26. A method for constructing a three-dimensional vibration analysis model of a carbody for high-frequency ranges
Various carbody vibration analysis models have been proposed to predict carbody vibration characteristics associated with structural modifications during vehicle design. However, existing analytical models struggled to accurately reproduce vibrations at high frequencies above 20 Hz. To accurately reproduce carbody vibrations at frequencies of 20 Hz and above, which increase at high speeds, we used the finite element method to model each carbody face and the connections between them as a three-dimensional elastic body. To efficiently and automatically adjust parameters not directly obtainable from drawings, such as the apparent Young’s modulus when each face of a carbody, composed of multiple members, is represented as a single elastic body, we developed a method to determine these parameters based on measured natural modes of vibration of the carbody (Figure 1).
As an example, we created a three-dimensional vibration analysis model of a Shinkansen carbody and compared the measured values of 14 observed natural modes of vibration up to 40 Hz with those predicted by the model. The results showed that the error in natural frequencies of structure was less than 5%, and the deformation shapes of the carbody faces were generally consistent (Figure 2). This confirms that the model can reproduce modes of vibration above 20 Hz, which could not be achieved with the existing analysis model.
This analysis model allows for the evaluation of the carbody’s elastic vibration characteristics up to approximately 40 Hz, which can be used to improve vibration characteristics by modifying the carbody structure during vehicle design.
