Meso-scale tool breakage prediction based on finite element stress analysis for shoulder milling of hardened steel

In this article, finite element method (FEM) based tool stress analysis and breakage prediction are advanced for meso-scale shoulder milling of hardened stainless steel. Rather than using simplified line loads or uniformly distributed loads, the tool stress analyses are conducted with realistic chip load predicted by the previously developed 3D coupled Eulerian-Lagrangian (CEL) FEM model. A reliable distribution of contact forces obtained with a continuous tool-chip contact region is transferred to a static FEM model for tool stress analysis and breakage prediction at each angular location of an end mill. The simulation results are validated through dedicated cutting experiments with short cutting distances under various cutting conditions. The developed FEM models are found to be capable of making accurate predictions of tool breakage. Some key features of feed rate-related tool breakage are identified. It is found that the maximum tensile stress in the tool does not coincide with the maximum resultant cutting force in terms of cutter rotation. The tensile stress in the tool is not positively correlated with the resultant cutting force. In down milling, the maximum tensile stress is found to occur just after the tool starts to contact with the workpiece. It is also observed that the tensile stresses of the tool are much smaller in up milling configuration compared to down milling processes.