This paper presents a method that systematically decomposes product geometry into a set of components considering the structural stiffness of the end product. A structure is represented as a graph of its topology, and the optimal decomposition is obtained by combining FEM analyses with a Genetic Algorithm. As the first case study, the side frame of a passenger car is decomposed for the minimum distortion of the front door panel geometry. As the second case study, the under body frame of a passenger car is decomposed for the minimum frame distortion. In both case studies, spot-weld joints are considered as joining methods, where each joint, which may contain multiple weld spots, is modeled as a torsional spring. First, the rates of the torsional springs are treated as constant values obtained in the literature. Second, they are treated as design variables within realistic bounds. By allowing the change in the joint rates, it is demonstrated that the optimal decomposition can achieve the smaller distortion with less amount of joint stiffness (hence less welding spots), than the optimal decomposition with the typical joint rates available in the literature.
