Application of Fatigue Crack Growth Prediction Models under In-Service Loads of the Side Beam of the Railway Bogie

In recent years, some railway accidents including train derailment and serious incident occurred due to the deformation of the bogie frame caused by the fatigue crack. In those accidents, cracks had initiated in the bottom plate of the side beam of the bogie frame and had propagated by cyclic loadings. Thus, the fatigue crack growth prediction under in-service loads in the bottom plate of the side beam is being emphasized. In this study, to examine the fatigue crack growth prediction models under in-service loads acting on the bottom plate of the side beam, crack propagation tests under constant amplitude loading and variable amplitude loading were conducted using the center cracked tension specimens made of the steel commonly used in bogie frames. In addition, the crack growth rates under in-service loads were predicted using some crack growth prediction models based on the equations for estimating crack growth rates. Afterwards, the test results and the prediction results were compared to consider suitable prediction models that match the test results. As a result, it was considered that the fatigue crack growth prediction model applying the modified miner’s law about the effective stress intensity factor range is in good agreement with the crack propagation test results under in-service loads acting on the bottom plate of the side beam.