1´╝ÄQuantitative assessment of the wheel flange contact shape

Information about the wheel flange/rail gage corner contact shape in sharp curves or when running through turnouts is fundamental for solving problems such as flange climb derailment, wear and noise emissions. As such an ultrasonic scanning method was developed which can be used for quantitative assessment of the wheel flange contact shape.

Ultrasonic waves passing through the contact zone of two objects made from the same material have a lower intensity response wave (echo height). In such circumstances, it is generally accepted that the reduction in echo height grows as contact pressure increases. Using this property, a system for monitoring contact shape was built (Fig.1), and a method was developed for quantitatively measuring the contact area.

This method was then applied to check the influence of the angle of attack and rail and wheel surface profiles on the contact area profile (Fig.2). It was discovered that the distribution of reduction in echo height changed along with the surface profile, and that a smooth flange surface produced a smooth distribution whereas wheel flanges chafed against rail produced a serrated distribution (Fig.3). Future developments on the ultrasonic scanning method will be aimed at improving accuracy so that it can be used as a tool for collecting essential data for forecasting wear and clarifying the mechanisms into flange climb derailments.