D. Dudzinski

A review of developments towards dry and high speed machining of Inconel 718 alloy

Abstract The increasing attention to the environmental and health impacts of industry activities by governmental regulation and by the growing awareness in society is forcing manufacturers to reduce the use of lubricants. In the machining of aeronautical materials, classified as difficult-to-machine materials, the consumption of cooling lubricant during the machining operations is very important. The associated costs of coolant acquisition, use, disposal and washing the machined components are significant, up to four times the cost of consumable tooling used in the cutting operations. To reduce the costs of production and to make the processes environmentally safe, the goal of the aeronautical manufacturers is to move toward dry cutting by eliminating or minimising cutting fluids. This goal can be achieved by a clear understanding of the cutting fluid function in machining operations, in particular in high speed cutting, and by the development and the use of new materials for tools and coatings. High speed cutting is another important aspect of advanced manufacturing technology introduced to achieve high productivity and to save machining cost. The combination of high speed cutting and dry cutting for difficult-to-cut aerospace materials is the growing challenge to deal with the economic, environmental and health aspects of machining. In this paper, attention is focussed on Inconel 718 and recent work and advances concerning machining of this material are presented. In addition, some solutions to reduce the use of coolants are explored, and different coating techniques to enable a move towards dry machining are examined.

Modelling of orthogonal cutting with a temperature dependent friction law

Abstract In this paper the process of orthogonal cutting is studied by analytical means. A thermomechanical model of the primary shear zone is combined with a modelling of the contact problem at the tool-chip interface. A friction law is introduced that accounts for temperature effects. The effects of cutting conditions and material behaviour on the temperature distribution along the contact zone, on the mean friction and on the global cutting forces are evaluated. The experimental trends are shown to be well described by the proposed model.

Perturbation analysis of thermoviscoplastic instabilities in biaxial loading

Abstract The sheet metal ductility for a thermoviscoplastic material is analysed by using a perturbation method. A significant rate of growth of the instability is characterized in terms of an effective instability analysis. Analytical results are obtained for quite general material behavior (including time-dependent effects). They match the results of Hill (1952. J. Mech. Phys. Solids 1 , 19) and Storen and Rice (1975, J. Mech. Phys. Solids 23 , 421) for time-independent behavior.

Thermoviscoplastic modelling of oblique cutting: forces and chip flow predictions

Abstract A modelling of oblique cutting for viscoplastic materials is presented. The thermomechanical properties and the inertia effects are accounted for to describe the material flow in the primary shear zone. At the tool–chip interface, a temperature-dependent friction law is introduced to take account of the extreme conditions of pressure, velocities and temperature encountered during machining. The chip flow angle is calculated by assuming that the friction force is collinear to the chip flow direction on the tool rake face. Due to the temperature dependence of the friction law at the tool–chip interface, the chip flow angle predicted by the model, is affected by the cutting speed, the undeformed chip thickness, the normal rake angle, the edge inclination angle and the thermomechanical behavior of the work material. This dependence and the trends predicted by the present approach are confirmed by experimental observations. Effects of cutting conditions on the cutting forces are also presented and compared to experiments.

Parametric geometry for modelling of milling operations

This paper presents a geometrical description of common end mills and of the engagement in the workpiece material for shoulder milling. The tool geometry is decomposed into elementary cutting edges in oblique cutting position and the elementary cutting forces are calculated from a thermomechanical approach and validated for a 42CrMo4 steel.

An Analytical Thermomechanical Modelling of Peripheral Milling Process Using a Predictive Machining Theory

In this work, a predictive machining theory, based on an analytical thermomechanical approach of oblique cutting [17,18], has been applied to the peripheral milling process. That leads to a three dimensional cutting force model for end milling operations which is an alternative approach in comparison with the mechanistic one. In this model, the material characteristics such as strain rate sensitivity, strain hardening and thermal softening are considered and thermomechanical coupling and inertia effects are accounted for. Calculated and experimental results are compared for up-milling.

Analytical and Finite Element Approaches for the Drilling Modelling

Perform drill point design is one of the major problems for the drill manufacturers. To enhance drill performance they have to elaborate prototypes and carry out many tests to progress step by step to an optimised geometry. Model and simulate drilling operations is a very interesting way to obtain useful information for the drill manufacturing process. In this work, a geometrical and thermomechanical analytical model and a finite element approach of drilling were used. While the first gives very quickly some global information, the second gives more details but after a long calculation time. It is shown that the two approaches are complementary and that they may be used with advantage for the drill design.

Analytical Modelling Of Milling For Tool Design And Selection

This paper presents an efficient analytical model which allows to simulate a large panel of milling operations. A geometrical description of common end mills and of their engagement in the workpiece material is proposed. The internal radius of the rounded part of the tool envelope is used to define the considered type of mill. The cutting edge position is described for a constant lead helix and for a constant local helix angle. A thermomechanical approach of oblique cutting is applied to predict forces acting on the tool and these results are compared with experimental data obtained from milling tests on a 42CrMo4 steel for three classical types of mills. The influence of some tool’s geometrical parameters on predicted cutting forces is presented in order to propose optimisation criteria for design and selection of cutting tools.