C. Ghnatios | Notre Dame University (Lebanon) (original) (raw)
Papers by C. Ghnatios
2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)
Spirometer testing is considered the most common method used to evaluate the pulmonary system. It... more Spirometer testing is considered the most common method used to evaluate the pulmonary system. It diagnoses asthma, chronic obstructive pulmonary disease (COPD) and other conditions that affect breathing. Nowadays many pharmaceutical companies produce spirometer devices for patients with asthma, designed for home use. However, the machines are replaced annually due to the lack of control and results’ reproducibility. Lacking a reliable mean of calibration leads to unnecessary replacement of expensive devices and/or inaccurate measurements. The objective of this work is designing and prototyping a controlled air flow machine, which will simulate the exhalation of a human based on correlations and predefined graphs found in medicine. This prototyped machine will be used to control and/or calibrate the spirometer device of the physician. The simulation of the human’s exhalation was accomplished by varying the rotational speed of an AC single phase motor using a Variable Frequency Drive in addition of a hardware device. The motor is connected directly to a centrifugal fan with forward curved blades. Using the digital pitot tube anemometer/manometer, the flow rate was measured by taking an average value of 40 frequency samples in the range 0 Hz to 100 Hz. After obtaining a relationship between the flow rate and the frequency, the data were implemented in a hardware controller, to adequately control the motor. The control was made from an Android mobile application as follows: Manual and Automatic. The Manual feature enables the user to control the flow rate manually by choosing the required maximum peak flow values to run the test. By adding an air flow sensor, the automatic feature runs automatically and the results of the test shall be obtained as a feedback on the application’s screen.
Volume 3: Advanced Composite Materials and Processing; Robotics; Information Management and PLM; Design Engineering, 2012
Automated tape placement (ATP) is a process recently developed for the production of large parts ... more Automated tape placement (ATP) is a process recently developed for the production of large parts (plates, shells) made of thermoplastic composites. In ATP a tape is placed on the previous ply and welded by a local heating and pressure to build up a laminated structure. The numerical modeling of such a process is a challenging issue since the thermal history of each ply is different, depending on its position within the structure. The evaluation of residual stresses is particularly important for determining the deformed shape of the piece at the end of the process. A numerical model based on the Proper Generalized Decomposition is proposed. The solution of the 3D thermal problem is performed first. Thermal contact resistances are in particular introduced in order to model the imperfect heat conduction at the interface of two neighboring plies. The computed temperature field is then introduced in the mechanical model considering a thermo-elastic behavior for the material. An increment...
Revue des composites et des matériaux avancés, 2014
Chinesta}@ec-nantes.fr mécanique des solides et des fluides, électromagnétisme) définies sur des ... more Chinesta}@ec-nantes.fr mécanique des solides et des fluides, électromagnétisme) définies sur des domaines à fort rapport d'aspect.
Revue des composites et des matériaux avancés, 2014
Chinesta}@ec-nantes.fr mécanique des solides et des fluides, électromagnétisme) définies sur des ... more Chinesta}@ec-nantes.fr mécanique des solides et des fluides, électromagnétisme) définies sur des domaines à fort rapport d'aspect.
Revue des composites et des matériaux avancés, 2011
La modélisation avancée des procédés de mise en forme de composites est confrontée à de nombreux ... more La modélisation avancée des procédés de mise en forme de composites est confrontée à de nombreux verrous malgré les avancées récentes en matière de modélisation mécanique, analyse numérique, stratégies de discrétisation et capacité de calcul. La mise en forme de composites nécessite la prise en compte des multiples échelles en espace et temps, des comportements non-linéaires anisotropes et fortement couplés, définis dans des géométries très complexes. L'optimisation des procédés ainsi que l'indentification inverse, ou encore le controle des procédés nécessite plusieurs résolutions. Dans ce contexte les techniques de réduction de modèles offrent de nouvelles possibilités, permettant d'accélérer les calculs de quelques ordres de grandeur, et même de résoudre des modèles jamais résolus jusqu'à présent. ABSTRACT. Efficient simulation of composites manufacturing processes remains today a challenging issue despite the impressive progresses reached in mechanical modeling, numerical analysis, discretization techniques and computer science during the last decade. Composites manufacturing involve multiscale models in space and time, highly non-linear and anisotropic behaviors, strongly coupled multiphysics and complex geometries. Moreover, optimization (shape and process optimization), inverse analysis (parameter identification, non destructive testing, ...) or process control need the solution of many direct problems, as fast and accurately as possible. In this context, model reduction techniques constitute an appealing simulation choice, accelerating the computations of several orders of magnitude, and even, enabling the solution of models never until now solved.
In the numerical modeling of composite materials and structures, microscopic heterogeneities intr... more In the numerical modeling of composite materials and structures, microscopic heterogeneities introduce the need for defining homogenized properties depending on microscopic details. Real time image-based calculations in the framework of the on-line control of manufacturing processes demands the prediction of the local homogenized properties of a heterogeneous material at different scanning scales, as fast as possible for a given acceptable error. Therefore, model reduction techniques open new routes for performing such kinds of efficient high-resolution homogenization. In this work we propose different reduced order models of thermal conductivities of heterogeneous microstructures, with low and high contrast between both materials, and then we extend the methodology for addressing the homogenization of mechanical properties or the one related to the flow in porous media.
International Journal of Material Forming
Dans le cadre de la mécanique de structures nous proposons une approche 3D des modèles thermoméca... more Dans le cadre de la mécanique de structures nous proposons une approche 3D des modèles thermomécaniques définis dans des géométries plaque ou coque par séparation des coordonnées dans le plan et l'épaisseur, nous permettant une riche représentation 3D tout en gardant une complexité de calcul typiquement 2D.
Revue des composites et des matériaux avancés, 2014
Revue des composites et des matériaux avancés, 2011
Volume 3: Advanced Composite Materials and Processing; Robotics; Information Management and PLM; Design Engineering, 2012
ABSTRACT Automated tape placement (ATP) is a process recently developed for the production of lar... more ABSTRACT Automated tape placement (ATP) is a process recently developed for the production of large parts (plates, shells) made of thermoplastic composites. In ATP a tape is placed on the previous ply and welded by a local heating and pressure to build up a laminated structure. The numerical modeling of such a process is a challenging issue since the thermal history of each ply is different, depending on its position within the structure. The evaluation of residual stresses is particularly important for determining the deformed shape of the piece at the end of the process. A numerical model based on the Proper Generalized Decomposition is proposed. The solution of the 3D thermal problem is performed first. Thermal contact resistances are in particular introduced in order to model the imperfect heat conduction at the interface of two neighboring plies. The computed temperature field is then introduced in the mechanical model considering a thermo-elastic behavior for the material. An incremental approach is therefore used on a control volume in order to compute the evolution of the stresses within the laminated structure during the process.
International Journal of Material Forming, 2014
ABSTRACT Composite materials and their related manufacturing processes involve many modeling and ... more ABSTRACT Composite materials and their related manufacturing processes involve many modeling and simulation issues, mainly related to their multi-physics and multi-scale nature, to the strong couplings and the complex geometries. In our former works we developed a new paradigm for addressing the solution of such complex models, the so-called Proper Generalized Decomposition based model order reduction. In this work we are summarizing the most outstanding capabilities of such methodology and then all these capabilities will be put together for addressing efficiently the simulation of a challenging composites manufacturing process, the automated tape placement.
Revue des composites et des matériaux avancés, 2014
2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)
Spirometer testing is considered the most common method used to evaluate the pulmonary system. It... more Spirometer testing is considered the most common method used to evaluate the pulmonary system. It diagnoses asthma, chronic obstructive pulmonary disease (COPD) and other conditions that affect breathing. Nowadays many pharmaceutical companies produce spirometer devices for patients with asthma, designed for home use. However, the machines are replaced annually due to the lack of control and results’ reproducibility. Lacking a reliable mean of calibration leads to unnecessary replacement of expensive devices and/or inaccurate measurements. The objective of this work is designing and prototyping a controlled air flow machine, which will simulate the exhalation of a human based on correlations and predefined graphs found in medicine. This prototyped machine will be used to control and/or calibrate the spirometer device of the physician. The simulation of the human’s exhalation was accomplished by varying the rotational speed of an AC single phase motor using a Variable Frequency Drive in addition of a hardware device. The motor is connected directly to a centrifugal fan with forward curved blades. Using the digital pitot tube anemometer/manometer, the flow rate was measured by taking an average value of 40 frequency samples in the range 0 Hz to 100 Hz. After obtaining a relationship between the flow rate and the frequency, the data were implemented in a hardware controller, to adequately control the motor. The control was made from an Android mobile application as follows: Manual and Automatic. The Manual feature enables the user to control the flow rate manually by choosing the required maximum peak flow values to run the test. By adding an air flow sensor, the automatic feature runs automatically and the results of the test shall be obtained as a feedback on the application’s screen.
Volume 3: Advanced Composite Materials and Processing; Robotics; Information Management and PLM; Design Engineering, 2012
Automated tape placement (ATP) is a process recently developed for the production of large parts ... more Automated tape placement (ATP) is a process recently developed for the production of large parts (plates, shells) made of thermoplastic composites. In ATP a tape is placed on the previous ply and welded by a local heating and pressure to build up a laminated structure. The numerical modeling of such a process is a challenging issue since the thermal history of each ply is different, depending on its position within the structure. The evaluation of residual stresses is particularly important for determining the deformed shape of the piece at the end of the process. A numerical model based on the Proper Generalized Decomposition is proposed. The solution of the 3D thermal problem is performed first. Thermal contact resistances are in particular introduced in order to model the imperfect heat conduction at the interface of two neighboring plies. The computed temperature field is then introduced in the mechanical model considering a thermo-elastic behavior for the material. An increment...
Revue des composites et des matériaux avancés, 2014
Chinesta}@ec-nantes.fr mécanique des solides et des fluides, électromagnétisme) définies sur des ... more Chinesta}@ec-nantes.fr mécanique des solides et des fluides, électromagnétisme) définies sur des domaines à fort rapport d'aspect.
Revue des composites et des matériaux avancés, 2014
Chinesta}@ec-nantes.fr mécanique des solides et des fluides, électromagnétisme) définies sur des ... more Chinesta}@ec-nantes.fr mécanique des solides et des fluides, électromagnétisme) définies sur des domaines à fort rapport d'aspect.
Revue des composites et des matériaux avancés, 2011
La modélisation avancée des procédés de mise en forme de composites est confrontée à de nombreux ... more La modélisation avancée des procédés de mise en forme de composites est confrontée à de nombreux verrous malgré les avancées récentes en matière de modélisation mécanique, analyse numérique, stratégies de discrétisation et capacité de calcul. La mise en forme de composites nécessite la prise en compte des multiples échelles en espace et temps, des comportements non-linéaires anisotropes et fortement couplés, définis dans des géométries très complexes. L'optimisation des procédés ainsi que l'indentification inverse, ou encore le controle des procédés nécessite plusieurs résolutions. Dans ce contexte les techniques de réduction de modèles offrent de nouvelles possibilités, permettant d'accélérer les calculs de quelques ordres de grandeur, et même de résoudre des modèles jamais résolus jusqu'à présent. ABSTRACT. Efficient simulation of composites manufacturing processes remains today a challenging issue despite the impressive progresses reached in mechanical modeling, numerical analysis, discretization techniques and computer science during the last decade. Composites manufacturing involve multiscale models in space and time, highly non-linear and anisotropic behaviors, strongly coupled multiphysics and complex geometries. Moreover, optimization (shape and process optimization), inverse analysis (parameter identification, non destructive testing, ...) or process control need the solution of many direct problems, as fast and accurately as possible. In this context, model reduction techniques constitute an appealing simulation choice, accelerating the computations of several orders of magnitude, and even, enabling the solution of models never until now solved.
In the numerical modeling of composite materials and structures, microscopic heterogeneities intr... more In the numerical modeling of composite materials and structures, microscopic heterogeneities introduce the need for defining homogenized properties depending on microscopic details. Real time image-based calculations in the framework of the on-line control of manufacturing processes demands the prediction of the local homogenized properties of a heterogeneous material at different scanning scales, as fast as possible for a given acceptable error. Therefore, model reduction techniques open new routes for performing such kinds of efficient high-resolution homogenization. In this work we propose different reduced order models of thermal conductivities of heterogeneous microstructures, with low and high contrast between both materials, and then we extend the methodology for addressing the homogenization of mechanical properties or the one related to the flow in porous media.
International Journal of Material Forming
Dans le cadre de la mécanique de structures nous proposons une approche 3D des modèles thermoméca... more Dans le cadre de la mécanique de structures nous proposons une approche 3D des modèles thermomécaniques définis dans des géométries plaque ou coque par séparation des coordonnées dans le plan et l'épaisseur, nous permettant une riche représentation 3D tout en gardant une complexité de calcul typiquement 2D.
Revue des composites et des matériaux avancés, 2014
Revue des composites et des matériaux avancés, 2011
Volume 3: Advanced Composite Materials and Processing; Robotics; Information Management and PLM; Design Engineering, 2012
ABSTRACT Automated tape placement (ATP) is a process recently developed for the production of lar... more ABSTRACT Automated tape placement (ATP) is a process recently developed for the production of large parts (plates, shells) made of thermoplastic composites. In ATP a tape is placed on the previous ply and welded by a local heating and pressure to build up a laminated structure. The numerical modeling of such a process is a challenging issue since the thermal history of each ply is different, depending on its position within the structure. The evaluation of residual stresses is particularly important for determining the deformed shape of the piece at the end of the process. A numerical model based on the Proper Generalized Decomposition is proposed. The solution of the 3D thermal problem is performed first. Thermal contact resistances are in particular introduced in order to model the imperfect heat conduction at the interface of two neighboring plies. The computed temperature field is then introduced in the mechanical model considering a thermo-elastic behavior for the material. An incremental approach is therefore used on a control volume in order to compute the evolution of the stresses within the laminated structure during the process.
International Journal of Material Forming, 2014
ABSTRACT Composite materials and their related manufacturing processes involve many modeling and ... more ABSTRACT Composite materials and their related manufacturing processes involve many modeling and simulation issues, mainly related to their multi-physics and multi-scale nature, to the strong couplings and the complex geometries. In our former works we developed a new paradigm for addressing the solution of such complex models, the so-called Proper Generalized Decomposition based model order reduction. In this work we are summarizing the most outstanding capabilities of such methodology and then all these capabilities will be put together for addressing efficiently the simulation of a challenging composites manufacturing process, the automated tape placement.
Revue des composites et des matériaux avancés, 2014