Mechanical joining of dissimilar materials by shear clinching processes without pre-punching (shear clinching)

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Political and environmental requirements demand the use of adapted materials in modern lightweight design structures. Joining these dissimilar materials challenges the development and advancement of existing technologies. Great potential offers the innovative shear-clinching technology which is investigated in this project. The single-stage process offers the opportunity to join material combinations with significantly different material properties without additional joining elements or pre-holing and retrieval of this pre-hole. The combined inner- and outer punch initialize a cutting operation in the die-sided brittle material as well as a drawing process in the punch-sided ductile joining partner for creating a form- and force-fitting joint. This reduces the required process time and avoids possible positioning errors that occur during multi-stage processes. The third funding phase focuses on investigating and improving the robustness of the shear-clinching process and the predictability of the properties of a shear-clinched joint. Therefore, three key research areas are set.To evaluate the tool-related design, the active elements are analyzed in terms of tool wear and the resistance of the tool materials. In addition to the identification of the process limits, the influence of process and batch-related deviations on the quality of the joint formation and the tool wear are examined. Based on these results the tool elements are adjusted for high local stresses and wear tests are carried out. The second focus is the evaluation of the process design. For this purpose, the previously analyzed single-element samples are replaced by multi-element samples to examine the influence of neighboring points on joint formation. An essential approach is identifying the influence of the radial material flow on the characteristic joint properties and set limits of a robust joining process. The influences on the joint formation of joint distance, sheet thickness and additional process based deviations are analyzed. Multi-element samples of the described material combinations are tested concerning joint strength and corrosive behavior.The final research topic is the review of the shear-clinching process regarding process safety and tested material combinations. Therefore, the findings from the first two phases of the project are combined with the tool- and process-sided results and evaluated in terms of process reliability. In particular, the failure modes of the joints are taken into account for enabling a prediction of the joint properties. The transferability of these findings will be evaluated by arranging different punch-sided aluminium alloys. The project is finalized with the summary of the results and a holistic review of the shear-clinching process.