Real-Time Measurement of Dynamic Wheel-Rail Contacts Using Ultrasonic Reflectometry

Abstract

The contact condition between the wheel and the rail is paramount to the lifespan, safety, and smooth operation of any rail network. The wheel/rail contact condition has been estimated, calculated, and simulated successfully for years, but accurate dynamic measurement has still not been achieved. Methods using pressure-sensitive films and controlled air flow have been employed, but both are limited. The work described in this paper has enabled, for the first time, the measurement of a dynamic wheel/rail contact patch using an array of 64 ultrasonic elements mounted in the rail. Previous work has successfully proved the effectiveness of ultrasonic reflectometry for static wheel/rail contact determination. The dynamic real-time measurement is based on previous work, but now each element of an array is individually pulsed in sequence to build up a linear measurement of the interface. These cross-sectional, line measurements are then processed and collated resulting in a two-dimensional contact patch. This approach is able to provide not only a contact patch, but more importantly, a detailed and relatively high-resolution pressure distribution plot of the contact. Predictions using finite element methods (FEM) have also been carried out for validation. Work is now underway to increase the speed of the measurement.

Real-time non-invasive measurement and monitoring of wheel–rail contact using ultrasonic reflectometry

“…Dynamic measurements showed good agreement with static test measurements and Hertz theoretical predictions in terms of general contact pressure levels. In contrast to previous work [17,18], the pitch-catch strategy achieves a truly non-invasive method of monitoring wheel-rail contact conditions, and no modification to the to the rail structure is required. With relevant software and hardware upgraded, the new approach is expected to characterise and monitoring contacts between the instrumented rail track and all passing train wheels on operating high-speed lines.…”

“…Ultrasonic reflectometry, however, has proved useful for machine–element contact measurements 15 and particularly for static wheel–rail contact determination. 16,17 A high-resolution characterisation technique for wheel–rail contacts using a 64-element ultrasonic array has been developed in previous work by Brunskill et al 17 and Zhou et al 18 Yet unlike conventional ultrasonic methods for defect detection, where defects can be indirectly inferred through inspection data or can be reached easily with guided waves, characterisation of contacts needs ultrasound beams striking precisely at the contact interfaces, whereas for the longitudinal elastic body waves normally used in this scenario, structural modifications of contact bodies are usually essential for proper sensor displacement. 18 In most cases, such modifications are strictly forbidden in railway engineering and hence limit the applicability of the technique.…”

“…16,17 A high-resolution characterisation technique for wheel–rail contacts using a 64-element ultrasonic array has been developed in previous work by Brunskill et al 17 and Zhou et al 18 Yet unlike conventional ultrasonic methods for defect detection, where defects can be indirectly inferred through inspection data or can be reached easily with guided waves, characterisation of contacts needs ultrasound beams striking precisely at the contact interfaces, whereas for the longitudinal elastic body waves normally used in this scenario, structural modifications of contact bodies are usually essential for proper sensor displacement. 18 In most cases, such modifications are strictly forbidden in railway engineering and hence limit the applicability of the technique. Facing this concern, in this article, a truly non-invasive pitch–catch ultrasonic array sensing technique is proposed for characterising real-time dynamic wheel–rail contact, where relatively abundant contact information can be obtained without any pre-machining or modification to the rail structure.…”

Transitions in rolling-sliding wheel/rail contact condition during running-in

“…Recently, dynamic ultrasonic measurement of a rolling-sliding contact has been achieved [25] [26]. Using this method, the dynamic contact in rolling-sliding can be obtained for repeated cycles.…”

“…Following these measurements, a comparison between contact stiffness and traction coefficient was carried out. Figure 1 shows a schematic diagram of the full-scale dynamic wheel/rail contact rig [25] [27], which was equipped with a full-scale wheel loaded onto a traversing rail. It could apply a normal force of up to 200 kN and tangential force of up to 60 kN using servocontrolled hydraulic cylinders.…”