A Study on the Development Process of a Body with High Stiffness

Design optimization of a vehicle is required to increase a product value for noise and vibration performances and for a fuel-efficient car. This paper describes the development process of a high stiffness and lightweight vehicle. A parameter study is carried out at the initial stage of design using the mother car, and a design guide with a good performance is achieved early prior to the development of the proto car. Influences of body stiffness based on the relative weight ratio of the floor and side structures are analyzed. Results show that bending and torsional stiffness has a significant effect on weight distribution ratio. Influences of the distribution of side joint stiffness are analyzed through numerical experiments. Results reveal that the stiffness difference between the upper and lower parts should be small to increase the stiffness of a body. In addition, the process of designing the body attachment stiffness is summarized to ensure the vibration isolation of the suspension mounting unit. In the case of the rear suspension mounting unit, the body attachment stiffness is found to increase in the left and right direction, when the package tray pass-through structure is used on the rear wheel housing and rear floor joint, to minimize rear seat noise. This paper is expected to shorten the development period by the present stiffness analysis process. And a body with high stiffness and lightweight is developed for the vibration and noise performance at the initial stage of design.