EMAT positioning

Stress control on train wheels is a key aspect of safety in the rail sector. The braking cycles of the wheels modify their stress profile from compression stress to traction stress. This traction stress can become extremely dangerous if there are small cracks on the wheel tread as these may grow bigger which eventually may lead to fracturing of the whole wheel.

To ensure a correct wheel stress, the ultrasound technology EMAT (Electromagnetic Acoustic Transducer) measures residual stress on the wheel using the physical phenomenon of birefringence. During this EMAT inspection, a sensor is moved to different points of the wheel rim to obtain the state of volumetric stress. This non-destructive technique is especially useful because of the accuracy and speed with which the measurement is carried out. However, the relative position of the sensor and the wheel is a key aspect to obtain accurate and reliable measurements of the state of stress.

IDEKO has relied on its experience to develop inspection systems to design a manual device to easily and quickly check the positioning of the EMAT sensor on train wheels. The device has the following features:
-It is easy to move and position on the wheel.
-The correct contact between the sensor and the wheel is assured because of the mechanical design.
-The sensor can be moved quickly and easily.
-The system does not require an electrical or pneumatic supply.

This new device has been tested and validated both at a laboratory level (Ideko) and at an industrial level (CAF) resulting in significant improvements in terms of accuracy, reliability and reduction of inspection time.