Mechanical and geometrical characterisation of tumbling self-piercing riveting joints in multi-material-systems

Increasing requirements on lightweight construction to preserve resources necessitate new processes and methods in the production of weight-optimised multi-material-systems. Common joining processes such as the conventional semi-tubular self-piercing riveting are reaching their limits because of the rigid process designs. To extend this process, the linear punch movement is superimposed by an orbital forming process with a tumbling kinematic and provides new possibilities to influence the joining process. The configuration of the tumbling strategy consisting of the parameters tumbling angle and tumbling kinematics enables a targeted control of the material flow for the production of tailored joints. Within the scope of the investigations, the influence of the two parameters is examined both for the joining process and for the resulting joint formation. Force-displacement diagrams, micrographs and rivet head geometries are analysed to determine the influence on the process itself. Further, shear tensile tests and cross section tests are carried out to characterise the load-bearing capacities of tumbled joints and to identify the effects of the tumbling strategy on the mechanical properties. The tested materials in form of a dual-phase steel HCT590X+Z and a precipitation-hardening aluminium alloy EN AW-6014 have widely varying mechanical properties to represent multi-material-systems.