The prediction of macro-defects during the isothermal forging process by the rigid-viscoplastic finite-element method

Macro-defects often occur during isothermal forging of workpieces of complicated shape. The occurrence of macro-defects is mainly attributable to an abnormal flow pattern of the metal. In order to reveal the cause of macro-defects during isothermal forging of a very large aluminium wheel for an aeroplane, the forging process is simulated by the rigid-viscoplastic finite-element method. The results so calculated show that the occurrence of a folding defect is caused by an abnormal flow pattern. Improvement in the die design and lubrication conditions are effective measures to avoid this kind of defect.