In general, the improvement of vehicle body stiffness involves a trade-off with the body weight. The objective of this research is to derive the lightest-weight solution from the original vehicle model by finding the optimized spot-weld layout and body panel thickness, while keeping the body stiffness and number of spot welds constant.
As the first step, a method of deriving the optimal layout of spot welds for maximizing body stiffness was developed by applying the topology optimization method. While this method is generally used in shape optimization of continuous solid structures, it was applied to discontinuous spot-weld positions in this work.
As a result, the effect of the spot-weld layout on body stiffness was clarified. In the case of the body used for this research, body stiffness was improved by about 10% with respect to torsion and vertical and lateral bending. The lightest-weight specification was then derived by simultaneously optimizing both the spot-weld layout and body panel thickness, while maintaining the same body stiffness as that of the original vehicle.
As the final result, the body weight was reduced by about 20% by utilizing the improvement of body stiffness in the first step to reduce the body panel thickness.