International Journal of Materials and Product Technology, Mar 20, 2015
... tipped tungsten carbide tools have been investigated when dry machining of multi-directional ... more ... tipped tungsten carbide tools have been investigated when dry machining of multi-directional carbon fibre ... defects during the machining of fibres with −45° are due to shearing along the ... Ferreira, JR, Coppini, NL and Miranda, GWA (1999) 'Machining optimisation in carbon fibre ...
La présente étude a permis, par une approche initiale purement expérimentale, de définir une géom... more La présente étude a permis, par une approche initiale purement expérimentale, de définir une géométrie d'outil et des conditions de coupe permettant d'effectuer des perçages dans un alliage d'aluminium-cuivre (2024) en garantissant une qualité aéronautique, sans avoir recours à l'utilisation d'un lubrifiant. La présence d'un revêtement diamant permet de porter cette durée de vie de 500 à 2000 trous. Dans un deuxième temps, une approche numérique simplifiée a permis de confirmer les résultats expérimentaux, et a montré que : (1) la géométrie de l'outil limite la température de surface de l'outil à des valeurs inférieure 300 °C, température à partir de laquelle l'aluminium diffuse significativement dans le cobalt pour former une solution solide et donc faciliter l'adhésion, (2) la présence d'un revêtement diamant permet de limiter le frottement et donc d'abaisser davantage les températures sur la face de coupe, (3) la combinaison géométrie d'outil/conditions de coupe permet de générer un copeau continu et une coupe stable garantissant une faible rugosité des surfaces et une bonne précision dimensionnelle. L'application des résultats de plasticité adiabatique a permis de définir un domaine de fonctionnement du procédé, et (4) ce régime de coupe stable facilite la présence d'une zone morte au voisinage de l'arête de coupe permettant d'assurer une plus grande longévité de l'outil.The present study allows through an initial experimental approach to define a tool geometry and cutting conditions permitting to drill an aluminum–copper alloy (2024) in dry conditions with an aeronautic quality. A diamond coating allows to increase the tool life from 500 to 2000 holes. A simplified numerical approach allows to confirm experimental results and points out that (1) the drill geometry limits the tool surface temperature below 300 °C, temperature above which aluminum diffuses significantly in cobalt to form a solid solution and then facilitates the adhesion, (2) the use of a diamond coating allows to decrease the friction on the cutting face and then to decrease heat generation, (3) the association of the tool geometry with the cutting conditions allows to generate a continuous chip and a stable cutting leading to a low roughness and a high dimensional accuracy of the machined surface. Using the adiabatic plasticity theory, the working domain of the process has been defined. This stable cutting conditions also facilitates (4) the rising of a dead zone near the cutting edge allowing a higher life of the tool.
... Academic Press New York London (1965). [4] LEFORT (M.). Théorie générale de la similitude e... more ... Academic Press New York London (1965). [4] LEFORT (M.). Théorie générale de la similitude et de l'analyse dimensionnelle appliquée à la chaleur. ... [4] LEFORT (M.). Théorie générale de la similitude et de l'analyse dimensionnelle appliquée à la chaleur. ...
... Academic Press New York London (1965). [4] LEFORT (M.). Théorie générale de la similitude e... more ... Academic Press New York London (1965). [4] LEFORT (M.). Théorie générale de la similitude et de l'analyse dimensionnelle appliquée à la chaleur. ... [4] LEFORT (M.). Théorie générale de la similitude et de l'analyse dimensionnelle appliquée à la chaleur. ...
ABSTRACT Machining is a process implying extremely high coupled thermo-mechanical stresses. The w... more ABSTRACT Machining is a process implying extremely high coupled thermo-mechanical stresses. The workpiece mechanical properties decrease with the temperature generated during the process and that temperature has a direct influence on wear intensity undergone by the tool. In the case of a drilling operation, the temperature generated by the cutting process can lead to metal burr formation and/or composite matrix degradation by burning. When these two materials are used in the form of a sandwich-type stacking, the temperature attained in the metallic part can cause new defects such as: i) a difference between the diameters measured in each material and ii) organic matrix damages due to heat diffusion from the metal towards the CFRP layer. Temperature reached at the tool/workpiece interface is difficult to measure during drilling operation, due to its enclosed configuration; numerical simulation is therefore a good alternative to access to this information. The purpose of this study is to develop and carry out numerical simulations in order to estimate the workpiece thermal field generated during drilling. The simulations are validated by comparing simulated and measured temperatures at 4 mm from the holes wall. This method is applied to evaluate thermal field generated during drilling (with chip removing cycles) of CFRP/Aluminum alloy stacks. The influence of the drilling kinematics on the workpiece thermal field is also investigated.
ABSTRACT During chip formation, material is subjected to high deformations and high strain rates ... more ABSTRACT During chip formation, material is subjected to high deformations and high strain rates which generate high pressures and temperatures. Cutting fluids have an important role but produce many constraints: cleaning of parts, environment quality degradation, cost increase, diseases as identified by the European Agency for Safety and Health at Work. Dry machining is one of the future challenges although its implementation remains delicate, in particular for TiAl6V alloy. This paper aims at correlating the contact conditions at the tool/chip interface with the tool wear to understand the wear mechanisms of carbide tools in dry machining. Numerical simulations, experimentally validated, allow pointing out that the temperature distribution at the tool/chip interface depends on chip type (continuous, serrated). For continuous chips, the temperature is fairly uniform and stationary throughout the interface. For segmented chips, a cold zone between two temperature peaks is observed and moves along the tool rake face during the formation of a chip segment. The evolution of the normal stress at the interface is similar for both types of chips at the beginning of the localization phenomenon. These pressure and temperature fields allow the titanium to diffuse into the tungsten carbide and form the mixed carbide (Ti, W)C, which is very sensitive to oxidation above 500 degrees C. This could explain the attrition of the tool, due to the brittleness of the oxycarbides. Contact conditions and tool wear are finally correlated.
International Journal of Materials and Product Technology, Mar 20, 2015
... tipped tungsten carbide tools have been investigated when dry machining of multi-directional ... more ... tipped tungsten carbide tools have been investigated when dry machining of multi-directional carbon fibre ... defects during the machining of fibres with −45° are due to shearing along the ... Ferreira, JR, Coppini, NL and Miranda, GWA (1999) 'Machining optimisation in carbon fibre ...
La présente étude a permis, par une approche initiale purement expérimentale, de définir une géom... more La présente étude a permis, par une approche initiale purement expérimentale, de définir une géométrie d'outil et des conditions de coupe permettant d'effectuer des perçages dans un alliage d'aluminium-cuivre (2024) en garantissant une qualité aéronautique, sans avoir recours à l'utilisation d'un lubrifiant. La présence d'un revêtement diamant permet de porter cette durée de vie de 500 à 2000 trous. Dans un deuxième temps, une approche numérique simplifiée a permis de confirmer les résultats expérimentaux, et a montré que : (1) la géométrie de l'outil limite la température de surface de l'outil à des valeurs inférieure 300 °C, température à partir de laquelle l'aluminium diffuse significativement dans le cobalt pour former une solution solide et donc faciliter l'adhésion, (2) la présence d'un revêtement diamant permet de limiter le frottement et donc d'abaisser davantage les températures sur la face de coupe, (3) la combinaison géométrie d'outil/conditions de coupe permet de générer un copeau continu et une coupe stable garantissant une faible rugosité des surfaces et une bonne précision dimensionnelle. L'application des résultats de plasticité adiabatique a permis de définir un domaine de fonctionnement du procédé, et (4) ce régime de coupe stable facilite la présence d'une zone morte au voisinage de l'arête de coupe permettant d'assurer une plus grande longévité de l'outil.The present study allows through an initial experimental approach to define a tool geometry and cutting conditions permitting to drill an aluminum–copper alloy (2024) in dry conditions with an aeronautic quality. A diamond coating allows to increase the tool life from 500 to 2000 holes. A simplified numerical approach allows to confirm experimental results and points out that (1) the drill geometry limits the tool surface temperature below 300 °C, temperature above which aluminum diffuses significantly in cobalt to form a solid solution and then facilitates the adhesion, (2) the use of a diamond coating allows to decrease the friction on the cutting face and then to decrease heat generation, (3) the association of the tool geometry with the cutting conditions allows to generate a continuous chip and a stable cutting leading to a low roughness and a high dimensional accuracy of the machined surface. Using the adiabatic plasticity theory, the working domain of the process has been defined. This stable cutting conditions also facilitates (4) the rising of a dead zone near the cutting edge allowing a higher life of the tool.
... Academic Press New York London (1965). [4] LEFORT (M.). Théorie générale de la similitude e... more ... Academic Press New York London (1965). [4] LEFORT (M.). Théorie générale de la similitude et de l'analyse dimensionnelle appliquée à la chaleur. ... [4] LEFORT (M.). Théorie générale de la similitude et de l'analyse dimensionnelle appliquée à la chaleur. ...
... Academic Press New York London (1965). [4] LEFORT (M.). Théorie générale de la similitude e... more ... Academic Press New York London (1965). [4] LEFORT (M.). Théorie générale de la similitude et de l'analyse dimensionnelle appliquée à la chaleur. ... [4] LEFORT (M.). Théorie générale de la similitude et de l'analyse dimensionnelle appliquée à la chaleur. ...
ABSTRACT Machining is a process implying extremely high coupled thermo-mechanical stresses. The w... more ABSTRACT Machining is a process implying extremely high coupled thermo-mechanical stresses. The workpiece mechanical properties decrease with the temperature generated during the process and that temperature has a direct influence on wear intensity undergone by the tool. In the case of a drilling operation, the temperature generated by the cutting process can lead to metal burr formation and/or composite matrix degradation by burning. When these two materials are used in the form of a sandwich-type stacking, the temperature attained in the metallic part can cause new defects such as: i) a difference between the diameters measured in each material and ii) organic matrix damages due to heat diffusion from the metal towards the CFRP layer. Temperature reached at the tool/workpiece interface is difficult to measure during drilling operation, due to its enclosed configuration; numerical simulation is therefore a good alternative to access to this information. The purpose of this study is to develop and carry out numerical simulations in order to estimate the workpiece thermal field generated during drilling. The simulations are validated by comparing simulated and measured temperatures at 4 mm from the holes wall. This method is applied to evaluate thermal field generated during drilling (with chip removing cycles) of CFRP/Aluminum alloy stacks. The influence of the drilling kinematics on the workpiece thermal field is also investigated.
ABSTRACT During chip formation, material is subjected to high deformations and high strain rates ... more ABSTRACT During chip formation, material is subjected to high deformations and high strain rates which generate high pressures and temperatures. Cutting fluids have an important role but produce many constraints: cleaning of parts, environment quality degradation, cost increase, diseases as identified by the European Agency for Safety and Health at Work. Dry machining is one of the future challenges although its implementation remains delicate, in particular for TiAl6V alloy. This paper aims at correlating the contact conditions at the tool/chip interface with the tool wear to understand the wear mechanisms of carbide tools in dry machining. Numerical simulations, experimentally validated, allow pointing out that the temperature distribution at the tool/chip interface depends on chip type (continuous, serrated). For continuous chips, the temperature is fairly uniform and stationary throughout the interface. For segmented chips, a cold zone between two temperature peaks is observed and moves along the tool rake face during the formation of a chip segment. The evolution of the normal stress at the interface is similar for both types of chips at the beginning of the localization phenomenon. These pressure and temperature fields allow the titanium to diffuse into the tungsten carbide and form the mixed carbide (Ti, W)C, which is very sensitive to oxidation above 500 degrees C. This could explain the attrition of the tool, due to the brittleness of the oxycarbides. Contact conditions and tool wear are finally correlated.
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