Spot Weld Layout Optimization With Manufacturing Constraints for Vehicle Structural Performance

Abstract

Spot weld layout on thin walled vehicle structures is an influencing factor to the structural performance such as NVH, durability and crashworthiness. The weld layout is also subject to manufacturing constraints such as minimum weld pitch, thickness and curvature of flanges, and accessibility of weld gun. Using an S-shaped thin walled tube as an example, this paper presents a study of spot weld layout optimization considering both structural performance and manufacturing constraints for reducing design iterations between the performance design and the manufacturing design. First, several complex manufacturing constraints, including minimum spot weld pitch, maximum curvature of flange, etc., are mathematically characterized. Then, with and without typical manufacturing constraints, the weld layout is optimized respectively for crash performance and torsion performance of the structure. The effects of adding manufacturing constraints on the spot weld layout optimization are evaluated. The analysis results reveal that the crash performance responses are generally less sensitive to the spot weld layout while the torsion stiffness is closely related to the spot weld layout. To analyze why the crash performance is less dependent on the weld layout, a detailed study is further conducted to reveal the relation between the weld layout and the crash performance of S-shaped thin walled tube. It shows that the parameters for assessing the structural crash performance have distinct sensitivity to the spot weld layout design. For instance, the peak impact force is generally sensitive to the spot welds placed in the curved segment and the total energy absorption capacity is mainly determined by the curvature design of the tube instead of the spot weld layout design.