No abstract

In this paper, a three-stage plate-forging process is simulated considering air-pockets enclosed by material, dies, or tools and a plane of symmetry. A new basic approach is presented to deal with the air-pocketing phenomena. The volumetric strain of each cavity of an air-pocket is traced when it has no air hole and its pressure, which is a function of the volumetric strain multiplied by the bulk modulus of elasticity of the air-pocket and maximum normal stresses of the neighbouring contact interfaces, is exerted onto the surface of the material inside the air-pocket. This approach is applied to a three-stage plate forging process in which the air-pocketing phenomena can be sensitive to the plastic deformation of the material. The predictions are 206 B. Kim et al. compared with experimental data and the effect of the bulk modulus of elasticity on the size of air-pocket is evaluated to examine the stability of the present approach.