An ALE approach for finite element ring-rolling simulation of profiled rings

The ring-rolling process involves compression of a small diameter ring-shaped workpiece between a mandrel and drive roll. This causes the ring to grow whilst allowing a profile to be developed on its surface. Compression can also take place in the axial direction between conical–axial rolls. Finite element (FE) simulation of this process is particularly difficult, suffering from excessive computational requirements and stability difficulties. Modelling using conventional Lagrangian FE codes is inefficient, involving high-density meshes. Moreover, a large number of incremental stages are typically required to complete a full simulation. This paper is concerned with a new approach founded on a split-operator arbitrary Lagrangian Eulerian (ALE) formulation, combined with a flow formulation and a novel iterative solution scheme called the successive preconditioned conjugate gradient method (SPCGM). The approach exploits the slowly evolving nature of the problem with the effect of reducing the time penalty for each deformation increment. The accuracy and stability of the method is tested against published experimental results. In addition, other modelling issues are addressed. In particular, the commonly used method of assuming zero-friction at a mandrel interface is shown to be inaccurate. This is achieved by a new approach, which properly invokes the effect of friction at the mandrel interface for arbitrarily shaped rollers.