Prédiction de la forme d'une fissure se propageant dans une structure épaisse d'aluminium réparée à l'aide d'un renfort collé en matériaux composites

Développée dans les années 70, la réparation des structures métalliques à l'aide de matériaux composites s'est avérée un moyen efficace et fiable pouvant être employé sur des structures aéronautiques. Ce type de réparation a été utilisé avec succès sur des avions civils et militaires afin de réparer des dommages causés par la présence des fissures ou simplement pour améliorer la vie en fatigue des structures très sollicitées. Cette technique a donc pour but de ralentir ou d'arrêter la progression des fissures afin de prolonger la vie des structures. Dans le but de répondre aux exigences des programmes de tolérance aux dommages visant à assurer la navigabilité de l'appareil, il est nécessaire de développer des modèles fiables permettant de prédire le taux de propagation des fissures se propageant sous des réparations en matériaux composites. Ces modèles permettraient d'établir les intervalles d'inspections sans avoir recourt à des programmes de tests dispendieux. Un modèle fiable de prédiction de la propagation des fissures est un des éléments clés qui aiderait à la reconnaissance de cette technologie dans le but qu'elle soit utilisée massivement dans l'industrie aéronautique. En 2001, Martec Limitée a complété une étude visant à évaluer différents outils d'initiation et de propagation des fissures dans des structures épaisses d'aluminium réparées à l'aide de renforts en matériaux composites. L'approche développée avait permis d'obtenir de bons résultats dans le cas des réparations où les deux cotés de la structure étaient réparés, mais n'avait pas permis d'obtenir le même niveau de fiabilité pour les réparations où la structure n'était réparée que d'un seul côté. Il avait donc été recommandé d'étudier l'effet de la forme de la fissure comme étant un facteur pouvant améliorer la précision des modèles permettant de prédire la vie en fatigue des structures réparées d'un seul côté. Par conséquent, une nouvelle méthodologie permettant de modéliser la propagation des fissures a été développée pour le cas des structures épaisses réparées à l'aide de renforts en matériaux composites. L'approche choisie repose sur l'utilisation des méthodes d'éléments finis en trois dimensions et considère les effets suivants : les contraintes thermiques résiduelles induites par la cuisson du renfort, les déplacements hors-plan et la forme particulière de la fissure se propageant dans une structure réparée d'un seul côté. La méthodologie fut validée en utilisant trois sources de données expérimentales indépendantes et en comparant la forme des fissures et la vie en fatigue des coupons testés avec celles obtenues numériquement. La méthodologie proposée a permis d'obtenir une corrélation très forte entre les résultats expérimentaux de vie en fatigue et ceux obtenus numériquement. De plus, il a été démontré que l'ajout de l'effet de la forme des fissures se propageant dans des structures réparées d'un seul côté permettait d'améliorer significativement la précision des analyses de vie en fatigue. Cette étude présente donc les résultats d'un projet de recherche amorcé par Martec Limitée et menée en collaboration avec le Ministère de la Défense nationale, le centre de recherche et développement pour la défense du Canada, ainsi que l'Université de Sherbrooke. Ce projet a été réalisé dans le cadre du régime de partenariat pour études de maîtrise et de doctorat en milieu de travail de l'université de Sherbrooke.Abstract: Developed in the 1970's, the composite bonded repair technology has been proven to be an efficient and reliable method for use on metallic aircraft structures. The purpose of this method is to slow or arrest crack growth, and thus, prolong the life of the structure. The technology has been successfully used in repair applications on both military and civil aircraft for fatigue enhancement and crack patching. However, the installation of composite bonded repairs on aircraft must satisfy their damage tolerance requirements to ensure the safe operation of the aircraft. To meet these requirements, reliable crack growth prediction models are one of the tools required to assess the safety of the repaired structures without the need for long and expensive test programs. Thus, accurate prediction tools are the key that will help this technology to be integrated in structural integrity programs by the aeronautical industry. In 2001, Martec Limited performed a research study intended to survey the available crack initiation and crack growth prediction tools for fatigue life evaluation of thick aluminium structures repaired using composite bonded doublers. The approach developed by Martec provided accurate crack growth predictions for the case of double-sided repairs, but did not provided the same level of accuracy for the single-sided repair configurations. It was therefore recommended by Martec to investigate the influence of crack shape on the crack growth predictions to achieve more accurate predictions for single-sided repair configurations. Consequently, a new systematic crack growth prediction methodology, based on 3D finite element methods, was developed for thick structures repaired using composite bonded doublers. The methodology considers effects specific to bonded composite repairs, such as the effect of thermal residual strains caused by the curing process, the effect of out-of-plane bending, and the crack shape. The methodology was tested using three different experimental tests found in literature. The experimental crack shapes and crack growth data were compared with numerical results. Good agreement between experimental and numerical crack growth predictions was obtained and the gain in accuracy acquired by including the shape of the crack was demonstrated. As part of a collaborative program on fatigue prediction of bonded repairs, Martec Limited has initiated this research project in collaboration with the Department of National Defence (DND), the Chief of Research And Development (CRAD), and Sherbrooke University. This project was conducted at Martec, under the auspices of the partnership program for masters and doctoral studies in the workplace of Sherbrooke University

Culturally Sensitive Carbohydrate Sources for Nepalese with Diabetes or Prediabetes

Over 8,000 refugees have started new lives in Vermont since 1980. Many of these people utilize the Community Health Centers of Burlington, for some this may be their first time navigating America\u27s healthcare system. This is a daunting task due to a multitude of barriers, including missing cultural competencies in various aspects of their care. This project focuses on dietary recommendations for Nepalese patients with prediabetes and type 2 diabetes, specifically carbohydrate sources based on fiber content. Type 2 diabetes is a very prevalent chronic disease that costs Vermont $520 million each year. Understanding healthy food options in a culturally sensitive approach, will allow better care and recommendations for the Nepalese. A Nepalese-focused handout on carbohydrate sources was generated based on local Asian markets that they frequent.https://scholarworks.uvm.edu/fmclerk/1901/thumbnail.jp

Balance And Gait Training To Reduce Fall Risk In A Patient With Bilateral Foot And Hand Deformities Secondary To Rheumatoid Arthritis: A Case Report

Each year, one out of three adults over the age of 65 sustains a fall. Although the risk of suffering a fall increases with age, falls are not an unavoidable aspect of the aging process. Fall risk can be heightened in patients with medical comorbidities that impact the physiological senses which help maintain balance. Rheumatoid arthritis (RA) is a chronic inflammatory disorder that affects the lining of the joints and causes painful swelling that can eventually result in bone erosion and joint deformity. The fall incidence rate in individuals with RA is 0.62 falls per person per year as compared to a fall incidence rate of 0.45 falls per person per year in healthy elderly individuals. The purpose of this case report was to provide an overview of the physical therapy plan of care for a patient at high risk for falls. Procedural interventions focused on balance and gait training while accommodating for the patient’s bilateral foot and hand deformities secondary to RA.https://dune.une.edu/pt_studcrposter/1048/thumbnail.jp

Evaluation of BART for measuring available bandwidth in an industrial application

We report results from a field study using the BART method for measuring available bandwidth in a local IP-network for use in train cars. The test was performed on physical hardware in a laboratory environment for a set of two cars. Test results indicate that BART measurement is viable

Algebraic properties of generalized Rijndael-like ciphers

We provide conditions under which the set of Rijndael functions considered as permutations of the state space and based on operations of the finite field \GF (p^k) ($p\geq 2$ a prime number) is not closed under functional composition. These conditions justify using a sequential multiple encryption to strengthen the AES (Rijndael block cipher with specific block sizes) in case AES became practically insecure. In Sparr and Wernsdorf (2008), R. Sparr and R. Wernsdorf provided conditions under which the group generated by the Rijndael-like round functions based on operations of the finite field \GF (2^k) is equal to the alternating group on the state space. In this paper we provide conditions under which the group generated by the Rijndael-like round functions based on operations of the finite field \GF (p^k) ($p\geq 2$) is equal to the symmetric group or the alternating group on the state space.Comment: 22 pages; Prelim0

Elliptic Reciprocity

The paper introduces the notions of an elliptic pair, an elliptic cycle and an elliptic list over a square free positive integer d. These concepts are related to the notions of amicable pairs of primes and aliquot cycles that were introduced by Silverman and Stange. Settling a matter left open by Silverman and Stange it is shown that for d=3 there are elliptic cycles of length 6. For d not equal to 3 the question of the existence of proper elliptic lists of length n over d is reduced to the the theory of prime producing quadratic polynomials. For d=163 a proper elliptic list of length 40 is exhibited. It is shown that for each d there is an upper bound on the length of a proper elliptic list over d. The final section of the paper contains heuristic arguments supporting conjectured asymptotics for the number of elliptic pairs below integer X. Finally, for d congruent to 3 modulo 8 the existence of infinitely many anomalous prime numbers is derived from Bunyakowski's Conjecture for quadratic polynomials.Comment: 17 pages, including one figure and two table

Evaluation of Adaptive FRIFS Method through Several Classification Comparisons

International audienceAn iterative method to select suitable features for pattern recognition context has been proposed (FRIFS). It combines a global feature selection method based on the Choquet integral and a fuzzy linguistic rule classifier. In this paper, enhancements of this method are presented. An automatic step has been added to make it adaptive to process numerous features. The experimental study, made in a wood defect recognition context, is based on several classifier result analysis. They show the relevancy of the remaining set of selected features. The recognition rates are also considered for each class separately, showing the good behavior of the proposed method

Concert recording 2018-03-06

[Track 1]. Songs of longing and desire, op. 156. I. Gift [Track 2]. II. Having Left [Track 3]. III. America / Bradley A. Bombardier text by Jonathan Dallas -- [Track 4]. Die Lebendigen und die Todten. I. Die Todten [Track 5]. II. Die Lebendigen / Robert K. Mueller -- [Track 6]. String quartet, no. 4. I. Flowing [Track 7]. II. Moderato [Track 8]. III. Scherzo-adagietto [Track 9]. IV. Cortege / Bombardier -- [Track 10]. Flowers of heaven. I. The home village [Track 11]. II. Wildflowers of the mountain [Track 12]. III. Return to heaven / Mueller -- [Track 13]. Into the lion\u27s den / Bombardier -- [Track 14]. A still small voice. I. Wind [Track 15]. II. Quake [Track 16]. III. Fire / Mueller

Solar Powered Electric Vehicle Charger

This project will look into how to create an efficiently-operated solar powered electric vehicle charger. The solar panel will harvest energy from the sun that will be stored a battery pack to be readily available to charge an electric vehicle. These stations could be commercialized to be located along a highway, or personalized for a in-house installation