The bidimensional model of the electric arc is enhanced with the plasma–electrodes interaction to predict the properties and the energy distribution of an argon arc operating with current intensities between 100 and 200 A and electrode gaps of 10 and 20 mm.An adaptive numerical insulation is applied to the cathode, to properly simulate its thermionic emission mechanism and overcome the dependence on empirical distributions of the current density at its tip.The numerical results are quantitatively compared with the data obtained from calorimetric and spectroscopical measurements, performed on a device which generates a transferred arc between a water cooled copper anode and a thoriated tungsten cathode enclosed in a stainless steel chamber.The calculation of the heat fluxes towards the electrodes permits to determine the amount of power delivered to each component of the arc system (the anode, the cathode assembly and the chamber) and to evaluate the overall efficiency of the process for different configurations.The agreement between theory and data, over the range of parameters investigated, is sensible both in the temperature profiles and in the energy distributions. In such configurations, the conduction from the hot gas is the most relevant term in the overall heat transferred to the anode, but it is the electron transfer which rules the heat transfer in the arc attachment zone.The arc attachment radius is also dependent on the process parameters and increases with the arc current (from approximately 5 mm at 100 A to 7 mm at 200 A) and the arc length. However the maximum heat flux reached on the axis decreases increasing the gap between the electrodes, although more power is delivered to the anode due to the radial spreading of the plasma.A 10 mm 200 A argon arc releases to the anode about 2.6 kW, which corresponds to 75% of the total arc power available. If the arc is extended to 20 mm the power transferred rises by nearly 350 W, but the overall efficiency drops to 65% due to the increased losses towards the chamber.The power delivered to the anode increases almost linearly with the arc current, presenting a slope of about 15 W A−1, independent of the arc length.

This paper presents a survey of the applications of Prognostics and Health Management maintenance strategy to machine tools. A complete perspective on this Industry 4.0 cutting-edge maintenance policy, through the analysis of all its preliminary phases, is given as an introduction. Then, attention is given to prognostics, whose different approaches are briefly classified and explained, pointing out their advantages and shortcomings. After that, all the works on prognostics of machine tools and their main subsystem are reviewed, highlighting current open research areas for improvement.

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The benefits of cryogenic cooling by liquid nitrogen in cutting of titanium alloys have often been evaluated as a comparison\ud to dry machining conditions. However, it is more interesting to quantitatively assess the performance of cryogenic\ud conditioning of the process with respect to standard industrial conditions, that is, with respect to flood emulsion cooling.\ud The technical and scientific literature is scarce and somehow contradictory, especially in terms of cutting forces and\ud coefficient of friction. The aim of this article is to enrich the common base of experimental data, by conducting a comparison\ud of traditional and cryogenic turning of Ti6Al4V in a region of cutting parameters particularly relevant to the\ud aerospace industry, where no previous data are available. This study confirms that cryogenic machining is able to\ud increase the tool life, even with respect to wet cutting. Besides, the results show that not only cutting forces are reduced\ud but also a small, albeit significant, reduction can be achieved in the coefficient of friction at the tool–workpiece interface