Deformation Behavior in Flow Forming of Cylindrical Cups using Finite Element Method

A 3D finite element model is proposed adopting the Arbitrary-Eulerian (ALE) formulation to simulate the deformation behavior in the flow forming of cylindrical cups using a commercial software, DEFORM 3D. The ALE formulation is an efficient alternative to deal with large discontinuities and mesh distortion that occurred in the typical Updated Langrangian formulation. Results predicted from the FE simulations were compared with experimental results and showed close agreement. It was found that feed rate has a large influence in the plastic deformation behavior, especially in the flow forming of short cylindrical cups where achieving steady plastic flow is important in the early stage of forming. For all wall thickness reductions investigated, the FE results predicted that a slow feed rate of 0.2 mm/rev will result in larger surface strain at the roller side (i.e. surface contact with the forming roller) and small strain distribution across the wall thickness. On the other hand, higher feed rate at 0.4mm/rev has resulted in smaller surface strain (as compare to slow feed rate) but larger strain distribution across the wall thickness which encouraged more axial material flow and hence better thickness accuracy. Hardness values measured from experimental samples confirmed this phenomenon predicted by the FE simulation. The paper also evaluated the state of stress around the region of the roller at different feed rates to understand the flow forming behavior.