https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Thu, 14 May 2026 10:59:37 GMT 2026-05-14T10:59:37Z http://hdl.handle.net/10985/9960 Numerical and Experimental Approach in Assisted Cryogenic Machining TRABELSI, Sabrine; BOUAZIZ, Zoubeir; MOREL, Anne; GERMAIN, Guénaël Understanding of local mechanisms chip forming during machining by removal of material is difficult, to this end; a cutting finite element modelling is required. This study aims initially to model orthogonal cutting of Ti17 titanium alloy in dry and cryogenic machining and in a second time to study the influence of the application of cryogen during machining on temperature fields and cutting forces in numerical simulation. An experimental study was also conducted to determine the mode of tool wear and the evolution of flank wear. Thu, 01 Jan 2015 00:00:00 GMT http://hdl.handle.net/10985/9960 2015-01-01T00:00:00Z TRABELSI, Sabrine BOUAZIZ, Zoubeir MOREL, Anne GERMAIN, Guénaël Understanding of local mechanisms chip forming during machining by removal of material is difficult, to this end; a cutting finite element modelling is required. This study aims initially to model orthogonal cutting of Ti17 titanium alloy in dry and cryogenic machining and in a second time to study the influence of the application of cryogen during machining on temperature fields and cutting forces in numerical simulation. An experimental study was also conducted to determine the mode of tool wear and the evolution of flank wear. http://hdl.handle.net/10985/8609 The influence of laser assistance on the machinability of the titanium alloy Ti555-3 BRAHAM-BOUCHNAK, Tarek; GERMAIN, Guénaël; MOREL, Anne; LEBRUN, Jean-Lou The Ti533-3 alloy is a new titanium alloy which is starting to see increased use in the aeronautical domain to improve the durability of components and to optimize the weight/resistance ratio. This alloy is characterized by greater resistance compared to the more commonly used titanium alloys such as Ti6Al4V. However, a disadvantage of the Ti533-3 alloy is that it is very difficult to machine. In this work, the use of laser-assisted machining has been tested to improve chip formation by a thermal softening phenomenon and to improve the machining productivity of the alloy. A parametric investigation of laser assistance on the machinability of the Ti555-3 titanium alloy shows that: (1) the cutting forces can be greatly decreased if the surface temperature is high; (2) the thermal gradient induced by laser heating modifies the surface integrity in terms of strain hardening and residual stresses in the workpiece; and (3) the chip formation mechanisms are also changed, by increasing the sawteeth frequency when using laser assistance Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/8609 2013-01-01T00:00:00Z BRAHAM-BOUCHNAK, Tarek GERMAIN, Guénaël MOREL, Anne LEBRUN, Jean-Lou The Ti533-3 alloy is a new titanium alloy which is starting to see increased use in the aeronautical domain to improve the durability of components and to optimize the weight/resistance ratio. This alloy is characterized by greater resistance compared to the more commonly used titanium alloys such as Ti6Al4V. However, a disadvantage of the Ti533-3 alloy is that it is very difficult to machine. In this work, the use of laser-assisted machining has been tested to improve chip formation by a thermal softening phenomenon and to improve the machining productivity of the alloy. A parametric investigation of laser assistance on the machinability of the Ti555-3 titanium alloy shows that: (1) the cutting forces can be greatly decreased if the surface temperature is high; (2) the thermal gradient induced by laser heating modifies the surface integrity in terms of strain hardening and residual stresses in the workpiece; and (3) the chip formation mechanisms are also changed, by increasing the sawteeth frequency when using laser assistance http://hdl.handle.net/10985/6914 Comparison between defects and micro-notches in multiaxial fatigue – The size effect and the gradient effect MOREL, Anne; NADOT, Yves; MOREL, Franck This paper attempts to improve the understanding of the multiaxial high cycle fatigue response of micro sized stress concentrations or notches of different geometries. The investigation is composed of an experimental part and a numerical part. In the former, three types of micro-notches or “artificial defects” are compared: spherical, elliptical and circumferential. All types have the same basic dimensions, the difference being the 3D geometry. The notches were machined on the surface of smooth cylindrical specimens made of mild steel. The fatigue limits under reversed tension (push–pull) and reversed torsional loading conditions for different micro-notch sizes have been experimentally determined. In the numerical part, finite elements simulations using a cyclic elasto-plastic material behaviour law show that the mechanical state ahead of the different stress concentrations change drastically with the loading mode and the geometry of the artificial defect. From a fatigue point of view, it is shown that a stress gradient correction is required for all the loading, size and geometry configurations. Once the gradient correction is made and a proper multiaxial criterion is used, it appears that the size effect due to increasing the loaded surface area at the notch tip for the different geometries is negligible compared to the gradient effect. Lien vers la version éditeur: http://www.sciencedirect.com/science/article/pii/S0142112308002156 Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/10985/6914 2009-01-01T00:00:00Z MOREL, Anne NADOT, Yves MOREL, Franck This paper attempts to improve the understanding of the multiaxial high cycle fatigue response of micro sized stress concentrations or notches of different geometries. The investigation is composed of an experimental part and a numerical part. In the former, three types of micro-notches or “artificial defects” are compared: spherical, elliptical and circumferential. All types have the same basic dimensions, the difference being the 3D geometry. The notches were machined on the surface of smooth cylindrical specimens made of mild steel. The fatigue limits under reversed tension (push–pull) and reversed torsional loading conditions for different micro-notch sizes have been experimentally determined. In the numerical part, finite elements simulations using a cyclic elasto-plastic material behaviour law show that the mechanical state ahead of the different stress concentrations change drastically with the loading mode and the geometry of the artificial defect. From a fatigue point of view, it is shown that a stress gradient correction is required for all the loading, size and geometry configurations. Once the gradient correction is made and a proper multiaxial criterion is used, it appears that the size effect due to increasing the loaded surface area at the notch tip for the different geometries is negligible compared to the gradient effect. http://hdl.handle.net/10985/6795 A new approach to model the fatigue anisotropy due to non-metallic inclusions in forged steels BELLETT, Daniel; MOREL, Anne; MOREL, Franck; PESSARD, Etienne The objective of this work is to propose an anisotropic fatigue criterion for the sizing of industrial forged components. The results from different experimental campaigns using three different rolled steels are first presented. The effect of inclusions and the microstructure on the fatigue behaviour are investigated. For the two ferrite-pearlitic steels tested, the presence of a microstructure consisting of elongated grains has no observable effects on the fatigue behaviour. For two of the three steels studied the presence of non-metallic inclusions, elongated in the rolling direction, form the origin of the anisotropic fatigue behaviour. The proposed probabilistic model is based on the competition between two possible fatigue crack initiation mechanisms. The anisotropic character of the fatigue resistance of forged components is taken into account by the definition of the geometry and the orientation of the non-metallic inclusion. This criterion results in the establishment of a probabilistic Kitagawa type diagram. Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/10985/6795 2012-01-01T00:00:00Z BELLETT, Daniel MOREL, Anne MOREL, Franck PESSARD, Etienne The objective of this work is to propose an anisotropic fatigue criterion for the sizing of industrial forged components. The results from different experimental campaigns using three different rolled steels are first presented. The effect of inclusions and the microstructure on the fatigue behaviour are investigated. For the two ferrite-pearlitic steels tested, the presence of a microstructure consisting of elongated grains has no observable effects on the fatigue behaviour. For two of the three steels studied the presence of non-metallic inclusions, elongated in the rolling direction, form the origin of the anisotropic fatigue behaviour. The proposed probabilistic model is based on the competition between two possible fatigue crack initiation mechanisms. The anisotropic character of the fatigue resistance of forged components is taken into account by the definition of the geometry and the orientation of the non-metallic inclusion. This criterion results in the establishment of a probabilistic Kitagawa type diagram. 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/10985/8339 Sub-millimeter measurement of finite strains at cutting tool tip vicinity POTTIER, Thomas; GERMAIN, Guénaël; CALAMAZ, Madalina; MOREL, Anne; COUPARD, Dominique The present paper details a simple and effective experimental procedure dedicated to strain measurement during orthogonal cutting operations. It relies on the use of high frame-rate camera and optical microscopy. A numerical post-procedure is also proposed in order to allow particle tracking from Digital Image Correlation (DIC). Therefore strain accumulation within finite strains framework is achieved. The significant magnitude of the calculated strains is partially due to a singular side effect that leads to local material disjunction. The strain localization in the Adiabatic Shear Band (ASB) exhibits different strain paths at various locations along this band and a non-linear evolution of the strain accumulation. A focus is made on the formation mechanisms of serrated chips obtained from Ti6Al4V titanium alloy. The side observation performed during this work allow to proposed three possible scenarios to explain this very phenomenon. Lien vers la version éditeur: http://link.springer.com/article/10.1007%2Fs11340-014-9868-0 Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/10985/8339 2014-01-01T00:00:00Z POTTIER, Thomas GERMAIN, Guénaël CALAMAZ, Madalina MOREL, Anne COUPARD, Dominique The present paper details a simple and effective experimental procedure dedicated to strain measurement during orthogonal cutting operations. It relies on the use of high frame-rate camera and optical microscopy. A numerical post-procedure is also proposed in order to allow particle tracking from Digital Image Correlation (DIC). Therefore strain accumulation within finite strains framework is achieved. The significant magnitude of the calculated strains is partially due to a singular side effect that leads to local material disjunction. The strain localization in the Adiabatic Shear Band (ASB) exhibits different strain paths at various locations along this band and a non-linear evolution of the strain accumulation. A focus is made on the formation mechanisms of serrated chips obtained from Ti6Al4V titanium alloy. The side observation performed during this work allow to proposed three possible scenarios to explain this very phenomenon. http://hdl.handle.net/10985/16584 Tool wear and cutting forces under cryogenic machining of titanium alloy (Ti17) TRABELSI, Sabrine; MOREL, Anne; GERMAIN, Guénaël; BOUAZIZ, Zoubeir Titanium alloy is well known for its difficulty to machine, owing to the important “tool wear” phenomenon. Machining assistance is an interesting solution to lengthen the tool lifetime. In this study, we focused on the effect of cryogenic assistance—during machining of Ti17—on the tool wear and cutting forces for different combinations of cutting speed, feed rate and depth of cut. Compared to conventional lubrication, cryogenic support lengthens the tool life for all tested conditions and has no significant influence on cutting force. A comparison of the cryogenic effect and high-pressure water jet assistance is also presented. Fri, 01 Jan 2016 00:00:00 GMT http://hdl.handle.net/10985/16584 2016-01-01T00:00:00Z TRABELSI, Sabrine MOREL, Anne GERMAIN, Guénaël BOUAZIZ, Zoubeir Titanium alloy is well known for its difficulty to machine, owing to the important “tool wear” phenomenon. Machining assistance is an interesting solution to lengthen the tool lifetime. In this study, we focused on the effect of cryogenic assistance—during machining of Ti17—on the tool wear and cutting forces for different combinations of cutting speed, feed rate and depth of cut. Compared to conventional lubrication, cryogenic support lengthens the tool life for all tested conditions and has no significant influence on cutting force. A comparison of the cryogenic effect and high-pressure water jet assistance is also presented. http://hdl.handle.net/10985/6889 Prise en compte du rôle des inclusions non métalliques dans le comportement anisotrope en fatigue d’aciers forgés MOREL, Anne; MOREL, Franck; PESSARD, Etienne L’objectif de cette étude est de proposer un critère de fatigue anisotrope pour le dimensionnement en fatigue de pièces industrielles forgées. Des résultats de différentes campagnes d’essais obtenus sur 3 nuances d’acier laminés sont tout d’abord présentés. Une attention particulière est portée à l’observation et à l’analyse des mécanismes d’amorçage à l’origine du comportement anisotrope en fatigue. Un critère de fatigue probabiliste permettant de tenir compte de la compétition possible entre différents types de mécanismes d’amorçage est ensuite développé. Ce critère permet notamment de tracer un diagramme de type Kitagawa probabiliste. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/10985/6889 2010-01-01T00:00:00Z MOREL, Anne MOREL, Franck PESSARD, Etienne L’objectif de cette étude est de proposer un critère de fatigue anisotrope pour le dimensionnement en fatigue de pièces industrielles forgées. Des résultats de différentes campagnes d’essais obtenus sur 3 nuances d’acier laminés sont tout d’abord présentés. Une attention particulière est portée à l’observation et à l’analyse des mécanismes d’amorçage à l’origine du comportement anisotrope en fatigue. Un critère de fatigue probabiliste permettant de tenir compte de la compétition possible entre différents types de mécanismes d’amorçage est ensuite développé. Ce critère permet notamment de tracer un diagramme de type Kitagawa probabiliste. http://hdl.handle.net/10985/7805 A Biaxial Fatigue Specimen for Uniaxial Loading BELLETT, Daniel; MOREL, Franck; MOREL, Anne; LEBRUN, Jean-Lou The aim of this paper is to present a novel un-notched fatigue test specimen in which a biaxial stress state is achieved using a uniaxial loading condition. This allows the problem of multi-axial fatigue to be studied using relatively common one-axis servo-hydraulic testing machines. In addition the specimen presented here is very compact and can be made using a small volume of material (100x40x4.5mm). For this specimen, the degree of biaxiality, defined by the parameter is equal to approximately 0.45. The specimen geometry was optimised using the Dang Van multi-axial fatigue criterion. In addition to use as a fatigue specimen, it has been demonstrated that the biaxial specimen presented here is also suitable for biaxial tensile tests, to determine the rupture strength of a material in a biaxial stress state. Two different materials have been investigated: The first was wrought aluminium 2024-O in the form of 5mm sheets. The second was a cast aluminium-silicon alloy AlSi7Cu0.5Mg0.3, commonly used in automotive and aeronautical applications. The fatigue strengths were determined at 2x106 cycles and at various R-ratios using a staircase procedure. For the aluminium 2024, it is shown that the biaxial stress state increases the maximum permissible first principal stress when compared to the uniaxial condition. However, in terms of the cast aluminium alloy, it has been demonstrated that this type of fatigue specimen is not suitable for materials containing casting defects, in particular micro-shrinkage pores, because the volume of material, in which the stress state is biaxial, is not large enough. Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/10985/7805 2011-01-01T00:00:00Z BELLETT, Daniel MOREL, Franck MOREL, Anne LEBRUN, Jean-Lou The aim of this paper is to present a novel un-notched fatigue test specimen in which a biaxial stress state is achieved using a uniaxial loading condition. This allows the problem of multi-axial fatigue to be studied using relatively common one-axis servo-hydraulic testing machines. In addition the specimen presented here is very compact and can be made using a small volume of material (100x40x4.5mm). For this specimen, the degree of biaxiality, defined by the parameter is equal to approximately 0.45. The specimen geometry was optimised using the Dang Van multi-axial fatigue criterion. In addition to use as a fatigue specimen, it has been demonstrated that the biaxial specimen presented here is also suitable for biaxial tensile tests, to determine the rupture strength of a material in a biaxial stress state. Two different materials have been investigated: The first was wrought aluminium 2024-O in the form of 5mm sheets. The second was a cast aluminium-silicon alloy AlSi7Cu0.5Mg0.3, commonly used in automotive and aeronautical applications. The fatigue strengths were determined at 2x106 cycles and at various R-ratios using a staircase procedure. For the aluminium 2024, it is shown that the biaxial stress state increases the maximum permissible first principal stress when compared to the uniaxial condition. However, in terms of the cast aluminium alloy, it has been demonstrated that this type of fatigue specimen is not suitable for materials containing casting defects, in particular micro-shrinkage pores, because the volume of material, in which the stress state is biaxial, is not large enough. http://hdl.handle.net/10985/6890 Modelling the role of non metallic inclusions on the anisotropic fatigue behaviour of forged steel PESSARD, Etienne; MOREL, Franck; MOREL, Anne; BELLETT, Daniel Forged components are known to show high cyclic and monotonic mechanical properties. This is mainly due to a better compactness and a finer microstructure introduced by the forming process. However, this good mechanical behaviour is sometimes a source of anisotropy especially when the microstructural heterogeneities are not randomly distributed and/or oriented. This study aims at describing the high cycle fatigue response of a forged bainitic steel. This material contains a lot of elongated manganese sulphide (MnS) inclusions, oriented as a function of the rolling or forging direction. Specimens with different orientations relative to the rolling direction are tested in fatigue under push-pull uniaxial and torsion loads. The influence of “inclusion clusters” is clearly demonstrated via the observation of the failure surfaces. Experiments show that the anisotropic fatigue behaviour is due to a change in the crack initiation mechanism. At 0°, when the inclusions are parallel to the applied stress, micro-crack initiation is controlled by the material matrix. At 45° and 90°, elongated manganese-sulfide inclusion clusters are the origin of crack initiation and the fatigue strength drops significantly. A statistical approach based on the competition between two different crack initiation mechanisms is proposed. One mechanism is modelled by local elastic shakedown concepts and the other by linear elastic fracture mechanics. This approach leads to a Kitagawa type diagram and explains the anisotropy in the material. The approach developed in this study demonstrates a framework using both the elastic shakedown concept and the weakest link theory to account for the loading mode, loading path and data scatter in High Cycle Fatigue. Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/10985/6890 2011-01-01T00:00:00Z PESSARD, Etienne MOREL, Franck MOREL, Anne BELLETT, Daniel Forged components are known to show high cyclic and monotonic mechanical properties. This is mainly due to a better compactness and a finer microstructure introduced by the forming process. However, this good mechanical behaviour is sometimes a source of anisotropy especially when the microstructural heterogeneities are not randomly distributed and/or oriented. This study aims at describing the high cycle fatigue response of a forged bainitic steel. This material contains a lot of elongated manganese sulphide (MnS) inclusions, oriented as a function of the rolling or forging direction. Specimens with different orientations relative to the rolling direction are tested in fatigue under push-pull uniaxial and torsion loads. The influence of “inclusion clusters” is clearly demonstrated via the observation of the failure surfaces. Experiments show that the anisotropic fatigue behaviour is due to a change in the crack initiation mechanism. At 0°, when the inclusions are parallel to the applied stress, micro-crack initiation is controlled by the material matrix. At 45° and 90°, elongated manganese-sulfide inclusion clusters are the origin of crack initiation and the fatigue strength drops significantly. A statistical approach based on the competition between two different crack initiation mechanisms is proposed. One mechanism is modelled by local elastic shakedown concepts and the other by linear elastic fracture mechanics. This approach leads to a Kitagawa type diagram and explains the anisotropy in the material. The approach developed in this study demonstrates a framework using both the elastic shakedown concept and the weakest link theory to account for the loading mode, loading path and data scatter in High Cycle Fatigue.