfaces, whilst also considering the economic costs and benefits of the different options. This paper focuses on the classification of the susceptibility to rail degradation in various parts of a mixed-traffic network using vehicle dynamics simulation. The metallurgical attributes of the currently available rail steels are summarised along with an assessment of the life-cycle costs and wider economic implications associated with selection of a rail steel which provides improved resistance to the key degradation mechanisms of rolling contact fatigue and wear. Overall, the proposed methodology, which incorporates engineering, metallurgical and economic assessments, provides guidance on the circumstances in which the introduction of alternative rail steels make sense (or not) from an economic perspective.