Effect of ironing on forming characteristics in the Lorentz-force-driven hole flanging process

Ironing that achieved by reducing the clearance between forming tools have been proved to be able to generate high collar, regular geometry and good formability in conventional flanging process. In this paper, the effect of ironing on flanging characteristics during the Lorentz-force-driven (LFD) hole flanging process were investigated with the use of 5182 aluminum alloy. The ironing phenomenon in the LFD flanging process were realized by decreasing the diameter of die and keeping the punch diameter constant. To reveal the formation mechanism with or without ironing in this high-speed process, the elastoplastic finite element simulation model was established. Typical features in the final profiles, including junction ridge, spring-back, tip inclination, that determined by three critical clearance-thickness ratios (R-cc1, R-cc2 and R-cc3) were analyzed. Especially, the evolution of spring-back and tip inclination with respect to the varying clearance-thickness ratios (R-c) were discussed in details. According to three Rcc values, ironing identification and ironing extents (mix-ironing and pureironing) separation could be achieved at the same time. Based on the analysis of radius, wall and tip in the flanged part, a height calculation method was proposed for the replacement of simulation in flanging cases with Rc lowered than R-cc2. The comparison with experimental heights proved the feasibility of prediction formula.