https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Tue, 21 Apr 2026 13:44:50 GMT 2026-04-21T13:44:50Z http://hdl.handle.net/10985/7176 Constitutive Modelling of AZ31B-O Magnesium Alloy for Cryogenic Machining GIRAUD, Eliane; ROSSI, FREDERIC; GERMAIN, Guénaël; MARTINS DO OUTEIRO, Jose Carlos The success of a FE model for metal cutting process is strongly dependent on the accurate characterization of the workpiece material, under similar conditions as those found in metal cutting. In this paper, dynamic shear tests using a Gleeble machine have been performed on 4 mm thickness disks of AZ31B-O magnesium alloy, using a special designed tool. In order to include the effects of the cryogenic cooling in the material behavior, the specimens have been submitted to temperatures ranging from -25ºC to 400ºC. A Johnson-Cook constitutive model has then been identified in order to describe the flow stress in machining. Lien vers la version éditeur: http://www.sciencedirect.com/science/article/pii/S2212827113004216 Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/7176 2013-01-01T00:00:00Z GIRAUD, Eliane ROSSI, FREDERIC GERMAIN, Guénaël MARTINS DO OUTEIRO, Jose Carlos The success of a FE model for metal cutting process is strongly dependent on the accurate characterization of the workpiece material, under similar conditions as those found in metal cutting. In this paper, dynamic shear tests using a Gleeble machine have been performed on 4 mm thickness disks of AZ31B-O magnesium alloy, using a special designed tool. In order to include the effects of the cryogenic cooling in the material behavior, the specimens have been submitted to temperatures ranging from -25ºC to 400ºC. A Johnson-Cook constitutive model has then been identified in order to describe the flow stress in machining. 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/10985/9960 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/10985/8603 Numerical integration of an advanced Gurson model for shear loading: Application to the blanking process ACHOURI, Mohamed; GERMAIN, Guénaël; DAL SANTO, Philippe; SAIDANE, Delphine A new extension of the Gurson damage model has been proposed recently to predict ductile fracture under shear dominated loads. The aim of this work is to verify the ability of this approach to simulate, in an accurate way, the damage evolution in shearing processes. An implicit stress integration algorithm is then developed to implement the new model in a finite element code. The numerical procedure is checked through simulations of shear and uniaxial tension tests on a single elements. The extended Gurson damage model is tested and applied to the punching process to compare its predictive ability with the original approach. The obtained numerical results are in good agreement with experimental results of the punching process, showing better ductile fracture predictions compared to the original Gurson model. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/8603 2013-01-01T00:00:00Z ACHOURI, Mohamed GERMAIN, Guénaël DAL SANTO, Philippe SAIDANE, Delphine A new extension of the Gurson damage model has been proposed recently to predict ductile fracture under shear dominated loads. The aim of this work is to verify the ability of this approach to simulate, in an accurate way, the damage evolution in shearing processes. An implicit stress integration algorithm is then developed to implement the new model in a finite element code. The numerical procedure is checked through simulations of shear and uniaxial tension tests on a single elements. The extended Gurson damage model is tested and applied to the punching process to compare its predictive ability with the original approach. The obtained numerical results are in good agreement with experimental results of the punching process, showing better ductile fracture predictions compared to the original Gurson model. http://hdl.handle.net/10985/6802 Development of a microscopic damage model for low stress triaxiality ACHOURI, Mohamed; GERMAIN, Guénaël; DAL SANTO, Philippe; BOUDE, Serge; LEBRUN, Jean-Lou; SAIDANE, Delphine This work deals a contribution to ductile damage of High-Strength Low-Alloy (HSLA) steel steels under low stress triaxiality. This work is based on micrographics observations and in situ shear tests to examine the evolution of microstructure in this kind of loading and to identify the damage process associated. Numerical simulations by finites elements has been performed to simulate the material behavior of nucleation mechanism and the interaction between cavities during the coalescence phase, as well as the effect of the relative position of the inclusions in the shear plane. The model used as a reference in this work is the Gurson-Tvergaard- Needleman (GTN) model. It has been recently improved in order to take into account the effects of low triaxiality during shearing. The implementation of this model in a finite element code is in progress. Sheet Metal 2011 Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/10985/6802 2011-01-01T00:00:00Z ACHOURI, Mohamed GERMAIN, Guénaël DAL SANTO, Philippe BOUDE, Serge LEBRUN, Jean-Lou SAIDANE, Delphine This work deals a contribution to ductile damage of High-Strength Low-Alloy (HSLA) steel steels under low stress triaxiality. This work is based on micrographics observations and in situ shear tests to examine the evolution of microstructure in this kind of loading and to identify the damage process associated. Numerical simulations by finites elements has been performed to simulate the material behavior of nucleation mechanism and the interaction between cavities during the coalescence phase, as well as the effect of the relative position of the inclusions in the shear plane. The model used as a reference in this work is the Gurson-Tvergaard- Needleman (GTN) model. It has been recently improved in order to take into account the effects of low triaxiality during shearing. The implementation of this model in a finite element code is in progress. http://hdl.handle.net/10985/6798 Implementation and validation of a Gurson damage model modified for shear loading: effect of void growth rate and mesh size on the predicted behavior ACHOURI, Mohamed; GERMAIN, Guénaël; DAL SANTO, Philippe; SAIDANE, Delphine The optimization of automotive security components requires good knowledge of the material state after fabrication, particularly with respect to damage that may have been done to the material by the manufacturing process. To achieve this, numerical simulation of the fabrication process is often undertaken. However, classical continuum damage models, like the Gurson [3] model, are not appropriate for the simulation of the blanking by punching operation because the material damage is primarily the result of shear stresses. This work is focused on the use and validation of a modified Gurson type damage model capable of modeling this process, which has recently been proposed by Nahshan [7]. After a brief description of the modification, the implementation and the validation of the modified Gurson model is detailed. A comparison between the original Gurson model and the modified model is presented in order to highlight the importance of the modification for a pure shear stress state and to show that the two models are equivalent for a purely hydrostatic stress state. It is also shown that the results from the modified model are dependent on the finite element mesh size. Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/10985/6798 2012-01-01T00:00:00Z ACHOURI, Mohamed GERMAIN, Guénaël DAL SANTO, Philippe SAIDANE, Delphine The optimization of automotive security components requires good knowledge of the material state after fabrication, particularly with respect to damage that may have been done to the material by the manufacturing process. To achieve this, numerical simulation of the fabrication process is often undertaken. However, classical continuum damage models, like the Gurson [3] model, are not appropriate for the simulation of the blanking by punching operation because the material damage is primarily the result of shear stresses. This work is focused on the use and validation of a modified Gurson type damage model capable of modeling this process, which has recently been proposed by Nahshan [7]. After a brief description of the modification, the implementation and the validation of the modified Gurson model is detailed. A comparison between the original Gurson model and the modified model is presented in order to highlight the importance of the modification for a pure shear stress state and to show that the two models are equivalent for a purely hydrostatic stress state. It is also shown that the results from the modified model are dependent on the finite element mesh size. 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/10985/11342 The effect of machining defects on the fatigue behaviour of the Al7050 alloy ABROUG, Foued; PESSARD, Etienne; GERMAIN, Guénaël; MOREL, Franck; CHOVE, Etienne During the High Speed Machining (HSM) of aircraft components, geometrical defects, such as mismatches or chatters, can be created. To obtain a high surface quality, an expensive manual grinding operation is systematically done to remove these defects. The aim of this study is to identify the impact of HSM defects on the fatigue behaviour of the aluminium alloy Al7050. After listing and reproducing the most frequently observed surface defects, fatigue tests are conducted under fully reversed plane bending loads. Investigations carried out in previous work showed that residual stresses and the strain hardening introduced by machining under these conditions can be neglected. Therefore, only the geometric aspect of the surface integrity is considered in this study. The results show that the fatigue strength decreases only when the surface roughness is significantly degraded. It is also pointed out that manual grinding allows the effect of the machining defects to be removed from the fatigue behaviour. In order to predict the influence of the surface condition on the fatigue behaviour, a numerical approach based on the real surface topology is also developed. Crack initiation sites that are numerically identified are in agreement with experimental results. Numerical simulation results are compared to the predictions of different fatigue criteria from the literature and discussed over a wide range of surface defects. Fri, 01 Jan 2016 00:00:00 GMT http://hdl.handle.net/10985/11342 2016-01-01T00:00:00Z ABROUG, Foued PESSARD, Etienne GERMAIN, Guénaël MOREL, Franck CHOVE, Etienne During the High Speed Machining (HSM) of aircraft components, geometrical defects, such as mismatches or chatters, can be created. To obtain a high surface quality, an expensive manual grinding operation is systematically done to remove these defects. The aim of this study is to identify the impact of HSM defects on the fatigue behaviour of the aluminium alloy Al7050. After listing and reproducing the most frequently observed surface defects, fatigue tests are conducted under fully reversed plane bending loads. Investigations carried out in previous work showed that residual stresses and the strain hardening introduced by machining under these conditions can be neglected. Therefore, only the geometric aspect of the surface integrity is considered in this study. The results show that the fatigue strength decreases only when the surface roughness is significantly degraded. It is also pointed out that manual grinding allows the effect of the machining defects to be removed from the fatigue behaviour. In order to predict the influence of the surface condition on the fatigue behaviour, a numerical approach based on the real surface topology is also developed. Crack initiation sites that are numerically identified are in agreement with experimental results. Numerical simulation results are compared to the predictions of different fatigue criteria from the literature and discussed over a wide range of surface defects.