Operating load measurement and assessment of fracture mechanics
Customer: RAlpin AG, Switzerland
Project tasks
- Operating load measurement
- Wheelset shaft calculation
- FE calculation
- Fracture mechanics assessment
Our approach
The customer required two fracture mechanics analyses. On the one hand, the aim was to investigate what causes cracks to form on the back of the wheel flange and which factors contribute to crack growth. On the other hand, there was a need to provide a mathematical basis for the specified inspection interval for the wheelset shafts. Real operating load data should be used as the basis for the fracture mechanics investigations of PROSE.
PROSE carried out an unaccompanied measurement to record the operating loads on the routes travelled. For this purpose, a measuring system was installed directly on a bogie frame. This recorded the position of the vehicle combination over several days using an associated GPS antenna as well as the lateral and vertical acceleration and the rotational speed of the bogie using appropriate sensors. The measurement signals were continuously sent to a central storage unit via the mobile phone network. The real operating loads measured in this way formed the basis for the subsequent fracture mechanics tests.
The wheel disc cracks were investigated using two wheel types used by the customer. The load on these wheel types was simulated using MBS simulation based on the real load data.
To assess the fracture mechanics of the wheelset shafts, a wheelset shaft calculation according to EN13103-1 was carried out in a first step for orientation and to assess the general utilisation of the wheelset shaft. In a second step, cyclic crack propagation calculations were carried out at the critical shaft positions (positions with the highest bending stresses).
Customer benefit
Our fracture mechanics tests confirmed that the cracks in the wheel discs were not caused by braking behaviour or contact with the wheel control arm. Residual stresses were identified as a possible cause of the crack propagation. However, the fracture mechanics assessment of the wheelset shaft also confirmed that the existing test interval provides sufficient safety.
PROSE’s neutral and independent position and in-depth technical understanding gave the customer a solid starting point for further investigations. By utilising data from operational load measurements, the investigation could be tailored to real operating conditions, improving the quality of the results and increasing the client’s confidence in the findings. PROSE’s unique railway engineering expertise and extensive experience with rolling stock provides a bespoke, unbiased analysis that supports effective decision-making and long-term asset management.