The idea of stiffening flat sheet metal structures by branching cross sections is orientated on models from nature. The technology offers enormous potential for lightweight construction and a wide range of applications, for example in the transportation sector or architecture. The sequence of the process chain shown in Figure  (bifurcation before forming process) plays an important role since the joining process between the stringer and the sheet metal in the planar state is much easier to carry out than in a three-dimensional component contour.
Objective and approach
The scientific feasibility of stringer sheet forming has been demonstrated within the work of the collaborative research center 666. In order to complete the scientific development of this technology, the knowledge transfer to the industry has been carried out since July 2017, as part of the DFG transfer project “stringer sheet forming for car body construction”. LÄPPLE Automotive, with its extensive experience and wide product range in car body construction, is the ideal partner for this. They may use this project to expand its portfolio by means of an innovative lightweight construction strategy and process know-how in laser welding and the manufacture of complex drawn parts. The aim of the project is the production of a prototype which impressively demonstrates the great lightweight potential of the technology based on an existing series product (e.g. a structural part of a car body).
To reach this goal within a period of two and a half years, the initial step will be to identify a suitable component for numerical and experimental process and product design. In numerical and experimental investigations, the entire potential of the technology is to be exploited. After defining the best possible design of the process chain with joining and forming processes, a corresponding tool design and manufacturing follows before demonstrators can be manufactured and characterized.
The formability of laser-welded stringer sheets with industry suitable solid tools has already been successfully demonstrated (see Figure ). Further work pursues the goal of expanding the process boundaries and developing design models for a sheet-metal component stiffened with stringers.
The transfer project is funded by Deutsche Forschungsgemeinschaft (DFG).