P 1010 – Pre-hole-free joining of steel-intensive lightweight structures by means of resistance element welding with pre-assembled structures

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P 1010 – Pre-hole-free joining of steel-intensive lightweight structures by means of
resistance element welding with pre-assembled structures

In recent years, the automotive industry has, due to legal requirements, increasingly focused on lightweight construction measures, especially in the body structure using various lightweight materials in accordance with the load. For the realization of lightweight but nevertheless rigid and crash-resistant body structures in monocoque construction, a mixed construction method is particularly suitable for series production, in which highstrength and ultra-high-strength, press-hardened sheet steel parts are combined with aluminum materials. The thermal-mechanical joining processes developed in recent years to series maturity and not exclusively for this application offer a high application potential and the first series applications have already been made. Due to the novelty of resistance element welding, the process-related properties and characteristics have so far been insufficiently investigated, so that sufficient knowledge about the welding, strength and failure behavior of corresponding joints and material combinations is lacking.
The aim of the research project was the development and qualification of resistance element welding with prefabrication of an Al or FRP composite partner as an economical joining method for joining these lightweight construction materials with high-strength and ultra-high-strength steel materials. Since resistance element welding is still a relatively new joining process, the requirements were initially adapted based on the investigations carried out to date. In this context, process-technological particularities of resistance element welding of prefabricated composite partners were analyzed and the properties of the resulting joints were characterized. By analyzing the joining process and the joint formation under consideration of the rivet element properties, important knowledge about the rivet element and process design as well as about the process-safe application could be gained. The evaluation of the service properties in terms of joint and handling strength was also part of the project. As a result, industrial users have been provided with information on the use of a flexible joining process for the realization of future lightweight structures. The implementation of the optimization derived from the results obtained marks an important contribution to the development of resistance element welding and the economic production of future lightweight structures in mixed steel construction.

Published in:
December 2020

Authors:
Prof. Dr.-Ing. G. Meschut , Dipl.-Wirt.-Ing. V. Janzen