Interlocking Seam Joining

• Applicant: Professor Dr.-Ing. Gerhard Hirt
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 504659266

In this project, the formation of an interlocking joint between two metal sheets made of different classes of materials along a continuous seam via a cold forming process is to be investigated. The process to be developed allows the use of material combinations that until now could technically only be joined in seam form with considerable effort. In addition, the cold forming process avoids a thermal influence and thus the resulting reduction in strength. The basic idea of the local interlocking longitudinal seam joining of sheet metals is to roll channel-like structures with undercuts into the harder joining partner along the later joining seam, to then be filled with the softer joining partner in a subsequent rolling pass. In the first step, the so-called structure rolling, undercut-free channels and ribs are produced in the sheet metal by structured rolls. In the flattening pass, these ribs are then reduced in height with flat rolls and thereby form an undercut by spreading in width direction. The third step is to embed the softer partner into this structure via rolling in such a way that the undercut is filled and interlocking is achieved. The creation of such channels with undercut has already been successfully demonstrated in a previous project with the aim of creating an interlocking between a steel sheet and aluminium die-cast. The aim of the current project is to gain a fundamental understanding of the possibilities and limitations of structure rolling and embedding via rolling to create an interlocking connection. Therefore, the process is to be tested for different classes and combinations of materials in order to create a broad basis for later applications. The materials considered are sheet metals from the classes steel, aluminium and copper. The preliminary investigations suggest that the production of longitudinal joints depends on the choice of the combination of materials, and especially on their strength ratio. In order to test the influence of the absolute strength as well, different strength levels are to be tested as well. The geometric parameters of the surface structure need to be regarded as an additional influencing factor on the process limits. Thus, both the influence of the materials and the structure geometry will be investigated via a numerical process model and then tested experimentally. Since, depending on the application, the components will be mechanically loaded, a high joint strength is decisive. Therefore, shear and peel tensile tests on experimental samples are planned to test and optimise the joint strength.

• DFG Programme: Research Grants
• Co-Investigator: Dr.-Ing. Johannes Lohmar (†)