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This paper presents an experimental/numerical methodology which aims to improve 3D welded tube considering their anisotropic effect, deometrical singularities found in the welded joint, and heat affected zone behaviour by hydroforming process. This process contributes to reduce the number of welding and assembly operations needed to generate complex structures, while improving the weight saving and quality of finished parts. In spite of the advances in the performance of this manufacturing technology, some problems are linked to particularities of certain raw materials and additional studies must be developed, like in the case of welded tubes. The experimental study is dedicated to the identification of stress-strain flow of the base metal and the heat-affected zone from the global measure of tube investigate the heat affected zone mechanical behaviour. Workpiece behaviour's models used to simulate the expansion tests, made it possible to highlight the combined effects of the inhomogeneous behaviour of basic material and heat affected zone, as well as the geometrical singularities found in the welded tubes. From the simulations carried out, it is clear the influence of the plastic flow behaviour of the welded tube in the final results (thickness distribution, stress instability, tube circularity, critical thinning and rupture).

In this paper, we present a new approach to improve the thermo-mechanical performance of the HEMT (high electron mobility transistor) technology. This study aims to solve two optimization problems. The first one is the optimization of the thermal behavior of the HEMT, through the optimization of its maximum operating temperature which influences the electrical characteristics such as electron mobility, and also influences the mechanical behavior of its structure. While the second problem will be the optimization of the mechanical behavior of the same technology, through the optimization of the stresses distribution that also influence the electrical characteristics and reliability of the HEMT structure. The resolution of these two optimization problems will be done, by the multi-objective optimization approach thanks to numerical tools such as Comsol multiphysics and Matlab software, which allows to solve these two problems simultaneously by taking into consideration the imposed constraints. The results obtained have optimized the thermo-mechanical behavior of the HEMT, which proves the efficiency of this approach to solve complex optimization problems.

The complexity challenges of mechatronic systems justify the need of numerical simulation to efficiently assess their reliability. In the case of solder joints in electronic packages, finite element methods (FEM) are commonly used to evaluate their fatigue response under thermal loading. Nevertheless, Experience shows that the prediction quality is always affected by the variability of the design variables. This paper aims to benefit from the statistical power of the R software and the efficiency of the finite element software ANSYS©, to develop a probabilistic approach to predicting the solder joint reliability in Mechatronic Packaging taking into account the uncertainties in material properties. The coupling of the two software proved an effective evaluation of the reliability of the T-CSP using the proposed method.

The electro-thermomechanical modeling study of the High Electron Mobility Transistor (HEMT) has been presented, all the necessary equations are detailed and coupled. This proposed modeling by the finite element method using the Comsol multiphysics software, allowed to study the multiphysics behaviour of the transistor and to observe the different degradations in the structure of the component. Then, an optimization study is necessary to avoid failures in the transistor. In this work, we have used the Covariance Matrix Adaptation-Evolution Strategy (CMA-ES) method to solve the optimization problem, but it requires a very important computing time. Therefore, we proposed the kriging assisted CMA-ES method (KA-CMA-ES), it is an integration of the kriging metamodel in the CMA-ES method, it allows us to solve the problem of optimization and overcome the constraint of calculation time. All these methods are well detailed in this paper. The coupling of the finite element model developed on Comsol Multiphysics and the KA-CMA-ES method on Matlab software, allowed to optimize the multiphysics behaviour of the transistors. We made a comparison between the results of the numerical simulations of the initial state and the optimal state of the component. It was found that the proposed KA-CMA-ES method is efficient in solving optimization problems.

In power electronics applications, embedded mechatronic systems (MSs) must meet the severe operating conditions and high levels of thermomechanical stress. The thermal fatigue of the solder joints remains the main mechanism leading to the rupture and a malfunction of the complete MS. It is the main failure to which the lifetime of embedded MS is often linked. Consequently, robust and inexpensive design optimization is needed to increase the number of life cycles of solder joints. This paper proposes an application of metamodel-assisted evolution strategy (MA-ES) which significantly reduces the computational cost of ES induced by the expensive finite element simulation, which is the objective function in optimization problems. The proposed method aims to couple the Kriging metamodel with the covariance matrix adaptation evolution strategy (CMA-ES). Kriging metamodel is used to replace the finite element simulation in order to overcome the computational cost of fitness function evaluations (finite element model). Kriging is used together with CMA-ES and sequentially updated and its fidelity (quality) is measured according to its ability in ranking of the population through approximate ranking procedure (ARP). The application of this method in the optimization of MS proves its efficiency and ability to avoid the problem of computational cost.

The actual use of computational fluid dynamics (CFD) by aerospace companies is the trade-off result between the perceived costs and benefits. Computational costs are restricted to swamp the design process even if the benefits are widely recognized. The need for fast turnaround, counting the setup time, is also crucial. CFD integrates mathematical relations and algorithms to analyze and solve fluid flow problems. CFD analysis of an airfoil produces results such as the lift and drag forces that determine the performance of an airfoil. Thus, optimizing these aerodynamic performances has proved extremely valuable in practice. The aim of this paper is to model a transonic, compressible and turbulent flow over a NACA 0012 airfoil, using a density based implicit solver, for which a comparison and a validation will be made throught the published experimental data. The numerical results show that the predicted aerodynamic coefficients are in a satisfying agreement with experimental data. Then an aerodynamic shape optimization algorithm, based on a multiobjective algorithm that is an extension of the Backtracking Search Algorithm which was initially developed for single-objective optimization problems only, was used in order to obtain an improved performance control of the aerodynamic coefficients of the optimized airfoil.

In this paper, we present a new method based on Optimal Safety Factors (OSF) in the context of the Reliability-Based Design Optimization (RBDO) analysis of ultrasonic motors with traveling wave taking into account the contact between the different components (stator and rotor). We will underline also the different methods of the RBDO analysis and we highlight the advantage of our approach based on OSF. Numerical results are given to illustrate the proposed method.