Numerical analysis of the effects of ultrasonic vibrations and elevated temperature in incremental sheet forming

Incremental sheet forming (ISF) is one of the novel processes practised for more than the last decade in the field of sheet metal forming. ISF, although recognised as a promising manufacturing process over conventional forming, does not give good results in terms of geometrical accuracy, sheet thinning, surface finish and the forming forces. To make the ISF process more efficient, strategies to enhance the forming limits and capabilities are constantly being developed. Two such adaptations to the ISF process are ultrasonic vibration-assisted incremental sheet forming (UVaISF) and elevated temperature incremental sheet forming (ET-ISF). In the present work, investigations have been carried out to compare ISF, UVaISF and ET-ISF on 1 mm thick AA1050 and Titanium Grade 2 sheets with the help of numerical simulations using Abaqus/CAE. Response parameters like stress, strain, thickness distribution, the final shape of the geometry, strain energy, energy dissipated during plastic deformation and the forming forces are evaluated to measure the effectiveness of the processes. It is observed that there is a considerable reduction in the forming forces and spring-back with the UVaISF and ET-ISF processes, in comparison to the ISF at room temperature. This considerable reduction in the forming forces and spring-back is due to the softening behaviour of sheet material and the drop in yield strength during UVaISF and ET-ISF processes. The work overcomes some of the limitations of the ISF process and enlarges the scope of application of the process.