Finite-element simulation of axisymmetric preforms in precision forging at elevated temperatures

The explicit FE code DYNA 3D was used to simulate precision forging at elevated temperatures (warm- and hot-working conditions) of two axisymmetric preforms, namely a conical shell and bevel gear preform. For simple and quick calculations the coupled thermomechanical process was simulated as an isothermal mechanical process for a particular temperature distribution of the steel preform. The metal flow, preform profiles, forging loads, stress and strain distributions in the workpiece and the tooling are well predicted by this technique. The upper-bound elemental technique (UBET), a kinematic admissible upper-bound approach, was also employed for quick engineering-approximation prediction of the forging loads and metal flow for the axisymmetric preform. The results obtained from the two simulating techniques are in good agreement for the forging loads, up to a particular degree of deformation, whilst the material flow is well predicted by the FEM but is only approximated when UBET is employed.