Hybrid (bolted/bonded) joints applied to aeronautic parts : analytical one-dimensional models of a single-lap joint

The load transfer in hybrid (bolted/bonded) single-lap joint is complex due to the association of two different transfer modes (discrete and continuous) through elements with different stiffness. Analytical methods exist for these two different modes, when considered separately. In this paper two one-dimensional elastic analytical models are presented for the determination of the load transfer in single lap configuration. The first one is developed by using the integration of the local equilibrium equations. From this first method an elastic-plastic approach is presented. The second one uses the Finite Element Method, introducing a new element called “bonded-bar”. These models are robust, easy to use and provide the same results. They allow to analyze the load transfer and to evaluate different geometric and mechanical parameters’ influence. Thus they represent the first step for the design of a hybrid joint able to replace its bolted equivalent used on aircraft

Contribution aux assemblages hybrides boulonnés collés aéronautiques : modélisation analytique unidimensionnelle en simple cisaillement

Le calcul du transfert de charge dans les jonctions a été traité par des approches analytiques d’une part dans le cas des jonctions boulonnées et d’autre part dans celui des jonctions collées. Dans cet article, nous étudions le cas d’une jonction hybride boulonnée collée qui associe les deux modes de transfert (discret et continu) dans une configuration en simple cisaillement. Nous présentons une modélisation analytique monodimensionnelle qui prend en compte la rigidité des différents composants. Simple à mettre en oeuvre, elle permet d’analyser le transfert de charge et d’évaluer l’influence des différents paramètres géométriques et mécaniques. Son exploitation est intéressante dans le cadre du pré-dimensionnement d’une jonction hybride apte à remplacer son équivalent boulonné sur avion

Load allocation problem for optimal design of aircraft electrical power system

More and more electric systems are embedded in today aircraft. As a result, the complexity of electrical power system design is increasing and the need of generic and efficient design methods is today required. Among numerous design tasks, the allocation of electric systems on the busbars of the electrical power system is considered as an important one since it has a direct impact on the aircraft mass. But due to the high number of possible allocations and regarding the large diversity of potential sizing cases for the equipments, finding the optimal allocation of electric loads is a hard task. In this paper, the problem is formalized mathematically. Then, four stochastic optimization methods are assessed on complex load allocation problems. Based on this assessment, a genetic algorithm using niching method is considered as the most appropriate algorithm for solving this aircraft design proble

Modélisation et mesure des efforts axiaux le long d'une fixations montées avec interférence. Application aux structures aéronautiques

Les assemblages à base de fixations montées avec interférence et prétension sont largement utilisés dans le domaine de la construction aéronautique, notamment dans les zones structurales fortement chargées et soumises à des sollicitations de fatigue. Les performances de ces assemblages sont sensibles à de nombreux paramètres liés à la géométrie et aux matériaux mis en jeu. Pour optimiser la qualité de ces liaisons et atteindre les gains de durée de vie attendus, il est important de disposer de modèles à la fois rapides et fiables qui permettent, dès la phase de conception, d évaluer l influence des paramètres d entrée sur les efforts caractéristiques de l assemblage. Les travaux s attachent, dans un premier temps, en s appuyant sur une modélisation par éléments finis très détaillée du processus d assemblage, à bien identifier les phénomènes mécaniques les plus caractéristiques des liaisons étudiées. Une approche analytique de premier niveau est ensuite développée. Elle conduit à un modèle d estimation des efforts et de contraintes présentes dans les pièces assemblées qui produit des résultats très voisins de ceux obtenus avec le modèle de référence. Un modèle numérique dédié,basé sur des éléments finis axisymétriques et codé sous Matlab, est ensuite proposé. Il est apte à évaluer l influence des variations des paramètres le long de l interface entre les pièces tout en considérant les effets de bords. Une étude expérimentale basée sur une instrumentation de l assemblage avec des fibres optiques à réseaux de Bragg est présentée. Les corrélations entre les résultats expérimentaux et ceux issus des modélisations sont très satisfaisantesAssemblies based on interference fit fastener and preload are widely used in the fieldof aircraft construction, especially on structures heavily loaded and subjected to fatigue stresses.The performances of these assemblies are sensitive to many parameters related to the geometry and to the constitutive materials. To improve the quality of these assemblies and achieve the assembled parts. This simple model produces results very similar to those obtained with thereference model. A dedicated numerical model, based on axisymmetric finite elements and developed using Matlab code, is also proposed. It is able to evaluate the influence of parameter variations along the interface between the parts while considering the side effects. An experimental study based on an assembly instrumented with Fiber Bragg Gratings is presented.The correlations between the experimental results and those from the models are very satisfactory lifetime gains expected, it is important to use, from the early design phase, fast and reliable models in order to evaluate the influence of input parameters on the most significant efforts that take place around the fastener. In a preliminary phase, the work focuses on clearly identifyingthe mechanical phenomena characterizing the behavior of the mechanical connections understudy, using a very detailed finite element reference model of the assembly process. An analytical approach is then developed. It leads to a first level model for estimating loads and stresses in the assembled parts. This simple model produces results very similar to those obtained with the reference model. A dedicated numerical model, based on axisymmetric finite elements and developed using Matlab code, is also proposed. It is able to evaluate the influence of parameter variations along the interface between the parts while considering the side effects. An experimental study based on an assembly instrumented with Fiber Bragg Gratings is presented.The correlations between the experimental results and those from the models are very satisfactoryTOULOUSE-INSA-Bib. electronique (315559905) / SudocSudocFranceF

Méthodes et outils pour la conception optimale des réseaux de distribution d'électricité dans les aéronefs

Dans le domaine aéronautique, la dernière décennie a été marquée par une augmentation constante et progressive du taux d électrification des systèmes embarqués. L avion plus électrique est aujourd hui vu comme un axe d amélioration majeure pour l industrie aéronautique permettant d atteindre des objectifs toujours plus ambitieux : réduction de l impact environnemental, rationalisation des coûts de maintenance Dans ce contexte, le réseau de distribution électrique joue un rôle majeur. Les architectes doivent imaginer de nouveaux concepts architecturaux afin d assurer le service de fourniture d électricité tout en minimisant la masse et le coût. Ainsi les travaux de cette thèse proposent des méthodes d aide à la conception pour les architectes de réseau. Le manuscrit se divise en 2 parties pouvant être vues comme 2 études distinctes et qui sont introduites dans le chapitre 1.La 1ère partie, traitée dans les chapitres 2 et 3, développe des méthodes et outils afin de résoudre de manière automatique et optimale 2 tâches de l architecte : la définition des reconfigurations du réseau et l identification de l allocation des charges. La formalisation de ces 2 problématiques met en lumière une caractéristique commune : l explosion combinatoire. Ainsi les résolutions sont réalisées à l aide de méthodes issues de la recherche opérationnelle. Un processus général est défini afin de traiter les 2 tâches de manière consistante. Les aspects liés à la reconfiguration sont traités à l aide de : la théorie des graphes pour modéliser la connectivité du réseau, un système expert capturant les règles métiers et la programmation linéaire sélectionnant les reconfigurations les plus performantes. La méthode a été appliquée avec succès sur des réseaux avions existants (A400M et A350) ainsi que sur des réseaux plus électriques prospectifs. La deuxième tâche consistant en l allocation des charges a été résolue à l aide de méthodes stochastiques. L algorithme génétique utilisant une méthode de nichage se révèle être le plus performant en proposant à l architecte réseau des solutions performantes et variées. La 2ème partie, traitée dans le chapitre 4, s intéresse à un nouveau concept le cœur électronique modulaire et mutualisé . Cet organe de distribution, étroitement lié à l avion plus électrique, se caractérise par la mutualisation de m modules électronique de puissance pour c charges électriques. Les méthodes développées dans le chapitre 4 vise à concevoir de manière optimale ce nouveau cœur en ayant 2 degrés de liberté : le nombre m de modules et les reconfigurations entre les m modules et les c charges. De nouveau, la formalisation du problème met en évidence l explosion combinatoire à laquelle est confronté le concepteur. Le principal objectif de cette étude est de proposer un cadre méthodologique pour la résolution de ce problème de conception. Ainsi une heuristique a été développée pour résoudre ce problème combinatoire. Une attention particulière a été portée pour développer des modèles de composants simples et génériques dans une procédure générale organisée. Enfin une cartographie a été réalisée afin de dégager d une part les formes de solutions les plus performantes et d identifier les éléments ayant les impacts les plus significatifs sur la masse du système complet.In the aeronautics field, the last decade has been marked by a constant and gradual increase of the electrification rate of the embedded systems. Today, the More Electric Aircraft (MEA) is seen as a major axis of improvement for the aviation industry to achieve increasingly ambitious objectives: reducing environmental impact, rationalisation of maintenance costs...In the more electrical aircraft concept, the electrical network plays a major role. Today engineers must imagine new architectural solutions to ensure the electricity supply while minimizing weight and cost. In this context, the PhD work consists in providing new methods to support the design of electrical network architectures. The PhD work is divided into 2 parts which can be seen as 2 separate studies which are introduced in the chapter 1.The 1st part, treated in the chapters 2 and 3, develops methods and tools to solve problems automatically for 2 architecture tasks: the definition of the network reconfiguration and the identification of the electrical load allocation on busbars. The formalization of these two issues highlights a common characteristic: the combinatorial explosion. As the consequence, methods from operational research area are selected to solve the 2 tasks in the frame of a general and consistent design process. The reconfiguration aspects are solved by a methodology coupling together: graph theory to model the network connectivity, an expert system capturing know-how rules and linear programming selecting the most efficient reconfiguration. The approach was successfully applied on existing aircraft electrical networks (A400M and A350) and on future architectures. The second task, related to the electrical load allocation, is solved using stochastic methods. The genetic algorithm using a niching method is the best assessed optimization method. It provides good and diversified load allocations to the electrical network architect. The 2nd part, treated in the chapter 4, focuses on a new technological concept the modular and mutualised power electronics center . This distribution system, closely linked to the more electrical aircraft, aims at sharing m power electronics modules to c electrical loads. The methods developed in this PhD aim at carrying out an optimal design of this new power center with 2 design variables: the number m of modules and the reconfigurations between the m modules and the c loads. Again, the formalization of the problem highlights that the designer must deal with a combinatorial explosion. The main objective of this study is to propose a methodological framework for solving this design problem. A heuristic-based algorithm is developed to solve this combinatorial optimization problem. A particular attention is paid to develop an organized weight estimation procedure using generic sizing models. Finally a mapping is performed to identify the best solutions and to highlight the technological elements having the most significant impact on the complete system weightTOULOUSE-INSA-Bib. electronique (315559905) / SudocSudocFranceF

Cost-effectiveness of a technology-supported multimodal prehabilitation program in moderate-to-high risk patients undergoing lung cancer resection: randomized controlled trial protocol

Background: Multimodal prehabilitation is a preoperative intervention with the objective to enhance cancer patients' functional status which has been showed to reduce both postoperative morbidity and hospital length of stay in digestive oncologic surgery. However, in lung cancer surgery patients further studies with higher methodological quality are needed to clarify the benefits of prehabilitation. The main aim of the current protocol is to evaluate the cost-effectiveness of a multimodal prehabilitation program supported by information and communication technologies in moderate-to-high risk lung cancer patients undergoing thoracic surgery. Methods: A Quadruple Aim approach will be adopted, assessing the prehabilitation program at the following levels: i) Patients' and professionals' experience outcomes (by means of standardized questionnaires, focus groups and structured interviews); ii) Population health-based outcomes (e.g. hospital length of stay, number and severity of postoperative complications, peak oxygen uptake and levels of systemic inflammation); and, iii) Healthcare costs. Discussion: This study protocol should contribute not only to increase the scientific basis on prehabilitation but also to detect the main factors modulating service adoption. Trial registration: NCT04052100 (August 9, 2019)

White Matter Changes-Related Gait and Executive Function Deficits: Associations with Age and Parkinson's Disease

Background: White matter changes (WMC) are a common finding among older adults and patients with Parkinson's disease (PD), and have been associated with, e.g., gait deficits and executive dysfunction. How the factors age and PD influence WMC-related deficits is, to our best knowledge, not investigated to date. We hypothesized that advanced age and presence of PD leads to WMC-related symptoms while practicing tasks with a low complexity level, and low age and absence of PD leads to WMC-related symptoms while practicing tasks with a high complexity level.Methods: Hundred and thirty-eight participants [65 young persons without PD (50–69 years, yPn), 22 young PD patients (50–69 years, yPD), 36 old persons without PD (70–89 years, oPn) and 15 old PD patients (70–89 years, oPD)] were included. Presence and severity of WMC were determined with the modified Fazekas score. Velocity of walking under single and dual tasking conditions and the Trail Making Test (TMT) were used as gait and executive function parameters. Correlations between presence and severity of WMC, and gait and executive function parameters were tested in yPn, yPD, oPn, and oPD using Spearman's rank correlation, and significance between groups was evaluated with Fisher's z-transformed correlation coefficient.Results: yPn and yPD, as well as oPn and oPD did not differ regarding demographic and clinical parameters. Severity of WMC was not significantly different between groups. yPn and yPD displayed significant correlations of WMC with executive function parameters at low levels of task complexity, oPn at intermediate, and oPD at high complexity levels.Conclusion: This study argues for a relevant association of age and PD-related brain pathology with WMC-related gait and executive function deficits

Corrigendum: White Matter Changes-Related Gait and Executive Function Deficits: Associations with Age and Parkinson's Disease.

[This corrects the article on p. 213 in vol. 9, PMID: 28713264.]

Metabolically-Defined Body Size Phenotypes and Risk of Endometrial Cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC)

Background: Obesity is a risk factor for endometrial cancer but whether metabolic dysfunction is associated with endometrial cancer independent of body size is not known. Methods: The association of metabolically defined body size phenotypes with endometrial cancer risk was investigated in a nested case-control study (817 cases/ 817 controls) within the European Prospective Investigation into Cancer and Nutrition (EPIC). Concentrations of C-peptide were used to define metabolically healthy (MH; _1st tertile) status among the control participants. These metabolic health definitions were combined with normal weight (NW); body mass index (BMI)_25 kg/m2 or WC >_80 cm or WHR >_0. 8) status, generating four phenotype groups for each anthropometric measure: (i) MH/NW, (ii) MH/OW, (iii) MU/ NW, and (iv) MU/OW. Results: In a multivariable-adjusted conditional logistic regression model, compared with MH/NW individuals, endometrial cancer risk was higher among those classified as MU/NW [ORWC, 1.48; 95% confidence interval (CI), 1.05-2.10 and ORWHR, 1.68; 95% CI, 1.21- 2.35] and MU/OW (ORBMI, 2.38; 95% CI, 1.73-3.27; ORWC, 2.69; 95% CI, 1.92-3.77 and ORWHR, 1.83; 95% CI, 1.32-2.54). MH/OW individuals were also at increased endometrial cancer risk compared with MH/NW individuals (ORWC, 1.94; 95% CI, 1.24-3.04). Conclusions: Women with metabolic dysfunction appear to have higher risk of endometrial cancer regardless of their body size. However, OW status raises endometrial cancer risk even among women with lower insulin levels, suggesting that obesity related pathways are relevant for the development of this cancer beyond insulin. Impact: Classifying women by metabolic health may be of greater utility in identifying those at higher risk for endometrial cancer than anthropometry per se

Predicting circulating CA125 levels among healthy premenopausal women

Background: Cancer antigen 125 (CA125) is the most promising ovarian cancer screening biomarker to date. Multiple studies reported CA125 levels vary by personal characteristics, which could inform personalized CA125 thresholds. However, this has not been well described in premenopausal women. Methods: We evaluated predictors of CA125 levels among 815 premenopausal women from the New England Case Control Study (NEC). We developed linear and dichotomous (≥35 U/mL) CA125 prediction models and externally validated an abridged model restricting to available predictors among 473 premenopausal women in the European Prospective Investigation into Cancer and Nutrition Study (EPIC). Results: The final linear CA125 prediction model included age, race, tubal ligation, endometriosis, menstrual phase at blood draw, and fibroids, which explained 7% of the total variance of CA125. The correlation between observed and predicted CA125 levels based on the abridged model (including age, race, and menstrual phase at blood draw) had similar correlation coefficients in NEC (r = 0.22) and in EPIC (r = 0.22). The dichotomous CA125 prediction model included age, tubal ligation, endometriosis, prior personal cancer diagnosis, family history of ovarian cancer, number of miscarriages, menstrual phase at blood draw, and smoking status with AUC of 0.83. The abridged dichotomous model (including age, number of miscarriages, menstrual phase at blood draw, and smoking status) showed similar AUCs in NEC (0.73) and in EPIC (0.78). Conclusions: We identified a combination of factors associated with CA125 levels in premenopausal women. Impact: Our model could be valuable in identifying healthy women likely to have elevated CA125 and consequently improve its specificity for ovarian cancer screening