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Nantes, France

Braham-Bouchnak T.,Arts et Metiers ParisTech | Germain G.,Arts et Metiers ParisTech | Morel A.,Arts et Metiers ParisTech | Furet B.,IUT Nantes
Machining Science and Technology | Year: 2015

The origin of this article is the quantification of productivity gains and the improvement in surface integrity seen for a recent titanium alloy that is seeing increasing use in the aeronautical industry. The Ti555-3 titanium alloy, which is starting to find greater application in the aeronautical field, exhibits certain difficulties in terms of machining. High Pressure Coolant (HPC) assisted turning consists of projecting a high pressure coolant jet between the chip and the tool. Comparisons are made between assisted turning using variable jet pressure and conventional turning (dry and classical lubrication). It is shown that it is possible to improve productivity by using HPC-assisted machining. The results highlight good chip fragmentation and a great improvement of tool life with HPC assistance. Surface integrity is also shown to be improved, through surface roughness parameters that decrease, and surface residual stresses that become more compressive. These effects have been attributed to the thermo-mechanical action of the coolant jet resulting in lower cutting forces, lower coefficient of friction and lower temperature in the cutting zone. © 2015 Taylor and Francis Group, LLC. Source


Ayed Y.,Arts et Metiers ParisTech | Germain G.,Arts et Metiers ParisTech | Ammar A.,Arts et Metiers ParisTech | Furet B.,IUT Nantes
Key Engineering Materials | Year: 2013

The article presents the results of an experimental study on titanium alloy Ti17. The purpose of this study is to determine the degradation mechanisms of an uncoated carbide tool. Two conditions, roughing and finishing, have been studied under different lubrication conditions. The tests are accompanied by measurement of the cutting forces, the observation of the phenomena of wear (flank, crater, and notch) and EDS analysis. The results showed that the wear mechanisms with and without high pressure water jet assistance are not identical. Indeed, in the roughing condition and in conventional machining, tool deforms plastically and eventually collapses quickly because the temperature in the cutting zone becomes too high. In contrast, this problem disappears under water jet assisted machining and the flank wear is stabilized. Tool life is greatly increased but its sudden rupture is due to the propagation of notch. Copyright © 2013 Trans Tech Publications Ltd. Source


Germain G.,Arts et Metiers ParisTech | Morel A.,Arts et Metiers ParisTech | Braham-Bouchnak T.,IUT Nantes
Journal of Engineering Materials and Technology, Transactions of the ASME | Year: 2013

Determining a material constitutive law that is representative of the extreme conditions found in the cutting zone during machining operations is a very challenging problem. In this study, dynamic shear tests, which reproduce, as faithfully as possible, these conditions in terms of strain, strain rate, and temperature, have been developed using hat-shaped specimens. The objective was to identify the parameters of a Johnson-Cook material behavior model by an inverse method for two titanium alloys: Ti6Al4V and Ti555-3. In order to be as representative as possible of the experimental results, the parameters of the Johnson-Cook model were not considered to be constant over the total range of the strain rate and temperature investigated. This reflects a change in the mechanisms governing the deformation. The shear zones observed in hat-shaped specimens were analyzed and compared to those produced in chips during conventional machining for both materials. It is concluded that the observed shear bands can be classified as white-etching bands only for the Ti555-3 alloy. These white bands are assumed to form more easily in the Ti555-3 alloy due to its predominately β phase microstructure compared to the Ti6Al4V alloy with a α + β microstructure. © 2013 by ASME. Source


Ayed Y.,Arts et Metiers ParisTech | Germain G.,Arts et Metiers ParisTech | Ammar A.,Arts et Metiers ParisTech | Furet B.,IUT Nantes
Wear | Year: 2013

This article presents the results of an experimental study on the Ti17 titanium alloy, which was carried out to analyze tool wear and the degradation mechanisms of an uncoated tungsten carbide tool insert. Two machining conditions, roughing and finishing, have been studied under different lubrication conditions. The experimental procedure included measurement of the cutting forces and the surface roughness. Different techniques have been used to explain the tool wear mechanisms. Distribution maps of the elemental composition of the titanium alloy and the tool inserts have been created using Energy Dispersive X-ray Spectroscopy (EDS). An area of material deposition on the tool rake face, characterized by a high titanium concentration has been observed. The width of this area and the concentration of titanium, decrease when increasing water jet pressure. The study shows that wear mechanisms, with and without high-pressure water jet assistance (HPWJA) are not the same. For example, for the roughing condition using conventional lubrication, the temperature in the cutting area becomes very high, this causes plastic deformation of the cutting edge which results in its rapid collapse. By contrast, this problem disappears when machining with HPWJA. In addition, the evolution of flank wear (VB) is stabilized with high-pressure lubrication. In this case, the most critical degradation mode is due to notch wear (VBn) leading to the sudden rupture of the cutting edge. © 2013 Elsevier Ltd. Source


Ayed Y.,Arts et Metiers ParisTech | Germain G.,Arts et Metiers ParisTech | Ammar A.,Arts et Metiers ParisTech | Furet B.,IUT Nantes
Precision Engineering | Year: 2015

This paper presents experimental results concerning the machinability of the titanium alloy Ti17 with and without high-pressure water jet assistance (HPWJA) using uncoated WC/Co tools. For this purpose, the influence of the cutting speed and the water jet pressure on the evolution of tool wear and cutting forces have been investigated. The cutting speed has been varied between 50 m/min and 100 m/min and the water jet pressure has been varied from 50 bar to 250 bar. The optimum water jet pressure has been determined, leading to an increase in tool life of approximately 9 times. Compared to conventional lubrication, an increase of about 30% in productivity can be obtained. © 2015 Elsevier Inc. All rights reserved. Source

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