FMEA analysis of pneumatic suspensions


Failure mode analysis of pneumatic suspensions

In this project, we have shown how the failure modes of the pneumatic suspension of a metro car can be analysed using computer models. The modelling approach is explained in details in the Pneumatic Suspension modelling project: it relies on the mass and energy balance equations for the air springs and the tanks and on mass flow formulations for the pipes and the valves. The pneumatic model of the suspension was coupled to a multibody model of the vehicle using a co-simulation approach in order to analyse and to understand the behaviour of the whole vehicle when a leakage appears in the pneumatic circuit. In particular, the wheel unloading has been calculated for more or less important leakages and it has been shown that the most critical case does not correspond to the largest leakage.

This approach is not limited to a specific failure mode and it can be applied to several situations such as:

  • a leakage in one element or at the connection of two components,
  • a levelling valve locked in constant admission or in constant exhaust,
  • a levelling valve not functioning or locked in neutral position,
  • a safety valve locked in neutral position or in constant exhaust.

For instance, the safety of the vehicle can be assessed if the failure occurs when passing through a curve. However, the large number of possible combinations makes this work tedious. Nevertheless, such an analysis should be perform as soon as possible in the design process of the suspension. This is why the present approach is used forestablishing the feasibility of novel suspension design inspired from an automotive suspension design which has shown promising results for railway application. The robustness of this solution with respect to failure mode has now to be checked to guarantee the possibility of a practical implementation.