Theoretical Study on the Relationship between Stiffness and Modal of Railway Passenger Car Bodies

［Objective］To analyze the relationship between carbody stiffness and modal, and to provide theoretical support for the modal analysis of lightweight carbodies, it is necessary to conduct a theoretical study on both aspects. ［Method］Taking the 25T passenger vehicle as the research object, a finite element model of the carbody is established. Static and dynamic performance analysis of the carbody is carried out to identify key structures affecting the carbody modal. A carbody plate-beam mixed finite element model is established based on carbody geometric features. Using the optimal Latin hypercube sampling method, 40 sets of design variables for the chassis are obtained, and the carbody modal and equivalent stiffness results under different geometric parameters are further calculated. The modal of the lightweight carbody is calculated and analyzed based on the function relationship between carbody stiffness and modal. ［Result & Conclusion］The equivalent bending stiffness and equivalent torsional stiffness of the carbody are linearly and positively correlated with the first-order vertical bending and torsional modal frequencies, respectively. The optimized finite element results of the carbody show that the first-order vertical bending modal frequency increases from 9.04 Hz to 9.24 Hz, and the first-order torsional modal frequency increases from 15.99 Hz to 16.66 Hz, which are consistent with the theoretical relationship between stiffness and modal frequency.