In the recent years train axle failures have caused incidents with major loss of life. The aim of this project is to research the feasibility of detecting axle cracks on trains using on-board self-powered monitoring. The vision is to use continuous live monitoring of axles with low cost self-powered wireless systems, that are easy to install, to replace expensive and disruptive NDT methods in maintenance sheds.
The monaxle rig is designed to allow research and development of insitu axle cracks detecting systems
The train carriage is carried on two boogies, each of which contained two axles.
Each axle is subjected to a 4 point rotating bend motion. This creates cyclic loading which can propagate any crack which may form within the axle
The MONAXLE rig is designed to test 1/3 scale axles under the same 4-point rotating bend motion
TWI have been initiating and propagating cracks into many 1/3 scaled axles using a 3 point bend (non rotating) arrangement.
At UoS the axles with known crack lengths have been run in the MONAXLE rig; multiple sensors including accelerometer, thermometers, displacement and rotation measurement devices record the axle behaviour
Perpetuum uses the recorded information from the MONAXLE rig to data mine for relationships between crack lengths and vibration frequencies – graph shows repeatability of data runs
The MONAXLE rig
In order to explore the use of accelerometers to detect the natural frequency of axles and monitor how this changes with cracks a rig has been designed and built with the instrumentation required to detect crack growth and to apply load to simulate the condition of a real train.
The objective is to enable axle inspection regimes to extend to major overhauls only; while currently axle inspections are required on every axle, every year, taking about 24 man-hours per a 4 car unit. This is expensive and disruptive to operations. This methodology will provide significant cost reductions for train operators and a greater certainty on safety.
The project is developing advanced low power sensing, signal processing and analytics using Perpetuum’s energy harvester powered sensor platform, a test rig built at the University of Southampton and key expertise of TWI Ltd. in non-destructive testing (NDT) and fatigue cracks.
Progress has been made on the sensor platform which will have to withstand a demanding rail freight vibration environment.
Initial tests have been carried out on two test axles: one with and one without a crack. The vibration data clearly show that this new technology will be able to detect the presence of cracks while the train is running. This image shows a phasogram of single axis accelerometer data collected for a cracked axle.