Edge chipping mechanism and failure time prediction on carbide cemented tool during drilling of CFRP/Ti stack

Abstract

To investigate the edge chipping during drilling of the CFRP/Ti stack with carbide cemented tools, a drilling experiment was carried out and a tool failure model was proposed. Thrust force, drilling temperature, and tool wear were analyzed. A tool stressing model and a tool failure model of edge chipping were constructed respectively. On the basis of these, the prediction model on the edge chipping was established to forecast the failure time. Drilling temperature, Vickers hardness, and cutting speed were considered during the prediction model building. The results demonstrate that adhesive wear has a great influence on the edge chipping. The damage of adhesive wear for tool rake face leads to the load variation on rake face and the initial crack. Under the action of shear stress, the crack starts at rake face and then expands to the flank face, resulting in tool edge chipping. The affinity interaction (between titanium alloy with carbide cemented) and the thermal residual stress are two critical factors for tool edge chipping. Tear easily occurs inside the binding phase or at the boundary between hard phase and binder phase. As the drilling temperature increases, the hardness of the carbide cemented will gradually decrease. The prediction result of failure time is similar to the experimental result, and the effectiveness of the prediction model is verified.