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Liège, Belgium

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. Source

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. Source

Tromme E.,University of Liege | Bruls O.,University of Liege | Emonds-Alt J.,University of Liege | 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. Source

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. Source

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. Source

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