FE SIMULATION OF THE DEVELOPMENT OF FLAWS DURING INJECTION FORGING

Several types of flaws develop during the injection forging of compone nts; among these a prominent form results from the instability of the free length of the billet. The material in the die cavity buckles or s lides laterally along the anvil; consequently, die filling is effected by asymmetrical deformation of the billet. This FE simulation conside rs the influence of several parameters which influence the development s of flaws during injection forging. By considering friction condition s at the anvil, the aspect ratio of the primary deformation zone, the exit geometry and the inhomogeneity of the material, the types of flaw s which are initiated and the subsequent die filling are simulated usi ng ABAQUS code. Marginal changes in the friction conditions influence the stability of the billet; billets which were unstable when mu = 0.0 1 were, generally, sufficiently stable when mu = 0.03 to effect flawle ss die filing. Simulation confirms the experimentally proven, limiting aspect ratio of the primary deformation zone to be between T = 1.6 an d 1.8. The deformation of the billet graduates from non-symmetrical de formation at aspect ratios greater than 1.7 to bending at ratios great er than 2.0 larger exist radii improve the flow characteristics and ha d been shown to reduce the energy requirements; however, the simulatio n shows that instability would occur at a lower aspect ratio when a la rge exit radius was incorporated in the injection chamber. Lack of inh omogeneity in the material will also result in instability and asymmet rical die filling at low aspect ratios.