Deformation Analysis in Ultrasonic-Assisted Multi-stage Incremental Sheet Forming

The multi-stage incremental sheet forming is a promising forming strategy to fabricate complex shapes through the rational design of intermediate shapes. To further improve the formability, the ultrasonic-assisted multi-stage incremental sheet forming is proposed. The present work aims to reveal the effect of ultrasonic vibration (UV) on the thickness distribution, strain–stress state and the forming force variation. First, the finite element (FE) model is established through ABAQUS software, in which the trajectory of the forming tool with the high-frequency vibration is defined via the user subroutine VUAMP. Then, after the verification of the FE model, the thickness evolution, the stress–strain state and the forming force are comprehensively analyzed. It is found that the thickness distribution can be effective improved by introducing UV. In addition, the stress concentration in the bending area is effectively alleviated and the equivalent plastic strain is obviously increased under the UV. Final, the application of UV can lead to a notable reduction of forming force and smoother forming force curves at the latter two stages. The findings of this work provides evidences that ultrasonic assistance is an effective strategy to improve the incremental forming process.