Joining and Forming by Plastic Deformation

Due to their efficiency, deformation joining processes requiring no pre-holing are increasingly used in the mobility sector. The focus is on processes that do not require the use of an auxiliary joining part, such as clinching. There is currently an acceptance problem in the field of aircraft construction, due in part to a lack of knowledge on the failure-behaviour of clinch-bonded connections under cyclic loading. The aim of the research project is therefore the in-depth analysis of crack initiation on deformation joined clinch-bonded connections and the prediction of the location and crack-related service life of these connections. A central task is to demonstrate the impact of friction-based crack initiation on the failure behaviour of clinch connections.

The industrial rolling of heavy plates in small batches is currently controlled exclusively manually. This has the consequence that the efficiency and economy of the forming process is dependent on the experience of the system operator. Consequently, in order to optimise the process, an objective real-time-enabled control approach based on a simplified substitute model is being developed in the context of the research project. With the help of experimental and numerical investigations plus a sensitivity analysis of the influencing factors, the substitute model can be specifically adapted for industrially relevant space parameters. Using the substitute model leads to a sustainable improvement in control of the rolling process, especially for SMEs.

Semi-tubular self-pierce riveting is an efficient joining process established in the structural assembly of motor vehicles. When joining high-performance fibre-plastic composites (FRP) and metals, process-related damage, such as delamination, results. The influence of this damage on the joining properties, especially under cyclical load, must be taken into account.

An essential part of the project is the analysis of the cyclical damage and failure behaviour of the individual components of the joint and the transfer of these to the damage analysis of the joint. As a consequence, correlations between the joint characteristics and the properties under cyclic loading can be derived, which increases the acceptance of the joint principle with FKV and ensures a safe design.

Production-related fluctuations in component
production lead to increasingly smaller tolerance
zones in the production process and therefore to
higher costs. The networking of production data
for individual production steps is insufficient and correlations between these data are unknown.
It therefore also follows that the potential for expanding the tolerance range is also unknown. The aim of this research project is the analysis and networking of the production steps of a selected product on the basis of the production data.

To achieve this, experimental and numerical analyses are carried out along the production chain. The production data are first subjected to a sensitivity analysis and then the correlation between production steps is analysed. In this way, tolerance specifications can be extended and costs reduced.

When joining aluminium alloys, which are widely used as ideal lightweight construction materials due to their low specific density, there are strong efforts to realise material-like joints. Thus, in addition to better recyclability, the risk of corrosion and thermal residual stresses between the joining partners can be effectively reduced. In the punching joining processes established in structural assembly, rivet elements made of steel are usually processed. In a previous project, however, a new high-strength aluminium alloy was successfully identified as a suitable rivet material. Following on from this, the development of the aluminium full-punch rivet is being continued - with the aim of joining practically relevant total sheet thicknesses in the range of 3 - 5 mm of high-strength aluminium alloys.