https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Wed, 13 May 2026 15:30:12 GMT 2026-05-13T15:30:12Z http://hdl.handle.net/10985/9940 Tool wear analysis and improvement of cutting conditions using the high-pressure water-jet assistance when machining the Ti17 titanium alloy AYED, Yessine; GERMAIN, Guénaël; AMMAR, Amine; FURET, Benoit 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. Thu, 01 Jan 2015 00:00:00 GMT http://hdl.handle.net/10985/9940 2015-01-01T00:00:00Z AYED, Yessine GERMAIN, Guénaël AMMAR, Amine FURET, Benoit 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. http://hdl.handle.net/10985/7417 Identification de lois de comportement représentatives des conditions d’usinage pour des alliages de titane à différentes teneurs alpha/beta GERMAIN, Guénaël; AYED, Yessine; BRAHAM-BOUCHNAK, Tarek; MOREL, Anne Determining a material constitutive law which 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 behaviour model by an inverse method for three titanium alloys: Ti6Al4V, Ti555-3 and Ti17. 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 analysed and compared to those produced in chips during conventional machining for both materials. It is concluded that, in the Ti555-3 alloy, the proportion of alpha-phase greatly reduces in high strain-rate zones. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/7417 2013-01-01T00:00:00Z GERMAIN, Guénaël AYED, Yessine BRAHAM-BOUCHNAK, Tarek MOREL, Anne Determining a material constitutive law which 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 behaviour model by an inverse method for three titanium alloys: Ti6Al4V, Ti555-3 and Ti17. 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 analysed and compared to those produced in chips during conventional machining for both materials. It is concluded that, in the Ti555-3 alloy, the proportion of alpha-phase greatly reduces in high strain-rate zones. http://hdl.handle.net/10985/16562 On the formation of adiabatic shear bands in titanium alloy Ti17 under severe loading conditions BEN BOUBAKER, Houssem; AYED, Yessine; MAREAU, Charles; GERMAIN, Guénaël For metallic materials, fabrication processes (e.g. machining and forging) may involve important strain rates and high temperatures. For such severe loading conditions, the development of damage is often associated with the formation of Adiabatic Shear Bands (ASB). In this work, the impact of loading conditions (strain rate, temperature) on the formation of ASB in a beta rich titanium alloy (Ti17) is investigated. In this perspective, uniaxial compression tests have been conducted on cylindrical samples with a Gleeble-3500 thermo-mechanical simulator at temperatures ranging from 25◦C to 800◦C and strain rates ranging from 0.1 to 50 s−1 with axial strains of approximately 50 %. According to the experimental results, the flow curves exhibit hardening from 25◦C to 550◦C and softening from 600◦C to 800◦C. When looking at the evolution of flow stress, the strain rate sensitivity is found to increase significantly with increasing temperatures. Also, adiabatic shear bands are preferably observed for high strain rates and low temperatures. The formation of ASB thus seems to be quite dependent on the evolution of the strain rate sensitivity of Ti17. Finally, metallographic observations have been carried out to better understand the process leading to the formation of ASB. Such observations demonstrate that the average width of ASB increases with increasing temperatures and decreasing strain rates. However, such observations do not allow for identifying whether some specific microstructural transformations (e.g. recrystallization or phase transformation) could explain the formation of ASB or not. Mon, 01 Jan 2018 00:00:00 GMT http://hdl.handle.net/10985/16562 2018-01-01T00:00:00Z BEN BOUBAKER, Houssem AYED, Yessine MAREAU, Charles GERMAIN, Guénaël For metallic materials, fabrication processes (e.g. machining and forging) may involve important strain rates and high temperatures. For such severe loading conditions, the development of damage is often associated with the formation of Adiabatic Shear Bands (ASB). In this work, the impact of loading conditions (strain rate, temperature) on the formation of ASB in a beta rich titanium alloy (Ti17) is investigated. In this perspective, uniaxial compression tests have been conducted on cylindrical samples with a Gleeble-3500 thermo-mechanical simulator at temperatures ranging from 25◦C to 800◦C and strain rates ranging from 0.1 to 50 s−1 with axial strains of approximately 50 %. According to the experimental results, the flow curves exhibit hardening from 25◦C to 550◦C and softening from 600◦C to 800◦C. When looking at the evolution of flow stress, the strain rate sensitivity is found to increase significantly with increasing temperatures. Also, adiabatic shear bands are preferably observed for high strain rates and low temperatures. The formation of ASB thus seems to be quite dependent on the evolution of the strain rate sensitivity of Ti17. Finally, metallographic observations have been carried out to better understand the process leading to the formation of ASB. Such observations demonstrate that the average width of ASB increases with increasing temperatures and decreasing strain rates. However, such observations do not allow for identifying whether some specific microstructural transformations (e.g. recrystallization or phase transformation) could explain the formation of ASB or not. http://hdl.handle.net/10985/16581 Orthogonal micro-cutting modeling of the Ti17 titanium alloy using the crystal plasticity theory AYED, Yessine; ROBERT, Camille; GERMAIN, Guénaël; AMMAR, Amine The development of computation means has allowed the simulation of complex mechanical problems. The first simulations of manufacturing processes at the microstructure scale, namely in the field of machining, have recently emerged. In this study, and on the basis of previous research, a novel approach to machining simulation is proposed. A crystal plasticity behavior law has thus been implemented and its parameters have been identified, for each of the two phases constituting the material. This is achieved through experimental tests conducted under extreme conditions of temperature and strain rates. Numerical models are composed of grains in the form of Voronoï cells. Random crystal orientations have also been assigned to each grain. This has subsequently allowed the simulation of the machining process. Access to local physical parameters such as crystal orientations, their evolution and phase transition thus presents a major breakthrough in this field. Sun, 01 Jan 2017 00:00:00 GMT http://hdl.handle.net/10985/16581 2017-01-01T00:00:00Z AYED, Yessine ROBERT, Camille GERMAIN, Guénaël AMMAR, Amine The development of computation means has allowed the simulation of complex mechanical problems. The first simulations of manufacturing processes at the microstructure scale, namely in the field of machining, have recently emerged. In this study, and on the basis of previous research, a novel approach to machining simulation is proposed. A crystal plasticity behavior law has thus been implemented and its parameters have been identified, for each of the two phases constituting the material. This is achieved through experimental tests conducted under extreme conditions of temperature and strain rates. Numerical models are composed of grains in the form of Voronoï cells. Random crystal orientations have also been assigned to each grain. This has subsequently allowed the simulation of the machining process. Access to local physical parameters such as crystal orientations, their evolution and phase transition thus presents a major breakthrough in this field. http://hdl.handle.net/10985/16577 High-pressure water-jet-assisted machining of Ti555-3 titanium alloy: investigation of tool wear mechanisms AYED, Yessine; GERMAIN, Guénaël The main objective of this study is to investigate uncoated tungsten carbide tool wear mechanisms for high-pressure waterjet machining of the Ti555-3 titanium alloy. A comparative study has been undertaken (i.e. conventional versus assisted machining) based on numerous experimental tests. These tests have been accompanied by the measurement of the cutting forces and flank wear. It is concluded that the high-pressure water-jet assistance can greatly increase tool life compared to conventional machining, for all cutting conditions. The gain in tool life depends on the severity of the cutting condition. The analyses performed for each test (i.e. SEM, EDS and 3D profilometer) made it possible to monitor the tool wear and to investigate the main wear mechanisms. Based on these analyses, adhesion wear appears to be the most influential mechanism and it is accelerated by an increase in water-jet pressure. Monitoring of the wear profile made it possible to study the evolution of crater wear and material chipping during machining. Mon, 01 Jan 2018 00:00:00 GMT http://hdl.handle.net/10985/16577 2018-01-01T00:00:00Z AYED, Yessine GERMAIN, Guénaël The main objective of this study is to investigate uncoated tungsten carbide tool wear mechanisms for high-pressure waterjet machining of the Ti555-3 titanium alloy. A comparative study has been undertaken (i.e. conventional versus assisted machining) based on numerous experimental tests. These tests have been accompanied by the measurement of the cutting forces and flank wear. It is concluded that the high-pressure water-jet assistance can greatly increase tool life compared to conventional machining, for all cutting conditions. The gain in tool life depends on the severity of the cutting condition. The analyses performed for each test (i.e. SEM, EDS and 3D profilometer) made it possible to monitor the tool wear and to investigate the main wear mechanisms. Based on these analyses, adhesion wear appears to be the most influential mechanism and it is accelerated by an increase in water-jet pressure. Monitoring of the wear profile made it possible to study the evolution of crater wear and material chipping during machining. http://hdl.handle.net/10985/16583 Impact of supply conditions of liquid nitrogen on tool wear and surface integrity when machining the Ti-6Al-4V titanium alloy AYED, Yessine; GERMAIN, Guénaël; PUBILL MELSIO, Anna-Maria; KOWALEWSKI, Pierre; LOCUFIER, Damien Cryogenic-assisted machining has already shown its advantages on the process and the machining parameters have been analysed. However, part of the coolant jet characteristics as the pressure and flow rate have not been completely studied and optimized. Hence, the main objective of this study is to investigate the impact of these parameters on tool wear and surface integrity when machining the titanium alloy Ti-6Al-4V. Several nozzle diameters have been therefore employed in order to vary the pressure and the flow rate. A new nozzle holder has been developed to ensure the replacement of these calibrated nozzles of different diameters. The machining tests have allowed to draw attention to the impact of the pressure and the flow rate oftheliquid nitrogenjet not only ontool life but also on surface integrity. Indeed, the increase of flow rate and pressure increases tool life. Moreover, surface integrity has been greatly improved notably atthe highest pressure and the highest flow rate. Sun, 01 Jan 2017 00:00:00 GMT http://hdl.handle.net/10985/16583 2017-01-01T00:00:00Z AYED, Yessine GERMAIN, Guénaël PUBILL MELSIO, Anna-Maria KOWALEWSKI, Pierre LOCUFIER, Damien Cryogenic-assisted machining has already shown its advantages on the process and the machining parameters have been analysed. However, part of the coolant jet characteristics as the pressure and flow rate have not been completely studied and optimized. Hence, the main objective of this study is to investigate the impact of these parameters on tool wear and surface integrity when machining the titanium alloy Ti-6Al-4V. Several nozzle diameters have been therefore employed in order to vary the pressure and the flow rate. A new nozzle holder has been developed to ensure the replacement of these calibrated nozzles of different diameters. The machining tests have allowed to draw attention to the impact of the pressure and the flow rate oftheliquid nitrogenjet not only ontool life but also on surface integrity. Indeed, the increase of flow rate and pressure increases tool life. Moreover, surface integrity has been greatly improved notably atthe highest pressure and the highest flow rate. http://hdl.handle.net/10985/17536 Impact of the initial microstructure and the loading conditions on the deformation behavior of the Ti17 titanium alloy BEN BOUBAKER, Houssem; MAREAU, Charles; AYED, Yessine; GERMAIN, Guénaël; TIDU, Albert In this work, the impact of the microstructure and the loading conditions on the mechanical behavior of a β-rich Ti17 titanium alloy is investigated. For this purpose, two different initial microstructures are considered : (i) a two-phase lamellar α + β microstructure and (ii) a single-phase equiaxed β-treated microstructure. First, compression tests are performed at different strain rates (from 10-1 to 10 s-1) and different temperatures (from 25 to 900°C) for both microstructures. Then, optical microscopy, scanning electron microscopy, EBSD and X-ray diffraction analyses of deformed specimens are carried out. Whatever the loading conditions are, the flow stress of the as-received α + β Ti17 is higher than that of the β-treated Ti17. Also, because of a higher strain-rate sensitivity, the β-treated Ti17 is less prone to shear banding. At low temperatures (i.e., T ≤ 450°C), the deformation behavior of both the as-received α + β and the β-treated Ti17 is controlled by strain hardening. For the β-treated Ti17 alloy, martensitic transformation is systematically detected in this temperature range. The softening behavior of the as-received α + β Ti17 observed at high temperatures is due to the joint effect of dynamic recrystallization, dynamic transformation, adiabatic heating and morphological texture evolution. For the β-treated Ti17 alloy, when the temperature exceeds 700°C, stress–strain curves display a yield drop phenomenon, which is explained by dynamic recrystallization. Tue, 01 Jan 2019 00:00:00 GMT http://hdl.handle.net/10985/17536 2019-01-01T00:00:00Z BEN BOUBAKER, Houssem MAREAU, Charles AYED, Yessine GERMAIN, Guénaël TIDU, Albert In this work, the impact of the microstructure and the loading conditions on the mechanical behavior of a β-rich Ti17 titanium alloy is investigated. For this purpose, two different initial microstructures are considered : (i) a two-phase lamellar α + β microstructure and (ii) a single-phase equiaxed β-treated microstructure. First, compression tests are performed at different strain rates (from 10-1 to 10 s-1) and different temperatures (from 25 to 900°C) for both microstructures. Then, optical microscopy, scanning electron microscopy, EBSD and X-ray diffraction analyses of deformed specimens are carried out. Whatever the loading conditions are, the flow stress of the as-received α + β Ti17 is higher than that of the β-treated Ti17. Also, because of a higher strain-rate sensitivity, the β-treated Ti17 is less prone to shear banding. At low temperatures (i.e., T ≤ 450°C), the deformation behavior of both the as-received α + β and the β-treated Ti17 is controlled by strain hardening. For the β-treated Ti17 alloy, martensitic transformation is systematically detected in this temperature range. The softening behavior of the as-received α + β Ti17 observed at high temperatures is due to the joint effect of dynamic recrystallization, dynamic transformation, adiabatic heating and morphological texture evolution. For the β-treated Ti17 alloy, when the temperature exceeds 700°C, stress–strain curves display a yield drop phenomenon, which is explained by dynamic recrystallization. http://hdl.handle.net/10985/11145 Numerical analysis of constitutive coefficients effects on FE simulation of the 2D orthogonal cutting process: application to the Ti6Al4V YAICH, Mariem; AYED, Yessine; BOUAZIZ, Zoubeir; GERMAIN, Guénaël In this paper, a deep study of constitutive parameters definition effect is done in order to guarantee sufficient reliability of the finite element machining modeling. The case of a particular biphasic titanium alloy Ti6Al4V known by its low machinability is investigated. The Johnson-Cook (JC) elasto-thermo-visco-plastic-damage model combined with the energy-based ductile fracture criteria is used. Segmentation frequency, chip curvature radius, shear band spacing, chip serration sensitivity and intensity, accumulated plastic strain in the formed chip segments, and cutting forces levels are determined where their dependency to every constitutive coefficient is examined and highlighted. It is demonstrated from the separate variation of every plastic and damage parameters that an interesting finite element modeling (FEM) relevance is reached with the adjustment of JC strain hardening coefficients term, thermal softening parameter, exponent fracture factor, and damage evolution energy. Moderate and high cutting speeds are applied to the cutting tool in the aim to test their impact on shear localization, chip segmentation, and numerical forces levels as well as to approve previous highlighted findings related to constitutive parameters definition. In general, this study focuses on a prominent decrease in identification process cost with the previous knowledge of the most affecting constitutive coefficients while keeping an interesting agreement between numerical and experimental results. Fri, 01 Jan 2016 00:00:00 GMT http://hdl.handle.net/10985/11145 2016-01-01T00:00:00Z YAICH, Mariem AYED, Yessine BOUAZIZ, Zoubeir GERMAIN, Guénaël In this paper, a deep study of constitutive parameters definition effect is done in order to guarantee sufficient reliability of the finite element machining modeling. The case of a particular biphasic titanium alloy Ti6Al4V known by its low machinability is investigated. The Johnson-Cook (JC) elasto-thermo-visco-plastic-damage model combined with the energy-based ductile fracture criteria is used. Segmentation frequency, chip curvature radius, shear band spacing, chip serration sensitivity and intensity, accumulated plastic strain in the formed chip segments, and cutting forces levels are determined where their dependency to every constitutive coefficient is examined and highlighted. It is demonstrated from the separate variation of every plastic and damage parameters that an interesting finite element modeling (FEM) relevance is reached with the adjustment of JC strain hardening coefficients term, thermal softening parameter, exponent fracture factor, and damage evolution energy. Moderate and high cutting speeds are applied to the cutting tool in the aim to test their impact on shear localization, chip segmentation, and numerical forces levels as well as to approve previous highlighted findings related to constitutive parameters definition. In general, this study focuses on a prominent decrease in identification process cost with the previous knowledge of the most affecting constitutive coefficients while keeping an interesting agreement between numerical and experimental results. http://hdl.handle.net/10985/25783 Experimental and numerical investigation of the mechanical behavior of the AA5383 alloy at high temperatures DU, Rou; MAREAU, Charles; AYED, Yessine; GIRAUD, Eliane; DAL SANTO, Philippe Because of its excellent properties, such as good corrosion resistance, high specific strength and important ductility, the AA5383 aluminum alloy is largely employed for naval applications. In this work, the mechanical behavior of the AA5383 alloy at elevated temperatures, which is an important aspect for the control of forming operations, is investigated. For this purpose, an experimental campaign, including uniaxial tension, biaxial tension, and shear tests, is performed to cover an important range of temperatures (623∼723 K) and strain rates (10⁻⁴∼10⁻ⁱ s⁻ⁱ). A constitutive model for the description of the high temperature behavior of the AA5383 alloy is then proposed. For the deformation behavior, this model combines a viscoplastic flow rule with the BBC2003 anisotropic yield criterion. Also, the prediction of ductile fracture, which is an important aspect for formability, relies on an extended version of the modified Mohr-Coulomb criterion. The extension allows including the impact of temperature and strain rate on ductile fracture as well as a cut-off value for stress triaxiality. Finally, numerical simulations of the experimental tests are performed to identify the flow rule, yield criterion and fracture criterion parameters by combining different optimization methods. The numerical and experimental results of the different tests are in good agreement, which indicates that the proposed constitutive model is well suited for investigating the impact of process conditions on the formability of the AA5383 alloy at high temperatures. Mon, 27 Jan 2020 00:00:00 GMT http://hdl.handle.net/10985/25783 2020-01-27T00:00:00Z DU, Rou MAREAU, Charles AYED, Yessine GIRAUD, Eliane DAL SANTO, Philippe Because of its excellent properties, such as good corrosion resistance, high specific strength and important ductility, the AA5383 aluminum alloy is largely employed for naval applications. In this work, the mechanical behavior of the AA5383 alloy at elevated temperatures, which is an important aspect for the control of forming operations, is investigated. For this purpose, an experimental campaign, including uniaxial tension, biaxial tension, and shear tests, is performed to cover an important range of temperatures (623∼723 K) and strain rates (10⁻⁴∼10⁻ⁱ s⁻ⁱ). A constitutive model for the description of the high temperature behavior of the AA5383 alloy is then proposed. For the deformation behavior, this model combines a viscoplastic flow rule with the BBC2003 anisotropic yield criterion. Also, the prediction of ductile fracture, which is an important aspect for formability, relies on an extended version of the modified Mohr-Coulomb criterion. The extension allows including the impact of temperature and strain rate on ductile fracture as well as a cut-off value for stress triaxiality. Finally, numerical simulations of the experimental tests are performed to identify the flow rule, yield criterion and fracture criterion parameters by combining different optimization methods. The numerical and experimental results of the different tests are in good agreement, which indicates that the proposed constitutive model is well suited for investigating the impact of process conditions on the formability of the AA5383 alloy at high temperatures. http://hdl.handle.net/10985/25745 Identification of friction coefficient between uncoated carbide tool and Ti-6Al-4V alloy under different lubrication conditions FERSI, Achraf; YESSINE, AYED; LAVISSE, BRUNO; GERMAIN, Guenael During machining, the friction between the tool and the workpiece (cutting face and flank face) is a significant tribological phenomenon because it strongly influences the cutting operation. Indeed, higher friction leads to an increase of cutting forces, a greater heat generation, a premature tool wear and a surface degradation. This study focuses on tool (WC/Co)/workpiece (Ti-6Al-4V) friction under different cooling conditions (dry, emulsion, cryogenic). Determining the friction coefficient requires numerical simulations to separate the tribological phenomena. For this purpose, several modeling methods are compared (Lagrangian, CEL, and ALE). Experimental tests revealed that the friction coefficient depends not only on the sliding velocity but also on lubrication modes. Specifically, the lowest friction coefficient is obtained under cryogenic condition. Adhesive phenomena on the WC/Co pin are observed in the friction zone, particularly at high sliding velocities. Wed, 15 May 2024 00:00:00 GMT http://hdl.handle.net/10985/25745 2024-05-15T00:00:00Z FERSI, Achraf YESSINE, AYED LAVISSE, BRUNO GERMAIN, Guenael During machining, the friction between the tool and the workpiece (cutting face and flank face) is a significant tribological phenomenon because it strongly influences the cutting operation. Indeed, higher friction leads to an increase of cutting forces, a greater heat generation, a premature tool wear and a surface degradation. This study focuses on tool (WC/Co)/workpiece (Ti-6Al-4V) friction under different cooling conditions (dry, emulsion, cryogenic). Determining the friction coefficient requires numerical simulations to separate the tribological phenomena. For this purpose, several modeling methods are compared (Lagrangian, CEL, and ALE). Experimental tests revealed that the friction coefficient depends not only on the sliding velocity but also on lubrication modes. Specifically, the lowest friction coefficient is obtained under cryogenic condition. Adhesive phenomena on the WC/Co pin are observed in the friction zone, particularly at high sliding velocities.