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Vol 4 - Issue 2

Uncertainties and Reliability of Multiphysical Systems

List of Articles

Springback of a U-draw bending part: study of the geometrical parameters influence on the twisting of the deep-stamped bottom
Oualid Kebdani, Bouchaib Radi

Based on numerical simulations on open curved U-type tools of springback and analysis of these, it was shown that five parameters would have an influence on springback. These five parameters are sheet thickness, die entry radius, punch radius, rolling direction and blank restraint (clamping). The stress delta along the bottom of the draw has a direct impact on the twisting of the draw.

Simulation & Prediction of sheet metal formability via AutoForm stamping simulator
Bouchaïb Radi, Oualid Kebdani

In recent years, enormous progress has been made in the industrial use of digital tools with the aim to simulate the formability of sheet metal processes. This is especially true for the automotive industry, in order to verify and validate stamping feasibility. Indeed cost and quality targets in industrial sheet metal forming processes, correct formability prediction in a very early project stage has become a crucial factor. This is the reason for the wide application of FLC for the purpose of measuring and predicting limit strains, thus to study the influence of various materials or process parameters on strain paths. This article attempts to give a brief introduction to the subject of stamping sheet metal forming and describe some of the forming defects that can occur, thus the failure criterion is presented and applied to a deep drawn part via the Autoform simulator.

Thermal behavior optimization of the high electron mobility transistor (HEMT) using the KA-CMA-ES method
Amar Abdelhamid, El Hami Abdelkhalak, Radi Bouchaib

The main objective of Optimization is to ensure a robust system design with minimal cost, in this paper we focus on the optimization of the behavior of the High Electron Mobility Transistor (HEMT), it is a very important element in high power mechatronic systems. It is composed of several layers of materials, the geometrical and thermal parameters of these layers influence the thermal behavior and in particular the operating temperature of the transistor, hence its performance. The CMA-ES method assisted by kriging (KA_CMA_ES) coded on Matlab coupled with a finite element model developed on Comsol multiphysics, this coupling allowed to optimize the transistor structure in order to reduce its maximum operating temperature, so that the transistor performs its function with less influence on the other characteristics. A comparison between the KA-CMA-ES and CMA-ES methods was made. The KA-CMA-ES method showed an efficiency in terms of accuracy and computation time.

A significant effect of bone anisotropy on reliability measurements of mini-plate fixation system used in multiple mandibular fractures: A clinical case of angular and parasymphysis fractures
Ghais Kharmanda, Hasan Mulki, Mohamed Yasser Kharma

Mechanical properties of bone tissues are very important when introducing fixed mini-plates into multiple fracture cases. The effect of these properties becomes more significant when dealing with reliability analysis where several failure modes can occur. In our previous work, the anisotropy case considering a single fracture case and a single failure mode, led to a low reliability index value during the convalescence period. In this work, the studied clinical case contains two different fractures that certainly leads to a very low reliability index value. This makes no sense to assess the reliability level at the convalescence period. Thus, the anisotropy effect is studied at the end of the healing period where the fracture surfaces must be bonded. Two material models are elaborated for the studied clinical case (a male patient at the age of 35 years) where two different fractures exist. In Study I, isotropic bone tissues are considered, while in Study II, anisotropic (orthotropic) bone tissues are considered. A successful healing requires that a number of constraints which are affected by the loading conditions are fulfilled, and since muscle activity is difficult to estimate, there is a strong need to introduce the uncertainty on the loading in order to obtain a reliable design. The failure mode occurs when the yield stress of one or more parts is reached. The results show that when performing a direct simulation, there is a significant difference of maximum von-Mises stresses in the cancellous bone tissues between the isotropy and anisotropy cases. In addition, the failure modes and the reliability indices are very affected when considering the bone anisotropy. It is recommended to consider bone anisotropy in order to obtain more realistic results.

Other issues :


Volume 23- 7

Issue 1
Issue 2


Volume 22- 6

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Issue 2


Volume 21- 5

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Issue 2


Volume 20- 4

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Issue 2


Volume 19- 3

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Issue 2


Volume 18- 2

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Issue 2


Volume 17- 1

Optimization and Reliability
Numéro 2