Damage mechanics analysis of failure mechanisms for ceramic cutting tools in intermittent turning

Al2O3-based ceramic is one of the most widely used materials for tools employed in hardened steel turning applications due to its high hardness, wear resistance, heat resistance and chemical stability. The objective of this work is to reveal the failure mechanisms of Al2O3-(W, Ti)C ceramic tools in intermittent turning of hardened AISI 1045 steel by means of damage mechanics. Intermittent turning test of hardened AISI 1045 steel is conducted. Results show that the cutting tools exhibit the characteristics of damage accumulation. A damage model is constructed by means of micromechanics in order to investigate the representative volume element (RVE) subjected to tri-axial stress induced by the mechanical and thermal loads. Based on the damage model, mathematical method is proposed to determine the initial and critical damage of the ceramic tool. Finite element simulation is applied to obtain distribution and evolution of tool stress in a single cutting cycle of intermittent turning process. The maximum damage equivalent stress (MDES), which is calculated from the tool stress and material damage, is used to reveal the differences of tool failure mechanisms under different cutting conditions. The effects of exit angle, tool rake and clearance angles on tool failure are identified. The MDES proposed in the present study can be applied to provide valuable information for the material design and geometry design of the ceramic cutting tool.