Fatigue Life Prediction of CRH3 Carbody Based on Rigid-Flexible Coupling Model and the Master S-N Curve

The fatigue problem is significant for the vehicle safety, especially the fatigue failure of weld joint can result in a serious safety problem along with a fast speed promotion. For the purpose of fatigue life predicting in the early design stage, a middle trailer car of CRH3 EMU (Electric multiple unit) made of Aluminum Alloy Extrusions was researched as an example, its finite element model of mid trailer EMU carbody was built, the strength was performed by use of the finite element method, and the computed results were compared with the test ones, therefore the validity of finite element model was verified. Then, by use of the improved modal synthesis method called the Craig-Bampton, the motion equations of the flexible carbody was built, this motion equations was integrated into the ADASM/Rail software, then a rigid-flexible coupling dynamic model with the rigid bogie and the flexible carbody was set up, the stress and deformation of carbody were computed by use of the modal synthesis method based on this model. The structure stress and equivalent structural stress of key weld joints of carbody such as the window corner, car body coupler and side wall et al were extracted, applying the main S-N curve method, the fatigue life was predicted; and according to ASME standard, the fatigue strength was evaluated. The results show that the carbody fatigue life and strength all meet the design requirement. In this research, it makes the technology route integrated from rigid-flexible coupling dynamic simulation to fatigue life predict of weld line according to the master S-N procedure, and provides theoretical support for the design.