A Study of Topology Optimization for Spot-Welding Locations in Automotive Body by Using Driving Simulation

An automotive body is made by joining over 500 components made from steel sheets. Since the joining locations for spot-welding are decided by the designer of each component, the number of spot-welding points tends to be either excessive or inadequate for the required automotive body stiffness. In this study, a topology method which is able to select effectively from design space was applied to optimization of spot-welding locations for vehicle stiffness performance by using a full vehicle model. Static stiffness using constraint of nodes cannot sufficiently express deformation during driving. Torsional deformation occurred in all parts of the body in the mode in which one point of the front bilateral suspension parts was forced and the other three points were constrained in the general static stiffness mode. However, because the automotive body is mounted on a suspension and the displacement of the suspension is not constrained, static stiffness is different from the condition during driving. For this reason, simulation under a loading condition that approximates the condition during driving is necessary. This paper describes stiffness optimizations for the locations of spot-welding in the automotive full vehicle model by using inertia relief under the loading condition decided by a driving simulation expressing the behaviour of the body during driving. The results show that the developed topology optimization method for joint locations using inertia relief and driving simulation is valuable in optimization of automotive bodies made of steel sheets. The results of optimization of the joint locations differed with static stiffness using constraints and stiffness while driving. In the analysis based on stiffness during driving, the locations of the remained points were the door openings. The reason for this result is identification of the actual loading conditions by the driving simulation.