The Numerical calculation of tool wear in industrial cold forging processes through further developments of the modelling of wear

Within the research of the sub-project A7, a new type of sheet bulk metal forming (SBMF) process was developed at the IFUM and its process limits were extended by adding an superimposed oscillation into the main force flow of the machine. The high contact stresses that occur in sheet bulk metal forming (SBMF) lead to increased tool wear, which is being investigated in subproject B7 based on production trials. In cold forging processes at Fischerwerke GmbH & Co. KG (Fischer company), as with the processes of sheet bulk metal forming, there is heavy tool wear due to very high contact stresses and therefore also high downtimes of the production systems. As tool wear cannot currently be realistically predicted, the numerical wear calculation for the two processes - cold forging processes at Fischerwerke and SBMF - is to be further developed as part of this project. The numerical wear modelling shall consider Shaw's friction law instead of the normal stresses and thus is based on the frictional shear stress. Furthermore, the influence of the forming temperature on the hardness of the tools will be taken into account for the wear calculation. By adding the overlaying vibration onto the full-forward extrusion process, the surface quality of the components will be improved and the friction minimised. For this purpose, both numerical and experimental investigations will be carried out on a demonstrator process, which is derived from a complex multi-stage cold forging process of the company Fischerwerke.

At the beginning of the project, the used billet material will be characterised by vibration-free cylinder upset tests and cylinder upset tests with a superimposed oscillation. The numerical wear model for the forming process shall be developed and implemented in the simulation software in collaboration with Simufact engineering GmbH. Experimental investigations will be carried out with and without superimposed oscillations to transfer and analyse the advantages regarding the industrial process. Based on the experimental data obtained, the developed wear model will be validated. Finally, optimal process parameters for a wear reduction are determined with the help of a parameter identification, which can be used for processes with high contact normal stresses, such as sheet bulk metal forming and cold forging.