Philippe DARNIS | Université de Bordeaux (original) (raw)
Papers by Philippe DARNIS
Strain
Many destructive methods for measuring residual stresses such as the slitting method require an i... more Many destructive methods for measuring residual stresses such as the slitting method require an inverse analysis to solve the problem. The accuracy of the result as well as an uncertainty component (the model uncertainty) depends on the basis functions used in the inverse solution. The use of a series expansion as the basis functions for the inverse solution was analysed in a previous work for the particular case where functions orders grew consecutively. The present work presents a new estimation of the model uncertainty and a new improved methodology to select the final basis functions for the case where the basis is composed of polynomials. Including nonconsecutive polynomial orders in the basis generates a larger space of possible solutions to be evaluated and allows the possibility to include higher‐order polynomials. The paper includes a comparison with two other inverse analyses methodologies applied to synthetically generated data. With the new methodology, the final error i...
Forces in Mechanics
Most of the cutting models developed in the literature attest only to the presence of cutting for... more Most of the cutting models developed in the literature attest only to the presence of cutting forces in the balance of mechanical energy resulting from cutting. However, several studies [1-4] have highlighted the presence of cutting moments during machining, and particularly for milling. From a theoretical point of view, a complete energy balance must integrate all the components of the mechanical actions (forces and moments). The predictive model of this study proposes to characterize the evolution of the moments in the cutting zone for milling. The objective is to determine a model similar to the cutting forces which expresses a relationship with the chip section define by the Kc coefficient but by integrating the specific behavior of the moments. This work gives perspectives from an energetic point of view for which the part of moments in the energy balance could be substantial for specific configurations as small-radius tools or high-speed milling.
The International Journal of Advanced Manufacturing Technology, 2017
Analytical and semi-analytical modelling of manufacturing processes involving material removal ar... more Analytical and semi-analytical modelling of manufacturing processes involving material removal are of great interest to scientists and industrialists. With this type of modelling, we are able to identify optimal cutting parameters based on geometric and thermomechanical quantities, without having to carry out experimental trials or costly simulations (thus saving time and reducing costs). Compared with other machining techniques, milling involves additional complexities arising from the variation in geometric parameters in the machining configuration and in kinematic parameters when operational. This paper presents a new 3D modelling analysis applied to milling, which takes into account phenomena generated by the three-dimensional kinematics of the process. To complete this thermomechanical approach to cutting, improvements have been made to a basic model configuration. The model that has been developed can now map strains, strain rates, stresses and temperatures along the cutting edge, in the primary, secondary and tertiary shear zones. Forces and cutting moments at the theoretical tool tip are estimated at a local then a global scale, and compared with experimental results from previous work.
Rezumat. Având în vedere complexitatea fenomenelor fizice prezente la prelucrarea prin aşchiere, ... more Rezumat. Având în vedere complexitatea fenomenelor fizice prezente la prelucrarea prin aşchiere, prelucrarea ortogonală a fost configuraŃia cea mai exploatată în modelarea analitică a procesului. Această configuraŃie nu mai este valabilă dacă avem în vedere orientarea reală în spaŃiu a sculei, cum ar fi în cazul procesului de frezare. De-a lungul tăişului parametrii geometrici şi cinematici variază foarte mult şi vectorul viteză a fiecărui punct este foarte sensibil cu poziŃia acestuia [1]. Acest studiu include evoluŃiile cinematice în spaŃiul de lucru, cu pante semnificative privind viteza de lucru, în configuraŃia de prelucrare 3D şi pentru fiecare din zonele de forfecare. Gradientul de viteză generează deplasări suplimentare ale aşchiei, în trei dimensiuni, prin urmare, există o nouă componentă a forŃei şi se remarcă apariŃia momentelor de aşchiere. Acest studiu prezintă o scurtă descriere a modelului de aşchiere ortogonală urmată de determinarea câmpului de viteze în fiecare zon...
Most of the cutting models developed in the literature attest only to the presence of cutting for... more Most of the cutting models developed in the literature attest only to the presence of cutting forces in the balance of mechanical actions resulting from cutting. However, several studies have highlighted the presence of cutting moments during machining, and particularly 3D cutting in milling. The objective of this paper is to characterise phenomena associated with cutting moments by performing experimental mechanistic modelling in 3D cutting. For this purpose, several modelling factors will be investigated, such as the 3D cutting reference frame, the undeformed chip section, the cutting parameters, the cutting zone, etc. The predictive model of this study proves to be relatively efficient for an experimental model and allows a global prediction of cutting moments in milling. Furthermore, beyond the aspect of stress fields in the workpiece caused by cutting moments, this paper gives perspectives from an energetic point of view for which the share of moments in the energy balance coul...
International Journal of Clothing Science and Technology, 2017
Purpose The purpose of this paper is to understand the impact of the cutting forces on the qualit... more Purpose The purpose of this paper is to understand the impact of the cutting forces on the quality of pieces in industrial cutting of multi-ply textile material. It also tries to establish a cutting model that can simulate the cutting forces in order to understand the behaviour of the blade. Design/methodology/approach Working on an industrial machine, a cutting head with an oscillating knife is instrumented with different sensors. Using this equipment, cutting forces can be analysed experimentally while the fabric is being cut along a straight line. Findings A model of the physical phenomena of the cutting forces is proposed, taking different parameters into account such as the geometry of the blade, the properties of the material being cut and the parameters of the cut. The simulated forces and the monitored forces are compared and parameters for minimising the cutting forces of fabrics are deduced. Research limitations/implications Due to the wide diversity of fabrics, all with d...
Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2016
In aerospace industry, the materials constituting aircraft evolved considerably in recent decades... more In aerospace industry, the materials constituting aircraft evolved considerably in recent decades. The choice of composite materials (carbon fiber–reinforced plastic or multi-material) reduces the weight of structures, but for critical parts that support important forces or temperature, the indicated materials are alloys based on nickel or titanium. Consumption of titanium for the aerospace industry is growing rapidly, and the new generations of aircraft show an increase in the percentage of titanium. The TA6V is mostly used for structural parts, especially for engine pylon. Due to its low thermal properties, it shows a poor machinability, leading tools to undergo severe wears. The aim of this work is to understand the relation between cutting conditions and chamfered tool geometries on chip formation and tool wear. Based on a model dedicated to the understanding of cutting process with chamfered tool and on experimental tests, this work will show the influence of feed, cutting spee...
Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2017
For a number of years, the rise in the number of titanium alloy grades and therefore of microstru... more For a number of years, the rise in the number of titanium alloy grades and therefore of microstructures has hampered the productivity of titanium parts. In order to understand the phenomena involved, this study presents a comparison of the chip formations between two microstructures obtained from the same alloy. The first part presents the two alloys, their microstructures and their methods of production. The chip formation of each material is then presented and shows two completely different processes. The first process is classical, for which shear mechanisms appear to be cyclical. Conversely, the second process depends on the orientation of the microstructure when the shear occurs. For a better understanding of the phenomena, the effect of cutting speed and feed is also discussed. Finally, in the last section, chip formations for the two microstructures are summarized and perspectives are presented.
Lecture Notes in Mechanical Engineering, 2016
Along the cutting edge, the geometric and kinematic parameters vary greatly and the velocity vect... more Along the cutting edge, the geometric and kinematic parameters vary greatly and the velocity vector at each point is very sensitive to the current position of the point considered on the cutting edge. The proposed study includes, for each of the three shear zones, the effect of velocity gradients on the strain fields and strain rates. These velocity gradients generate additional displacements of the chip, in three dimensions and, therefore, new force components and cutting moments. This study presents the overall approach for calculating cutting action starting with a detailed description of each feature area. The wrench of action is determined at the tip of the tool based on the elementary forces along the edge.
Applied Surface Science, 2015
Abstract The subsurface damage (SSD) introduced during bound abrasive grinding of fused silica gl... more Abstract The subsurface damage (SSD) introduced during bound abrasive grinding of fused silica glass was measured using a wet etch technique. Various process parameters and grinding configurations were studied. The relation between the SSD depth, the process parameters and forces applied by the grinding wheel on the sample was investigated and compared to a simulation using a discrete element method to model the grinding interface. The results reveal a relation between the SSD depth and the grinding forces normalized by the abrasive concentration. Regarding the creation of the SSD, numerical simulations indicate that only a small fraction of the largest particles in the diamond wheel are responsible for the depth of the damaged layer.
Conference code: 86584, Export Date: 21 October 2011, Source: Scopus, doi: 10.1016/j.proeng.2011.... more Conference code: 86584, Export Date: 21 October 2011, Source: Scopus, doi: 10.1016/j.proeng.2011.04.381, Language of Original Document: English, Correspondence Address: Royer, R.; Université de Bordeaux, I2M - MPI, UMR CNRS 5295, 351 Cours de la Libration, 33405 Talence, France; email: raphael.royer@u-bordeaux1.fr, References: Cahuc, O., Darnis, P., Gérard, A., Battaglia, J.-L., Experimental and analytical balance sheet in turning applications (2001) Int. J. Adv. Manuf. Technol., 18 (9), pp. 648-656;
International Optical Design Conference and Optical Fabrication and Testing, 2010
... 3D metrology Jean-Philippe Champreux ab*, Olivier Cahuc a, Philippe Darnis b, Jean-Yves K... more ... 3D metrology Jean-Philippe Champreux ab*, Olivier Cahuc a, Philippe Darnis b, Jean-Yves K'nevez a, Raynald Laheurte ab, Nathalie Darbois c, Jérôme Néauport c ... Figure 2 illustrates that after the first etching the maximum of fracture have been removed. ...
International Journal of Forming Processes, 2007
International Journal of Forming Processes, 2007
ABSTRACT In order to optimize drill geometry according to cutting resistance, experiments have be... more ABSTRACT In order to optimize drill geometry according to cutting resistance, experiments have been carried out, trying to evaluate the influence of local edge angles (direction and rake). Many works deal with drill point geometry models, however, some of them have a ...
International Journal of Material Forming, 2008
Strain
Many destructive methods for measuring residual stresses such as the slitting method require an i... more Many destructive methods for measuring residual stresses such as the slitting method require an inverse analysis to solve the problem. The accuracy of the result as well as an uncertainty component (the model uncertainty) depends on the basis functions used in the inverse solution. The use of a series expansion as the basis functions for the inverse solution was analysed in a previous work for the particular case where functions orders grew consecutively. The present work presents a new estimation of the model uncertainty and a new improved methodology to select the final basis functions for the case where the basis is composed of polynomials. Including nonconsecutive polynomial orders in the basis generates a larger space of possible solutions to be evaluated and allows the possibility to include higher‐order polynomials. The paper includes a comparison with two other inverse analyses methodologies applied to synthetically generated data. With the new methodology, the final error i...
Forces in Mechanics
Most of the cutting models developed in the literature attest only to the presence of cutting for... more Most of the cutting models developed in the literature attest only to the presence of cutting forces in the balance of mechanical energy resulting from cutting. However, several studies [1-4] have highlighted the presence of cutting moments during machining, and particularly for milling. From a theoretical point of view, a complete energy balance must integrate all the components of the mechanical actions (forces and moments). The predictive model of this study proposes to characterize the evolution of the moments in the cutting zone for milling. The objective is to determine a model similar to the cutting forces which expresses a relationship with the chip section define by the Kc coefficient but by integrating the specific behavior of the moments. This work gives perspectives from an energetic point of view for which the part of moments in the energy balance could be substantial for specific configurations as small-radius tools or high-speed milling.
The International Journal of Advanced Manufacturing Technology, 2017
Analytical and semi-analytical modelling of manufacturing processes involving material removal ar... more Analytical and semi-analytical modelling of manufacturing processes involving material removal are of great interest to scientists and industrialists. With this type of modelling, we are able to identify optimal cutting parameters based on geometric and thermomechanical quantities, without having to carry out experimental trials or costly simulations (thus saving time and reducing costs). Compared with other machining techniques, milling involves additional complexities arising from the variation in geometric parameters in the machining configuration and in kinematic parameters when operational. This paper presents a new 3D modelling analysis applied to milling, which takes into account phenomena generated by the three-dimensional kinematics of the process. To complete this thermomechanical approach to cutting, improvements have been made to a basic model configuration. The model that has been developed can now map strains, strain rates, stresses and temperatures along the cutting edge, in the primary, secondary and tertiary shear zones. Forces and cutting moments at the theoretical tool tip are estimated at a local then a global scale, and compared with experimental results from previous work.
Rezumat. Având în vedere complexitatea fenomenelor fizice prezente la prelucrarea prin aşchiere, ... more Rezumat. Având în vedere complexitatea fenomenelor fizice prezente la prelucrarea prin aşchiere, prelucrarea ortogonală a fost configuraŃia cea mai exploatată în modelarea analitică a procesului. Această configuraŃie nu mai este valabilă dacă avem în vedere orientarea reală în spaŃiu a sculei, cum ar fi în cazul procesului de frezare. De-a lungul tăişului parametrii geometrici şi cinematici variază foarte mult şi vectorul viteză a fiecărui punct este foarte sensibil cu poziŃia acestuia [1]. Acest studiu include evoluŃiile cinematice în spaŃiul de lucru, cu pante semnificative privind viteza de lucru, în configuraŃia de prelucrare 3D şi pentru fiecare din zonele de forfecare. Gradientul de viteză generează deplasări suplimentare ale aşchiei, în trei dimensiuni, prin urmare, există o nouă componentă a forŃei şi se remarcă apariŃia momentelor de aşchiere. Acest studiu prezintă o scurtă descriere a modelului de aşchiere ortogonală urmată de determinarea câmpului de viteze în fiecare zon...
Most of the cutting models developed in the literature attest only to the presence of cutting for... more Most of the cutting models developed in the literature attest only to the presence of cutting forces in the balance of mechanical actions resulting from cutting. However, several studies have highlighted the presence of cutting moments during machining, and particularly 3D cutting in milling. The objective of this paper is to characterise phenomena associated with cutting moments by performing experimental mechanistic modelling in 3D cutting. For this purpose, several modelling factors will be investigated, such as the 3D cutting reference frame, the undeformed chip section, the cutting parameters, the cutting zone, etc. The predictive model of this study proves to be relatively efficient for an experimental model and allows a global prediction of cutting moments in milling. Furthermore, beyond the aspect of stress fields in the workpiece caused by cutting moments, this paper gives perspectives from an energetic point of view for which the share of moments in the energy balance coul...
International Journal of Clothing Science and Technology, 2017
Purpose The purpose of this paper is to understand the impact of the cutting forces on the qualit... more Purpose The purpose of this paper is to understand the impact of the cutting forces on the quality of pieces in industrial cutting of multi-ply textile material. It also tries to establish a cutting model that can simulate the cutting forces in order to understand the behaviour of the blade. Design/methodology/approach Working on an industrial machine, a cutting head with an oscillating knife is instrumented with different sensors. Using this equipment, cutting forces can be analysed experimentally while the fabric is being cut along a straight line. Findings A model of the physical phenomena of the cutting forces is proposed, taking different parameters into account such as the geometry of the blade, the properties of the material being cut and the parameters of the cut. The simulated forces and the monitored forces are compared and parameters for minimising the cutting forces of fabrics are deduced. Research limitations/implications Due to the wide diversity of fabrics, all with d...
Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2016
In aerospace industry, the materials constituting aircraft evolved considerably in recent decades... more In aerospace industry, the materials constituting aircraft evolved considerably in recent decades. The choice of composite materials (carbon fiber–reinforced plastic or multi-material) reduces the weight of structures, but for critical parts that support important forces or temperature, the indicated materials are alloys based on nickel or titanium. Consumption of titanium for the aerospace industry is growing rapidly, and the new generations of aircraft show an increase in the percentage of titanium. The TA6V is mostly used for structural parts, especially for engine pylon. Due to its low thermal properties, it shows a poor machinability, leading tools to undergo severe wears. The aim of this work is to understand the relation between cutting conditions and chamfered tool geometries on chip formation and tool wear. Based on a model dedicated to the understanding of cutting process with chamfered tool and on experimental tests, this work will show the influence of feed, cutting spee...
Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2017
For a number of years, the rise in the number of titanium alloy grades and therefore of microstru... more For a number of years, the rise in the number of titanium alloy grades and therefore of microstructures has hampered the productivity of titanium parts. In order to understand the phenomena involved, this study presents a comparison of the chip formations between two microstructures obtained from the same alloy. The first part presents the two alloys, their microstructures and their methods of production. The chip formation of each material is then presented and shows two completely different processes. The first process is classical, for which shear mechanisms appear to be cyclical. Conversely, the second process depends on the orientation of the microstructure when the shear occurs. For a better understanding of the phenomena, the effect of cutting speed and feed is also discussed. Finally, in the last section, chip formations for the two microstructures are summarized and perspectives are presented.
Lecture Notes in Mechanical Engineering, 2016
Along the cutting edge, the geometric and kinematic parameters vary greatly and the velocity vect... more Along the cutting edge, the geometric and kinematic parameters vary greatly and the velocity vector at each point is very sensitive to the current position of the point considered on the cutting edge. The proposed study includes, for each of the three shear zones, the effect of velocity gradients on the strain fields and strain rates. These velocity gradients generate additional displacements of the chip, in three dimensions and, therefore, new force components and cutting moments. This study presents the overall approach for calculating cutting action starting with a detailed description of each feature area. The wrench of action is determined at the tip of the tool based on the elementary forces along the edge.
Applied Surface Science, 2015
Abstract The subsurface damage (SSD) introduced during bound abrasive grinding of fused silica gl... more Abstract The subsurface damage (SSD) introduced during bound abrasive grinding of fused silica glass was measured using a wet etch technique. Various process parameters and grinding configurations were studied. The relation between the SSD depth, the process parameters and forces applied by the grinding wheel on the sample was investigated and compared to a simulation using a discrete element method to model the grinding interface. The results reveal a relation between the SSD depth and the grinding forces normalized by the abrasive concentration. Regarding the creation of the SSD, numerical simulations indicate that only a small fraction of the largest particles in the diamond wheel are responsible for the depth of the damaged layer.
Conference code: 86584, Export Date: 21 October 2011, Source: Scopus, doi: 10.1016/j.proeng.2011.... more Conference code: 86584, Export Date: 21 October 2011, Source: Scopus, doi: 10.1016/j.proeng.2011.04.381, Language of Original Document: English, Correspondence Address: Royer, R.; Université de Bordeaux, I2M - MPI, UMR CNRS 5295, 351 Cours de la Libration, 33405 Talence, France; email: raphael.royer@u-bordeaux1.fr, References: Cahuc, O., Darnis, P., Gérard, A., Battaglia, J.-L., Experimental and analytical balance sheet in turning applications (2001) Int. J. Adv. Manuf. Technol., 18 (9), pp. 648-656;
International Optical Design Conference and Optical Fabrication and Testing, 2010
... 3D metrology Jean-Philippe Champreux ab*, Olivier Cahuc a, Philippe Darnis b, Jean-Yves K... more ... 3D metrology Jean-Philippe Champreux ab*, Olivier Cahuc a, Philippe Darnis b, Jean-Yves K'nevez a, Raynald Laheurte ab, Nathalie Darbois c, Jérôme Néauport c ... Figure 2 illustrates that after the first etching the maximum of fracture have been removed. ...
International Journal of Forming Processes, 2007
International Journal of Forming Processes, 2007
ABSTRACT In order to optimize drill geometry according to cutting resistance, experiments have be... more ABSTRACT In order to optimize drill geometry according to cutting resistance, experiments have been carried out, trying to evaluate the influence of local edge angles (direction and rake). Many works deal with drill point geometry models, however, some of them have a ...
International Journal of Material Forming, 2008