Investigation and numerical analysis of impulsive hydroforming of aluminum 6061-T6 tube

Abstract

Nowadays impulsive forming processes have become popular among scientists and industrial companies due to their unique capability at increasing formability in various materials and reduction in production time and cost. In this research, finite element analysis of impulsive hydroforming on the sheet and tube was carried out using an explicit scheme and the interaction between the fluid and the shell elements representing the workpiece was approximated through the use of the surface based acoustic-structural interaction. This allowed transferring the pressure from the electrical discharge in the fluid medium, determined by the Geers and Hunter model, to the nodes representing the workpiece. The behavior of the sheet and tube was assumed to follow the Johnson–Cook structural model and the physical constants for the model were taken from other research papers. The proposed finite element model was verified by comparing the results of the model to the experiments published by another researcher and were found to be in good agreement. The FE model was applied to the impulsive forming of the tube so that the effect of discharge energy, die radius and friction coefficient could be studied in the tube electrohydraulic forming process. It is observed that the discharge energy value has major effect on the process and the friction coefficient has minor effect relative to the others. Results showed that Al6061-T6 tube did not sustain any damage even by experiencing stresses near the ultimate strength stress due to the high strain rate of the process. Elastic spring back of the tube decreased with increasing in the energy level, die radius and friction coefficient, due to the impact with the die and the lower induced stresses. Material flow into the die cavity improved by increasing in the die radius, resulting in formability improvement.