Method and tool for optimal design of spiral bevel gears

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 analysésThe 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 analyze

Dispositifs législatifs et réglementaires du Code de l’environnement relatifs à la destruction des spécimens d’espèces non domestiques

Les mots « malfaisants ou nuisibles » ont été remplacés dans la partie législative du Code de l’environnement par les mots « susceptibles d’occasionner des dégâts » en application de la loi du 8 août 2016 relative à la reconquête de la biodiversité, de la nature, et des paysages (loi « biodiversité »). La modification dans la partie réglementaire de ce Code doit faire l’objet d’un décret en Conseil d’État. La destruction des animaux causant des dégâts, dommages ou nuisances (dénommés « nuisib..

Méthodes et outil pour la conception optimale d'une denture spiroconique

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 analysésThe 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 analyzedTOULOUSE-INSA-Bib. electronique (315559905) / SudocSudocFranceF

A simple and robust method for spiral bevel gear generation and tooth contact analysis

International audienceA simple and robust method to simulate spiral bevel gears generating and meshing processes is proposed. In a first part, a mathematical model of universal hypoid tooth surfaces generator is formulated. It is based on Fong’s approach. The model takes into account all the kinematic motions of common CNC machine tools dedicated to hypoid gears machining. It is general enough to enable the simulation of various hypoid gears cutting methods such as face-hobbing, face-milling, plunge cutting and bevel-worm-shaped-hobbing processes. In this paper, only developments related to face-milled spiral bevel gear generation are presented. We show that the results obtained are in good agreement with those of certified software. In a second part, a simple and numerically stable algorithm is proposed for unloaded tooth contact analysis. The simulation method is based on a discretization of one of the two tooth flank surfaces in contact and a specific projection of the points on the opposite flank. It gives a good approximation of the contact pattern location. The accuracy of the contact point locations and computing time is directly dependent on the mesh density. However, this approach enables obtaining in a very short time sufficiently accurate results to meet the needs of designers, particularly in the preliminary stages of design. The relative displacements of the gears can be taken into consideration. The robustness of the proposed computing process and the adjustable accuracy of the results are the two main advantages of the presented approaches

A simple and robust method for spiral bevel gear generation and tooth contact analysis

International audienceA simple and robust method to simulate spiral bevel gears generating and meshing processes is proposed. First, a mathematical model of universal hypoid tooth surfaces generator is formulated, based on Fong’s approach and taking into account all the kinematic motions of common CNC machine tools dedicated to hypoid gears generation. This model is general enough to allow the simulation of various hypoid gears cutting methods such as facehobbing, face-milling, plunge cutting and bevel-worm-shapedhobbing processes. In this paper, only developments related to facemilled spiral bevel gear generation are presented. It is shown that the results obtained are in good agreement with those of certified software. A simple and numerically stable algorithm is then proposed for unloaded tooth contact analysis. The simulation method is based on a discretization of one of the two conjugated tooth flank surfaces, and a specific projection of the different nodes of this discretization on the other flank. The contact path location can be easily approximated using this method. The accuracy of the location of contact is directly dependent on the mesh density. Although improving the accuracy requires an increase in computation time, this method allows obtaining in a very short time sufficiently accurate results to meet the needs of designers, particularly in the preliminary stages of design. The relative displacements of the gears can be taken into consideration. The robustness of the proposed computing process and the adjustable accuracy of the results are the two main advantages of the presented approaches

A simple and robust method for spiral bevel gear generation and tooth contact analysis

International audienceA simple and robust method to simulate spiral bevel gears generating and meshing processes is proposed. First, a mathematical model of universal hypoid tooth surfaces generator is formulated, based on Fong’s approach and taking into account all the kinematic motions of common CNC machine tools dedicated to hypoid gears generation. This model is general enough to allow the simulation of various hypoid gears cutting methods such as facehobbing, face-milling, plunge cutting and bevel-worm-shapedhobbing processes. In this paper, only developments related to facemilled spiral bevel gear generation are presented. It is shown that the results obtained are in good agreement with those of certified software. A simple and numerically stable algorithm is then proposed for unloaded tooth contact analysis. The simulation method is based on a discretization of one of the two conjugated tooth flank surfaces, and a specific projection of the different nodes of this discretization on the other flank. The contact path location can be easily approximated using this method. The accuracy of the location of contact is directly dependent on the mesh density. Although improving the accuracy requires an increase in computation time, this method allows obtaining in a very short time sufficiently accurate results to meet the needs of designers, particularly in the preliminary stages of design. The relative displacements of the gears can be taken into consideration. The robustness of the proposed computing process and the adjustable accuracy of the results are the two main advantages of the presented approaches

A new methodology to optimize spiral bevel gear topography

International audienceThis paper aims to present the new method developed to generate optimized spiral bevel gear surfaces. Thanks to a complex non linear finite element model, the geometrical gear meshing positions under operational loads are first precisely computed. These meshing positions are then used as inputs of a calculation process that seeks to define the best tooth surface topography. So far, this activity was based on sensitivity studies conducted directly by the designer, which led to repeat calculations whose progress was difficult to control.EUROCOPTER uses now optimization algorithms to compute automatically the surfaces of the tooth contact flanks. This approach leads to higher performances of the gear while reducing the development time. This paper describes the new process implemented to design the tooth shape, and illustrates its interest through an example

New methodology to reduce the transmission error of the spiral bevel gears

International audienceNew methods and tools have been developed the last years to improve the understanding of gear meshing. Mechanical industries attach growing attention to the dynamic behavior of mechanical transmissions, including vibration and noise that result. The transmission error of the gear, which measures the intensity of one of the main causes of dynamic phenomena, can be considered as a relevant indicator of gear performance. This paper presents a new design method of spiral bevel gears, the objective of this method being to reduce their quasi-static transmission error. The proposed approach is based on an optimization process including loaded meshing simulations. The simulation model has been evaluated using a helicopter tail gearbox as bench test. Measurement results are given, showing a good correlation with predictions

New methodology to reduce the transmission error of the spiral bevel gears

International audienceNew methods and tools have been developed the last years to improve the understanding of gear meshing. Mechanical industries attach growing attention to the dynamic behavior of mechanical transmissions, including vibration and noise that result. The transmission error of the gear, which measures the intensity of one of the main causes of dynamic phenomena, can be considered as a relevant indicator of gear performance. This paper presents a new design method of spiral bevel gears, the objective of this method being to reduce their quasi-static transmission error. The proposed approach is based on an optimization process including loaded meshing simulations. The simulation model has been evaluated using a helicopter tail gearbox as bench test. Measurement results are given, showing a good correlation with predictions

Successful Late Removal of Endobronchial Coils

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