Reduction method applied to viscoelastically damped finite element models

International audienceWe propose in this paper to combine the GHM (Golla-Hughes-Mc Tavish) method with model reduction technique, especially direct condensation methods to resolve the problem of increased model order of viscoelastically structures. In fact, modeling structures using the GHM method leads to global systems of equation of motion whose numbers of degrees-offreedom largely exceeds the order of the associated undamped system. As result, the numerical resolution of such equations can require prohibitive computational (CPU) time. So, to overcome this problem, both Static and Dynamic methods are used to reduce the order of finite elements matrices while preserving its capability to represent the dynamic behavior of viscoelastically damped structures. This paper intends to compare these two methods in direct reduction. Numerical example applied to cantilever beam structure is presented. This example will highlight the domain of validity of the studied methods. Results obtained from these two reduction methods are compared with the full model in order to illustrate its performances and its practical interest in the dynamic analysis of viscoelastically damped structures

Vibration pumping of mdof structures using optimised multiple dynamic absorbers

International audienceThe concept of energy pumping is an innovative dynamic phenomenon; it gives rise to new generation of dynamic absorbers. Theoretical studies and feasibility tests are necessary for better understanding of their dynamic behaviour and to be applied on real structures or machines. In this paper, numerical evidence is firstly given for the passive and broadband targeted energy transfer in the case of a linear system under shock excitation with Multiple Dynamic Absorbers or Nonlinear Energy Sink (NES). Secondly, it is shown that many NES absorb shock energy in only way and dissipate this energy locally, without "spreading" it returns to the linear system. The numerical results of optimisation in the case of NES linked to a linear beam are compared to Tuned Mass Dampers (TMD) linked to the same beam

Optimisation multi-objectifs en mécanique des structures : approche basée sur les surfaces de réponse adaptative

International audienceL'optimisation multi-objectifs est un outil d'aide à la décision en conception de structures dans une phase d'avant projet ou de projet. Les procédures fréquemment employées en optimisation nécessitent plusieurs réanalyses qui sont indispensables pour calculer des fonctions performance ou coûts généralisés. Mais, la complexité des modèles et de la modélisation associés (modèles éléments finis de grande taille, modèles non linéaires,…) rend ces réanalyses longues et parfois non envisageables pour des raisons de coût de calcul. Pour surmonter ces difficultés, on propose dans ce papier d'associer l'optimisation multi-objectifs et le calcul approché des fonctions coût basé sur les surfaces de réponses (RSM). Cela consiste à remplacer la réponse complexe de la structure par un polynôme standard, plus simple à utiliser. Ce choix est justifié par le coût d'évaluation minimal des RSM, ce qui engendre une minimisation du coût de calcul lors de l'optimisation

Multi-objective optimization in dynamics of the structures with nonlinear behavior : contributions of the metamodels

International audienc

Robust design of complex mechanical structures using metamodels approach with uncertainties

17-20 aprilInternational audienc

Pompage énergétique par voie non linéaire : conception et expérimentation

International audienc