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Bruyneel M.,LMS Samtech | Beghin C.,ISMANS | Craveur G.,ISMANS | Zein S.,LMS Samtech
European Space Agency, (Special Publication) ESA SP | Year: 2012

This paper deals with the solution of the optimal stacking sequence problem for laminated composite structures made of conventional plies oriented at 0°, 45°, 90° and -45°. A constraint of the optimization problem is to be able to take into account the classical design rules, such as a minimum amount of each kind of orientation must be present in the laminate, which moreover must be balanced and symmetric. Two optimization approaches are compared. The first one is based on a discrete formulation of the problem, which can directly solve the combinatorial optimization problem. In the second approach, continuous design variables are used, with a specific parameterization of the material properties based on a multi-phase topology optimization formulation. The efficiency of the approaches is compared on a representative test case, which consists in a panel submitted to buckling.

Bruyneel M.,LMS Samtech | Beghin C.,ISMANS | Craveur G.,ISMANS | Sosonkina M.,LMS Samtech
Structural and Multidisciplinary Optimization | Year: 2012

In this paper, an optimization procedure based on multi-phase topology optimization is developed to determine the optimal stacking sequence of laminates made up of conventional plies oriented at -45°, 0°, 45 and 90°. The formulation relies on the SFP (Shape Functions with Penalization) parameterization, in which the discrete optimization problem is replaced by a continuous approach with a penalty to exclude intermediate values of the design variables. In this approach, the material stiffness of each physical ply is expressed as a weighted sum over the stiffness of the candidate plies corresponding to -45°, 0°, 45 and 90? orientations. In SFP, two design variables are needed for each physical ply in the laminate to parameterize the problem with respect to the 4 candidate orientations. Even if only constant stiffness laminates of constant thickness are considered in this paper, specific design rules used in aeronautics for composite panels (i.e., no more than a maximum number of consecutive plies with the same orientation in the stacking sequence) are however formulated and taken into account in the optimization problem. The methodology is demonstrated on an application. It is discussed how the different design rules can affect the solution. © Springer-Verlag 2012.

Tromme E.,University of Liège | Bruls O.,University of Liège | Emonds-Alt J.,University of Liège | Bruyneel M.,LMS Samtech | And 2 more authors.
Structural and Multidisciplinary Optimization | Year: 2013

This paper is dedicated to the structural optimization of flexible components in mechanical systems modeled as multibody systems. While most of the structural optimization developments have been conducted under (quasi-)static loadings or vibration design criteria, the proposed approach aims at considering as precisely as possible the effects of dynamic loading under service conditions. Solving this problem is quite challenging and naive implementations may lead to inaccurate and unstable results. To elaborate a robust and reliable approach, the optimization problem formulation is investigated because it turns out that it is a critical point. Different optimization algorithms are also tested. To explain the efficiency of the various solution approaches, the complex nature of the design space is analyzed. Numerical applications considering the optimization of a two-arm robot subject to a trajectory tracking constraint and the optimization of a slider-crank mechanism with a cyclic dynamic loading are presented to illustrate the different concepts. © 2013 Springer-Verlag Berlin Heidelberg.

Morelle P.,Lms International | Kill N.,LMS Samtech | D'Ambrosio F.,Lms International
SAE Technical Papers | Year: 2013

The paper presents first a description of the methods used for the analysis of global dynamics of rotating systems like jet engines but also auxiliary power units. Different methodologies are described so to model rotating parts using beam, but also Fourier multi-harmonic, three dimensional models or to take into account cyclic symmetry and multistage cyclic symmetry concepts. Advantages and disadvantages of the different model types are discussed and compared. The coupling of the rotating parts with casings and stators is then discussed both in the inertial frame and in the rotating frame. The effect on global dynamics of bearing and other linking devices is taken into account for different type of analysis from critical speed analysis, to harmonic and transient analysis. The effect of gears and gear boxes coupling different rotors (like it is the case for auxiliary power units in a jet engine) is then discussed and appropriate methods described so to model this coupling effect. Finally, the question of the simulation of bearings with clearances is discussed and a new formulation proposed for the harmonic analysis of such situation. Numerical examples of such a simulation are given. Copyright © 2013 SAE International.

Zein S.,LMS Samtech | Bruyneel M.,LMS Samtech
ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite Materials | Year: 2012

A combinatorial optimization method is proposed for finding the optimal stacking sequence and the ply drop-offs scheme of a blended composite structure. This method assumes that the thicknesses of the regions in the structure are fixed in advance. It is able to handle efficiently design and manufacturing rules which are of combinatorial type. The optimization problem is formulated as a constrained binary programming problem and it is solved by applying both a primal and dual backtracking procedures with a local search method. Some numerical experiments are carried out to show the efficiency of the optimization method with respect to both computational time and quality criteria.

Cugnon F.,LMS Samtech | Jetteur P.,LMS Samtech | Pascon F.,LMS Samtech | Van Eekelen T.,LMS Samtech
Proceedings of the ECCOMAS Thematic Conference on Multibody Dynamics 2013 | Year: 2013

Today's vehicle dynamics engineers are facing many different challenges at the same time, such as achieving full vehicle response target requirements for ride and handling, simulating accurate road loads prediction for comfort and durability analyses, integrating complex active subsystems, keeping a good balancing compromised solution with other vehicle performances such as road noise and NVH. In order to answer to such complex panorama, those engineers are using CAE for the development of a vehicle with usage of 1D modeling, 3D MBD and FEA. The concurrent use of these technologies is a standard in the automotive industry [1]. The current simulation process is not efficient because there is limited integration between the different tools. Also, local geometrical and material nonlinearities are not accurately modeled in classical MBD software. Coupling MBD and FEA tools in order to account for those in dynamics simulations generally yield to stability issues [2]. This paper introduces an integrated methodology for vehicle dynamics simulation with particular application to MBD nonlinear FEA environment. The integration of MBD capabilities in one single nonlinear FEA solver as SAMCEF Mecano enables an accurate modeling of nonlinearity in vehicles meshing components as coil springs, torsion bar or tires, with special focus on tire modeling for this work. Today, such simulations are still marginal because of prohibitive computational time. Knowing that those large models (several millions of unknowns) are usually solved using explicit solvers [3], we will first demonstrate that time integration can be efficiently performed using the implicit method. In addition, a multi-model solver is presented allowing optimizing the performances of the parallel resolution of such models.

Zein S.,LMS Samtech | Basso P.,Airbus | Grihon S.,Airbus
Computers and Structures | Year: 2014

An algorithm is proposed to generate stacking sequences which comply with the requirements of the composite manufacturers. These rules are the blending and the design rules. The novelty of the proposed algorithm is that it can handle a general blending scheme, where a stacking sequence can be blended with other stacking sequences and it can also be the base of others. This algorithm can have two purposes: generating a manufacturable structure given the results of a preliminary design or defining a design space of a composite structure in a design process. © 2014 Elsevier B.V.

Computers and Structures | Year: 2013

We study the efficiency of applying the numerical simulation of a moving interface to the problem of defining fiber placement trajectories for composite structures. This new approach, which is based on an adaptation of the Fast Marching Method, presents two advantages. Firstly, it simulates the mechanism of an Automated Fiber Placement machine by producing equidistant fiber courses, without undesirable gaps or overlaps between the successive courses. Secondly, it is able to handle complex surfaces by working directly on a mesh instead of geometric equations. This approach is illustrated through examples from real case studies for straight and curved fiber trajectories. © 2013 Published by Elsevier Ltd.

Zein S.,LMS Samtech | Colson B.,LMS Samtech
ECCOMAS 2012 - European Congress on Computational Methods in Applied Sciences and Engineering, e-Book Full Papers | Year: 2012

This document provides information and instructions for preparing a paper to be included in the Proceedings of the 6th European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2012). The paper can be written in Latex or Word. The first page is reserved for the title of the paper, the authors, affiliation, key words, and the Abstract. The introduction must begin at the top of the second page. All the instructions as well as the source for the example files for Latex or Word can be found in the website of the Congress.

Zein S.,LMS Samtech | Colsoul F.,LMS Samtech | Bruyneel M.,LMS Samtech
International SAMPE Technical Conference | Year: 2013

The definition of the fiber placement trajectories or the determination of the draped fabric configuration is an important step in the analysis of a composite part. In this paper, we study the efficiency of applying the numerical simulation of a moving interface to the problem of defining fiber placement trajectories for composite structures. This new approach is based on the Fast Marching Method. It has two main advantages: first, it simulates the mechanism of an Automated Fiber Placement machine by producing equidistant fiber courses, without undesirable gaps or overlaps between the successive courses; secondly, this method is very general and can be easily applied to complex surfaces, as it works directly on a mesh of the composite part and not on its representation by geometric equations. The method is extended here to deal with the draping of fabrics on surfaces which may be non-developable. The method is then able to identify zones with large shear due to the fabric deformation resulting from the draping process. This approach is illustrated through examples from real case studies for straight and curved fiber placement trajectories, and is compared to finite element solutions in the case of a fabric draping. Copyright 2013 by Aurora Flight Sciences.

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