EVOLUTION OF THE COMPACTION PROCESS AND STRESS-STRAIN STATE OF POROUS BILLETS DURING HOT FORGING IN DIES WITH A DOUBLE-SIDED conical flash GUTTER

Abstract

Hot forging of a porous billet in a semi-closed die with a double-sided sided conical flash gutter was modeled using the finite element method with the DEFORM 2D/3D software package. Analysis of the modeling results identified three consecutive stages of the process, driven by variations in the stress-strain state of the forged workpiece. A significant uneven distribution of axial and radial strains over the workpiece cross-section was established at different stages of the process. At the initial stage, the density distribution over the forged material was characterized by significantly higher values in the central region of the forged workpiece compared to the peripheral areas. However, after the die cavity was filled, the material density averaged over the workpiece cross-section. At the final forging stage, the entire volume of the forged workpiece was compacted to an almost nonporous state. This indicated that the axial component significantly influenced the compaction process at the initial and intermediate forging stages. Nevertheless, after the die cavity was filled, intense flow was observed predominantly in the radial direction, and therefore the radial strain component directly influenced the compaction process. The effective stress distribution, closely correlating with the relative density distribution over the workpiece cross-section at the initial and intermediate forging stages, changed after the die cavity was filled and the excess material was extruded into the flash gutter.