Automated Inspection System for Train Wheel and Axle Defects​

Train wheels and axles are critical underframe components which are very tedious to inspect. Currently, train wheels are inspected every 3-weeks at the maintenance track in depots, while the axles are inspected every 3 to 4 years during workshop overhauls. Automated NDE systems are being developed to enable in-situ screening of the structural integrity of train wheels and axles and provide early warning of potential defects. The systems will improve the reliability and efficiency of inspection through automation and enhance the predictive maintenance capabilities of SMRT.

Inspection on train wheel defects:

Rail-embedded sensors are being investigated to inspect the train wheels as the train passes. The train is not required to be stationary on a maintenance track for wheel inspection thus enabling more frequent checks in an automated fashion. Another system inspects wheel body defects and on the wheel circumference. So far this system has been tested on the prototype rail and wheel as shown in Figure.1.  


Figure 1: Prototype of wheel and rail section


In the current design, two standard phased array probes are installed on the track.

One of them is used for defects inside the wheel body while the other one is used for surface or subsurface circumferential defects. 

A customized GUI was designed for this wheel inspection system.

Real-time A-scan and S-scan images are included in this GUI. The internal wheel body defects can be identified in the sectorial-scan image while the surface circumferential defects can be found in A-scan image as shown in Figure.2.


(A)  scan image showing surface defects


(B)  S-scan image showing internal defects

Figure 2 : Customized GUI


Inspection on train axle defects:

During overhaul, NDE inspectors in SMRT depot use several probes with different sweeping angles to inspect the axle. This manual process is tedious. A portable phased array system is designed and manufactured to replace the current inspection method as shown in Figure.3. In this design, a clamping rig with a phased array probe and encoder is mounted on the axle end. An open array control system is used. Defects in the critical area can be identified with one rotation of the probe.


Figure 3: Portable phased array system