Lalaonirina Rakotomanana - Academia.edu (original) (raw)

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Papers by Lalaonirina Rakotomanana

HAL (Le Centre pour la Communication Scientifique Directe), Aug 24, 2009

Covariance and Gauge Invariance in Continuum Physics, 2018

This work investigates the mass transfer of the Airborne Molecular cross Contamination (AMCs) bet... more This work investigates the mass transfer of the Airborne Molecular cross Contamination (AMCs) between the Front Opening Uni ed Pod (FOUP) and wafer (silicon substrates) during the microelectronics devices manufacturing. Such crosscontamination phenomena lead to detrimental impact on production yield in microelectronic industry and a predictive approach using modeling and computational methods is a very strong way to understand and qualify the AMCs cross contamination processes. The FOUP is made of polymeric materials and it is considered as a heterogeneous porous medium, thus the modeled processes are the contamination of two-component in transient ow under isothermal conditions. The present methodology is, rst using the optimization methods with the analytical solution in order to de ne the physical constants of various materials which have been studied experimentally and separately, and the second using the nite element method including these physical constants and relevant interf...

Riemann-Cartan geometry is used to model continuum with defect. If elastic waves propagate in an ... more Riemann-Cartan geometry is used to model continuum with defect. If elastic waves propagate in an infinite continuum with uniform and stationary defects density we observe dispersion, attenuation and anisotropy with a large spectral dependence. Chi-rality and uniform breathing vibrations are observed too. In a second test, defects are concentrated in a cylindrical domain. We compare results obtained with this con-tinuum model when the cylinder's radius tends toward zero with other works related to diffraction of a single screw-dislocation line.

Bio-medical materials and engineering, 2004

To study bone adaptation to detraining in growing rats, nine weeks-old immature female Wistar rat... more To study bone adaptation to detraining in growing rats, nine weeks-old immature female Wistar rats (n=110) were subjected to treadmill running programs (30 or 60 minutes-a-day) for up to 15 weeks, followed by unrestricted cage activities for the subsequent 15 weeks. The results revealed that (1) the cross-sectional area and mechanical properties of the midshaft bone significantly increased in response to running exercise, (2) its structural properties remained unchanged after the cessation of exercise, whereas the material properties returned to control level at a relatively early stage, (3) in the metaphysis, cortical bone area remained unchanged but trabecular bone area decreased in response to running exercise, (4) both areas slightly increased after the cessation of exercise, and (5) the changes in the mechanical properties and morphology of bone depended upon the repetition number and/or the duration of exercise, and were larger with longer duration of exercise.

Computer Methods in Biomechanics & Biomedical Engineering – 2, 2020

In the present study, we developed a finite element model of the human ACL taking into account th... more In the present study, we developed a finite element model of the human ACL taking into account the anatomical insertion zones of the ligament, a knee passive 3D kinematics and a realistic constitutive law. This study was performed in three steps. The first step was to determine the three dimensional kinematics of the knee during a passive flexion. The second step was to quantify the mechanical properties of the human ACL. Identification process allowed to determine an elastic potential which describes the non linear elastic behavior of the ligament. This potential formulation was suitable for large strain situations. Finally the third step was to incorporate the measured kinematics, the ligament insertion zones and the identified elastic law into a three dimensional finite element model. Different situations were then tested. Stress within the ligament was calculated for knee flexion till 70° under neutral, internal and external flexion. Anterior tibial drawer tests at 20° of flexion were also performed with the knee in neutral, internal and external rotation. As illustration, for the anterior tibial drawer tests, the hydrostatic stress field was almost comparable for the knee in neutral and external position. It was found that the hydrostatic and von Mises stresses during an anterior tibial drawer test were more important when the knee was in internal rotation.

A model of the tissue differentiation at the bone-implant interface is proposed. The basic hypoth... more A model of the tissue differentiation at the bone-implant interface is proposed. The basic hypothesis of the model is that the mechanical environment determines the tissue differentiation. The stimulus chosen is related to the bone-implant micromotions. Equations describing the evolution of the interfacial tissue are proposed and combined with a finite element code to determine the evolution of the fibrous tissue around prostheses for clinical situations. The model is applied to a simplified case of a hip prosthesis.

Revue européenne de mécanique numérique, 2009

ABSTRACT Dynamical behavior of the head during an impact is important for analyzing the nduced lo... more ABSTRACT Dynamical behavior of the head during an impact is important for analyzing the nduced local damage or diffuse damage in the brain tissue. We determine in the present tudy the natural frequencies and the modal shapes of the system of brain, cerebro-spinal luid and skull. Two models are presented in this work: an elastic-acoustic model assuming a igid skull and an elastic-acoustic-elastic model assuming a deformable skull. It is shown that atural frequencies and more significantly the modal shapes are strongly influenced by the nteraction between solid phases (brain and skull) and the cerebro-spinal fluid.

Acta Mechanica, 2016

The present paper proposes analytical formulations of the eigenvalues and eigenfunctions (frequen... more The present paper proposes analytical formulations of the eigenvalues and eigenfunctions (frequencies and modes) of vibrating rings of any cross-section shape, so as to be applied to engineering problems, like design optimization or life duration improvement. This is done by means of the Timoshenko beam theory accounting for the curved metric through new constitutive laws. An original non-dimensionalization reduces the number of independent parameters to only four. The motion is governed by a system of six differential equations applied to six independent variables. However, the reference curvature is found to induce fundamental changes to the mode structure. In that sense, a classical series decomposition is not efficient to provide analytical expressions of the mode shapes. The Chapman-Enskog method is proposed and explained to overcome this difficulty. Then, all modes (flexural, shear, torsional and longitudinal) are formulated explicitly, showing the coupling order of each of the six degrees of freedom of the cross-section. These results are compared to computations using a 3D elastodynamic model in order to validate the model and to point out its limitations. The latter is finally discussed with respect to other models proposed in the literature.

ndt.net

We are concerned by the design of a non destructive ultrasonic method quantifying porosity of cov... more We are concerned by the design of a non destructive ultrasonic method quantifying porosity of cover concrete. Modification of porosity is a major cause of reinforcing bar corrosion that induces bar swelling and macro-cracks which may cause the ruin of the structure. It is then necessary to characterize the porosity in the first cm above the steel bars. For surface measurements the most energetic mode is the Rayleigh wave whose investigation depth is around a half wavelength. A large spectrum, with frequency between 50 kHz and 600 kHz, is used in order to obtain a porosity depth profile of the concrete cover. We consider the concrete as a two phases media composed of aggregates with various radii embedded in a homogeneous mortar. The porosity of mortar is modeled through wave damping.For strongly heterogeneous media, the wave field can be analyzed as the superposition of a coherent part and an incoherent part. Here we focused on the coherent field by using dynamical homogenization theories. The model is coupled to dispersion relation of Rayleigh waves in order to depict the behavior of coherent surface waves. This model allows us to evaluate the sensitivity of surface waves to a variations of mortar properties such as an increase of its porosity.

Nowadays, with the increasing of the wafer's size and the decreasing of critical si... more Nowadays, with the increasing of the wafer's size and the decreasing of critical size of integrated circuit manufacturing in modern high-tech, microelectronics industry needs a maximum attention to challenge the contamination control. The move to 300 [mm] is accompanied by the use of Front Opening Unified Pods for wafer and his storage. In these pods an airborne cross contamination may occur between wafers and the pods. A predictive approach using modeling and computational methods is very powerful method to understand and qualify the AMCs cross contamination processes. This work investigates the required numerical tools which are employed in order to study the AMCs cross-contamination transfer phenomena between wafers and FOUPs. Numerical optimization and finite element formulation in transient analysis were established. Analytical solution of one di...

During the last two centuries, the concept of absolute spacetime has been extended in two main di... more During the last two centuries, the concept of absolute spacetime has been extended in two main directions, and accordingly the definition of a continuum has following more or less these evolutions. Galilean physics, and namely the Newton mechanics, is mainly based on the existence of an absolute rigid space and time. For both special and general relativistic physics, Einstein and numerous other authors which were involved in, revised the concept of space and time into spacetime by relativizing the time (Minkowski spacetime) and by transforming of absolute and rigid space into a variable and dynamical four-metric to model the interaction of Einstein spacetime and matter. Further extension of the relativistic continuum physics was obtained when Cartan added the torsion as dynamical variable to obtain the Einstein–Cartan spacetime. More generally, the basic geometry underlying any physics theory may thus be proposed to include metric and affine connection, not necessarily associated to...