Le rendement d’un hélicoptère est étroitement lié à son poids. L’allègement des composants profite à la charge utile transportable. Il implique généralement une diminution de leur rigidité, donc une augmentation de leur déformation. Les boites de transmission par engrenages sont particulièrement concernées. Elles doivent assurer la transmission de puissances importantes à masse minimale. Les axes des roues dentées se désalignent alors progressivement au fur et à mesure de l’application du chargement. Les topographies des dentures spiroconiques sont corrigées pour tolérer ce déplacement et optimiser les performances du mécanisme. La portée d’engrènement ne doit pas toucher une arête afin d’éviter toute surpression par effet de bord et une dégradation prématurée des dents. Il faut améliorer la répartition de l’effort transmis et des pressions de contact. L’erreur de transmission induit des vibrations et du bruit. Il faut donc la minimiser. L’étude de la correction à appliquer à la denture est fastidieuse et requiert une longue période d’apprentissage lorsqu’elle est réalisée manuellement. Les travaux présentés s’inscrivent dans le cadre d’une automatisation du processus. L’usinage et l’engrènement des dentures sont simulés numériquement. Les méthodes proposées sont simples et robustes. Trois problèmes d’optimisation différents sont traités et analysés / The performance of a helicopter is closely linked to its weight. The components are lightened to benefit the carried payload. That usually involves a reduction in their stiffness, so an increase in their deformation. The transmission gear boxes are particularly affected. They must ensure the transmission of high powers with a minimal mass. The load makes the axes of the gears misaligned. The topographies of the spiral bevel gear teeth are corrected in order to tolerate the displacement and optimize the mechanism performances. The contact path must not touch tooth edges to avoid any overpressure and premature degradation. The distribution of the transmitted load and of the contact pressures must be improved. The transmission error induces vibrations and noise. Therefore, it must be minimized. The study of the correction to be applied to the teeth is tedious and requires a long learning period when it is done manually. The presented works fit into the scheme of an automated process. The machining and meshing of the teeth are simulated numerically. The proposed methods are simple and robust. Three different optimization problems are discussed and analyzed

Machining components out of tolerances is of no use in competitiveproduction. The machining system sets the limitations of dimensionalaccuracy and surface quality of a machined component. The capabilityof the machining system describes these limits in terms of specifiedvalues. This thesis deals with machining system capability analysismainly focused on machine tool static and dynamic stiffness.The influence of stiffness and flexibility on machining systemcapability is analytically and experimentally investigated. Theexperimental work presented in the thesis complies with the theoriesand shows the relation between machine tool capability and theoutcome on the machine component.The concept of capability analysis by elastic linked system andthe currently available tools for such an evaluation is presented anddiscussed. The basis of elastic linked system analysis is the use ofmeasurements under loaded condition. The machine tool is loadedwith a known force creating a test condition closer to real machining,compared to current methods of unloaded machine tools. Twomeasurement tools for elastic linked system capability analysis areexplained in the thesis: Loaded Double Ball Bar and ContactlessExcitation and Response System.The thesis consists of an analytical base and an experimental casestudy on spiral bevel gear face milling. The experiments are discussedand compiled with the given theories. / <p>QC 20130513</p>

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