A physics-based flow stress model for chip formation simulation when machining Alloy 718

Artikel i vetenskaplig tidskrift, 2026

In research on machining technology, simulating chip formation is increasingly essential for understanding the interaction between the cutting edge and workpiece in the shear zones. For this purpose, accurate descriptions of material-specific flow behaviour are decisive and in particular phenomenological models commonly used to approximate the strains and stresses involved. However, challenges remain in accounting for the effects of varying microstructure on chip formation and thermomechanical loads. This study introduces a physics-based constitutive model designed to address this limitation. The flow stress model incorporates microstructure characteristics, such as grain size and the size and volume fractions of strengthening precipitates, to enhance the numerical analysis of chip formation and related thermomechanical loads on cutting tools during machining. A comprehensive material characterisation, including metallographic analyses and Split-Hopkinson-Pressure-Bar (SHPB) tests, reveals the alloy’s flow behaviour, allowing for the establishment of flow stress models for different material conditions of the difficult-to-machine nickel-based Alloy 718. In comparison with reference simulations using a Johnson–Cook flow stress model to analyse a drilling process, the accuracy of a physics-based constitutive model in 3D simulations is evaluated, showing a deviation in drilling torque of ΔMz = - 0.88% compared to experimentally measured process forces. Validation is achieved through experimental data providing mechanical tool loads and in-situ high-speed recordings to assess calculated chip formation.