Simulation and analysis of low-frequency vibrations in rotational vibration-assisted incremental sheet forming

Incremental sheet forming (ISF) has demonstrated its potential of flexible manufacturing for low-volume or prototyping applications. Rotational vibration-assisted incremental sheet forming (RV-ISF) is a new process variant that advances the capability of the ISF technology for processing hard-to-form materials. New tools have been developed for RV-ISF, including a double offset tool and quad-grooved tool, to induce low-frequency vibrations into the deformed sheet in the range of 50-300 Hz, created by tool rotations. These imparted low-frequency vibrations result in vibration softening phenomena of the material which has been shown to lead to improvements in formability. However, the nature of the vibration generated during this new process and its impact on forming force reduction and softening effect have yet to be thoroughly examined. In this paper, a finite element model is developed to simulate the vibration of the sheet material induced by the RV-ISF tool, with the aim to predict the vibration frequency and amplitude during the process. The results show that the tool induced sheet vibration is localised at the tool-sheet contact which is validated by experimental measurement results. The frequency of the sheet vibration is dependent on the rotational speed and the number of grooves or offsets of the tool, while the vibration amplitude is associated with formed geometry and the tool design.