Recent advances in modelling of metal machining processes

Temperature and wear of cutting tools in high-speed machining of Inconel 718 and Ti6Al6V2Sn

Nickel-based superalloy is widely employed in aircraft engines and the hot end components of various types of gas turbines with its high strength, strong corrosion resistance and excellent thermal fatigue properties and thermal stability. However, nickel-based superalloy is one of the extremely difficult-to-cut materials. During the machining process, the interaction between the tool and the workpiece causes the severe plastic deformation in the local area of workpiece, and the intense friction at the tool–workpiece interface. The resulting cutting heat coupled with the serious work hardening leads to a series of flaws, such as excessive tool wear, frequent tool change, short tool life, low productivity, and large amount of power consumption etc., in which the excessive tool wear has become one of the main bottlenecks that constraints the machinability of nickel-based superalloys and its wide range of applications. In this article, attention is mainly focused on the tool wear characteristics in the machining of nickel-based superalloys, and the state of the art in the fields of failure mechanism, monitoring and prediction, and control of tool wear are reviewed. The survey of existing works has revealed several gaps in the aspects of tool self-organizing process based on the non-equilibrium thermodynamics, tool wear considering the tool nose radius, thermal diffusion layer in coated tools, tool life prediction based on the thermal–mechanical coupling, and industrial application of tool wear online monitoring devices. The review aims at providing an insight into the tool wear characteristics in the machining of nickel-based superalloys and shows the great potential for further investigations and innovation in the field of tool wear.

Tool wear characteristics in machining of nickel-based superalloys

A review of machine vision sensors for tool condition monitoring

Cryogenic machining is an environmentally safe alternative to conventional emulsion cooling. In this study, liquid nitrogen (LN2) is applied to cutting Ti-6Al-4V, a difficult-to-machine but widely used material in aerospace industry. With the goal of identifying the cooling approach for most effectively and economically using cryogenic machining, this study evaluated cutting temperatures obtained under various cooling conditions. In addition to analyzing cooling approaches reported in previous cryogenic machining literatures (i.e., precooling the workpiece and conductive remote cooling), this paper introduces an innovative and economical dispensing method that directs LN2 through micro jets to the flank, the rake, or both near the cutting edge. The cutting temperatures were theoretically estimated by finite element method and the influence of cutting speed was analyzed. They were experimentally verified using the thermocouple imbedded at the carbide insert. Temperatures in cryogenic machining were compared with conventional dry cutting and emulsion cooling. Findings showed that a small amount of liquid nitrogen applied locally to the cutting edge is superior to emulsion cutting in lowering the cutting temperature. The study found that cooling approaches in order of effectiveness (worst to best) to be: dry cutting, cryogenic tool back cooling, emulsion cooling, precooling the workpiece, cryogenic flank cooling, cryogenic rake cooling, and simultaneous rake and flank cooling.

Cooling approaches and cutting temperatures in cryogenic machining of Ti-6Al-4V

Analytical prediction of cutting tool wear

Through the energy method proposed in the previous parts of this study, it is possible to predict chip formation and cutting force for a single point tool of arbitrary geometry. By using the predicted results together with an assumption made on the stress distribution on the tool face, the temperature distribution within chip and tool is obtained through a numerical analysis. A characteristic equation of crater wear of carbide tool is derived theoretically and verified experimentally. Computer simulation of crater wear development is then carried out by using the characteristic equation, and the predicted distributions of the stress and the temperature.

E. Usui

Papers

Analytical prediction of cutting tool wear

Analytical Prediction of Three Dimensional Cutting Process—Part 3: Cutting Temperature and Crater Wear of Carbide Tool

Analytical Prediction of Three Dimensional Cutting Process—Part 1: Basic Cutting Model and Energy Approach

Analytical Prediction of Three Dimensional Cutting Process—Part 2: Chip Formation and Cutting Force with Conventional Single-Point Tool