Younes Aoues

7 – Optimizing Reliability of Electronic Systems

The deterministic optimization of embedded electronic systems does not take uncertainties into account and does not guarantee a reliable design. This chapter provides a probabilistic approach for the design optimization of embedded mechatronic systems. This approach takes into account the inherent nature of uncertainties which are due to insufficient knowledge of the material properties of the materials, the geometric dimensions and the load fluctuations. The rational approach for optimizing embedded systems consists of considering the propagation of uncertainties in multi-physical behavior (electrical, thermal, mechanic, etc.) by using a probabilistic modeling of uncertainties of the input parameters. The reliability-based optimization approach aims to find the best design with a compromise between reducing the objective function (cost, weight, etc.) and ensuring reliability.

Optimal design of deteriorating timber components under climate variations

The mechanical and physical properties of timber structures could be affected by a combination of loading, moisture content, temperature, biological activity, etc. This paper focuses on the optimal design of new timber structures subjected to fungal decay. Among the optimization methods available in the literature, this study considers a Time-Dependent Reliability Based-Design Optimization (TD-RBDO) approach. The TD-RBDO aims at ensuring a target reliability level during the operational life by considering deterioration and the uncertainties related inherent to materials properties, models and climate. This approach is applied to design optimization of a timber truss subjected to an aggressive (very humid) French climate. The performance of the optimized solution is compared, in terms of safety, with solutions estimated from Deterministic Design Optimization (DDO) and Reliability-Based Design Optimization (RBDO) approaches. The overall results indicate that the optimized solution of TD-RBDO reduces ensures a target reliability level during the whole structural lifetime.

5 – Electro-Thermo-Mechanical Modeling

Abstract The main aim of this chapter is to demonstrate the use of the finite element method (FEM) to model electronic boards subjected to electrical, thermal and vibratory stresses. The study of electrical, thermal and mechanical behavior of a mechatronic device is presented. Two types of coupling of physical phenomena are described. The first is strong coupling: it uses finite elements with all degrees of freedom necessary for an electro-thermo-mechanical study. The second is weak coupling which consists of decoupling the three physical phenomena by using a sequential calculation. This method is applied in two scenarios. The first is an electronic board of an engine control unit. The second is a radar power amplifier. To understand the mechanical behavior of the electronic board, it is necessary to model several physical phenomena. A multiphysical model is presented which takes into account the interdependencies and interactions between the various physical phenomena: electrical, thermal and vibratory.

10 – Study on the Thermomechanical Fatigue of Electronic Power Modules for Traction Applications in Electric and Hybrid Vehicles (IGBT)

Abstract: The reliability of the power module is mainly related to that of its electronic components (IGBT power chips and diodes). These components undergo severe and varied stresses. Indeed, the electrical pulses due to the internal operations of these components cause thermal loadings inducing mechanical deformations which can go beyond the thresholds desired. Furthermore, these electronic components are subjected to vibrations which can affect the state the solder joints and the electrical wire connections, causing damage by thermomechanical fatigue. To this end, knowledge of the mechanical response of the power module is vital for the electronics industry as these modules fulfill strategic functions, as is the case for electric and hybrid vehicles. Knowledge of the mechanical behavior of this power module requires the modeling of several physical phenomena. Multi-physical modeling aims at considering the interdependencies and interactions between different physical phenomena such as electrical, thermal and mechanical. In this study, multi-physical coupling is performed using ANSYS software.

Estimation of Fatigue Damage of a Control Board Subjected to Random Vibration

Abstract: On-board electronic systems are often exposed to different types of loading due to their operating environment. These loadings are represented mainly by thermal and vibration effects. In this chapter, the study is limited to vibration loads. In the framework of the FIRST-MFP project, an industrial application, the Valeo S97 demonstrator, of the effect under the influence of random vibrations is measured. The behavior of the control board for the DC–DC converter inverter of a hybrid vehicle is the subject of this study. The objective of this chapter is to estimate the fatigue damage at the soldered joints. The random stresses and the properties of the materials present a wide range of uncertainties. Experimental tests as well as numerical simulations will make it possible to study the uncertainties that influence the behavior of the structure.