Adhesive Distribution and Global Deformation between Hybrid Joints

Abstract

In multi-material-design, e.g. in the automotive industry, mechanical joining processes like self-pierce riveting are well established, because of their amount of advantages. However, adhesive bonding with one-component structural adhesives is increasingly being used. The combination of the specific advantages of both joining techniques in the form of hybrid joints leads to synergies of quality and reliability, such as high corrosion resistance and better damping properties. A critical issue is the generation of global deformations of the different parts of the mechanical joints. These global deformations of the sheet metal between two or more mechanical connectors (e.g. rivets) are caused by the formation of adhesive bags during the riveting process, before the adhesive curing takes place. This research focuses on the time-dependent formation process of these bags. The aim is to achieve a reduction of global deformations based on detailed knowledge of the adhesive flow during the manufacturing of the joint by means of experiments and simulations. For this purpose experimental techniques and measurement methods for deformations over time are presented for different setups of hybrid joint types of self-piercing rivets in combination with adhesive bonding. The challenge is to track rapid and small surface deformations very accurately in the ongoing mechanical joining process. High-speed optical measurement technology like Point-Tracking and surface scanning are used to track the resulting deformations experimentally. Numerical investigations, which include the interaction of the solid matter influenced in the mechanical joining process and the fluid adhesive, are presented. On the basis a fully coupled fluid-structure interaction simulation of a single hybrid joint, a surrogate model for a multi-point hybrid joint is developed. The comparison of experimental data with simulations allows deriving the pressure distribution and flow velocities inside the adhesive layer. The influence of various parameters can be interpreted based on the physics of the interacting system, ultimately resulting in optimization helpful to the automotive industry.