An interdisciplinary view on the formulation of a process force model for milling processes

Janis Kimm, Lehrstuhl Werkstofftechnik, Ruhr-Universität Bochum, Bochum, Germany
Jim A. Bergmann, Virtual Machining, TU Dortmund University, Dortmund, Germany
Simon Kugai, Institut für Mechanik, Universität Duisburg-Essen, Essen, Germany
Jörg Schröder, Institut für Mechanik, Universität Duisburg-Essen, Essen, Germany
Werner Theisen, Lehrstuhl Werkstofftechnik, Ruhr-Universität Bochum, Bochum, Germany
Petra Wiederkehr, Virtual Machining, TU Dortmund University, Dortmund, Germany

In this contribution a collaboration of material science, mechanical engineering and applied computer science is established to obtain new insights on the field of metal cutting. By combining aspects of material characterization and mechanical calculations, a new approach for identifying process forces is introduced. During machining operations, complex cutter workpiece engagements lead to varying process forces. Correlations between material properties, process parameters and resulting forces have to be analyzed to ensure predictability of manufacturing processes. Common numerical simulation systems like the Finite Element Method are currently not able to accurately predict ductile fracture and shear band deformation during metal cutting. Additionally, cutting conditions can differ due to varying microstructures within the material as a result of a prior heat treatment or the temperature flow during milling. Experimental reference data were acquired by conducting orthogonal cutting experiments and by using a single pass pendulum to characterize the chip formation of materials at large deformation rates. The cutting forces and reaction forces were measured for differently heat treated specimen of the low alloyed steel 42CrMo4. By using standardized material testing experiments, such as the uniaxial tensile test, a set of material characteristics were used to initialize simulations to verify the material flow. The mechanical simulations were performed based on non-ordinary state-based peridynamics. By incorporating a stress based approach, the method can be used to compute process forces during milling on a macroscopic level. With this interdisciplinary view on metal cutting, a force model for milling processes can be derived with respect to findings from material testing experiments and mechanical simulations. This approach yields a novel formulation for a process force model regarding arbitrary interactions between tool geometries and workpiece material.

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