Modelling multi-scale microstructures with combined Boolean random sets: A practical contribution

Boolean random sets are versatile tools to match morphological and topological properties of real structures of materials and particulate systems. Moreover, they can be combined in any number of ways to produce an even wider range of structures that cover a range of scales of microstructures through intersection and union. Based on well-established theory of Boolean random sets, this work provides scientists and engineers with simple and readily applicable results for matching combinations of Boolean random sets to observed microstructures. Once calibrated, such models yield straightforward three-dimensional simulation of materials, a powerful aid for investigating microstructure property relationships. Application of the proposed results to a real case situation yield convincing realisations of the observed microstructure in two and three dimensions

Integration of a Normal Field without Boundary Condition

ISBN 2-7261-1297 8International audienceWe show how to use two existing methods of integration of a normal eld in the absence of boundary condition, which makes them more realistic. Moreover, we show how perspective can be taken into account, in order to render the 3D-reconstruction more accurate. Finally, the joint use of both these methods of integration allows us to obtain very satisfactory results, from the point of view of CPU time as well as that of the accuracy of the reconstructions. As an application, we use this new combined method of integration of a normal eld in the framework of photometric stereo, a technique which aims at computing a normal field to the surface of a scene from several images of this scene illuminated from various directions. The performances of the proposed method are illustrated on synthetic, as well as on real image

Analytical study of coupling between subsystems of a vehicule NVH model

International audienceThe design of an automotive powertrain mounting system plays an important role in improving vehicle noise, vibration and harshness (NVH). One of the main problems encountered in the automotive design remains the isolation of the low frequencies vibrations of the engine from the rest of the vehicle. Several engine mounting schemes have been developed to deal with this problem. Most of these strategies stem from arranging the rigid body modes of the engine mounted on resilient supports to have certain coupled or decoupled characteristics. It is currently admitted in literature that a decoupled powertrain mounting system improves NVH characteristics. The significant engine mass makes the right frequencies and modes arrangement a critical design decision. But it can not be stated that decoupling the on-ground rigid body modes of the engine will systematically reduce chassis vibrations. In this paper, a new analytical method is proposed to examine the mechanisms of coupling between the engine and the vehicle body structure. The analytical procedure enable to define the domain of validity of the mounting schemes based on a 6 degreesof- freedom engine model and to assess NVH improvement

New analytical method to evaluate the powerplant and chassis coupling in the improvement vehicle NVH

International audienceThe design of an automotive powerplant mounting system is an essential part in vehicle safety and improving the vehicle noise, vibration and harshness (NVH) characteristics. One of the main problems encountered in the automotive design is isolating low frequency vibrations of the powerplant from the rest of the vehicle. The significant powerplant mass makes the choice of frequency and mode arrangements a critical design decision. Several powerplant mounting schemes have been developed to improve NVH properties concentrating on the positioning and design of resilient supports. However these methods are based on decoupling rigid body modes from a grounded powerplant model which ignores chassis and suspension system interactions. But it cannot be stated that decoupling the grounded rigid body modes of the powerplant will systematically reduce chassis vibrations. In this paper, a new analytical method is proposed to examine the mechanisms of coupling between the powerplant and the vehicle chassis and subsystems. The analytical procedure expands the equation of motion of the vehicle components to such that a domain of boundary conditions used in the 6 degrees-of-freedom powerplant mounting model can be defined. An example of this new procedure is given for improving NVH chassis response at idle speed using the torque roll axis decoupling strategy

Multi-objective robust design optimization of an engine mounting system

International audienceThis paper introduces a new method to support designers to find optimal and robust solutions of engine mounting system. The mounting system design is a compromise between isolation of the vehicle from engine vibration and constraining the motion of the powertrain within vehicle packaging. Based on the classical pendulum mounting system of a front wheel drive vehicle with a transversely four-cylinder engine, this study deals with the definition of a new global engine mounting concept for the NVH (Noise Vibration and Harshness) improvement of the vehicle characteristics at idle speed. The practical application of the numerical optimization is complicated by the fact that engine mounting system is a stochastic system. Its characteristics have a probabilistic nature. Multi-Objective Genetic Algorithm (MOGA), i.e. Pareto-optimization, is taken as the appropriate framework for the definition and the solution of the addressed multi-objective robust optimization problem. An experimental correlation analysis has been conducted on a Pareto-optimal solution to show the model accuracy

Longue mémoire pour des séries irrégulièrement observées. Application aux Black-out électriques.

International audienceCette note est dédiée à l'estimation du paramètre de longue mémoire dans les séries temporelles observées à des temps aléatoires. L'existence de corrélations à long terme dans la distribution des pannes électriques, i.e. "black-out", doit trouver son origine dans la politique de maintenance et de restauration des opérateurs de réseaux. Les travaux portent sur deux transformations des séries visant à préserver l'exposant de mémoire et à récupérer un échantillonnage régulier. A la suite, une méthode d'estimation prenant en compte les temps d'observation et les valeurs observées est dérivée. Le lien entre persistance (H > 0.5) et restauration des réseaux électriques est validé

Experimental Transfer Path Analysis in the Diagnosis of Engine Mounting System for Idle Shake Vibrations

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Torque starting rocker bar for motor vehicle, has contact element producing dampening effect by alternate adherence and sliding of element with respect to body to displace slide and plate around amplitude threshold value of displacement

The bar has a rigid external plate (1) having an elongated shaped body and a large articulation (3) having large volume and less stiffness. A slide (6) is integrated in one of rigid internal cores (5, 7) and is displaced with respect to the plate (1) in a direction along a longitudinal direction, and a rubbing contact element (4) is disposed between the slide and the plate (1). The element produces a dampening effect by alternate adherence and sliding of the element with respect to the body for displacing the slide and the plate (1) around an amplitude threshold value of the displacement