Determination of Local Friction Conditions in Hot Forging and Application to the Flash Section of Die in Crankshaft Forging

To accurately predict the shape of an automobile product, such as a crankshaft, produced by hot die forging, a preliminary simulation of the forging process indicated the significant impacts of local and varying friction coefficients between the complex-shaped die and the material. This study identified the friction coefficients through ring compression and tapered plug penetration tests, focusing on regions with high pressure or large contact areas. The results revealed variations in the friction coefficients across different regions. Consequently, the study suggests implementing locally appropriate friction coefficients on specific die surfaces exhibiting conditions akin to those observed in the friction tests. Specifically, a Coulomb’s friction coefficient of 0.14 was assigned to the product shape region of the crankshaft die. Additionally, a friction model transitioning from a Coulomb’s friction coefficient of 0.5 to a shear friction coefficient of 0.6 was applied in the flash region with significant sliding distances. By incorporating these tailored friction conditions into the simulation of hot die forging for crankshaft manufacturing, the study achieves more accurate material flow, die filling, and underfill replication.