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Ingénierie et systèmes   > Accueil   > Incertitudes et fiabilité des systèmes multiphysiques   > Numéro

Vol 3 - Numéro 2

Incertitudes et fiabilité des systèmes multiphysiques


Articles parus

Etude des écoulements en charge autour d’un obstacle par la méthode de Lattice-Boltzmann

La mécanique des fluides décrit des phénomènes physiques des fluides qui sont souvent gouvernés par des équations de type dérivées partielles à savoir l’équation de continuité et l’équation de Navier-Stokes . La résolution de ces équations en utilisant des méthodes classiques rencontre certaines difficultés lorsqu’il s’agit de traiter des problèmes où la géométrie du milieu est complexe ou lorsqu’on se trouve en présence de plusieurs phases d’un fluide ou de plusieurs
fluides [TAO 16]. La tendance actuelle s’oriente vers une nouvelle approche pour la recherche en simulation [CFD], qui a gagné beaucoup de popularité ces dernières années, elle est appelée en anglais « Lattice Boltzmann Method » (LBM), qui est un développement relativement nouveau dans la CFD. La méthode de Lattice-Boltzmann est une méthode de dynamique des fluides (CFD). À la place des équations de Navier-Stokes, l’équation discrète de Boltzmann est résolue pour simuler le comportement de fluides à l’aide d’un schéma de collision-propagation. Dans ce travail, on a intégré la LBM dans un code python afin de simuler en 2D le comportement d’un fluide en charge à l’encontre d’un obstacle, chose qui va nous servir par la suite à déterminer dans les conduites
les zones les plus sollicités (vitesse maximale et pression maximale) pour mieux dimensionner à la fois la conduite et ses accessoires (vanne, clapet, etc.) et éviter leur dégradation rapide.


Modélisation et Simulation Multi-corps des Systèmes d’engrenages avec prise en compte des incertitudes

Review of the capabilities of multibody simulation models and their short comings are discussed in this article. Finally an attempt was made to evolve a methodology which leads to dynamically efficient robust design of mechanical systems like gear box.


Analyse probabiliste de la tige améliorée Austin-Moore utilisée dans l’arthroplastie totale de la hanche sans ciment compte tenu de l’incertitude de chargement

Austin-Moore hemiarthroplasty had been critically utilized for aged patients with femoral neck fractures. However, this implant became no longer favorable when increasing life activity. A multiobjective shape optimization has been integrated to improve its performance. The resulting configuration is called Improved Austin-Moore (IAM) model. Probabilistic analysis is very important when the input data are random, that leads to stochastic results. In this paper, a probabilistic analysis is applied to solid and IAM stems implanted in a proximal femur in order to show their advantages. This way it is possible to control the biomechanical effects of the implanted femur to determine its performance. The applied loads are generated randomly using Monte Carlo Simulations (MCS). MSC sampling technique is applied and the different von-Mises stresses of the layers (bone and metal) are selected as performance indicators. Two simple 2D implant-bone models of the solid and IAM designs are studied with a target reliability index
equals to  3 t , which corresponds to a high level of confidence (reliability) 99.87%. The major finding of this article is that the skewness values of all output parameters of the IAM stem are positive which means that the majority of the maximum von-Mises stress values are closer to their minimum values than those associated with the solid stem. In addition, the sensitivity analysis shows that the input parameters for the IAM stem are more effective on the output
parameters relative to those associated with the solid stem. The IAM stem shows a high interdependence (correlation) between the input and output parameters when comparing with the solid stem. Since this study is carried out considering loading uncertainty, the geometry can affect the load transfer. Therefore, a correlation study between the input parameters is carried out and showed significant coefficient values for the IAM stem relative to the solid one. The results show that the IAM stem is much more advantageous than the solid stem.


Influence de l’anisotropie osseuse sur l’évaluation de la fiabilité de la stabilisation du système de fixation par mini-plaques dans les fractures mandibulaires de la symphyse : Deux cas étudiés sous la période de la guérison

The reliability analysis is used to in order to measure the stability of the mini-plate fixation system used in the human fractured mandibles after the chirurgical operation. The failure is assumed to take place when the Most Probable failure Point (MPP) is found. In this work, two studied cases of 3-dimensional finite element models are considered for the same fracture situation. A successful fracture healing requires that a number of constraints which are influenced by the loading conditions are fulfilled, and since muscle activity is difficult to evaluate, there is a strong need to introduce loading uncertainties in order to obtain a reliable design. Several categories of critical failure scenarios are considered in this study : The first category of failure scenarios is that of the relative displacement between two fracture surfaces should not exceed a critical threshold to ensure rapid healing. The second category is failure of the mini-plates which in this work is interpreted as when the yield stress within the mini-plates is reached, and the third category of failure scenarios is that of the yield stress in the mandible bone tissues should not be exceeded. Two fractured mandibles are studied under the convalescence period : Case I (a single isotropic bone tissue) and Case II (composite anisotropic bone tissues). During the fixation of the mini-plates, the drilling positions in the two cases can vary when considering a composite bone tissue mandible relative to a homogeneous bone tissue one. To show the effect of the bone anisotropy, an analytical formulation is developed as a helpful technique to analyze the effect of the mini-plate position changes. The bone properties used in the anisotropic case (Case II) are orthotropic. The results show that the reliability indices are very affected when considering the bone anisotropy.


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2017

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2018

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2019

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2020

Volume 20- 4

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