Etienne Arnoult | Sorbonne University (original) (raw)
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Papers by Etienne Arnoult
This paper presents a new way to deal with contact within an implicit finite element code. The co... more This paper presents a new way to deal with contact within an implicit finite element code. The contact detection is realised with an analytical method using B-spline functions, and contact analysis is done with a contact element based on penalty function method using a new contact stiffness.
The overall performance (efficiency, noise, gas pulsation, ...) of piston compressors is strongly... more The overall performance (efficiency, noise, gas pulsation, ...) of piston compressors is strongly influenced by valve dynamics. In general, the dynamic behavior of the valve is modeled using finite element methods. While the free vibration of the valve can be accurately investigated using this technique, the simulation of the overall dynamics of the valve has to include a number of non-linear phenomena which influence the behavior. The most important are: the impacts, the oil stiction, the gas flow through the ports, the gas pulsation. An accurate numerical model of the dynamic behavior of valves has to account for all these phenomena. This increases the accuracy of input data, but increases the computation time to such an extent that it limits the use of such simulation software in the valve design process. This paper deals with the development of a numerical model of valve behavior aimed for use in the design office. The valve dynamics and the thermodynamics of gas under compressi...
Les problemes de facetisation en elements finis peuvent conduire, lors de simulations numeriques,... more Les problemes de facetisation en elements finis peuvent conduire, lors de simulations numeriques, a des resultats tres eloignes de ce qui est observe experimentalement. Les deux principales difficultes generees par la discretisation sont d'une part la discontinuite du vecteur normal au passage des elements, et d'autre part, la mauvaise prise en compte de la courbure des structures etudiees. Les developpements presentes s'inscrivent plus particulierement dans le cadre des etudes des contacts aubes/carter de turboreacteurs. La premiere partie du memoire concerne la mise en place d'une nouvelle methode de recherche du contact applicable dans un code elements finis en dynamique. Cette methode repose sur la construction d'entites analytiques (une courbe et une surface) utilisant les fonctions splines a partir des nuds du maillage. La recherche du contact est alors realisee entre ces entites suivant le schema suivant : une boule, dont le rayon diminue entre chaque iter...
Mécanique & Industries, 2001
The overall performance (efficiency, noise, gas pulsation, …) of piston compressors is strongly i... more The overall performance (efficiency, noise, gas pulsation, …) of piston compressors is strongly influenced by valve dynamics. In general, the dynamic behavior of the valve is modeled using finite element methods. While the free vibration of the valve can be accurately investigated using this technique, the simulation of the overall dynamics of the valve has to include a number of non-linear phenomena which influence the behavior. The most important are: the impacts, the oil stiction, the gas flow through the ports, the gas pulsation. An accurate numerical model of the dynamic behavior of valves has to account for all these phenomena. This increases the accuracy of input data, but increases the computation time to such an extent that it limits the use of such simulation software in the valve design process. This paper deals with the development of a numerical model of valve behavior aimed for use in the design office. The valve dynamics and the thermodynamics of gas under compression are modeled simultaneously. The model functions in the time domain. The non-linear behavior of the valve due to the impacts, the oil stiction and the gas flow are modeled as external forces. These are in general functions of valve displacement and velocity. The valve body is modeled using beam finite elements. A restrained number of modes are used to compute the valve response. An existing valve is modeled using the developed technique. The results obtained are compared with experimental results on a simple valve test rig in air. The measurements are carried out using a LASER vibrometer. The measured results are used to improve the accuracy of the model by modifying the input impact parameters. The number of modes needed for an accurate computation is discussed at the end of the paper.
Finite Elements in Analysis and Design, 2011
ABSTRACT In this paper the modal stability procedure (MSP), for the calculation of natural freque... more ABSTRACT In this paper the modal stability procedure (MSP), for the calculation of natural frequencies and frequency response functions (FRFs) of finite element systems with random parameters, is investigated. The perturbed natural frequencies and FRFs are calculated in an approximate way by using the modal stability assumption. This method requires only one finite element analysis and a post-processing procedure. The MSP has been applied to an academic example: a 1D beams assembly, and to an industrial application: a windscreen. Small and large numbers of random parameters, as well as moderate and high variability levels, have been considered. Systematically, a comparison between the MSP and Monte Carlo simulation approach, considered as a reference, are reported and commented. A detailed study of the possibilities and the limitations of the method has been carried out. For the academic as well as for the industrial example, the results are satisfactory in terms of mean value, standard deviation, probability density functions of the natural frequencies and FRFs. Moreover, the MSP is very efficient from a computational time point of view.
Finite Elements in Analysis and Design, 2012
The main purpose of this paper is to present and evaluate the new Certain Generalized Stresses Me... more The main purpose of this paper is to present and evaluate the new Certain Generalized Stresses Method (CGSM) to take into account variability in finite element models for static applications. The method is dedicated to thin-walled structures and is presented here for bar and beam trusses. All physical properties may be uncertain. The method relies on the assumption that the generalized stresses are quite stable in presence of variability. This assumption is strictly satisfied for specific cases, when the structure is statically determinate or when the perturbation due to variability is uniform throughout the structure, so the CGSM is an exact method in these cases. The objective of this study is to assess the relevance of this assumption in a statistical sense, for the general case. The method only requires two finite element analyses. The displacement mean value, the standard deviation and the distribution of the displacement are obtained by a mixed CGSM þMonte Carlo approach. However, generally, the displacement mean value and the standard deviation can be obtained in an analytical way. In the examples presented, the variability of displacements is studied. The CGSM has been applied to statically determinate bar and beam structures and indeed exact results have been obtained for this class of examples. It has also been applied to statically indeterminate bar and beam trusses. Very precise results are obtained for the mean value, the standard deviation and the statistical distribution of the displacements. A detailed analysis of errors has been performed in order to justify the high quality level of the results obtained for these examples. The method is quite economical from a computational time point of view.
Integrated Design and Manufacturing in Mechanical Engineering ’98, 1999
The present work aims at studying contact phenomena within aircraft engines. These events occur f... more The present work aims at studying contact phenomena within aircraft engines. These events occur for instance when severe manoeuvrings are operated or when the engine bears a blade-off event. Two approaches are used simultaneously. The former is a numerical one and consists in a fine rotor/stator contact simulation. Various contactimpact algorithms and time integration schemes are tested on elementary cases. The Lagrange multiplier method appears to be the most appropriate one for dynamic studies. The latter approach is an experimental one and consists in a vibratory study of the mechanical coupling between the casing and the fan bladed disk so as to determine what parameters generate interaction. A simplified experimental test rig is used. Interaction is produced with selected casing and blade modes.
Mecanique Industrielle Et Materiaux, 1998
Méthode des Efforts Généralisés Certains ou MEGC, déjà présentée dans d'autres articles, perm... more Méthode des Efforts Généralisés Certains ou MEGC, déjà présentée dans d'autres articles, permet de prendre en compte les incertitudes dans les analyses par éléments finis. Elle s'appuie sur l'hypothèse d'indépendance des efforts généralisés vis-à-vis des variables incertaines. C'est une méthode économique puisqu'elle nécessite seulement deux analyses éléments finis, associées à des développements analytiques. Les résultats déjà publiés concernaient des problèmes isostatiques, pour lesquels la méthode MEGC fournit des résultats statistiques exacts. Sont publiés ici les résultats obtenus pour trois problèmes de treillis de barres hyperstatiques. La quantité incertaine est le module d'Young et on étudie la variabilité des déplacements. Des résultats très précis sont obtenus pour la moyenne, l'écart-type et la densité de probabilité des déplacements. La méthode MEGC s'avère très performante pour ces problèmes. ABSTRACT. The Certain Generalized Stresse...
Integrated Design and Manufacturing in Mechanical Engineering, 2002
The purpose of this communication is to develop a method of analytic contact search applied to a ... more The purpose of this communication is to develop a method of analytic contact search applied to a finite element code and to present the first numerical results. This method is based on the construction of geometrical entities being sufficiently continuous to get rid off the facetisation problems due to the spatial discretisation of the studied structure by finite elements. These geometrical entities are built up using the mathematical notion of spline applied to some nodes of the mesh. The search of contact is then realised with these entities, and then the obtained results are projected on the initial mesh. Our method, developed in the particular context of contact studies between casing and blades of turbojet engine, has been implemented in two finite element codes of different nature: Samcef (implicit formulation) and Plexus (explicit formulation), and then tested on some configurations.
This paper presents a new way to deal with contact within an implicit finite element code. The co... more This paper presents a new way to deal with contact within an implicit finite element code. The contact detection is realised with an analytical method using B-spline functions, and contact analysis is done with a contact element based on penalty function method using a new contact stiffness.
The overall performance (efficiency, noise, gas pulsation, ...) of piston compressors is strongly... more The overall performance (efficiency, noise, gas pulsation, ...) of piston compressors is strongly influenced by valve dynamics. In general, the dynamic behavior of the valve is modeled using finite element methods. While the free vibration of the valve can be accurately investigated using this technique, the simulation of the overall dynamics of the valve has to include a number of non-linear phenomena which influence the behavior. The most important are: the impacts, the oil stiction, the gas flow through the ports, the gas pulsation. An accurate numerical model of the dynamic behavior of valves has to account for all these phenomena. This increases the accuracy of input data, but increases the computation time to such an extent that it limits the use of such simulation software in the valve design process. This paper deals with the development of a numerical model of valve behavior aimed for use in the design office. The valve dynamics and the thermodynamics of gas under compressi...
Les problemes de facetisation en elements finis peuvent conduire, lors de simulations numeriques,... more Les problemes de facetisation en elements finis peuvent conduire, lors de simulations numeriques, a des resultats tres eloignes de ce qui est observe experimentalement. Les deux principales difficultes generees par la discretisation sont d'une part la discontinuite du vecteur normal au passage des elements, et d'autre part, la mauvaise prise en compte de la courbure des structures etudiees. Les developpements presentes s'inscrivent plus particulierement dans le cadre des etudes des contacts aubes/carter de turboreacteurs. La premiere partie du memoire concerne la mise en place d'une nouvelle methode de recherche du contact applicable dans un code elements finis en dynamique. Cette methode repose sur la construction d'entites analytiques (une courbe et une surface) utilisant les fonctions splines a partir des nuds du maillage. La recherche du contact est alors realisee entre ces entites suivant le schema suivant : une boule, dont le rayon diminue entre chaque iter...
Mécanique & Industries, 2001
The overall performance (efficiency, noise, gas pulsation, …) of piston compressors is strongly i... more The overall performance (efficiency, noise, gas pulsation, …) of piston compressors is strongly influenced by valve dynamics. In general, the dynamic behavior of the valve is modeled using finite element methods. While the free vibration of the valve can be accurately investigated using this technique, the simulation of the overall dynamics of the valve has to include a number of non-linear phenomena which influence the behavior. The most important are: the impacts, the oil stiction, the gas flow through the ports, the gas pulsation. An accurate numerical model of the dynamic behavior of valves has to account for all these phenomena. This increases the accuracy of input data, but increases the computation time to such an extent that it limits the use of such simulation software in the valve design process. This paper deals with the development of a numerical model of valve behavior aimed for use in the design office. The valve dynamics and the thermodynamics of gas under compression are modeled simultaneously. The model functions in the time domain. The non-linear behavior of the valve due to the impacts, the oil stiction and the gas flow are modeled as external forces. These are in general functions of valve displacement and velocity. The valve body is modeled using beam finite elements. A restrained number of modes are used to compute the valve response. An existing valve is modeled using the developed technique. The results obtained are compared with experimental results on a simple valve test rig in air. The measurements are carried out using a LASER vibrometer. The measured results are used to improve the accuracy of the model by modifying the input impact parameters. The number of modes needed for an accurate computation is discussed at the end of the paper.
Finite Elements in Analysis and Design, 2011
ABSTRACT In this paper the modal stability procedure (MSP), for the calculation of natural freque... more ABSTRACT In this paper the modal stability procedure (MSP), for the calculation of natural frequencies and frequency response functions (FRFs) of finite element systems with random parameters, is investigated. The perturbed natural frequencies and FRFs are calculated in an approximate way by using the modal stability assumption. This method requires only one finite element analysis and a post-processing procedure. The MSP has been applied to an academic example: a 1D beams assembly, and to an industrial application: a windscreen. Small and large numbers of random parameters, as well as moderate and high variability levels, have been considered. Systematically, a comparison between the MSP and Monte Carlo simulation approach, considered as a reference, are reported and commented. A detailed study of the possibilities and the limitations of the method has been carried out. For the academic as well as for the industrial example, the results are satisfactory in terms of mean value, standard deviation, probability density functions of the natural frequencies and FRFs. Moreover, the MSP is very efficient from a computational time point of view.
Finite Elements in Analysis and Design, 2012
The main purpose of this paper is to present and evaluate the new Certain Generalized Stresses Me... more The main purpose of this paper is to present and evaluate the new Certain Generalized Stresses Method (CGSM) to take into account variability in finite element models for static applications. The method is dedicated to thin-walled structures and is presented here for bar and beam trusses. All physical properties may be uncertain. The method relies on the assumption that the generalized stresses are quite stable in presence of variability. This assumption is strictly satisfied for specific cases, when the structure is statically determinate or when the perturbation due to variability is uniform throughout the structure, so the CGSM is an exact method in these cases. The objective of this study is to assess the relevance of this assumption in a statistical sense, for the general case. The method only requires two finite element analyses. The displacement mean value, the standard deviation and the distribution of the displacement are obtained by a mixed CGSM þMonte Carlo approach. However, generally, the displacement mean value and the standard deviation can be obtained in an analytical way. In the examples presented, the variability of displacements is studied. The CGSM has been applied to statically determinate bar and beam structures and indeed exact results have been obtained for this class of examples. It has also been applied to statically indeterminate bar and beam trusses. Very precise results are obtained for the mean value, the standard deviation and the statistical distribution of the displacements. A detailed analysis of errors has been performed in order to justify the high quality level of the results obtained for these examples. The method is quite economical from a computational time point of view.
Integrated Design and Manufacturing in Mechanical Engineering ’98, 1999
The present work aims at studying contact phenomena within aircraft engines. These events occur f... more The present work aims at studying contact phenomena within aircraft engines. These events occur for instance when severe manoeuvrings are operated or when the engine bears a blade-off event. Two approaches are used simultaneously. The former is a numerical one and consists in a fine rotor/stator contact simulation. Various contactimpact algorithms and time integration schemes are tested on elementary cases. The Lagrange multiplier method appears to be the most appropriate one for dynamic studies. The latter approach is an experimental one and consists in a vibratory study of the mechanical coupling between the casing and the fan bladed disk so as to determine what parameters generate interaction. A simplified experimental test rig is used. Interaction is produced with selected casing and blade modes.
Mecanique Industrielle Et Materiaux, 1998
Méthode des Efforts Généralisés Certains ou MEGC, déjà présentée dans d'autres articles, perm... more Méthode des Efforts Généralisés Certains ou MEGC, déjà présentée dans d'autres articles, permet de prendre en compte les incertitudes dans les analyses par éléments finis. Elle s'appuie sur l'hypothèse d'indépendance des efforts généralisés vis-à-vis des variables incertaines. C'est une méthode économique puisqu'elle nécessite seulement deux analyses éléments finis, associées à des développements analytiques. Les résultats déjà publiés concernaient des problèmes isostatiques, pour lesquels la méthode MEGC fournit des résultats statistiques exacts. Sont publiés ici les résultats obtenus pour trois problèmes de treillis de barres hyperstatiques. La quantité incertaine est le module d'Young et on étudie la variabilité des déplacements. Des résultats très précis sont obtenus pour la moyenne, l'écart-type et la densité de probabilité des déplacements. La méthode MEGC s'avère très performante pour ces problèmes. ABSTRACT. The Certain Generalized Stresse...
Integrated Design and Manufacturing in Mechanical Engineering, 2002
The purpose of this communication is to develop a method of analytic contact search applied to a ... more The purpose of this communication is to develop a method of analytic contact search applied to a finite element code and to present the first numerical results. This method is based on the construction of geometrical entities being sufficiently continuous to get rid off the facetisation problems due to the spatial discretisation of the studied structure by finite elements. These geometrical entities are built up using the mathematical notion of spline applied to some nodes of the mesh. The search of contact is then realised with these entities, and then the obtained results are projected on the initial mesh. Our method, developed in the particular context of contact studies between casing and blades of turbojet engine, has been implemented in two finite element codes of different nature: Samcef (implicit formulation) and Plexus (explicit formulation), and then tested on some configurations.