Machining difficult-to-machine materials such as alloys used in aerospace, nuclear and medical industries are usually accompanied with low productivity, poor surface quality and short tool life. Despite the broad use of the term difficult-to-machine or hard-to-cut materials, the area of these types of materials and their properties are not clear yet. On the other hand, using cutting fluids is a common technique for improving machinability and has been acknowledged since early 20th. However, the environmental and health hazards associated with the use of conventional cutting fluids together with developing governmental regulations have resulted in increasing machining costs. The aim of this paper is to review and identify the materials known as difficult-to-machine and their properties. In addition, different cutting fluids are reviewed and major health and environmental concerns about their usage in material cutting industries are defined. Finally, advances in reducing and/or eliminating the use of conventional cutting fluids are reviewed and discussed.

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Environmentally conscious machining of difficult-to-machine materials with regard to cutting fluids

This article is a state-of-the-art review of the use of cryogenic cooling using liquefied gases in machining. The review is classified into two major categories, namely cryogenic processing and cryogenic machining. In cryogenic processing also known as cryo-processing, the cutting tool material is subjected to cryogenic temperatures as a part of its heat treatment process. The majority of the reported studies identify that cryo-processing can considerably increase cutting tool life especially for high speed steel tools. It also identified that, in cryogenic machining, a cryogen is used as a cooling substance during cutting operations. The cryogen can be used to freeze the workpiece material and/or cutting tool. This article concludes that cryogenic cooling has demonstrated significant improvements in machinability by changing the material properties of the cutting tool and/or workpiece material at the cutting zone, altering the coefficient of friction and reducing the cutting temperature.

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State-of-the-art cryogenic machining and processing

This paper gives a bibliographical review of the finite element methods applied to the analysis and simulation of welding processes The bibliography is an addendum to the finite element analysis and simulation of welding: a bibliography (1976–96) published in Modelling Simul Mater Sci Eng (1996) 4 501–33 The added bibliography at the end of this paper contains approximately 550 references to papers and conference proceedings on the subject that were published in 1996–2001 These are classified in the following categories: modelling of welding processes in general; modelling of specific welding processes; influence of geometrical parameters; heat transfer and fluid flow in welds; residual stresses and deformations in welds; fracture mechanics and welding; fatigue of welded structures; destructive and non-destructive evaluation of weldments and cracks; welded tubular joints, pipes and pressure vessels/components; welds in plates and other structures/components

Finite element analysis and simulation of machining: an addendum: A bibliography (1996–2002)

A review on heat exchanger thermal hydraulic models for cryogenic applications

The concept of self-lubricating and self-cooling tools is proposed by combining the pulsating heat pipe and surface texturing technologies. The laser beam machining and electrical discharge machining are used to prepare the micro-texture self-lubricating and pulsating heat pipe self-cooling tools. The machining performance of the prepared tools and conventional tool in dry cutting of Ti-6Al-4V alloy is assessed in terms of cutting forces, cutting temperature, chip morphology and tool wear. Results show that the cutting forces, cutting temperature, friction coefficient at the tool–chip interface, and the tool wear of the micro-texture self-lubricating and pulsating heat pipe self-cooling tool are reduced compared with that of the conventional one. Coiling chips are produced with the micro-texture self-lubricating and pulsating heat pipe self-cooling tool while long and continuous chips are formed with the conventional tool. Two mechanisms responsible are found, first of all, the advanced tool's textured grooves were filled with solid lubricants which may be released and smeared at the tool–chip interface in cutting process; on the other hand, the pulsating heat pipe embedded in the tool could accelerate heat dissipation of the cutting insert.

Performance of the micro-texture self-lubricating and pulsating heat pipe self-cooling tools in dry cutting process

A combined numerical and experimental study is performed to analyze the feasibility of using heat pipe cooling in drilling applications. A parametric study is conducted to analyze the effect of different geometrical parameters expected for a heat pipe drill configuration, such as depth of the heat pipe within the drill, heat pipe diameter, heat flux input magnitude and length of the heat input zone. In this model, it is assumed that the drill is subjected to a static heat source which verifies the analysis and feasibility of using heat pipe cooling in drilling operations. The performance of the heat pipe drill model is approximated using a solid cylinder model of pure conduction. To validate the assumptions, numerical results are compared with experimental data that are based on the solid cylinder model. Both the numerical and experimental studies show that the use of a heat pipe in a drill can reduce the temperature field significantly. The results of this study can be used to define geometrical parameters for ‘optimal’ design and the setup for further analysis.

S. Eapen

Papers

Investigation of heat pipe cooling in drilling applications. Part I: preliminary numerical analysis and verification