Synthesis of random vibration environment spectra for the fatigue analysis and optimization of railway vehicles

Abstract

In railway vehicle environments, mechanical and electronic equipment are subjected to repeated environmental vibration loads. A possible qualifying method for such loads involves shock and vibration tests utilizing shakers or simulations. However, the input excitations provided by shakers considering standards such as IEC 61373 cannot reflect the real vibration environment, especially considering wheel/rail wear and wheel polygons. Considering these shortcomings, an environmental vibration profile synthesis method using field-tested power spectral density (PSD) data and a corresponding fatigue prediction model were proposed in this study. For the non-normally distributed vibration data of railway vehicles, the Johnson transformation was applied to calculate the upper tolerance limit of the profile. Then, the pseudo-excitation method was introduced to connect the synthesised spectrum to the simulation model, and the calculation procedure using a vibration fatigue algorithm was investigated. To validate the proposed methods, the potential causes of failure, fatigue damage, and optimisation of a shackle on an axle box were investigated using the proposed methods. The results show that the synthesised PSD can reflect the characteristics of environmental vibrations, including the additional excitation of rail wear, and compared with the fatigue results of the tests and simulations conducted under the standard spectrum, the predicted results under the synthesised spectrum were determined to be most similar to real-world scenarios, while the use of the standard spectrum exhibited infinite life. In addition, the potential advantage of optimisation using a synthesised spectrum instead of traditional transmissibility is presented and supported by the results of this case study.