High performance components require high strength multi material systems in order to increase the specific strength and hence the performance of the component. Determined by the system, such multi-material components show a higher amount of joints between dissimilar materials, so the control of suitable joining techniques is crucial.

The ultrasonic welding technique is currently applied in the packaging industry for consumer goods, but also in automotive, lightweight construction, in medicine and the electric industry. Apart from the advantages of a low energy consumption, short process durations, low temperature and the absence of additional materials, its main potential lies in its capability of joining dissimilar materials. There are two forms of ultrasonic welding with different fields of application: ultrasonic metal welding (UMW) and ultrasonic plastic welding (UPW), which differ in their direction of the ultrasonic oscillation in relation to the surface of the joining partners.

For the secure implementation of the joining technique, precise assumptions about the mechanical properties of the joint are needed. In order to reliably calculate the properties of ultrasonically welded components, it is required to take into account the conditions of contact between the joining partners. For UMW, approximated models including simplified geometries and simplified contact restrictions or models borrowed from adhesive bonding have been the basis of calculation models so far. In order to gain accuracy in the calculation of UMW seams, a new model for contact properties is being developed.

The performance of an UMW weld seam is strongly dependent on the exact combination of material, process, welding tool and manufacturing parameters used. This creates a large variety of options for the properties of the joint and presents a challenge for a widely applicable contact model. Aiming to conquer this difficulty, the interface morphology in the weld seam are examined in combination with mechanical properties. This data is being collected for a variety of welding combinations and characteristic contact zone formations are identified. Focusing on a micro-scale basis, a FE-model is developed to fit different combinations of the weld seam zones in order to depict a range of mechanical properties realised by different UMW processes. Finally, this model is gradually scaled to real components to accurately calculate the mechanical properties of a given joint manufactured with UMW.