Modal Analysis And Size Optimizing Study Of Vehicle Seat Frame Based On Mass Distribution

The vehicle seat is not only one of important part of vehicle interiors, but also a main part that connects occupants and the car body directly. The vehicle seat directly affects the safety and dynamic comfort of both drivers and passengers. For this reason, the design and optimization on the vehicle seat has become increasingly attractive.This Dissertation takes a developing vehicle seat frame of a certain company as an object of research. The vehicle seat frame is separately analyzed by modal analysis and modal test, on the basis of vibration and modal theory, finite element method(FEA), etc, to proof the correctness of the FEA modal. Then, the influence of mass distribution to vehicle seat frame modal characteristics is investigated by changing the local mass distribution of the vehicle seat. Finally, by optimizing the structure of the vehicle seat frame based on the above conclusion, the dynamic characteristics of vehicle seat were improved, and the safety and dynamic comfort was enhanced. The main contents of this dissertation arranges as follows:(1) In finite element modeling, carrying out a series of processes, such as cleanup geometry, meshing and fitting joint with Hyperworks software, and the computational modal analysis was adapted to extract the low order modes of the vehicle seat frame. Then the experimental modal analysis was completed by LMS Test.Lab 13 A, and the experiment results were certified by modal assurance criterion(MAC). The comparison of the computational modal and experimental modal results was analyzed, which verified that the finite element modal of vehicle seat frame was right.(2) According to the respective computational modal analyses of the vehicle seat frame which conducted in six different conditions through adding same mass to six represented position in the vehicle seat, the influence degree of mass distribution to vehicle seat frame modal characteristics is investigated. According to the further research of changing the local mass of upper backrest, the influence of different positions and different mass distribution of upper backrest to the vehicle seat frame modal characteristics were obtained.(3) Based on the conclusion of the influence of mass distribution to the vehicle seat frame modal characteristics, dimensions which great affects the change of modal characteristics as design variables. Structure optimization has been conducted for enhancing the resonant frequencies of vehicle seat. The results showed that the first and second order resonant frequencies were enhanced, the dynamic characteristics of the vehicle seat was improved, and the safety and dynamic comfort were increased.