The three major objectives of a car design are reduced costs, maximized performance and improved fuel economy. The total mass of a car has a direct effect on all these three objectives. Around 25% of the total mass of a typical car is accumulated in its Body-In-White (BIW). Thus, reducing the total mass of the BIW while satisfying the target stiffness is of utmost importance in the early stages of design. Reducing the total mass of the BIW involves the identification of potential sites for mass reduction and stiffness improvement. The joints of the BIW are often the most critical locations that decide the overall stiffness of the BIW. Understanding the contribution of each joint towards the overall stiffness is thus of paramount importance towards improving the stiffness of the BIW.
This paper describes a new approach of identifying the contribution of each joint in a BIW towards the overall stiffness of the BIW. The joints in the BIW are parametrized and a size optimization (parametric optimization) technique with Altair OPTISTRUCT is used to find optimum values of all parameters. The contribution of different joints to the overall stiffness is different for different loads. Hence, the methodology was applied to multiple loadcases and also for the combination of two loadcases. The methodology was applied to a simplified BIW model and the results were studied. The entire methodology has also been automated in a pre-processor to reduce the time involved.