| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 98 === This paper studies the structural analyses of a low-floor electrical bus chassis and presents a method for structural design and optimization of a low-floor electrical bus chassis for improving static structural characteristics. The structural characteristics of the bus chassis are analyzed by static finite element analysis method. The static finite element analyses considered in this research include full-loaded stress, bending stiffness and torsional stiffness analyses for the bus chassis. The redesign purpose is to increase the strength and stiffness of the bus chassis with minimum weight. The complex bus chassis structure is improved by two stage optimizations. In the first stage optimization, components in the neighbor of few locations with high stresses are selected, and then sensitivities of stress and weight of selected components with respect to component thicknesses are computed. Component thicknesses with high sensitivities ratio of stress to weight are chosen as design variables. Then the structural optimization is performed to reduce the high stress regions with minimum increased weight. In the second stage optimization, thick components not in the neighbor of the locations with high stresses are selected, and then sensitivities of stiffness and weight of selected components with respect to component thicknesses are computed. Component thicknesses with low sensitivities ratio of stiffness to weight are chosen as design variables. Then the structure optimization is performed to reduce the chassis weight while maintaining the improved strength and original stiffness. Finally, static structural characteristics of the original and improved chassis structures are compared, and it shows that the improved chassis is a better structural design.
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