Gerard Maurice - Academia.edu (original) (raw)
Papers by Gerard Maurice
Computer Methods in Applied Mechanics and Engineering, 1992
ABSTRACT This paper presents the numerical study of the elastic contact problem with Coulomb fric... more ABSTRACT This paper presents the numerical study of the elastic contact problem with Coulomb friction between both deformable sphere and support, using the finite element method. We solve this problem, governed by a variational inequality, with a successive approximations method, each iteration of which being constituted by the solution of an intermediate problem with normal pressure fixed. To compute stresses in contact, we couple the finite elements with the boundary elements. Our results are conform to the Hertz theory and the analytical solution of Spence. Moreover, our study shows the influence of friction on parameters such as the contact radius and the normal pressure.
Journal des maladies vasculaires, 1998
As in most living tissues, a network of nutritional vessels, the so-called vasa vasorum, irrigate... more As in most living tissues, a network of nutritional vessels, the so-called vasa vasorum, irrigates the vessel wall under physiological conditions. An alteration or obstruction of this network can induce severe lesions. Most normal arteries and veins are irrigated by a vasa vasorum network located mainly in the adventice. They essentially supply oxygen to the outer layers of the vascular wall, the inner layer being mainly oxygenated by direct diffusion from bloodstream. Vasa vasorum responds to vasomotor stimuli and can even regress, e.g., after vascularization of arterial grafts. Their pathophysiological importance for arteries is now established. Indeed, it is known that an infusion disorder or vasa vasorum alteration may induce or promote early atherosclerotic lesions, fibrodysplasia or even media necrosis. From a mechanical point of view, and considering the three layers as a unique material, the vessel shows non-isotropic linear elastic and incompressible (v = 0.5) behaviour in ...
Damage and Fracture Mechanics, 2009
A hybrid weight function technique is presented. It consists of dividing an elliptical crack into... more A hybrid weight function technique is presented. It consists of dividing an elliptical crack into two zones, then using the appropriate weight function in the area where it is more efficient. The proportion between zones is determined by optimizing two crack parameters (axis ratio and curvature radius). Stress intensity factors are hence computed by a self developed computer code. Static and fatigue loadings are considered. The results found by the present approach are in good correlation with the analytical and experimental solutions (when available) as well as with those obtained numerically by other researchers.
Tribology Series, 1999
ABSTRACT The viscoelastic properties of porous media are studied as a function of their moisture ... more ABSTRACT The viscoelastic properties of porous media are studied as a function of their moisture content; Water content can be divided in two classes. Free water at high moisture content which acts only as a dead weight and bound water at low water content which greatly influences the viscoelastic properties of the materials. On hydrophilic surfaces, the water film sticks to the inner pores and increases the stiffness of the sample. On hydrophobic surfaces the reverse is true. The water films damp the materials. During transients, the damping factor exhibits large maxima. This is related to the mechano-sorptive effect. A discussion on the subject is presented.
Rheologica Acta, 1988
Ce travail porte sur l'6tude de solutions dilu6es d'un polym6re de l'acide acrylique dans l'eau (... more Ce travail porte sur l'6tude de solutions dilu6es d'un polym6re de l'acide acrylique dans l'eau (concentration en poids ~-0,1%). Ce fluide pr6sente des effets de seuil. La mesure du champ de vitesse par v61ocim~trie laser permet une d6termination pr6cise de l'indice rh6ologique, n', 6tant un param6tre essentiel de la loi de comportement propos6e: ~ =z~ + K~" ' + t/~ ~. Les autres constantes peuvent ~tre d~duites d'essais rh6ologiques classiques,/t fort taux de cisaillement. I1 est possible de corriger le gradient de pression mesur6 AP/L, afin d'obtenir la valeur v@itable de ce gradient, not6e dp/dz. L'analyse de l'6coulement dans un 61argissement brusque montre que le seuil a une forte influence sur les zones de recirculation.
IEEE Transactions on Biomedical Engineering, 2001
In order to investigate the three-dimensional (3-D) mechanical properties of blood vessels, a new... more In order to investigate the three-dimensional (3-D) mechanical properties of blood vessels, a new experimental device is described allowing in vitro static and dynamic measurements on segments of arteries with high technical performances. Static tests are applied to sheep common carotid arteries. Considering a thick-walled cylindrical model of orthotropic material under large deformations, a classical 3-D approach based on strain energy density is used to calculate the resulting mechanical behavior law in radial and circumferencial directions and stresses distribution throughout the wall thickness. Results are presented with reference to unloaded and zero-stress initial state thanks to simple measurements of inner and outer circumferences. A particular ratio relating the two main stresses (circumferential and longitudinal) is calculated that put into the forth the progressive modifications in the direction of the predominant stress in the wall and the specific radial location where these changes occur. We observe that this point location is a function of the test conditions of the specimen, i.e., stretching length and level of pressure. Index Terms-Anisotropy, biorheology, blood vessels, in vitro instrumentation, large strains. I. INTRODUCTION O N a clinical point of view, the mechanical properties of the arterial wall [34] are responsible for the blood pressure wave propagation and play an important role in cardiovascular diseases [9], [27] (like hypertension, aneurysm development or atherosclerosis). The three-dimensional (3-D) mechanical properties of human allografts need also to be investigated in order to determine how they may be modified by cryopreservation. On this point, recent studies did not collect enough data to formally assess that cryopreservation of arteries has no effects on their mechanical properties [30]. Mechanical behaviors of vascular prosthesis [18], allografts [25] and pathological human vessels Manuscript
Advances in Engineering Software, 1999
In this paper, we study the problem of indentation of an elastic support by a sphere, using a dom... more In this paper, we study the problem of indentation of an elastic support by a sphere, using a domain decomposition method coupled with the boundary elements method. The decomposition method has the advantage of solving the problem on each solid separately. The contact is governed only by boundary conditions. Therefore, the Hennizel method, a non-overlapping technique is particularly well adapted. Indeed only information on interface is transmitted from one sub-domain to another. This leads us naturally to associate it with the boundary elements method, since it needs only the discretization of the boundaries of solids. We have implemented three programs on a microcomputer (boundary elements, domain decomposition and solution of contact). The latter gives results in conformity with the Hertz theory and the analytical solution of Spence.
Proceedings of the First Joint BMES/EMBS Conference. 1999 IEEE Engineering in Medicine and Biology 21st Annual Conference and the 1999 Annual Fall Meeting of the Biomedical Engineering Society (Cat. No.99CH37015)
Abstract In this work a numerical simulation of the deformation of a model endothelial cell (EC) ... more Abstract In this work a numerical simulation of the deformation of a model endothelial cell (EC) in a laminar flow was presented. The EC was considered as a two-dimensional isotropic elastic material with a less deformable nucleus. It was supposed that identical ...
Biorheology, 1984
The determination of a constitutive law of a fluid, the red blood can be obtained by fitting the ... more The determination of a constitutive law of a fluid, the red blood can be obtained by fitting the parameters of a theorical law with experimental results. For an experience, several expressions can be agreed, each of them explain a particular property. The aim of my purpose is to describe some mathematical and numerical methods, in relation with two experiences, able to give the value of an unknown quantity by computation and to fit it with measured quantity. The first method use finite element to modelize a couette nonlineer flow. It can be approach by a very simple model using only the computation of a nonlinear differential equation. The second use the perturbation method and the expansion in power serie.
Known since a long time but relatively neglected, the venous vasa vasorum forms a tiny network to... more Known since a long time but relatively neglected, the venous vasa vasorum forms a tiny network to irrigate and drain the wall. Actually it is re-realized that, just like any tissues, the vein is a living tissue and the vasa vasorum plays a key role in the maintenance of its homeostasis. Under the effects of intraluminal pressure, the Young’s modulus (E) of the vein following an empirical relationship (LogE) 2 =-(αLog(p)+β), can vary in a very large range (a factor of 100) even in physiological conditions. We simulated the deformation of venous vasa vasorum by finite element method. Thus it can be suggested that, at first, a permanent venous hypertension provoques a local modification of the wall’s mechanical properties (decrease of E) to favorise a large deformation which will lead to a decrease of the irrigation, and secondly, with the decreased irrigation, the wall will loose its elasticity, become rigidified and keep its large deformation. A vicious cycle could be thus created.
Orthopedie Traumatologie, 1993
Optimisations du profil et de la vis6e de la tige centro-m6dullaire pour la pose d'une proth se d... more Optimisations du profil et de la vis6e de la tige centro-m6dullaire pour la pose d'une proth se de genou New profile design of the intra medullary stem for total knee replacement
Clinical hemorheology and microcirculation, 1998
The authors present analytical and numerical approaches of the deformation of venous and arterial... more The authors present analytical and numerical approaches of the deformation of venous and arterial vessels vasa vasorum. An elastic behaviour of the vessel wall is supposed. It is shown that a normal range of intraluminar pressure induces a small deformation in the vasa vasorum in arteries. According to the nonlinear elastic behaviour, a larger deformation is induced in venous vasa vasorum is rapidly obtained. Increased pressure has serious consequences, especially on the flow in vasa vasorum and induces decrease of oxygen transport. This phenomenon could be one of the generating factors of atherogenesis and ischemia.
Computational Methods and Experimental Measurements, 1982
This work is part of a study which aims to characterize quantitatively the behaviour of non newto... more This work is part of a study which aims to characterize quantitatively the behaviour of non newtonian fluids sumitted to transient shear.
Damage and Fracture Mechanics, 2009
... Int J Numer Meth Eng, 50: 9931013. [11] Bachene M, Tiberkak R, Rechak S, Hachi BEK (2007) An... more ... Int J Numer Meth Eng, 50: 9931013. [11] Bachene M, Tiberkak R, Rechak S, Hachi BEK (2007) Analyse du comportement vibratoire des plaques fissurées par la X-FEM. 18th French Congress on Mechanics, Grenoble, France, August. New Jersey, 07458. ...
Rheologica Acta, 1990
The use of the Couette viscometer with coaxial cylinders for the evaluation of rheological proper... more The use of the Couette viscometer with coaxial cylinders for the evaluation of rheological properties and the establishment of behaviour laws of fluids, generally requires the knowledge of the shear rate at each instant and at any point in the gap. This quantity, which is generally unknown, can be approximated by simple mathematical expressions which are satisfactory for the applied
Polymer Engineering & Science, 2012
A numerical model using homogenization techniques is proposed to simulate the evolution of elasti... more A numerical model using homogenization techniques is proposed to simulate the evolution of elastic properties of nanocomposite polymer-nanoparticles, depending on the concentration of nanoparticles and the rigidity of the particle-matrix interface. To validate this model, it was confronted to several physical systems having different interface behavior, the nanocomposite systems: poly(vinylidene fluoride trifluoroethylene)/Al 2 O 3 (alumina nanoparticles incorporated into copolymer of vinylidene difluoride and trifluoroethylene to form nanocomposite), PMMA/CNT (carbon nanotube/poly(methyl methacrylate) composite) and PMMA/SiO 2 with nanoparticles with or without surface treatment of silanization. For all these systems, the Young's modulus (nanoparticles and matrix) has been obtained experimentally from the elastic modulus C 11 obtained by Brillouin spectroscopy. These macroscopic measurements coupled with the theoretical model allow a multiscale approach of the elastic behavior of nanocomposite systems, providing information on the global elastic properties of polymernanoparticle material, and also indications about the strength of physical and chemical bonds between the nanoparticles and the matrix. Our results validate the hypothesis of the crucial role of the interface module, provided by numerical simulation which shows that incorporation of nanoparticles may lead to a strengthening or a weakening of the matrix.
Mechanics Research Communications, 1987
Computer Methods in Applied Mechanics and Engineering, 1992
ABSTRACT This paper presents the numerical study of the elastic contact problem with Coulomb fric... more ABSTRACT This paper presents the numerical study of the elastic contact problem with Coulomb friction between both deformable sphere and support, using the finite element method. We solve this problem, governed by a variational inequality, with a successive approximations method, each iteration of which being constituted by the solution of an intermediate problem with normal pressure fixed. To compute stresses in contact, we couple the finite elements with the boundary elements. Our results are conform to the Hertz theory and the analytical solution of Spence. Moreover, our study shows the influence of friction on parameters such as the contact radius and the normal pressure.
Journal des maladies vasculaires, 1998
As in most living tissues, a network of nutritional vessels, the so-called vasa vasorum, irrigate... more As in most living tissues, a network of nutritional vessels, the so-called vasa vasorum, irrigates the vessel wall under physiological conditions. An alteration or obstruction of this network can induce severe lesions. Most normal arteries and veins are irrigated by a vasa vasorum network located mainly in the adventice. They essentially supply oxygen to the outer layers of the vascular wall, the inner layer being mainly oxygenated by direct diffusion from bloodstream. Vasa vasorum responds to vasomotor stimuli and can even regress, e.g., after vascularization of arterial grafts. Their pathophysiological importance for arteries is now established. Indeed, it is known that an infusion disorder or vasa vasorum alteration may induce or promote early atherosclerotic lesions, fibrodysplasia or even media necrosis. From a mechanical point of view, and considering the three layers as a unique material, the vessel shows non-isotropic linear elastic and incompressible (v = 0.5) behaviour in ...
Damage and Fracture Mechanics, 2009
A hybrid weight function technique is presented. It consists of dividing an elliptical crack into... more A hybrid weight function technique is presented. It consists of dividing an elliptical crack into two zones, then using the appropriate weight function in the area where it is more efficient. The proportion between zones is determined by optimizing two crack parameters (axis ratio and curvature radius). Stress intensity factors are hence computed by a self developed computer code. Static and fatigue loadings are considered. The results found by the present approach are in good correlation with the analytical and experimental solutions (when available) as well as with those obtained numerically by other researchers.
Tribology Series, 1999
ABSTRACT The viscoelastic properties of porous media are studied as a function of their moisture ... more ABSTRACT The viscoelastic properties of porous media are studied as a function of their moisture content; Water content can be divided in two classes. Free water at high moisture content which acts only as a dead weight and bound water at low water content which greatly influences the viscoelastic properties of the materials. On hydrophilic surfaces, the water film sticks to the inner pores and increases the stiffness of the sample. On hydrophobic surfaces the reverse is true. The water films damp the materials. During transients, the damping factor exhibits large maxima. This is related to the mechano-sorptive effect. A discussion on the subject is presented.
Rheologica Acta, 1988
Ce travail porte sur l'6tude de solutions dilu6es d'un polym6re de l'acide acrylique dans l'eau (... more Ce travail porte sur l'6tude de solutions dilu6es d'un polym6re de l'acide acrylique dans l'eau (concentration en poids ~-0,1%). Ce fluide pr6sente des effets de seuil. La mesure du champ de vitesse par v61ocim~trie laser permet une d6termination pr6cise de l'indice rh6ologique, n', 6tant un param6tre essentiel de la loi de comportement propos6e: ~ =z~ + K~" ' + t/~ ~. Les autres constantes peuvent ~tre d~duites d'essais rh6ologiques classiques,/t fort taux de cisaillement. I1 est possible de corriger le gradient de pression mesur6 AP/L, afin d'obtenir la valeur v@itable de ce gradient, not6e dp/dz. L'analyse de l'6coulement dans un 61argissement brusque montre que le seuil a une forte influence sur les zones de recirculation.
IEEE Transactions on Biomedical Engineering, 2001
In order to investigate the three-dimensional (3-D) mechanical properties of blood vessels, a new... more In order to investigate the three-dimensional (3-D) mechanical properties of blood vessels, a new experimental device is described allowing in vitro static and dynamic measurements on segments of arteries with high technical performances. Static tests are applied to sheep common carotid arteries. Considering a thick-walled cylindrical model of orthotropic material under large deformations, a classical 3-D approach based on strain energy density is used to calculate the resulting mechanical behavior law in radial and circumferencial directions and stresses distribution throughout the wall thickness. Results are presented with reference to unloaded and zero-stress initial state thanks to simple measurements of inner and outer circumferences. A particular ratio relating the two main stresses (circumferential and longitudinal) is calculated that put into the forth the progressive modifications in the direction of the predominant stress in the wall and the specific radial location where these changes occur. We observe that this point location is a function of the test conditions of the specimen, i.e., stretching length and level of pressure. Index Terms-Anisotropy, biorheology, blood vessels, in vitro instrumentation, large strains. I. INTRODUCTION O N a clinical point of view, the mechanical properties of the arterial wall [34] are responsible for the blood pressure wave propagation and play an important role in cardiovascular diseases [9], [27] (like hypertension, aneurysm development or atherosclerosis). The three-dimensional (3-D) mechanical properties of human allografts need also to be investigated in order to determine how they may be modified by cryopreservation. On this point, recent studies did not collect enough data to formally assess that cryopreservation of arteries has no effects on their mechanical properties [30]. Mechanical behaviors of vascular prosthesis [18], allografts [25] and pathological human vessels Manuscript
Advances in Engineering Software, 1999
In this paper, we study the problem of indentation of an elastic support by a sphere, using a dom... more In this paper, we study the problem of indentation of an elastic support by a sphere, using a domain decomposition method coupled with the boundary elements method. The decomposition method has the advantage of solving the problem on each solid separately. The contact is governed only by boundary conditions. Therefore, the Hennizel method, a non-overlapping technique is particularly well adapted. Indeed only information on interface is transmitted from one sub-domain to another. This leads us naturally to associate it with the boundary elements method, since it needs only the discretization of the boundaries of solids. We have implemented three programs on a microcomputer (boundary elements, domain decomposition and solution of contact). The latter gives results in conformity with the Hertz theory and the analytical solution of Spence.
Proceedings of the First Joint BMES/EMBS Conference. 1999 IEEE Engineering in Medicine and Biology 21st Annual Conference and the 1999 Annual Fall Meeting of the Biomedical Engineering Society (Cat. No.99CH37015)
Abstract In this work a numerical simulation of the deformation of a model endothelial cell (EC) ... more Abstract In this work a numerical simulation of the deformation of a model endothelial cell (EC) in a laminar flow was presented. The EC was considered as a two-dimensional isotropic elastic material with a less deformable nucleus. It was supposed that identical ...
Biorheology, 1984
The determination of a constitutive law of a fluid, the red blood can be obtained by fitting the ... more The determination of a constitutive law of a fluid, the red blood can be obtained by fitting the parameters of a theorical law with experimental results. For an experience, several expressions can be agreed, each of them explain a particular property. The aim of my purpose is to describe some mathematical and numerical methods, in relation with two experiences, able to give the value of an unknown quantity by computation and to fit it with measured quantity. The first method use finite element to modelize a couette nonlineer flow. It can be approach by a very simple model using only the computation of a nonlinear differential equation. The second use the perturbation method and the expansion in power serie.
Known since a long time but relatively neglected, the venous vasa vasorum forms a tiny network to... more Known since a long time but relatively neglected, the venous vasa vasorum forms a tiny network to irrigate and drain the wall. Actually it is re-realized that, just like any tissues, the vein is a living tissue and the vasa vasorum plays a key role in the maintenance of its homeostasis. Under the effects of intraluminal pressure, the Young’s modulus (E) of the vein following an empirical relationship (LogE) 2 =-(αLog(p)+β), can vary in a very large range (a factor of 100) even in physiological conditions. We simulated the deformation of venous vasa vasorum by finite element method. Thus it can be suggested that, at first, a permanent venous hypertension provoques a local modification of the wall’s mechanical properties (decrease of E) to favorise a large deformation which will lead to a decrease of the irrigation, and secondly, with the decreased irrigation, the wall will loose its elasticity, become rigidified and keep its large deformation. A vicious cycle could be thus created.
Orthopedie Traumatologie, 1993
Optimisations du profil et de la vis6e de la tige centro-m6dullaire pour la pose d'une proth se d... more Optimisations du profil et de la vis6e de la tige centro-m6dullaire pour la pose d'une proth se de genou New profile design of the intra medullary stem for total knee replacement
Clinical hemorheology and microcirculation, 1998
The authors present analytical and numerical approaches of the deformation of venous and arterial... more The authors present analytical and numerical approaches of the deformation of venous and arterial vessels vasa vasorum. An elastic behaviour of the vessel wall is supposed. It is shown that a normal range of intraluminar pressure induces a small deformation in the vasa vasorum in arteries. According to the nonlinear elastic behaviour, a larger deformation is induced in venous vasa vasorum is rapidly obtained. Increased pressure has serious consequences, especially on the flow in vasa vasorum and induces decrease of oxygen transport. This phenomenon could be one of the generating factors of atherogenesis and ischemia.
Computational Methods and Experimental Measurements, 1982
This work is part of a study which aims to characterize quantitatively the behaviour of non newto... more This work is part of a study which aims to characterize quantitatively the behaviour of non newtonian fluids sumitted to transient shear.
Damage and Fracture Mechanics, 2009
... Int J Numer Meth Eng, 50: 9931013. [11] Bachene M, Tiberkak R, Rechak S, Hachi BEK (2007) An... more ... Int J Numer Meth Eng, 50: 9931013. [11] Bachene M, Tiberkak R, Rechak S, Hachi BEK (2007) Analyse du comportement vibratoire des plaques fissurées par la X-FEM. 18th French Congress on Mechanics, Grenoble, France, August. New Jersey, 07458. ...
Rheologica Acta, 1990
The use of the Couette viscometer with coaxial cylinders for the evaluation of rheological proper... more The use of the Couette viscometer with coaxial cylinders for the evaluation of rheological properties and the establishment of behaviour laws of fluids, generally requires the knowledge of the shear rate at each instant and at any point in the gap. This quantity, which is generally unknown, can be approximated by simple mathematical expressions which are satisfactory for the applied
Polymer Engineering & Science, 2012
A numerical model using homogenization techniques is proposed to simulate the evolution of elasti... more A numerical model using homogenization techniques is proposed to simulate the evolution of elastic properties of nanocomposite polymer-nanoparticles, depending on the concentration of nanoparticles and the rigidity of the particle-matrix interface. To validate this model, it was confronted to several physical systems having different interface behavior, the nanocomposite systems: poly(vinylidene fluoride trifluoroethylene)/Al 2 O 3 (alumina nanoparticles incorporated into copolymer of vinylidene difluoride and trifluoroethylene to form nanocomposite), PMMA/CNT (carbon nanotube/poly(methyl methacrylate) composite) and PMMA/SiO 2 with nanoparticles with or without surface treatment of silanization. For all these systems, the Young's modulus (nanoparticles and matrix) has been obtained experimentally from the elastic modulus C 11 obtained by Brillouin spectroscopy. These macroscopic measurements coupled with the theoretical model allow a multiscale approach of the elastic behavior of nanocomposite systems, providing information on the global elastic properties of polymernanoparticle material, and also indications about the strength of physical and chemical bonds between the nanoparticles and the matrix. Our results validate the hypothesis of the crucial role of the interface module, provided by numerical simulation which shows that incorporation of nanoparticles may lead to a strengthening or a weakening of the matrix.
Mechanics Research Communications, 1987