Improving the formability during ultrasonic-assisted multi-stage incremental sheet forming

Multi-stage sheet forming is an encouraging technique to obtain complex geometries by change of the design of intermediate stages. Due to the occurrence of stepped feature during multi-stage forming, the final geometry shape is affected and the formability is deteriorated. To eliminate fracture and enhance formability, ultrasonic assistance is integrated with the multi-stage sheet forming process. The present work aims to investigate the effect of ultrasonic-vibrations (UV) on formability and thickness evolution using two multi-stage strategies through experiments. A frequency of 29 kHz and an amplitude of 10 μm are taken for the ultrasonic-assisted incremental forming process. Firstly, two distinct strategies are compared by experiments. Secondly, thorough investigation of formability experiments is performed by applying the UV at only one or two stages instead of the complete multi-stage forming process. The results show that formability of the part is increased while applying UV at intermediate stages. Similarly, it is confirmed that UV is more advantageous during latter stage of experiment. This work provides an effective strategy to improve the formability of the incremental sheet forming process by using the ultrasonic vibrations in a smart way.