https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Sun, 17 May 2026 09:08:17 GMT 2026-05-17T09:08:17Z 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/10985/19439 Surface Integrity When Machining Inconel 718 Using Conventional Lubrication and Carbon Dioxide Coolant CHAABANI, Sana; ARRAZOLA, Pedro José; AYED, Yessine; MADARIAGA, Aitor; TIDU, Albert; GERMAIN, Guénaël Surface integrity induced by machining process affects strongly the performance of functional products, for instance, the fatigue life as well as the resistance to stress corrosion cracking. Consequently, it is relevant to evaluate the induced properties on and beneath the machined surfaceto ensure the good performance of the mechanical components while operating under either static or cyclic loads. Furthermore, this is even more important when designing critical components that withstand high loads at high temperatures. In this context, many studies have been carried out in order to characterize the surface integrity (residual stresses, surface roughness, micro-hardness of the affected layer) when machining Inconel 718. However, so far, the cryogenic effect on surface integrity of Inconel 718 is not well established although some preliminary works have already been developed. Therefore, this work aimed to point out the performance of cryogenic machining using the carbon dioxide CO2 as a cryogenic cutting fluid, considering as a reference the conventional lubrication. A comparative study has been carried out during turning operations of Inconel 718 using the same cutting parameters and the same tool geometry. Microhardness measurements showed that the CO2 condition induced higher strain hardening near the surface while conventional condition did not generate notable difference compared to the bulk material microhardness. With respect to residual stresses, results showed that conventional lubrication generated higher tensile residual stress near the surface along the cutting direction when using new tools. As for CO2 cryogenic condition, lower tensile residual stresses have been obtained near the surface. In addition, CO2 condition induced the largest compressive peak when using new and semi−worn tools in comparison with conventional lubrication. Wed, 01 Jan 2020 00:00:00 GMT http://hdl.handle.net/10985/19439 2020-01-01T00:00:00Z CHAABANI, Sana ARRAZOLA, Pedro José AYED, Yessine MADARIAGA, Aitor TIDU, Albert GERMAIN, Guénaël Surface integrity induced by machining process affects strongly the performance of functional products, for instance, the fatigue life as well as the resistance to stress corrosion cracking. Consequently, it is relevant to evaluate the induced properties on and beneath the machined surfaceto ensure the good performance of the mechanical components while operating under either static or cyclic loads. Furthermore, this is even more important when designing critical components that withstand high loads at high temperatures. In this context, many studies have been carried out in order to characterize the surface integrity (residual stresses, surface roughness, micro-hardness of the affected layer) when machining Inconel 718. However, so far, the cryogenic effect on surface integrity of Inconel 718 is not well established although some preliminary works have already been developed. Therefore, this work aimed to point out the performance of cryogenic machining using the carbon dioxide CO2 as a cryogenic cutting fluid, considering as a reference the conventional lubrication. A comparative study has been carried out during turning operations of Inconel 718 using the same cutting parameters and the same tool geometry. Microhardness measurements showed that the CO2 condition induced higher strain hardening near the surface while conventional condition did not generate notable difference compared to the bulk material microhardness. With respect to residual stresses, results showed that conventional lubrication generated higher tensile residual stress near the surface along the cutting direction when using new tools. As for CO2 cryogenic condition, lower tensile residual stresses have been obtained near the surface. In addition, CO2 condition induced the largest compressive peak when using new and semi−worn tools in comparison with conventional lubrication. http://hdl.handle.net/10985/22983 Investigations of grinding burn on a nitrided steel LAVISSE, Bruno; WEISS, Laurent; KOKANYAN, Ninel; LEFEBVRE, André; HENRION, Emerik; SINOT, Olivier; TIDU, Albert Grinding process may lead to the occurrence of grinding burn. When the temperature in the contact zone gets too high, it may lead to damage of the workpiece. The target of this study was to characterize changes occurring in the material after grinding burn on a nitrided steel. The microstructural changes after burn were quantified, by using residual stresses, Raman spectroscopy was also use to detect and characterize different oxides, appearing after grinding burn. The study highlights the possibilities of using this last non destructive method for detecting and quantifying grinding burn. Wed, 01 Jun 2022 00:00:00 GMT http://hdl.handle.net/10985/22983 2022-06-01T00:00:00Z LAVISSE, Bruno WEISS, Laurent KOKANYAN, Ninel LEFEBVRE, André HENRION, Emerik SINOT, Olivier TIDU, Albert Grinding process may lead to the occurrence of grinding burn. When the temperature in the contact zone gets too high, it may lead to damage of the workpiece. The target of this study was to characterize changes occurring in the material after grinding burn on a nitrided steel. The microstructural changes after burn were quantified, by using residual stresses, Raman spectroscopy was also use to detect and characterize different oxides, appearing after grinding burn. The study highlights the possibilities of using this last non destructive method for detecting and quantifying grinding burn. http://hdl.handle.net/10985/22989 A crystal plasticity-based constitutive model for near-β titanium alloys under extreme loading conditions: Application to the Ti17 alloy BEN BOUBAKER, Houssem; MAREAU, Charles; AYED, Yessine; GERMAIN, Guénaël; TIDU, Albert A crystal plasticity-based constitutive model is proposed to describe the thermo-mechanical behavior of the Ti17 titanium alloy subjected to extreme loading conditions. The model explicitly incorporates the effect of the crystallographic orientation of the hcp and bcc phases. The constitutive equations are built in the context of continuum thermodynamics with internal variables. The general framework of continuum damage mechanics is used to consider the impact of ductile damage on the mechanical behavior. The proposed model is implemented in a finite element method solver. The material parameters are identified from an extensive experimental dataset with an inverse method. According to the results, the impact of the strain rate and the temperature on the mechanical behavior is correctly depicted. The model is then used to evaluate the impact of temperature on strain localization. The role of the local texture on the development of ductile damage is also discussed for different specimen geometries. Finally, the impact of heat exchanges on the mechanical behavior at low and high temperatures is investigated. Fri, 07 Jan 2022 00:00:00 GMT http://hdl.handle.net/10985/22989 2022-01-07T00:00:00Z BEN BOUBAKER, Houssem MAREAU, Charles AYED, Yessine GERMAIN, Guénaël TIDU, Albert A crystal plasticity-based constitutive model is proposed to describe the thermo-mechanical behavior of the Ti17 titanium alloy subjected to extreme loading conditions. The model explicitly incorporates the effect of the crystallographic orientation of the hcp and bcc phases. The constitutive equations are built in the context of continuum thermodynamics with internal variables. The general framework of continuum damage mechanics is used to consider the impact of ductile damage on the mechanical behavior. The proposed model is implemented in a finite element method solver. The material parameters are identified from an extensive experimental dataset with an inverse method. According to the results, the impact of the strain rate and the temperature on the mechanical behavior is correctly depicted. The model is then used to evaluate the impact of temperature on strain localization. The role of the local texture on the development of ductile damage is also discussed for different specimen geometries. Finally, the impact of heat exchanges on the mechanical behavior at low and high temperatures is investigated. http://hdl.handle.net/10985/19396 Comparison between cryogenic coolants effect on tool wear and surface integrity in finishing turning of Inconel 718 CHAABANI, Sana; ARRAZOLA, Pedro José; AYED, Yessine; MADARIAGA, Aitor; TIDU, Albert; GERMAIN, Guénaël The most important challenges when machining difficult-to-cut alloys used in critical applications consist mainly in increasing tool life as well as improving the component surface integrity. In particular, the nickel based alloys exhibit very low thermal conductivity inducing higher cutting temperature and thereby rapid tool wear. In this context, cryogenic machining is a promising approach that enhances cooling efficiency either when using the liquid nitrogen LN2 or the carbon dioxide LCO2. According to previous works, cryogenic machining has been carried out on several work materials such as titanium alloys and nickel based alloys. Their findings figured out that longer tool life and better surface integrity were obtained when machining titanium alloys, unlike nickel based alloys. In this work, a comparative study has been carried out in order to investigate the cryogenic machining performance during turning operation of Inconel 718 with respect to tool wear behavior and surface integrity of the machined part. In fact, two cryogenic fluids were employed namely LN2 and LCO2 considering as a reference the conventional lubrication. This study illustrates that conventional lubrication and LCO2 cryogenic cooling allowed to obtain similar machining time, tool wear and surface finish. Nevertheless, LN2 cryogenic machining resulted in the lowest tool life as well as the poorest surface finish. Moreover, residual stresses have been measured beneath the machined surfaces when machining using new tools and tools with different levels of tool flank wear. It was observed that compared to conventional lubrication, both cryogenic conditions showed better results with respect to residual stress profiles along the machined surfaces Wed, 01 Jan 2020 00:00:00 GMT http://hdl.handle.net/10985/19396 2020-01-01T00:00:00Z CHAABANI, Sana ARRAZOLA, Pedro José AYED, Yessine MADARIAGA, Aitor TIDU, Albert GERMAIN, Guénaël The most important challenges when machining difficult-to-cut alloys used in critical applications consist mainly in increasing tool life as well as improving the component surface integrity. In particular, the nickel based alloys exhibit very low thermal conductivity inducing higher cutting temperature and thereby rapid tool wear. In this context, cryogenic machining is a promising approach that enhances cooling efficiency either when using the liquid nitrogen LN2 or the carbon dioxide LCO2. According to previous works, cryogenic machining has been carried out on several work materials such as titanium alloys and nickel based alloys. Their findings figured out that longer tool life and better surface integrity were obtained when machining titanium alloys, unlike nickel based alloys. In this work, a comparative study has been carried out in order to investigate the cryogenic machining performance during turning operation of Inconel 718 with respect to tool wear behavior and surface integrity of the machined part. In fact, two cryogenic fluids were employed namely LN2 and LCO2 considering as a reference the conventional lubrication. This study illustrates that conventional lubrication and LCO2 cryogenic cooling allowed to obtain similar machining time, tool wear and surface finish. Nevertheless, LN2 cryogenic machining resulted in the lowest tool life as well as the poorest surface finish. Moreover, residual stresses have been measured beneath the machined surfaces when machining using new tools and tools with different levels of tool flank wear. It was observed that compared to conventional lubrication, both cryogenic conditions showed better results with respect to residual stress profiles along the machined surfaces