Set-based design of mechanical systems with design robustness integrated

This paper presents a method for parameter design of mechanical products based on a set-based approach. Set-based concurrent engineering emphasises on designing in a multi-stakeholder environment with concurrent involvement of the stakeholders in the design process. It also encourages flexibility in design through communication in terms of ranges instead of fixed point values and subsequent alternative solutions resulting from intersection of these ranges. These alternative solutions can then be refined and selected according to the designers’ preferences and clients’ needs. This paper presents a model and tools for integrated flexible design that take into account the manufacturing variations as well as the design objectives for finding inherently robust solutions using QCSP transformation through interval analysis. In order to demonstrate the approach, an example of design of rigid flange coupling with a variable number of bolts and a choice of bolts from ISO M standard has been resolved and demonstrated

Gear metrology of statistical tolerancing by numerical simulation

Tolerance verification permits to check the product conformity and to verify assumptions made by the designer. For conformity assessment, the uncertainty associated with the values of the measurands must be known. In the ISO TS 17450 part 2, the notion of the uncertainty is generalized to the specification and the verification. The uncertainty is divided into correlation uncertainty, specification uncertainty and measurement uncertainty. Correlation uncertainty characterizes the fact that the intended functionality and the controlled characteristics may not be perfectly correlated. Therefore, we propose a new specified characteristics based on the statistical tolerancing approach which is directly in relationship with the design intent: the probability distribution of maximum range of the transmission error (the transmission error is the main source of vibratory and acoustic nuisances), and the evaluation of this characteristic based on 3D acquisition by Monte Carlo simulation and Tooth Contact Analysis. Moreover, the measurement uncertainty of the evaluation of this characteristic is estimated by Monte Carlo Simulation

Gear metrology of statistical tolerancing by numerical simulation

Tolerance verification permits to check the product conformity and to verify assumptions made by the designer. For conformity assessment, the uncertainty associated with the values of the measurands must be known. In the ISO TS 17450 part 2, the notion of the uncertainty is generalized to the specification and the verification. The uncertainty is divided into correlation uncertainty, specification uncertainty and measurement uncertainty. Correlation uncertainty characterizes the fact that the intended functionality and the controlled characteristics may not be perfectly correlated. Therefore, we propose a new specified characteristics based on the statistical tolerancing approach which is directly in relationship with the design intent: the probability distribution of maximum range of the transmission error (the transmission error is the main source of vibratory and acoustic nuisances), and the evaluation of this characteristic based on 3D acquisition by Monte Carlo simulation and Tooth Contact Analysis. Moreover, the measurement uncertainty of the evaluation of this characteristic is estimated by Monte Carlo Simulation

Contribution à l'optimisation de la conception des engrenages coniques à denture droite (analyse et synthèse de la géométrie et des tolérances)

La maîtrise accrue des matériaux et des procédés de forgeage permet aujourd'hui d'obtenir des engrenages coniques d'une qualité suffisante pour pouvoir les utiliser sans autre procédé de finition. Ce sont les pièces dites net shape . Grâce à cette évolution technologique, il est nécessaire de d'optimiser la définition géométrique de ces engrenages en tenant compte des possibilités des procédés de forgeage, en particulier. Tout d'abord, la définition de la géométrie nominale des engrenages coniques à denture droite basée sur les propriétés géométriques et cinématiques du profil en développante de cercle sphérique est réétudiée et a abouti à une modélisation paramétrique des surfaces actives en intégrant un bombé longitudinal. Afin de garantir un certain niveau de qualité de l'engrènement, il est nécessaire de limiter les variations inhérentes au procédé de forgeage et aux ressources de fabrication, il s'agit de l'analyse et de la synthèse des tolérances. Cette analyse a nécessité une modélisation géométrique des engrenages incluant les écarts intrinsèques et les écarts de situation. L'analyse de l'impact de ces écarts sur l'erreur cinématique (Tooth Contact Analysis) repose sur la résolution d'un système d'équations non linéaires pour chaque position du pignon et d'un traitement de ces résultats; la difficulté de cette analyse est la grande sensibilité des résultats aux écarts. Cet outil TCA est le module principal de l'analyse des tolérances qui est réalisée de façon statistique par simulation de Monte Carlo. L'analyse des tolérances permet de valider une solution d'allocation de celles-ci mais ne permet pas son allocation automatique. Ainsi une approche de synthèse des tolérances a été validée, il s'agit de l'optimisation par algorithme génétique où la fonction objectif est de minimiser le ratio coût des tolérances sur la probabilité de respect des exigences. Cette analyse et cette synthèse ont été menées dans un premier temps sans charge, en considérant l'engrenage comme indéformable. Puis, la prise en compte des déformations est réalisée par la méthode des coefficients d'influences. Le problème de contact et de déformation globale de la denture sont découplés. Les coefficients d'influences de contact sont estimés par la méthode de Boussinesq et Cerruti. Les coefficients d'influence de flexion sont estimés par interpolation et méthode des éléments finis. Ce modèle permet l'analyse de l'engrènement sous charge mais les temps de calculs restent un handicap pour l'analyse des tolérances. Ces modèles de comportement pourront être affinés dans de futurs travaux et être le support de nouveaux modèles de spécification des engrenages, de suivi du processus de fabrication, d'une meilleure connaissance des interactions géométrie-mécanique-matériau, etc.As technology increases and performance requirements continually tighten, the cost and required precision of assemblies increase as well. The forging evolution enables us to realize bevel gear net shape. Therefore, this work focuses on the parametric and tolerance design optimization of bevel gear. The synthesis of bevel gear nominal model is based on geometrical properties and kinematic properties of spherical involute. To ensure a quality level of meshing, it is necessary to limit the geometrical variations which are due to the manufacturing process (tolerance analysis and tolerance synthesis). To achieve this, we establish a geometrical model which includes the deviations (form, orientation and position). This model enables the evaluation of the impact of these deviations on the kinematic behaviour. This evaluation is T.C.A. (Tooth Contact Analysis) is based on the simulation of tangency of tooth surfaces being in mesh. The tolerance analysis is based on TCA and Monte Carlo simulation which computes the probability that the product respects the requirements of the kinematic error, under given individual tolerances. Moreover, to optimize the ratio of tolerance cost (tolerance synthesis) on probability that the product respects the requirements, genetic algorithm is improved. These tolerance analysis and synthesis do not take into account the teeth distortions. To do so, we propose to integrate the distortions which are evaluated by the influence coefficient method. Contact problem and bending problem of teeth are delinked. The contact influence coefficients are estimated by Boussinesq and Cerruti method. The bending influence coefficients are evaluated by interpolation and finite elements method. This model allows gearing analysis under load but the calculation time is a handicap for tolerance analysis. This behaviour models may be refined in future works and support the new geometrical specification models, process control and better knowledge of geometry-mechanic-material interaction.CACHAN-ENS (940162301) / SudocPARIS-Arts et Métiers (751132303) / SudocMETZ-Arts et Métiers (574632301) / SudocSudocFranceF

Contributions à la maîtrise de la robustesse des produits (formalisation par logique formelle, applications à la conception ensembliste et au tolérancement)

Ces travaux sont situés sur les domaines de la conception mécanique, l'informatique, et les mathématiques appliqués pour proposer une solution globale de gestion des variations pendant le processus de la conception d'un produit afin de rechercher l'ensemble des solutions robustes. Ils visent plus particulièrement à répondre à la question : "Comment exprimer et intégrer la variabilité admissible des paramètres du produit (espace des solutions), et sur le tolérancement de celles-ci : les variations admissibles (tolérances) simultanément pendant la phase de la conception d'un produit mécanique le plutôt possible ? Pour répondre à cette question, cette thèse presente, une formalisation généralisée pour définir, modéliser et exprimer la problème de la gestion des variations dans le processus de la conception du produit utilisant la philosophie de la conception basée sur les ensembles "Set Based Design" et la logique formelle. Cette formalisation permet la prise en compte simultanée des incertitudes et variations lors de la définition d'un produit. Les travaux aussi développent et expose les outils pour appliquer la formalisation développé au recherche des ensembles des solutions robustes des système mécanique et l'analyse des tolérances des mécanismes hyperstatiques.This work is oriented towards the variation management within the embodiment design phase of a product. It focuses on management and integration of design parameter variation and manufacturing variations in design phase. In this work, a generalized framework for definition, modeling, expression and interaction, of the design variables and the variations, for the mechanical product design, using the philosophy of set based design developed and logic has been developed. The developed framework integrates the notion of concurrent engineering design while considering the design parameters in terms of sets, instead of point based design, as well as the notion of the noise (variation/uncertainty), arising from different sources, enabling an expression of flexible and robust design. The research also sets down the complete approach from abstract expression of the framework description to the operational application to examples in the mechanical engineering design of products in the embodiment design phase. This is achieved through definition of a common framework for expression of concurrent product design problem with management of variation, its transformation for the set based robust design and tolerance analysis applications , within an integrated design context through appropriate tools, methods and techniques.PARIS-Arts et Métiers (751132303) / SudocSudocFranceF

Mechanical ventilation alters the development of staphylococcus aureus pneumonia in rabbit

Ventilator-associated pneumonia (VAP) is common during mechanical ventilation (MV). Beside obvious deleterious effects on muco-ciliary clearance, MV could adversely shift the host immune response towards a pro-inflammatory pattern through toll-like receptor (TLRs) up-regulation. We tested this hypothesis in a rabbit model of Staphylococcus aureus VAP. Pneumonia was caused by airway challenge with S. aureus, in either spontaneously breathing (SB) or MV rabbits (n = 13 and 17, respectively). Pneumonia assessment regarding pulmonary and systemic bacterial burden, as well as inflammatory response was done 8 and 24 hours after S. aureus challenge. In addition, ex vivo stimulations of whole blood taken from SB or MV rabbits (n = 7 and 5, respectively) with TLR2 agonist or heat-killed S. aureus were performed. Data were expressed as mean +/- standard deviation. After 8 hours of infection, lung injury was more severe in MV animals (1.40 +/- 0.33 versus [vs] 2.40 +/- 0.55, p = 0.007), along with greater bacterial concentrations (6.13 +/- 0.63 vs. 4.96 +/- 1.31 colony forming units/gram, p = 0.002). Interleukin (IL)-8 and tumor necrosis factor (TNF)-alpha serum concentrations reached higher levels in MV animals (p = 0.010). Whole blood obtained from MV animals released larger amounts of cytokines if stimulated with TLR2 agonist or heat-killed S. aureus (e.g., TNF-alpha: 1656 +/- 166 vs. 1005 +/- 89; p = 0.014). Moreover, MV induced TLR2 overexpression in both lung and spleen tissue. MV hastened tissue injury, impaired lung bacterial clearance, and promoted a systemic inflammatory response, maybe through TLR2 overexpression

National prospective study on the use of local haemostatic agents during partial nephrectomy

International audienceOBJECTIVE:To assess the use of local haemostatic agents (HAs) in a prospective multicentre large series of partial nephrectomies (PNs).PATIENTS AND METHODS:Prospective National Observational Registry on the Practices of Haemostasis in Partial Nephrectomy (NEPHRON): the study was conducted in 54 French urological centres from 1 June to 31 December 2010. In all, 570 consecutive patients undergoing a PN were enrolled in this study in a prospective manner. The data was collected prospectively via an electronic case-report form: five different sheets were included for preoperative, perioperative, postoperative and follow-up data respectively. Information related to haemostasis was analysed.RESULTS:The median patient age was 60 years and the mean (range) tumour size was 3.68 (0.19-15) cm. An HA was primarily used in 71.4% of patients, with a statistically significant difference among surgical approaches (P = 0.024). In 91.8% of cases, a single use of a HA was sufficient for achieving haemostasis. The HA was used either alone (13.9%) or in association with sutures (80.3%). One or more additional haemostatic action(s) was needed in 12.3% of the cases. When comparing patients who received a HA with those who did not receive a HA, there was no statistical difference between the groups for tumour size (P = 0.542), collecting system drainage (P = 0.538), hospital stay (P = 0.508), operation time (P = 0.169), blood loss (P = 0.387) or transfusion rate (P = 0.713).CONCLUSION:HAs are widely used by urologists during PN. Progress is needed for standardising HA application, especially for the timing of application. For the time being, the role of the HA in nephron-sparing surgery is still to be evaluated

Renal cell carcinoma (RCC) in patients with end-stage renal disease exhibits many favourable clinical, pathologic, and outcome features compared with RCC in the general population.

International audienceBACKGROUND: Patients with end-stage renal disease (ESRD) are at risk of developing renal tumours. OBJECTIVE: Compare clinical, pathologic, and outcome features of renal cell carcinomas (RCCs) in ESRD patients and in patients from the general population. DESIGN, SETTING, AND PARTICIPANTS: Twenty-four French university departments of urology participated in this retrospective study. INTERVENTION: All patients were treated according to current European Association of Urology guidelines. MEASUREMENTS: Age, sex, symptoms, tumour staging and grading, histologic subtype, and outcome were recorded in a unique database. Categoric and continuous variables were compared by using chi-square and student statistical analyses. Cancer-specific survival (CSS) was assessed by Kaplan-Meier and Cox methods. RESULTS AND LIMITATIONS: The study included 1250 RCC patients: 303 with ESRD and 947 from the general population. In the ESRD patients, age at diagnosis was younger (55 ± 12 yr vs 62 ± 12 yr); mean tumour size was smaller (3.7 ± 2.6 cm vs 7.3 ± 3.8 cm); asymptomatic (87% vs 44%), low-grade (68% vs 42%), and papillary tumours were more frequent (37% vs 7%); and poor performance status (PS; 24% vs 37%) and advanced T categories (≥ 3) were more rare (10% vs 42%). Consistently, nodal invasion (3% vs 12%) and distant metastases (2% vs 15%) occurred less frequently in ESRD patients. After a median follow-up of 33 mo (range: 1-299 mo), 13 ESRD patients (4.3%), and 261 general population patients (27.6%) had died from cancer. In univariate analysis, histologic subtype, symptoms at diagnosis, poor PS, advanced TNM stage, high Fuhrman grade, large tumour size, and non-ESRD diagnosis context were adverse predictors for survival. However, only PS, TNM stage, and Fuhrman grade remained independent CSS predictors in multivariate analysis. The limitation of this study is related to the retrospective design. CONCLUSIONS: RCC arising in native kidneys of ESRD patients seems to exhibit many favourable clinical, pathologic, and outcome features compared with those diagnosed in patients from the general population