-Dynamic analysis of industrial structures may be costly from a numerical point of view. Thus, the need and the importance of reducing the size of the problem become obvious. One of the main hypothesises in the use of component mode synthesis method is that the model is deterministic. That is to say the parameters used in the model have defined and fixed values. Furthermore, carrying out the structure's response involving uncertain material, geometrical parameters, limit conditions, manufacturing tolerances and/or loading conditions is essential in a global design process. Our main aim in the present work is to test and validate a method which consists in condensing the system (i.e. to reduce the number of unknowns) and carrying out the stochastic study with a noniterative method. This method makes it possible to solve these problems without using the classical method whereby a direct modal calculation combined with the Monte Carlo simulation is made. The classical method is by nature iterative and hence CPU intensive. A propeller is taken as an example in order to validate the proposed methods. The results obtained agree well with references results and show the effectiveness of the proposed method.

2009) Stochastic and reliability analysis of a propeller with model reduction, European Journal of Computational Mechanics/Revue Européenne de Mécanique Numérique, 18:2, 195-215To link to this article: http://dx.ABSTRACT. Nowadays, design based on purely deterministic analyses has been replaced by stochastic and reliability analyses which consider the uncertainties affecting the design parameters. But from a numerical point of view, these analyses become costly for industrial mechanical applications (modelled by finite elements method) because of their great number of freedom degrees. In this work, we take an interest in reducing the CPU time for stochastic and reliability analyses of an industrial mechanical application by the modal condensation of his numerical model with the component mode synthesis method. The example of a propeller is studied to validate the proposed methods. The results of this study tend to show the considerable gain in CPU which we save by the using of our methodology. RÉSUMÉ. De nos jours, la conception basée sur des analyses purement déterministes a été remplacée par des analyses stochastiques et fiabilistes qui prennent en considèration les incertitudes affectant les paramètres de conception. Mais d'un point de vue numérique, ces analyses deviennent coûteuses pour des applications mécaniques industrielles (modélisées par éléments finis) en raison de leur grand nombre de degrés de liberté. Dans ce travail, nous nous intéressons à la réduction du temps CPU pour des analyses stochastiques et de fiabilité d'uneapplication mécanique industrielle par la condensation modale de son modèle numérique avec la méthode de synthèse modale. L'exemple d'une hélice est étudié pour valider les méthodes proposées. Les résultats de cette étude tendent à montrer le gain considérable en temps CPU que nous économisons par l'emploi de notre démarche.

A dynamic analysis of a four-bar mechanism shows that it has many critical speeds where the response of the system is large compared to the response at neighboring speeds. Some of these critical speeds are limiting critical speeds. The lowest of these limiting speeds cannot be exceeded because stresses in one of the links would become greater than the safe working stress. This paper examines methods for computing critical speeds and suggests a method whereby the first limiting critical speed of a mechanism can be adjusted either continuously or discretely so that speeds above the first limiting critical speed can be achieved without the mechanism ever experiencing undue duress.

No abstract