Applications of numerical simulation to the analysis of bulk-forming processes-case studies

摘要

Three bulk-forming processes are simulated with DEFORM~TM. Rotary forging of a flange with a rod is a successful application of the mushroom effect of rotary forging. During the initial stage, the radial elongation of the material at the top plays a significant role in flange forming. When the flange contacts with the lower die, the tangential elongation is larger than the radial elongation. Subsequently, the lower die is filled and the flange is formed. Analysis of the stress and strain rate during the rotary forming of a circular disk with a central hole suggests that the deformation conditions are not absolutely axisymmetrical because of the partial loading during rotary forging. The final part is, therefore, not absolutely axisymmetrical. At the same time, underfilling defects may be predicted to assist in the design of the dies and the process. In the combined extrusion-upsetting of a tyre nut, a cup shape is produced through the combined extrusion of a cylinder billet, and the top is formed by upsetting into a flange with a spherical profile. By means of the simulation, the causes of the fracture of the punch are clarified. It is shown that unreasonable punch dimensions affect the metal flow and increase the tensile stresses in the punch, when it withdraws from the nut hole.