An Analytical Model of the Temperature Distribution in the Chip Breakage Location of Metal Cutting Operations

Chip breakage is a major machinability criterion. Stable processes in automated manufacturing systems depend on favorable chip forms, which are efficiently manageable and not hazardous to the machine operators.It is well known that chip breakage initiates with ductile material failure on the chip-free-surface. The ductile failure strain is mainly in-fluenced by the stress-state, the temperature and the strain rate. Little theoretic knowledge exists concerning the relationships between these state variables and the tool/process parameters, which is required for developing predictive methodologies for efficient tool/process design. The task can be approached by relating the state variables to the chip geometry: Both are interdependent results of the complex interactions between the tool/process parameters and the material properties. However, while the influence of the tool/process parameters on the chip geometry is experimentally obtainable by High-Speed-Cameras, state variables like the temperature on the chip-free-surface are hardly measurable. Accordingly, understanding the relationship between chip geometry and state variables on the chip-free-surface creates the foundation for understanding the relationship between tool/process parameters and chip breakability.This work presents an analytical model of the relationship between chip geometry and temperature distribution on the chip-free-surface. The temperature is derived as a function of the 3D-chip geometry parameters, the tool/process parameters and the thermo-mechanical workmaterial properties. It is shown how each of these parameters influences the temperature fields. The derivation assumes a strain dependent fraction of the plastic energy transforming into thermal energy. The model is programmed and confirmed by longitudinal turning experiments and a validated FEM-model of longitudinal turning of steel AISI 1045.