Fundamental investigation of ultrasonic-assisted forming of metallic materials under compression and shear loading
Final Report Abstract
The use of high-strength metallic materials in lightweight material construction is shaping developments in cold forming. These materials cause increased process forces with reduced forming capacity. Hot forming to reduce the forming forces and extend the forming limits is not always suitable. A promising approach is to superimpose a high-frequency vibration on the tool movement. This way, a significant force or stress reduction is achieved, as initially observed 1955. The superimposed vibration thus has the potential to reduce tool and workpiece stresses and enables lightweight design. Despite numerous studies, the underlying effects of the force reduction and its influence on the forming limit of metallic materials are still unclear. The aim of the research project was to characterize the vibration-based softening and to investigate the deformation limits of metallic materials under ultrasonic impact in compression, tensile and shear loading. Furthermore, based on the findings obtained, existing explanatory approaches were to be reviewed and the softening mechanisms separated. In the course of the research work, the dynamic properties of the test setup were identified as a significant factor influencing the superimposed vibration processes. Moderately excited oscillations in stationary tool components are significantly dependent on the excitation frequency and amplify or attenuate the nominal amplitude. The achievable softening effect is in turn significantly determined by the oscillation amplitude. The influence of the process speed was also analyzed. Longer vibration intervals lead to more pronounced specimen heating, which in turn enhances the softening effect. With the consideration of the frequencydependent transfer behavior, the explanatory approaches could be reduced by the stresssuperposition principle and restricted to surface and volume effects. In this context, it was demonstrated for the test concept used that, material-independently, about one third of the softening effect can be attributed to thermal flow stress reduction. By means of vibrationsuperimposed tensile tests, the proportional stress reduction based on surface effects was narrowed down in more detail. Due to the close interaction of interfacial friction with specimen heating, no precise separation from thermally based softening could be realized in this context. Analyses of the forming limit with ultrasonic assistance showed a reduction compared to conventional processes for both shear and tensile loads. The causes identified were cyclic alternating loading and strain localization, respectively.
Publications
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Residual effects of ultrasonic-assisted compression testing on pure copper. In Pedro Arrazola, Eneko Saenz de Argandona, Nagore Otegi, Joseba Mendiguren, Mikel Saez de Buruaga, Aitor Madariaga, Lander Galdos (Eds.), AIP Conference Proceedings. Vitoria-Gasteiz, ES: American Institute of Physics Inc.
Jäckisch, M., Michalski, M. & Merklein, M.
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Investigation of thermal effects during ultrasonic-assisted upsetting. Procedia Manufacturing, 50, 220-225.
Jäckisch, Manuel & Merklein, Marion
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Influence of Ultrasonic Assistance on the Forming Limits of Steel. The Minerals, Metals & Materials Series, 1281-1290. Springer International Publishing.
Jäckisch, Manuel & Merklein, Marion
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A novel ultrasonic-assisted staking process for mechanical fasteners. Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, 236(6), 1176-1186.
Jäckisch, M. & Merklein, M.
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Residual effects of ultrasonic assistance in metal forming. In Lucas F M da Silva (Eds.), Proceedings of the 1st International Conference on Engineering Manufacture 2022 (EM 2022) (pp. 31). Porto, PT.
Jäckisch, M. & Merklein, M.
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Ultrasonic-assisted forming - Influence of unavoidably induced tool oscillations. In Univ.-Prof. Dipl.-Ing. Dr. techn. Martin Stockinger (Eds.), Proceedings of the XL. Conference on Metal Forming (pp. 110-115). Zauchensee, AT.
Jäckisch, M. & Merklein, M.
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Mechanical joining of high-strength multi-material systems − trends and innovations. Mechanics & Industry, 24, 16.
Merklein, Marion; Jäckisch, Manuel; Kuball, Clara-Maria; Römisch, David; Wiesenmayer, Sebastian & Wituschek, Simon
