Abstract:Upper case is a key part in the driving system of a helicopter, the ear portion of the upper case is difficult to be formed owing to its complex geometry and high demands for microstructure and mechanical property. The forming of the ear is simulated by rigid plastic finite element method. According to the sim- ulation result, it was found that, during the ear forming, the metal fulfills the axial ring first, then the ear, at the last stage of the ear forming, the metal flows inversely, which causes the generation of the lap defect. To avoid the generation of the lap, the pre-forming procedure, which gathers sufficient metal round the ear, was adopted to make sure the ear and the rib fulfills simultaneously.

Key words: die forging　finite element method　upper case