Benefits and limitations of parametric design implementation in helicopter gearbox design phase

International audiencehis paper describes a parametric design methodology implemented to reduce gearbox design phase. A helicopter gearbox is a complex mechanical system, in which parts are heavily loaded in order to save weight but that have to run for thousands of hours without failure. Such a system is strongly optimized therefore the smallest change in specifications or in geometrical environments can drastically jeopardize the scheduling. In order to speed up the gearbox design process and to strengthen its robustness regarding specifications variability, a parametric design methodology has been developed thanks to a close collaboration between the laboratories and Eurocopter

Tools and techniques for product design

For product designers, tools and techniques are essential in driving the design cycle. Nevertheless, their employment usually is implicit, while passing over e.g. the design and project environments empowering their adequate use. This publication presents an overview of approaches in structuring and using tools/techniques, based on the effectuation of creativity and decision-making in the design environment. In elaborating on characteristics of tools/techniques and ensuing ways of selecting them, the designer's portfolio of tools/techniques is characterised. Representative problems of tool/technique usage are depicted and contextualised by illustrating their industrial application. Prospects for future developments are also reviewe

Modélisation complète d'une boite de transmission d'hélicoptère

Les boites de transmission d’hélicoptère ont la particularité de transmettre des puissances mécaniques élevées en minimisant la masse embarquée. Cette particularité ne permet pas d’étudier d’une manière isolée le comportement de chacune des pièces. Pour maîtriser le comportement de chaque élément, il est nécessaire d’effectuer une modélisation complète du mécanisme. Cet article, présente une méthode permettant de calculer les efforts dans les guidages en rotation par éléments roulants

On the role of kinking in the bearing failure of composite laminates

Fibre kinking is one of the main failure modes of composite laminates under compression loading. In this paper, the role of kinking in the failure of quasi-isotropic composites subjected to a bearing load is investigated. High-resolution CT scans show that kinking is largely involved in the events leading to laminate collapse, notably by triggering other damage modes such as delamination. Kink bands develop extremely progressively, leading to the formation of a wide localization zone (or FPZ, failure process zone). Such behaviour calls for a non-local modelling approach. Local damage models would lead to overly conservative sizing. A simple model, based on Hashin failure criteria and non-local effective stresses is confronted to experiments, and its limits are highlighted. It will be shown that proper modelling of the bearing failure requires the characteristic behaviour of kink bands to be taken into account

Automatisation du diagnostic vibratoire des transmissions de puissance d'hélicoptère

PARIS-Arts et Métiers (751132303) / SudocSudocFranceF

Etude des méthodes de calcul des pressions de contact dans les roulements à pistes int́egŕees des boîıtes de transmission aéronautiques

International audienceStudy of methodologies for contact pressure calculation in integrated raceways bearings for aeronautical gearbox. More and more designers use advanced calculation methodologies for the optimisation of mechanical part performance. This is even truer in the aeronautic industry, where the power weight ratio must be as low as possible. Some CAD softwares (CATIA, SOLIDWORKS, PRO ENGINEER, etc.) provide the possibility to do complex computation. However these kinds of tools aren't currently able to easily estimate the contact pressure between two parts. This paper deals with the various methodologies usable in a CAD environment for the calculation of contact pressures in integrated raceways bearings for aeronautic gearbox. These methodologies may be analytical (Hertz theory), numerical (F.E.M.) or hybrid. They are analyzed and compared according to their precision, calculation time and readiness to be integrated in the industrial design process. An optimum contact pressure calculation methodology will be presented based upon the results of this analysis.De plus en plus, les concepteurs utilisent des méthodes avancées de calcul, pour optimiser les performances des systèmes mécaniques. Ce constat est d'autant plus vrai dans le milieu aéronautique où le rapport poids puissance doitêtredoitêtre le plus faible possible. Certains logiciels de CAO (CATIA, SO-LIDWORKS, PRO ENGINEER, etc.) off rent la possibilité d'eff ectuer des calculs de dimensionnement. Néanmoins, ce type d'outil ne permet pas, a ` ce jour, d'estimer facilement les pressions de contact entre deuxpì eces. Cet article présente les différentesdifférentes méthodologies utilisables dans un environnement CAO pour le calcul des pressions de contact dans les roulementsàroulementsà pistes intégrées de boˆıteboˆıte de transmission aéronautique. Ces méthodologies sont analytiques (théorie de Hertz), numériques (´ eléments-finis) ou hy-brides. Ces différentesdifférentes approches sont analysées et comparées suivant les critères de précision, de temps de calcul et de leurs aptitudes a ` s'intégrer dans un processus de conception industriel. A partir de cette analyse, il sera proposé une méthodologie de calcul des pressions de contact. Mots clés : Roulement / CAO / ´ eléments-finis / théorie de Hertz / boˆıteboˆıte de transmissio

Joint loading estimation method for horse forelimb high jerk locomotion: jumping

International audienceMaximal local loads in animal joints are necessary to design bio-inspired mechanical joints. Many studies presented methods to determine joint reaction forces in humans and animals. However, many of these methods are invasive, and no work has been published yet about the joint reaction forces in the horse forelimb during jumping. Non-invasive methods to measure the kinematics and ground reaction force of a horse forelimb were used in this work. A musculoskeletal model of horse forelimb was built with mechanical methods for the estimation of joint reaction forces. The entire forelimb was reconstructed by scanning real bones geometry with a 3D optical scanner and modeling all the muscles on a Computer Assisted Design (CAD) software. The model dynamics were simulated with OpenSim in order to estimate the joint loading. This study allows knowing an order of magnitude of the loads at the joints at jumping in order to determine latter the maximal joint contact loading values that will be a key at designing bio-inspired joints for mechanical assemblies

Wear behavior of a bio-inspired bearing for off-center loads

International audienceMisalignment is one of the most common causes of wear in bush bearings. Design improvements have been proposed by research studies for years. Unfortunately, it did not efficiently reduce the phenomenon. Classic geometrical designs sometimes reach their limits. For this reason, a bio-inspired design is proposed to solve the impediment. In this article, a bio-inspired bearing suited to misalignment was tested and compared to a classical bush bearing. The contact pressures of both bearings were compared with static finite element simulations for off-center load. Due to the complex shape of the involved contact, the performances of both bearings were also studied over time. Their wear behaviors were predicted with a numerical method. The methodologies emplaced to simulate the wear are described in this paper. Particularly, the wear coefficient determination obtained by experimental testing is detailed. The results for the classical bearing are in accordance with the literature. The pressure value, the contact zone and the wear depth are compared and discussed. Although the pressure is not uniformly distributed over the bio-inspired bearing, the simulations show a deeper wear on the classical bush bearing than on the bio-inspired bearing. Therefore, the superiority of this bearing is proved

Determination of biological joint reaction forces from in-vivo experiments using a hybrid combination of biomechanical and mechanical engineering software

In biomechanical field, several studies used OpenSim software to compute the joint reaction forces from kinematics and ground reaction forces measurements. The bio-inspired joints design and their manufacturing need the usage of mechanical modeling and simulation software tools. This paper proposes a new hybrid methodology to determine biological joint reaction forces from in vivo measurements using both biomechanical and mechanical engineering softwares. The methodology has been applied to the horse forelimb joints. The computed joint reaction forces results would be compared to the results obtained with OpenSim in a previous study. This new hybrid model used a combination of measurements (bone geometry, kinematics, ground reaction forces…) and also OpenSim results (muscular and ligament forces). The comparison between the two models showed values with an average difference of 8% at trotting and 16% at jumping. These differences can be associated with the differences between the modelling strategies. Despite these differences, the mechanical modeling method allows the computation of advanced simulations to handle contact conditions in joints. In future, the proposed mechanical engineering methodology could open the door to define a biological digital twin of a quadruped limb including the real geometry modelling of the joint

Computational Design Synthesis Using Model-Driven Engineering and Constraint Programming

International audienceThis paper introduces a new process for computational design synthesis. It starts from functional requirements to generate one or more topologies of components. This process is implemented using Model-Driven Engineering techniques and Constraint Programming solving capabilities. Model transformations are used to transform functions and available components to a CSP. This problem is solved with a CSP solver, which solutions are transformed to topological architectures. The process is successfully applied on the design synthesis of an autonomous generator. It produces about 60 relevant solutions from which we found some existing product architectures