Simulated and experimental analysis on serrated chip formation for hard milling process

Due to the intermittent cutting processes and variation of undeformed chip thickness, hard milling process displays evident differences regarding thermo-mechancial loads compared to turning process; therefore, a comprehensive understanding of chip formation mechanism in hard milling operation is urgent. In this study, the effect of cutting speed on chip characteristics was experimentally investigated concurently with finite element simulation. The main objective of this study concerns the serrated chip formation accompanying micro-cracks and physical phenomena which was achieved using finite element method (FEM). First, hard milling simulation model was proposed based on Johnson-Cook visco-plastic constitutive material model combined with Johnson Cook damage accounting for shear localization. Second, the proposed FE model was validated using acquired experimental results. The predicted results are in a good agreement with experimental results regrading chip morphology and cutting forces. In addition, the physical phenomena governing the formation of serrated segment and micro-cracks were discussed and clarified deeply through FE analysis. Finally, the localized plastic strain state on the machined surface associated with serrated segment formation was observed and indentified. This research, on one hand, can deepen the understanding of the formation mechanism of serrated segment; on the other hand, the results also provide guidance for cutting parameters optimization and desired machined surface integrity control.