Description
The superposition of mechanical tool vibrations with frequencies in the ultrasonic range is an approach that enables a considerable reduction of forming forces. So far, however, the incomplete understanding of the detailed process behaviour constrains the technologies broad industrial application.
The central purposes of this thesis are the identification of responsible mechanisms for the phenomenon of vibration-based softening and the investigation of the ultrasonic influence on material forming limits. Metallic materials of four different classes are tested: martensitic stainless steel X17CrNi16-2, mild steel S235JR, wrought aluminium AW-6082 T6 and cast aluminium AC-43400. Apart from the known effect of vibration-induced force reduction, substantial specimen heating was recorded in a fundamental process analysis. In addition, a strongly altered forming behaviour was observed. Thermal softening and material-related influences have been identified as crucial mechanisms regarding force reduction. With respect to the forming limits of metallic materials under the influence of ultrasonic vibration, a significant reduction was found for all investigated materials.
For the practical application of the technology, this implies potentials concerning reduced tool and workpiece loading as well as a more flexible press selection. This applies in particular to less critical forming operations regarding material failure.
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