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Vol 1 - Optimization and Reliability

Uncertainties and Reliability of Multiphysical Systems

List of Articles

A novel method for measuring interoperability of systems

Developing inter organizational collaboration implies that the degree of interoperability is periodically evaluated and improved. This paper aims initially at presenting the basic concepts related to the measurement of interoperability degree. In a second stage, it proposes a novel approach for interoperability assessment. This approach takes into account all the significant aspects, namely potentiality, compatibility and operational performance.

Integration of reliability concept into orthodontic prosthesis design: Application on mini-plate fixation systems used in fractured mandibles

Orthodontic prostheses can be used to replace teeth (dental implants, bridges, crowns …) or reconstruct teeth (retraction …) or fractures (fixation systems ...). In this work, we are interested in fixation systems especially the fixation of mandible fractures using mini-plates. A numerical simulation of a fractured mandible is carried out in order to identify the failure mode (or scenario). Next a reliability analysis is carried out in order to evaluate the stabilization of the fixation systems
for the mandible fractures.

Securing mobile environment Combination of MPSS Framework with ALSD Firewall

The main objective of this study is to definite a global policy to secure the mobile environment, by setting up procedures and mechanisms for the security and protection of mobile devices Which meets the user’s needs, whether in terms of mobile networks traffic or at mobile applications level.
At mobile networks level: The study focuses on limiting the malware spread via SMS, MMS and emails. It describes the steps involved identifying, analyzing and securing mobile network traffic. To this effect, the MPSS Framework (Mobile Phone Security Scheme) has been used to be part of the mobile telecom operator’s infrastructure. MPSS aims to increase the level of information security through the telecom operator’s network and to solve problems related to limited resources on mobile devices.
At the mobile applications level: The study proposes the ALSD Firewall (Anti-Leak of Sensitive Data), allowing reliable protection against leakage of sensitive personal and professional data on mobile devices, thus notifying the user. This solution, integrated into the mobile OS, is based on the mobile applications automated analysis of the mobile platform store (Play Store, App Store ...); This firewall allows control and block malicious requests on sensitive data while ensuring the proper functioning of the applications installed on the mobile.

Electrical power transmission optimization based on a new version of PSO algorithm

In this paper, we suggest a new version of PSO algorithm, that allows the amelioration of its performance by introducing its parallelization associated to the concept of evolutionary neighborhood. The main objective of our approach is to overcome to the two essential disadvantages of PSO: high running time and premature convergence. The proposed algorithm was tested in order to improve the performance and reliability of mechanical structures; more precisely on the electricity pylon example; the objective is to maximize resistance to load while reducing material usage and cost. Experimental results demonstrate that the proposed method is effective and outperforms basic PSO in terms of solution quality, accuracy, constraint handling, and time consuming.

Taking account of Multi-domains interactions in predictive reliability assessment of mechatronic systems

The mechatronic systems are hybrid, dynamic, interactive and reconfigurable. Therefore their dysfunctional modeling is very difficult. Multi-physical interactions between components have impacts on the degradation or on system failures, leading thus to more uncertainty in reliability evaluation. The work presented in this paper aims to improve the integration of multi-domain interactions in the reliability assessment of mechatronic systems.
After a presentation of the state of the art of mechatronic systems reliability estimation methods, we propose to represent multi domain interactions by influential factors in the dysfunctional model.
We generally use proportional hazard models ; in the case of an interaction represented by a temperature stress, Arrhenius model is used.

Structural optimization in fluid-structure interaction

Structural optimization problems for elastic structures in flows arise frequently in many applications that form a particularly important of multi-physics problems. This paper presents general and efficient applications for structural optimization analysis of systems characterized as strongly coupled fluid-structure interaction (FSI) problems. Design,
shape and topological optimization were studied in this case and the obtained results were then presented and discussed. n FSI problems, due to the interaction with the fluid domain, resulting in geometrically nonlinear structural behaviour and
nonlinear interface coupling conditions. The fluid-structure interaction simulations were traited using ANSYS/Mechanical and ANSYS/Flotran for fluid computational dynamics.

Numerical simulation of vibroacoustic problems by the modal synthesis

In the vibroacoustic studies of coupled fluid-structure systems, reducing the size of the problem is important because we must add all the degrees of freedom of the fluid domain to those of the structure. We propose a modal synthesis method for solving this type of problem, coupling dynamic substructure of Craig and Bampton type and acoustic subdomain based on a pressure formulation. The application of the proposed method is performed on a boat propeller with four blades, in air and water. Our numerical results are confronted to some experimental study which allows validate jointly the calculation process and the proposed method.

Validation of numerical model in aerodynamics : application to aircraft’s wing

Fluid structure coupling can occur in many fields of engineering, and it has a crucial consideration in the design of many engineering systems ; for example, stability and response of aircraft wings in aerospace industry and response of bridges and tall buildings to winds in civil engineering. These problems are often too complex to solve analytically and so they have to be analyzed by means of numerical simulations. This paper aims to contribute to the discussion on the efficiency of two different discretization methods used as computational fluid dynamics (CFD) solvers for the simulation of the airflow’s aerodynamic loading around the ONERA M6 wing. We compare the accuracy and computational efficiency of two simulation codes (ANSYS/Flotran and ANSYS/Fluent) based on the Finite Element Method (FEM) and the Finite Volume Method (FVM) respectively, and then coupled with a computational structure dynamics solver (ANSYS/Mechanical) to describe the aeroelastic behavior of the wing due to aerodynamic loads.

Multiobjective optimization of trusses using Backtracking Search Algorithm

In engineering, under complex nonlinear constraints, the majority of design problems are generally multiobjective. For multi-objective problems, the computing effort can often rise significantly through the number of objectives and constraints evaluations. Metaheuristics are nowadays seen as powerful algorithms to deal with multiobjective optimization problems. In this paper, we using Backtracking Search Algorithm (BSA) as a tool to solve multiobjective optimization problems in structures, named (BSAMO). A well known benchmark multi-objective problem has been chosen from the literature to demonstrate the validity of the proposed method, applicability of the method for structural problems has been tested through a truss problem and promising results were obtained. The numerical results show not only the effectiveness and the best performance of BSAMO compared to NSGA-II, but also its rapidity and efficiency.

Experimental study of the reliability of a power module

In use, electric vehicle power modules are submitted to harsh thermal loads. The resulting thermo-mechanical stresses have an effect on their lifetime. As specific mounting and cooling conditions have a strong impact on reliability, it is important to test power modules in their specific use conditions and verify that lifetime matches warranty duration requirements
which may extend to 15 years. To provoke failures which are significant of application wear and aging, repeated stress cycles are applied to power modules. Stress levels correspond to worst case scenarios. To evaluate the degradation level, aging is characterized measuring electric and thermal parameters (emettor- collector voltage Vce, thermal resistance Rth). The test leading to lifetime assessment of various power module technologies are based on applying power cycles.

Integration of reliability and optimization conception into orthopedic prosthesis design: Application on hip prosthesis

The integration of optimization and reliability concepts into prosthesis design allows to understand the different biomechanical effects. In this work, the integration is carried out in the orthopedic prosthesis design in order to increase the performance and also to guarantee a required reliability level. An numerical application on the hip prosthesis design is selected considering the mechanical material uncertainties.

Probabilistic study of an embedded system

Embedded systems can be defined as autonomous electronic and computer systems which are increasingly used to control complex systems, they are found in medical equipment, ATMs, etc. The known drop test on the name "drop-test" is the most used method for assessing the reliability of solder joints, using the description of the procedure of the drop test according to the JEDEC standard [3]. In this article, we present a simulation of finite element model to reflect the maximum deformation due to temperature using the simulation software ANSYS Mechanical. It is considered that the parameters are random and proposed a probabilistic study of mechatronic system.

Overview of Structural Reliability Analysis Methods — Part III: Global Reliability Methods

In Part III of the overview of structural reliability analysis methods, global reliability methods, which are based on global approximation model of performance function using Gaussian process model, are reviewed. Gaussian process model is the basis for these global reliability methods. This category of methods, firstly, approximates the performance function by Gaussian process model, and then perform sampling methods based on the built surrogate model to calculate
the failure probability. The computational cost is significantly reduced with the aid of surrogate model, since the surrogate model is cheap to evaluate. Additionally, global reliability methods can give accurate results because Gaussian process model can adequately model the nonlinear limit state function. After the introduction of Gaussian process model, two global reliability methods, EGRA and AK-MCS are described and illustrated by an example.

Overview of Structural Reliability Analysis Methods — Part II: Sampling Methods

In Part II of the overview of structural reliability analysis methods, the category of sampling methods is reviewed. The basic Monte Carlo simulation is the foundation for sampling methods of reliability analysis. Sampling methods can evaluate the failure probability defined by both explicit and implicit performance function. With sufficient number of samples, simulation methods can give accurate results. However, for complex problem the computational cost is expensive. Thus, based on variance reduction techniques, some variants of basic Monte Carlo simulation method are proposed to reduce the computational cost. Monte Carlo simulation and its variants, including importance sampling, adaptive sampling, Latin hypercube sampling, directional simulation, and subset simulation, are presented and summarized in this paper.

Overview of Structural Reliability Analysis Methods — Part I: Local Reliability Methods

Our work presents an overview of structural reliability analysis, which plays important roles in structural design. In Part I of the overview, the so-called local reliability methods are summarized. The term “local reliability methods” refers to reliability analysis methods that use the local approximate of actual limit state function in calculation of failure probability. From this perspective of view, the mean value first-order second moment (MVFOSM) method, design pointbased
methods (FORM/SORM and RSM) are included in local reliability methods. Local reliability methods are basic approaches for reliability analysis and commonly used in research and applications.

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