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Modelling of variable friction in cold forging

In metal forming operations, the friction between die and workpiece is a complex phenomenon and has a strong influence on the metal forming parameters and the product quality This study aims to investigate the effect of friction in cold forging operations using different friction models. In the analyses, the forging operations are simulated using the Coulomb and constant friction models, and the results are compared with the simulation results obtained by using the variable friction models developed by Wanheim-Bay (general friction model) and Levanov, which are integrated into the program. Cylinder upsetting and bolt head forging are numerically simulated and the cylinder upsetting results are compared with the experimental data. The results showed that depending on the workpiece geometry and the contact pressure, the coefficient of friction may change significantly during the process and the constant coefficient of friction may not simulate the actual friction condition in the cold forging process.