"Does god play dice with corrugations?": Environmental effects on growth

Corrugation growth has perplexed many researchers for several decades with remaining challenges including it's reliable prediction in the field. In the present paper, the effect of environmental variations on corrugation growth are investigated using field measurements and mechanics-based modelling. Specifically, relationships between average daily rainfall, humidity and the growth of rail corrugation were observed by comparing weather data to results from the monitoring of longitudinal rail profileon a metropolitan network test site with a recurring rail corrugation of about 95mm wavelength. Corrugation growth rate (Gr ) was determined by systematically measuring the rail profile with a Corrugation Analysis Trolley (CAT)on the 240m radius, narrow gauge, concrete-sleepered curve. The weather data used was obtained from records held by the Bureau of Meteorology. The modelling is used to provide insight and mechanics based analysis of the field corrugation growth under changes in environmental conditions and vehicle speed variability. Results show a strong correlation between rainfall and corrugation growth that is consistent with changes in steady state wear. Contact patch widening as the corrugation amplitude grows is shown to be an important effect. The results are used to explain observed changes in corrugation growth rate under variable speed control at the same site.