Main Types of Defects on Train Wheels

Railway locomotive and vehicle wheels are crucial components for ensuring the safe operation of trains, as they bear the load and provide guidance. If a wheel malfunctions, it can lead to wheel fractures and axle cutting, potentially causing severe train derailments and accidents. Therefore, detecting and maintaining wheel safety is of paramount importance.

Major Defects in Railway Wheels

• Cracks in railway wheel rims

  
  

When the train is running, a certain depth range (10 mm~20 mm) under the train wheel contact surface is the maximum distribution area of wheel-rail contact shear stress, and if there are metallurgical defects such as non-metallic inclusions in the region, the inclusions will become the source of fatigue cracks under the action of shear stress, and then the fatigue cracks continue to expand. 

Wheel-rail contact shear stress is inherent in the wheel pair when the train is running, when the crack source nucleates and prompts the crack to sprout under the action of shear stress, the faster the train runs, the faster the crack expansion will be, when the crack develops to a larger size of the rapid expansion stage, the crack will develop to the outer side of the wheel rim, the inner side or the tread surface, such as not detected in time will result in the wheels ‘falling block If not detected in time, it will cause the wheel to ‘fall off the block’. This type of defect is called rim crack.

Fatigue cracks on rail wheel rims

Railway wheel rims falling out

From the open rim crack defect it is clear that the rim crack defect has a fatigue source and a fatigue extension process (shell crack). From the development process of the rim crack, it expands along the circumference of the wheel, so it is called a circumferential defect.

• Cracked rail wheel

Radial chipping of wheels due to abnormal strong braking, internal metallurgical defects in the wheels or defects in the manufacturing process may cause train upsets in train operation.

Train wheel cracks along the direction of the wheel diameter, known as radial defects.

Ultrasonic flaw detection process for train wheel defects

• Detection of circumferential cracks

According to the principle of ultrasonic flaw detection, the ultrasonic reflection energy is maximum when the ultrasonic wave is perpendicular to the crack surface. Ultrasonic waves incident along the radial direction of the wheel is exactly perpendicular to the circumferential defects. Therefore, the use of ultrasonic radial incidence detection of wheel circumferential defects

• Detection of radial defects

Detection using conventional ultrasound transverse waves