Effect of layer lay-up on formability of Al–Cu two-layer sheet in electromagnetic forming

Abstract

In this article, the electromagnetic forming (EMF) of Al–Cu two-layer sheet has been simulated and the effect of layer lay-up and layers thickness on dome height and formability of this sheet has been investigated. In dynamic conditions, the limit of dome height increased by considering the strain rate in the hydraulic bulge test equations. Even by considering the strain rate in the hydraulic bulge test, the dome height prediction is not in agreement with simulation results in EMF at the same pressure. Unlike the hydraulic bulge test, the pressure distribution in the electromagnetic sheet forming is not uniform. Also, the sheet is moved away from the pressure source during forming. The differences in electrical conductivity of layers lead to the induction of a higher eddy current in Cu. So, the magnetic pressure in Cu–Al lay-up is 19% higher than Al–Cu lay-up in the same discharge voltage. The Cu–Al lay-up has a 15% greater dome height in comparison to Al–Cu lay-up in the same discharge voltage because of higher magnetic pressure. However, the J-C damage and the probability of fracture increased in Cu–Al lay-up due to higher strain in the outer layer (Al). In the same magnetic pressure for both layer lay-ups, the Al–Cu lay-up has a higher dome height before necking and a lower J-C damage of about 30% because of higher formability of the outer layer (Cu). The Al–Cu lay-up with 0.5-mm initial thickness for both layers was ideal for better formability in this research. There is a 5% difference between the simulation and the experimental results for the dome height.