Academic literature on the topic 'Rupture par fatigue'

Les travaux présentés dans cet article s’inscrivent dans un projet de R&D mis en place par RTE (Réseau de Transport d’Electricité) et visant à évaluer le vieillissement des conducteurs électriques de lignes aériennes par des outils de simulation numérique. Après avoir rappelé la géométrie de tels conducteurs et l’utilisation qui en est faite, le principal risque d’endommagement de ces derniers est présenté. Il s’agit du phénomène de fretting-fatigue intervenant à proximité des systèmes de fixation des conducteurs au niveau des pylônes, pouvant produire la rupture de brins les constituant. Ainsi, une méthodologie originale est proposée de façon à évaluer, par l’intermédiaire d’un modèle éléments finis, la durée de vie des conducteurs vis-à-vis de ce risque. Cette méthodologie est ensuite appliquée sur un cas-test dont les données proviennent de la littérature. Enfin, des perspectives sont données concernant le modèle numérique employé et l’intégration de la démarche dans le projet de R&D concerné.

Une des étiquettes diagnostiques qu’il ne faut souhaiter à personne est peut-être celle de « patient bien connu du service ». Car il est souvent question alors de répétitions, de chronicité et de fatigue, sinon d’épuisement de l’imagination thérapeutique. Confronté à ces expériences difficiles les équipes évoquent alors le caractère bienvenu d’un « séjour de rupture ». Mais si ce dernier apporte à chacun un repos bien mérité, il ne permet guère, en général, d’aller plus loin. La Maison Hospitalière, ouverte en juillet 2011, à Cergy-le-Haut, a pour vocation d’utiliser de manière active ces fameux séjours de rupture. Accueillant non le patient en tant que tel, mais la situation en question, la Maison Hospitalière propose de réunir sur un rythme mensuel : le patient qui y est hospitalisé, sa famille, l’équipe soignante qui a prescrit le séjour et l’équipe de la Maison Hospitalière. Ces échanges ont lieu au cours de la Réunion Partenaires conduite par un thérapeute systémicien externe (qui ne fait pas partie de l’équipe de la Maison Hospitalière). L’organisation générale, topographique (il s’agit d’une clinique psychiatrique insérée dans un hôtel-restaurant ouvert à la clientèle extérieure) et fonctionnelle (équipe soignante, hôtelière, éducative, administrative différenciées et non hiérarchisées) sera présentée. Une première évaluation des résultats de ce type de travail sera discutée, tant sous l’angle de la modification des parcours de ces patients multi-hospitalisés que sous l’angle de la surprise et de la créativité retrouvée par les protagonistes d’une situation…dont l’impasse et la répétition n’étaient, dans une importante proportion, qu’une figure possible « d’évolution ».

Les contraintes que le gel développe dans une roche poreuse humide sont de deux espèces : 1) des contraintes d’origine thermique intrinsèquement en régime transitoire; 2) des contraintes dues au gonflement de l’eau humectant la roche lors de l’engel. Ce sont ces contraintes que nous étudions ici à partir d’un modèle mathématique simple : une sphère creuse à l’intérieur de laquelle se développe une pression pi. Lamé (1852) a donné l’équation des contraintes qui apparaissent en un point quelconque de la masse solide en fonction de pi. Par ailleurs, les théories de l’élasticité permettent de déterminer la pression Peq qui se développe dans la cavité au moment de l’engel. Connaissant cette pression, la répartition des contraintes qu’elle provoque dans la matière et la résistance de la roche, on peut déterminer s’il y a ou non fissuration ou éclatement de la roche sphérique. En étendant ce principe aux roches poreuses, il est possible de déterminer un taux critique de porosité au-dessus duquel le gel conduit à la rupture. Mais dans les roches, il faut tenir compte du fait que les canalicules du réseau de porosité débouchant à l’extérieur, il y a extrusion de la glace au moment de l’engel. D’autre part, les roches de la couche superficielle de l’écorce terrestre ayant subi de nombreux cycles de contraintes dues aux variations de température en particulier accusent une certaine fatigue qui diminue leur résistance mécanique.

An important link in the analysis of the longevity of details by the criterion of fatigue strength is the calculation of parameters that take into account the peculiarities of the technological regime in terms of load and the corresponding number of cycles that affect the accumulation of fatigue failure. The final range of loads of knitting needles of automatic half-hose machine was based on the systematization of amplitudes of forces depending on the frequency of their implementation. Previous works has assumed the assumption of a one interaction of the needle heel with the cams, which is experimentally refuted by the example of modern high-speed automatic half-hose machine. The aim of the work is to adjust the provisions of calculating the load of knitting needles of half-hose machines for design estimate of longevity, taking into account the specific features of the impacts of needles with the cams of the knitting system, which affect the total number of load cycles. The condition of rupture of the contact in the pair of the needle heel and the inclined cam after their impact is considered, taking into account the inertial and rigid parameters of the system, including the resisting force of the needle in the groove of the cylinder. According to the results of the dynamic analysis, the expressions of the minimum speed at which the needle can rebound from the cam and the vertical component of the needle rebound speed at the moment of its separation from the cam are obtained. The analysis of the influence of the force of resistance of the needle movement in the race on the vertical speed of the needle is performed. The issue of the bounce of the heels of unselected needles from the lower edge of the inclined cam due to their inertial run-out was studied separately. It is established that at certain circular speeds of the needle cylinder leads to additional impacts of the needles with the horizontal limiting cams and increases their destruction. The results of studies of the possible rebound of the needle heel from the inclined cam and the interaction of the needle with the limiting horizontal cams are a supplement to the method of calculating the loading of needles and are aimed at improving the accuracy of design longevity of needles.

En France, en Allemagne et en Belgique, la durée annuelle moyenne de travail par personne en emploi est passée de près de 3000 heures en 1870 à environ 2300 heures en 1938 en Allemagne et en Belgique (1850 heures en France). Après la seconde guerre mondiale, la tendance à la diminution s’est poursuivie. Depuis une vingtaine d’années, la durée de travail hebdomadaire à temps plein, telle que fixée par les conventions collectives, ne baisse que très lentement en Belgique. D’autres phénomènes, dont le développement du temps partiel, expliquent toutefois que la durée annuelle moyenne de travail continue à baisser. En 2003, elle s’élèverait selon l’OCDE à environ 1450 heures/an. Or, voici que depuis quelques mois, les médias font grand cas d’entreprises où la durée hebdomadaire de travail s’allonge sans compensation salariale. Cette inversion de la tendance historique est clairement une rupture, au contenu économique mais aussi symbolique chargé. Que penser de ce retournement, actuellement limité à un petit nombre d’entreprises ?
 En comparaison internationale, la durée hebdomadaire moyenne de travail à temps partiel est plus longue en Belgique. Concernant les travailleurs à temps plein, la durée hebdomadaire moyenne habituelle est en Belgique proche de la moyenne dans la zone EURO. Au niveau sectoriel, si l’on excepte le secteur des hôtels et des restaurants, notre durée hebdomadaire habituelle se situe également à un niveau proche de la moyenne dans la zone EURO. Notre pays ne paraît donc pas se démarquer sensiblement des voisins. La dispersion des durées hebdomadaires habituelles augmente en revanche entre les individus à un rythme qui n’a guère d’égal dans l’OCDE. Au plan régional, entre 1992 et 2002, un écart d’une heure par semaine s’est créé entre les travailleurs flamands et wallons à temps plein, ces derniers ayant une durée habituelle de travail relativement stable.
 Aucune "loi économique" ne nous dit quel serait le temps de travail idéal. En revanche, des divergences sensibles de coût de production ne peuvent persister pour des produits similaires soumis à la concurrence. Les coûts de production ne s’expliquent évidemment pas que par les coûts et la productivité du travail. Dans les limites de cette étude, nous n’avons toutefois pas abordé d’autres dimensions. Nous avons aussi mené notre réflexion dans les limites du cadre actuel marqué notamment par une concurrence accrue sur les marchés, une forte mobilité du capital et une monnaie unique. La loi de juillet 1996 relative "à la promotion de l’emploi et à la sauvegarde préventive de la compétitivité" se préoccupe de l’évolution de nos coûts salariaux horaires nominaux dans le secteur privé en comparaison avec celle de l’Allemagne, des Pays-Bas et de la France. Après quelques années d’alignement quasi parfait de notre croissance salariale sur l’évolution moyenne de nos trois voisins, la Belgique a récemment accumulé un écart relatif de 2 points de pourcentage. Si l’on tient compte des écarts existants avant la loi de 1996 et que l’on remonte plus haut dans le temps jusqu’en 1987, le FEB aboutit à un surcroît de coût salarial horaire de 8 points de pourcentage par rapport à la moyenne pondérée de nos trois voisins. Dans l’industrie manufacturière, selon le Bureau of Labor Statistics, nos coûts salariaux horaires sont 6 % plus bas qu’en Allemagne mais 5 % plus élevés qu’aux Pays-Bas et 32 % plus élevés qu’en France. Des coûts salariaux élevés engendrent une série d’ajustements dans les entreprises : disparition d’entreprises privées manquant de rentabilité, recherche de gains de productivité par élimination de main d’œuvre et surtout de main d’œuvre moins qualifiée, etc. La productivité du travailleur belge est, de fait, fort élevée. Il ne nous paraît cependant pas souhaitable d’avoir des performances exceptionnelles en matière de hausses de productivité du travail si cela se réalise au prix de disparitions supplémentaires d’emplois moyennement ou peu qualifiés. La capacité des personnes concernées à saisir les opportunités d’emploi dans d’autres segments de l’économie apparaissent en effet trop limitées.
 Dans un contexte où les nations européennes et leurs partenaires sociaux sont responsables de l’évolution des coûts salariaux, il est possible d’intervenir sur trois variables : les salaires horaires bruts, les cotisations patronales et la durée du travail. Le niveau élevé des cotisations patronales mais aussi l’importance des allégements de cotisation mis en place sont notoires en Belgique. Le meilleur usage des allégements structurels (c’est-à-dire durables et attribués par travailleur occupé, nouvellement ou non) se situe au niveau des travailleurs à bas salaires. Nous avons déjà argumenté en ce sens. De même, nous avons déjà rappelé la nécessité de la modération des salaires horaires en Belgique et nous avons évoqué les avantages et les limites de la "norme salariale" belge. Dans le cadre de celle-ci, la résorption de notre écart de coût salarial horaire ne pourra être que lente, fort probablement trop lente. De là, l’intérêt d’une réflexion sur le temps de travail.
 A court terme, considérant le niveau de production comme fixe, une durée de travail plus longue entraînera une diminution du volume d’effectifs souhaité par l’entreprise. Moins les heures ajoutées seront productives (effet de fatigue du travailleur), plus les effets de court terme seront faibles. Au-delà de ces réactions de court terme, l’entreprise peut se réorganiser de telle sorte que la durée d’utilisation du capital suive – là où c’est possible - l’allongement de la durée du travail. La variation du coût salarial sera l’autre déterminant essentiel de l’ajustement à moyen terme des quantités produites et de l’emploi. Notre analyse micro-économique indique que l’allongement de la durée hebdomadaire de travail mais aussi la poursuite de la réduction de celle-ci peuvent être des réponses microéconomiques alternatives face à des phénomènes tels que l’accroissement de la concurrence de pays à bas salaires. Mais dans un cas comme dans l’autre, ce ne sera vrai que si on accompagne ces modifications de durée du travail d’ajustements de nature et d’ampleur appropriés. En cas de hausse de la durée hebdomadaire, le coût salarial hebdomadaire ne peut croître proportionnellement. En cas de baisse de la durée, il ne peut demeurer à son niveau initial. Il faut aussi souligner l’importance de l’ajustement de la durée d’utilisation du capital. Celle-ci ne peut diminuer proportionnellement à la durée du travail. Elle doit croître lorsque cette durée s’allonge. Il faut dès lors vérifier la faisabilité des réorganisations du processus de production qui en découlent. Au-delà, il faut s’interroger sur leur désirabilité du point de vue des travailleurs. La conciliation des vies professionnelle et privée est au cœur du questionnement.

En France, en Allemagne et en Belgique, la durée annuelle moyenne de travail par personne en emploi est passée de près de 3000 heures en 1870 à environ 2300 heures en 1938 en Allemagne et en Belgique (1850 heures en France). Après la seconde guerre mondiale, la tendance à la diminution s’est poursuivie. Depuis une vingtaine d’années, la durée de travail hebdomadaire à temps plein, telle que fixée par les conventions collectives, ne baisse que très lentement en Belgique. D’autres phénomènes, dont le développement du temps partiel, expliquent toutefois que la durée annuelle moyenne de travail continue à baisser. En 2003, elle s’élèverait selon l’OCDE à environ 1450 heures/an. Or, voici que depuis quelques mois, les médias font grand cas d’entreprises où la durée hebdomadaire de travail s’allonge sans compensation salariale. Cette inversion de la tendance historique est clairement une rupture, au contenu économique mais aussi symbolique chargé. Que penser de ce retournement, actuellement limité à un petit nombre d’entreprises ?
 En comparaison internationale, la durée hebdomadaire moyenne de travail à temps partiel est plus longue en Belgique. Concernant les travailleurs à temps plein, la durée hebdomadaire moyenne habituelle est en Belgique proche de la moyenne dans la zone EURO. Au niveau sectoriel, si l’on excepte le secteur des hôtels et des restaurants, notre durée hebdomadaire habituelle se situe également à un niveau proche de la moyenne dans la zone EURO. Notre pays ne paraît donc pas se démarquer sensiblement des voisins. La dispersion des durées hebdomadaires habituelles augmente en revanche entre les individus à un rythme qui n’a guère d’égal dans l’OCDE. Au plan régional, entre 1992 et 2002, un écart d’une heure par semaine s’est créé entre les travailleurs flamands et wallons à temps plein, ces derniers ayant une durée habituelle de travail relativement stable.
 Aucune "loi économique" ne nous dit quel serait le temps de travail idéal. En revanche, des divergences sensibles de coût de production ne peuvent persister pour des produits similaires soumis à la concurrence. Les coûts de production ne s’expliquent évidemment pas que par les coûts et la productivité du travail. Dans les limites de cette étude, nous n’avons toutefois pas abordé d’autres dimensions. Nous avons aussi mené notre réflexion dans les limites du cadre actuel marqué notamment par une concurrence accrue sur les marchés, une forte mobilité du capital et une monnaie unique. La loi de juillet 1996 relative "à la promotion de l’emploi et à la sauvegarde préventive de la compétitivité" se préoccupe de l’évolution de nos coûts salariaux horaires nominaux dans le secteur privé en comparaison avec celle de l’Allemagne, des Pays-Bas et de la France. Après quelques années d’alignement quasi parfait de notre croissance salariale sur l’évolution moyenne de nos trois voisins, la Belgique a récemment accumulé un écart relatif de 2 points de pourcentage. Si l’on tient compte des écarts existants avant la loi de 1996 et que l’on remonte plus haut dans le temps jusqu’en 1987, le FEB aboutit à un surcroît de coût salarial horaire de 8 points de pourcentage par rapport à la moyenne pondérée de nos trois voisins. Dans l’industrie manufacturière, selon le Bureau of Labor Statistics, nos coûts salariaux horaires sont 6 % plus bas qu’en Allemagne mais 5 % plus élevés qu’aux Pays-Bas et 32 % plus élevés qu’en France. Des coûts salariaux élevés engendrent une série d’ajustements dans les entreprises : disparition d’entreprises privées manquant de rentabilité, recherche de gains de productivité par élimination de main d’œuvre et surtout de main d’œuvre moins qualifiée, etc. La productivité du travailleur belge est, de fait, fort élevée. Il ne nous paraît cependant pas souhaitable d’avoir des performances exceptionnelles en matière de hausses de productivité du travail si cela se réalise au prix de disparitions supplémentaires d’emplois moyennement ou peu qualifiés. La capacité des personnes concernées à saisir les opportunités d’emploi dans d’autres segments de l’économie apparaissent en effet trop limitées.
 Dans un contexte où les nations européennes et leurs partenaires sociaux sont responsables de l’évolution des coûts salariaux, il est possible d’intervenir sur trois variables : les salaires horaires bruts, les cotisations patronales et la durée du travail. Le niveau élevé des cotisations patronales mais aussi l’importance des allégements de cotisation mis en place sont notoires en Belgique. Le meilleur usage des allégements structurels (c’est-à-dire durables et attribués par travailleur occupé, nouvellement ou non) se situe au niveau des travailleurs à bas salaires. Nous avons déjà argumenté en ce sens. De même, nous avons déjà rappelé la nécessité de la modération des salaires horaires en Belgique et nous avons évoqué les avantages et les limites de la "norme salariale" belge. Dans le cadre de celle-ci, la résorption de notre écart de coût salarial horaire ne pourra être que lente, fort probablement trop lente. De là, l’intérêt d’une réflexion sur le temps de travail.
 A court terme, considérant le niveau de production comme fixe, une durée de travail plus longue entraînera une diminution du volume d’effectifs souhaité par l’entreprise. Moins les heures ajoutées seront productives (effet de fatigue du travailleur), plus les effets de court terme seront faibles. Au-delà de ces réactions de court terme, l’entreprise peut se réorganiser de telle sorte que la durée d’utilisation du capital suive – là où c’est possible - l’allongement de la durée du travail. La variation du coût salarial sera l’autre déterminant essentiel de l’ajustement à moyen terme des quantités produites et de l’emploi. Notre analyse micro-économique indique que l’allongement de la durée hebdomadaire de travail mais aussi la poursuite de la réduction de celle-ci peuvent être des réponses microéconomiques alternatives face à des phénomènes tels que l’accroissement de la concurrence de pays à bas salaires. Mais dans un cas comme dans l’autre, ce ne sera vrai que si on accompagne ces modifications de durée du travail d’ajustements de nature et d’ampleur appropriés. En cas de hausse de la durée hebdomadaire, le coût salarial hebdomadaire ne peut croître proportionnellement. En cas de baisse de la durée, il ne peut demeurer à son niveau initial. Il faut aussi souligner l’importance de l’ajustement de la durée d’utilisation du capital. Celle-ci ne peut diminuer proportionnellement à la durée du travail. Elle doit croître lorsque cette durée s’allonge. Il faut dès lors vérifier la faisabilité des réorganisations du processus de production qui en découlent. Au-delà, il faut s’interroger sur leur désirabilité du point de vue des travailleurs. La conciliation des vies professionnelle et privée est au cœur du questionnement.

Boxing is a purely masculine activity and it inhabits a purely masculine world. […] Boxing is for men, and it is about men, and is men. (Joyce Carol Oates) IntroductionWriting about boxing is an intimate, private, and unusual activity. Although a decade has passed since I first “stepped into the ring” (sparring or fighting), I have not engaged with boxing in academic terms. I undertook a doctoral degree from 2012 to 2016, during which I competed and won amateur titles in three different countries. Boxing, in a sense, shadowed my research. My fieldwork, researching heritage foods networks, brought me to various locales, situating my body in reference to participants and academics as well as my textual analysis. My daily interactions and reflections in the boxing gym, though, were marginalised to give priority to my doctorate. In a mirrored journey to Wacquant’s “carnal ethnography of the skilled body” (Habitus 87), I boxed as a hobby. It was a means to escape my life as a doctoral student, my thesis, and the library. Research belonged to the realm of academia; boxing, to the realm of the physical. In this paper, I seek to implode this self-imposed distinction.Practising the “noble art,” as boxing is commonly called, profoundly altered not only my body but also my way of seeing the world, myself, and others. I explore these themes through an autoethnographic account of my experience in the ring. Focusing on sparring, rather than competing, I explore conceptualisations of my face as a material, as well as part of my body, and also as a surface for violence and apprenticeship. Reflecting upon a decade of sparring, the analysis presented in this paper is grounded in the phenomenological tradition whereby knowledge is not an abstract notion that exists over and above felt experience: it is sensed and embodied through practice.I delve into the narratives of my personal “social logic of a bodily craft” of boxing (Wacquant, Habitus 85). More specifically, I reflect upon my experiences of getting hit in the face by men in the ring, and the acclimatisation required, evolving from feelings of intrusion, betrayal, and physical pain to habit, and at times, excitement. As a surface for punching, my face became both material and immaterial. It was a tool that had to be tuned to varying degrees of pain to inform me of my performance as well as my opponent’s. Simultaneously, it was a surface that was abstracted and side-lined in order to put myself purposefully in harm’s way as one does when stepping into the ring. Through reflecting on my face, I consider how the sport offered new embodied experiences through which I became keenly aware of my body as a delineated target for—as well as the source of—violence. In particular, my body boundaries were profoundly reconfigured in the ring: sparring partners demonstrated their respect by hitting me, validating both my body and my skill as a boxer. In this manner, I discuss the spatiality of the ring as eliciting transitions of felt and abstracted pain as well as shaping my self-image as a re-gendered boxer in the ring and out. Throughout my account, I briefly engage with Wacquant’s discussion of “pugilistic habitus” (Body 99) and his claims that boxing is the epitome of masculine valour. In the final section, I conclude with deliberations upon the new bodily awareness(es) I gained through the sport, and the re-materiality I experienced as a strong woman.Methodological and Conceptual FrameworksThe analysis in this paper is based on the hybrid narrative of ethnography and autobiography: autoethnography. In the words of Tami Spry, autoethnography is “a self-narrative that critiques the situatedness of self and others in social context” (710). As such, I take stock in hindsight (Bruner; Denzin) of the evolution of my thoughts on boxing, my stance as a boxer, and the ways the ring has affected my sense of self and my body.Unlike Wacquant's “carnal ethnography” (Habitus 83) whose involvement with boxing was foregrounded in an academic context where he wrote detailed field-notes and conducted participant observation, my involvement was deliberately non-academic until I began to write this paper. Based on hindsight, the data collected through this autoethnography are value-inflected in ways that differ from other modes of data collection. But I have sought to recreate a dialectic between perceptual experience and cultural practices and patterns, in a manner aligned with Csordas’s paradigm of embodiment. My method is to “retrospectively and selectively write about epiphanies that stem from, or are made possible by, being part of a culture” (Ellis et al. 276) of boxing. These epiphanies, as sensed and embodied knowledge, were not solely conceptual moments but also physical realisations that my body performed, such as understanding—and executing—a well-timed slip to the side to avoid a punch.Focusing on my embodied experiences in the ring and out, I have sought to uncover “somatic modes of attention:” the “culturally elaborated ways of attending to and with one’s body in surroundings that include the embodied presence of others” (Csordas 138). The aim of this engagement is to convey my self-representation as a boxer in the ring, which emerged in part through the inter-subjectivity of interacting with other boxers whilst prioritising representations of my face. As such, my personal narrative is enmeshed with insights gleaned during embodied epiphanies I had in the ring, interweaving storytelling with theory.I have chosen to use the conventions of storytelling (Ellis and Ellingson) to explore the defining moments that shaped the image I hold of myself as a boxer. My personal narrative—where I view myself as the phenomenon—seeks “to produce aesthetic and evocative thick descriptions of personal and interpersonal experience” (Ellis et al. 287) whilst striving to remain accessible to a broader audience than within academia (Bochner). Personal narratives offer an understanding of the “self or aspect of a life as it intersects with a cultural context, connect to other participants as co-researchers, and invite readers to enter the author's world and to use what they learn there to reflect on, understand, and cope with their own lives” (Ellis 14; see also Ellis et al. 289).As the focus of my narrative is my face, I used my body, in Longhurst et al.’s words, as the “primary tool through which all interactions and emotions filter in accessing subjects and their geographies” (208). As “the foundation of the entire pugilistic regimen”, the body is the site of an intimate self-awareness, of the “body-sense” (Heiskanen 26). Taking my body as the starting point of my analysis, my conceptual framework is heavily informed by Thrift’s non-representational theory, enabling me to inquire into the “skills and knowledges [people] get from being embodied beings” (127), and specifically, embodied boxers. The analysis presented here is thus based on an “epistemic reflexivity” (Wacquant, Habitus 89) and responds to what Wacquant coins the “pugilistic habitus” (Body 99): a set of acquired dispositions of the boxer. Bourdieu believes that people are social agents who actively construct social reality through “categories of perception, appreciation and action” (30). The boxing habitus needs to be grasped with one’s body: it intermingles “cognitive categories, bodily skills and desires which together define the competence and appetence specific to the boxer” (Wacquant, Habitus 87). Through this habitus, I construct an image of myself not only as a boxer, but also as a re-gendered being, directly critiquing Wacquant’s arguments of the “pugilist” as fundamentally male.Resistance to Female BoxingMischa Merz’s manuscript on her boxing experience is the most accurate narrative I have yet read on female boxing, as a visceral as well as incorporeal experience, which led Merz to question and reconsider her own identity. When Merz published her manuscript in 2000, six years before I put the gloves on, the boxing world was still resisting the presence of women in the ring. In the UK, licenses for boxing were refused to women until 1998, and in New South Wales, Australia, it was illegal for women to compete until December 2008. It was not until 2012 that female boxing became internationally recognised as a sport in its own right. During the London Olympics, after a sulphurous debate on whether women should be made to box in skirts to “differentiate” them from men, women were finally allowed to compete in three weight categories, compared to ten for men.When I first started training in 2006 at the age of 21, I was unaware of the long list of determined and courageous women who had carved their way—and facilitated mine—into the ring, fighting for their right to practise a sport considered men’s exclusive domain. By the time I started learning the “sweet science” (another popular term used for boxing), my presence was accepted, albeit still unusual. My university had decreed boxing a violent sport that could not be allowed on campus. As a result, I only started boxing when I obtained a driving licence, and could attend training sessions off-campus. My desire to box had been sparked five years before, when I viewed Girlfight, a film depicting a young woman’s journey into the ring. Until then, I had never imagined a woman could box, let alone be inspirational in the use of her strength, aggression, and violence; to be strong was, for me, to be manly—which, as a woman, translated as monstrous or a perversion. I suddenly recognised in boxing a possibility to rid myself of the burden of what I saw as my bulk, and transform my body into a graceful pugilist—a fighter.First Sparring SessionTwo months after I had first thrown a punch in my coach’s pad—the gear coaches wear to protect their hands when a boxer is punching them to train—I was allowed into the ring to spar. Building up to this moment, I had anticipated and dreaded my first steps in the ring as the test of my skill and worthiness as a boxer. This moment would show my physical conditioning: whether I had trained and dieted correctly, if I was strong or resilient enough to fight. More crucially, it would lay bare my personality, the strength of my character, the extent of my willpower and belief in myself: it would reveal, in boxing terminology, if I had “heart.” Needless to say I had fantasised often about this moment. It was my initiation into the art of being punched and I hoped I would prove myself a hardened individual, capable of withstanding pain without flinching or retreating.The memory of the first punch to my face—my nose, to be exact—remains clear and vivid. My sparring partner was my coach, a retired boxer who hit me repeatedly in the head during the entirety of my first round. Getting hit in the face for the first time is a profound moment of rupture. Until then, my face had been a bodily surface reserved for affective gestures by individuals of trust: kisses of greeting on the cheeks or caresses from lovers. Only once had I been slapped, in an act of aggression that had left me paralysed with shock and feeling violated. Now in the ring, being punched in the face by a man I trusted, vastly more experienced and stronger than I, provoked a violent reaction of indignation and betrayal. Feelings of deceit, physical intrusion, and confusion overwhelmed me; pain was an entirely secondary concern. I had, without realising, assumed my coach would “go easy” on me, softening his punches and giving me time to react adequately to his attacks as we had practised on the pads. A couple of endless minutes later, I stepped out of the ring, breathless and staring at the floor to hide my tears of humiliation and overwhelming frustration.It is a common experience amongst novices, when first stepping into the ring, to forget everything they have been taught: footwork, defence, combinations, chin down, guard up … etc. They often freeze, as I did, with the first physical contact. Suddenly and concretely, with the immediacy of pain, they become aware of the extent of the danger they have purposely placed themselves in. The disturbance I felt was matched in part by my belief that I was essentially a coward. In an act condemned by the boxing community, I had turned my face away from punches: I tried to escape the ring instead of dominating it. Merz succinctly describes this experience in the boxing realm: “aspects of my character were frequently tossed in my face for assessment. I saw gaping holes in my tenacity, my resilience, my courage, my athleticism” (49). That night, I felt an unfamiliar sting as I took my jumper off, noticing a slight yet painful bruise on the bridge of my nose. It reminded me of my inadequacy and, I believed at the time, a fundamental failure of character: I lacked heart.My Face: A Tool for Sensing and Ignoring PainTo get as accustomed as a punching bag to repeated hits without flinching I had to mould my face into a mask of impassivity, revealing little to my opponent. My face also became a calibrated tool to measure my opponent’s skill, strength, and intent through the levels of pain it would experience. If an opponent repeatedly targeted my nose, I knew the sparring session was not a “friendly encounter.” Most often though, we would nod at each other in acknowledgement of the other’s successful “contact,” such as when their punches hurt my body. The ring is the only space I know and inhabit where the display of physical violence can be interpreted as a “friendly gesture” (Merz 12).Boxers, like most athletes, are carefully attuned to measuring the degrees of pain they undergo during a fight and training, whilst accomplishing the paradoxical feat—when they are hit—of setting aside that pain lest it be a distraction. In other words, boxers’ bodies are both material and immaterial: they are sites for accessing sensory information, notably pain levels, as well as tools that—at times detrimentally—have learned to abstract pain in the effort to ignore physical limitations, impediments or fatigue. Boxers with “heart,” I believe, are those who inhabit this duality of material and immaterial bodies.I have systematically been questioned whether I fear bruising or scarring my face. It would seem illogical to many that a woman would voluntarily engage in an activity that could blemish her appearance. Beyond this concern lies the issue, as Merz puts it, that “physical prowess and femininity seem to be so fundamentally incompatible” (476). My face used to be solely a source of concern as a medium of beautification and the platform from which I believed the world judged my degree of attractiveness. It also served as a marker of distinction: those I trusted intimately could touch my face, others could not. Throughout my training, my face evolved and also became an instrument that I conditioned and used strategically in the ring. The bruises I received attested to my readiness to exchange punches, a mark of valour I came to relish more than looking “nice.”Boxing has taught me how to feel my body in new ways. I no longer inhabit an “absent body” (Leder). I intimately know the border between my skin and the world, aware of exactly how far my body extends into that world and how much “punishment” (getting hit) it can withstand: boxing—which Oates (26) observed as a spectator rather than boxer—“is an act of consummate self-determination—the constant re-establishment of the parameters of one’s being.” A strong initial allure of boxing was the strict discipline it gave to my eating habits, an anchor—and at times, a torture—for someone who suffered from decade-long eating disorders. Although boxing plagued me with the need to “make weight”—to fight in a designated weight category—I no longer sought to be as petite as I could manage. As a female boxer, I was reminded of my gender, and my “unusual” body, as I am uncommonly big, strong, and heavy compared to most female fighters. I still find it difficult to find women to spar with, let alone fight. Unlike in the world outside the gym, though, my size is something I continuously learn to value as an advantage in the ring, a tool for affirmation, and significantly, a means of acceptance by, and equality with, men.The Ring: A Place of Re-GenderingAs sparring became routine, I had an epiphany: what I had taken as an act of betrayal from my coach was actually one of respect. Opponents who threw “honest” (painful) punches esteemed me as a boxer. I have, to this day, very rarely sparred with women. I often get told that I punch “like a guy,” an ability with which I have sought to impress coaches and boxers alike. As such, I am usually partnered with men who believe, as they have told me, that hitting a “girl”—and even worse, hitting a girl in the face—is simply unacceptable. Many have admitted that they fear hurting me, though some have quickly wanted to after a couple of exchanges. I have found that their views of “acceptable” violence seem unchanged after a session, as I believe they have come to view me as a boxer first and as a woman second.It would be disingenuous to omit that boxing attracted me as much for the novelty status I have gained within and outside of it. I have often walked a thin line between revelling in the sense of belonging that boxing provides me—anchored in a feeling that gender no longer matters—and the acute sense of feeling special because I am a woman performing as a man in what is still considered a man’s world. I have wavered between feeling as though I am shrugging off the very notion of gender in the ring, to deeply reconsidering what my gender means to me and the world, embracing a more fluid and performative understanding of gender than I had before (Messner; Young).In a way, my sense of self is shaped conflictingly by the ways in which boxers behave towards me in the ring, and how others see me outside of the boxing gym. As de Bruin and de Haan suggest, my body, in its active dimension, is open to the other and grounds inter-subjectivity. This inter-subjectivity of embodiment—how other bodies constitute my own sensory and perceptual experience of being-in-the-world—remains ambivalent. It has led me to feel at times genderless—or rather, beyond gender—in the ring and, because of this feeling, I simultaneously question and continuously re-explore more vividly what can be understood as “female masculinity” (Halberstam). As training progressed, I increasingly felt that:If women are going to fight, we have to be reminded, at every chance available, time and again, that they are still feminine or capable, at least, of wearing the costume of femininity, being hobbled by high heels and constrained by tight dresses. All female athletes in a way are burdened with having to re-iterate this same public narrative. (Merz)As I learned to box, I also learned to delineate myself alongside the ring: as I questioned notions of gender inside, I consequently sought to reaffirm a specific and static idea of gender through overt femininity outside the ring, as other female athletes have also been seen to do (Duncan). During my first years of training, I was the only woman at the gyms I trained in. I believed I had to erase any physical reminders of femininity: my sport clothes were loose fitting, my hair short, and I never wore jewellery or make-up. I wanted to be seen as a boxer, not a woman: my physical attractiveness was, for once, irrelevant. Ironically, I could not conceive of myself as a woman in the ring, and did not believe I could be seen as a woman in the ring. Outside the gym, I increasingly sought to reassert a stereotypical feminine appearance, taking pleasure in subverting another set of beliefs. People are usually hesitant to visualise a woman in a skirt, without a broken nose, as a competitive fighter with a mouth guard and headgear. As Wacquant succinctly put it, “I led a sort of Dr. Jekyll-and-Mr. Hyde existence” (Habitus 86), which crystallised when one of my coaches failed to recognise me on three occasions outside the gym, in my “normal” clothes.I have now come to resent profoundly the marginal, sensationalised status that being a boxer denotes for a woman. This is premised on particular social norms surrounding gender, which dictate that if a woman boxes, she is not “your usual” woman. I have striven to re-gender my experience, especially in light of the recent explosion of interest in female boxing, where new norms are being established. As I have trained around the world, including in Cuba, France, and the USA, and competed in the UK, Mexico, and Belgium, I have valued the tacit connection between those who practice the “noble art.” Boxing fashions a particular habitus (Bourdieu), the “pugilistic habitus” (Wacquant, Body 12). Stepping into the ring, and being able to handle getting hit in the face, constitutes a common language that boxers around the world, male and female, understand, value, and share; a language that transcends the tacit everyday embodiments of gender and class. Boxing is habitually said to give access to an upward mobility (Wacquant, Habitus; Heiskanen). In my case, as a white, educated, middle-class woman, boxing has given me access to cross-class associations: I have trained alongside men who had been shot in Coventry, were jobless in Cuba, or dealt with drug gangs in Mexico. The ring is an equalising space, where social, gender—and in my experience, ethnic—divides can be smoothed down to leave the pugilistic valour, the property of boxing excellence, as the main metric of appreciation.The freedom I have found in the ring is one that has allowed my gendered identity to be thought of in new and creative ways that invite continuous revision. I have discovered myself not solely through the prism of a gendered lens, but as an emotive athlete, and as a person desperate to be accepted despite—or because of—her physical strength. I find myself returning to Merz’s eloquence: “boxing cannot help but make you question who you really are. You cannot hide from yourself in a boxing ring. It might seem a crazy path to self-knowledge, but to me it has been the most rich, rewarding, and perhaps, the only true one” (111). Using Wacquant’s own words to disprove his theory that boxing is fundamentally a virile activity that reaffirms specific notions of masculinity, to become a boxer is to “efface the distinction between the physical and the spiritual [...] to defy the border between reason and passion” (Body 20). In my view, it is to implode the oppositional definitions that have kept males inside the ring and females, out. The ring, in ways unrivalled elsewhere, has shown me that I am not reducible, as the world has at times convinced me, to my strength or my gender. I can, and indeed do, coalesce and transcend both.ConclusionAfter having pondered the significance of the ring to my life, I now begin to understand Merz’s journey as “so much more than a mere dalliance on the dark side of masculine culture” (21). When I box, I am always boxing against myself. The ring is the ultimate space of revelation, where one is starkly confronted with one’s own weaknesses and fears. As a naked mirror, the ring is also a place for redemption, where one can overcome flaws, and uncover facets of who one is. Having spent almost as much time at university as I have boxing, it was in the ring that I learned that “thinking otherwise entails being otherwise, relating to oneself, one’s body, and ambient beings in a new way” (Sharp 749). Through the “boxing habitus,” I have simultaneously developed a boxer’s body and habits as well as integrated new notions of gender. As an exercise in re-gendering, sparring has led me to reflect more purposefully on the multiplicity of meanings that gender can espouse, and on the possibilities of negotiating the world as both strong and female. Practising the “noble art” has given me new tools with which to carve out, within the structures of the society I inhabit, liberating possibilities of being a pugilistic woman. However, I have yet to determine if women have fashioned a space within the ring for themselves, or if they still need to reaffirm a gendered identity in the eyes of others to earn the right to get hit in the face.References Bochner, Arthur P. “It’s about Time: Narrative and the Divided Self.” Qualitative Inquiry 3.4 (1997): 418–438.Bourdieu, Pierre. The Logic of Practice. Stanford, California: Stanford UP, 1990.Bruner, Jerome. “The Autobiographical Process.” The Culture of Autobiography: Constructions of Self-Representation. Ed. Robert Folkenflik. Vol. 6. Stanford UP, 1993. 38–56.Csordas, Thomas. “Somatic Modes of Attention.” Cultural Anthropology 8.2 (1993): 135–156.De Bruin, Leon, and Sanneke de Haan. “Enactivism and Social Cognition: In Search of the Whole Story.” Cognitive Semiotics 4.1 (2009): 225–50.Denzin, Norman K. Interpretive Biography. London: Sage, 1989.Duncan, Margaret C. “Gender Warriors in Sport: Women and the Media.” Handbook of Sports and Media. Eds. Arthur A. Raney and Jennings Bryant. Lawrence Erlbaum Associates, 2006. 231–252.Ellis, Carolyn. The Ethnographic I: A Methodological Novel about Autoethnography. Walnut Creek, CA: AltaMira Press, 2004.Ellis, Carolyn, Tony E. Adams, and Arthur P. Bochner. “Autoethnography: An Overview.” Historical Social Research/Historische Sozialforschung (2011): 273–90.Ellis, Carolyn, and Laura Ellingson. “Qualitative Methods.” Encyclopedia of Sociology. Eds. Edgar F. Borgatta and Rhonda JV Montgomery. Macmillan Library Reference, 2000. 2287–96.Halberstam, Judith. Female Masculinity. Durham: Duke UP, 1998.Heiskanen, Benita. The Urban Geography of Boxing: Race, Class, and Gender in the Ring. Vol. 13. Routledge, 2012.Girlfight. Dir. Karyn Kusama. Screen Gems, 2000.Leder, Drew. The Absent Body. Chicago: U of Chicago P, 1990.Longhurst, Robyn, Elsie Ho, and Lynda Johnston. “Using ‘the Body’ as an Instrument of Research: Kimch’i and Pavlova.” Area 40.2 (2008): 208–17.Messner, Michael. Out of Play: Critical Essays on Gender and Sport. New York: SUNY Press, 2010.Merz, Mischa. Bruising: A Boxer’s Story. Sydney: Pan Macmillan, 2000.Oates, Joyce Carol. On Boxing. Garden City, New York: Harper Collins, 1987.Sharp, Hasana. “The Force of Ideas in Spinoza.” Political Theory 35.6 (2007): 732–55.Spry, Tami. “Performing Autoethnography: An Embodied Methodological Praxis.” Qualitative Inquiry 7.6 (2001): 706–32.Thrift, Nigel. “The Still Point: Resistance, Expressive Embodiment and Dance.” Geographies of Resistance (1997): 124–51.Wacquant, Loïc. Body & Soul. New York: Oxford UP, 2004.———. “Habitus as Topic and Tool: Reflections on Becoming a Prizefighter.” Qualitative Research in Psychology 8.1 (2011): 81–92.Young, Iris Marion. Throwing like a Girl and Other Essays in Feminist Philosophy and Social Theory. Bloomington, Indiana: Indiana UP, 1990.

Thèse (D.Eng.) -- Université du Québec à Chicoutimi, 2008.<br>La p. de t. porte en outre: Doctorat en ingénierie, thèse pour l'obtention du titre de Philosophiae Doctor en ingénierie. CaQQUQ Comprend des réf. bibliogr. (f. 174-178). Publié aussi en version électronique. CaQQUQ

Cette thèse est une contribution à l'analyse probabiliste des ponts métalliques ou mixtes en fatigue. Dans cette thèse, nous proposons des méthodes originales, pour calculer l'indice de fiabilité ß et évaluer la probabilité de ruine, basées respectivement sur le modèle d'endommagement linéaire de Miner et sur la loi de propagation de fissure de Paris à seuil, qui prennent en compte les aléas quantifiés sur les charges de trafic réel et sur la résistance déduite des essais de fatigue. L'application du théorème central limite permet des calculs analytiques explicites du dommage cumulé. La modélisation de l'avancement de fissure par processus Markovien simplifie les calculs de la distribution de probabilité. Un programme informatique est fait pour calculer l'intégrale J et pour déterminer le facteur d'intensité de contraintes.

Cette étude a pour objectif de déterminer un outil de galetage optimisé, et donc de diminuer les frais indirects de production pour Renault. Elle s'appuie sur des observations expérimentales et sur des simulations numériques afin de comprendre les phénomènes entrant en jeu dans la rupture de l'outil de galetage, qui permettent de conclure à une rupture de sous-couche et une rupture superficielles selon les conditions de contact dans l'outil. Cette analyse préliminaire permet en outre de mettre au point un modèle numérique utilisé pour l'optimisation de l'outil. La phase d'optimisation est composée d'une partie numérique, qui permet de tracer une première esquisse des paramètres optimaux pour l'outil de galetage, et d'une partie expérimentale, qui confirme de manière très claire les tendances des simulations numériques. Enfin, ces travaux ont permis d'aboutir à un outil performant, qui a permis de réduire les frais de production de Renault. D'autres outils brevetés ont été testés.

Cette etude a pour objet de comparer les mecanismes de fissuration par fatigue d'un alliage d'aluminium-lithium du type 8090c t851 et le 2024 t351, sous chargements d'amplitude constante et sous spectres representatifs des sollicitations subies par l'intrados d'une aile d'avion. Sous chargement d'amplitude constante, la resistance a la fissuration, a l'air et sous vide, du 8090c t851 est superieure ou egale a celle du 2024 t351. La difference s'amenuise lorsqu'il s'agit d'essais a l'air et a r eleve. Ce comportement est attribue a l'effet de fermeture. Sous chargement d'amplitude variable, la resistance a la fissuration sous vide de l'alliage aluminium-lithium est nettement superieure a celle de l'alliage 2024 alors que, sous air, les vitesses de fissuration sont quasi similaires pour les deux alliages. L'etude des micro-mecanismes permet d'identifier trois mecanismes principaux: 1) un mecanisme appele stade i-like, a caractere cristallographique dominant du a l'activation d'un seul systeme de glissement selon un plan 111, 2) un mecanisme associe a la propagation suivant un plan 100 par activation de glissement selon deux plans 111, 3) le mecanisme associe a l'activation de plusieurs systemes de glissement simultanes (stade ii) avec un plan moyen de fissuration 100. L'analyse quantitative des facies de rupture montre que dans le 8090c t851 le mode de rupture predominant depend des conditions de sollicitation et d'environnement, tandis que dans le 2024 t351, le mecanisme de fissuration predominant est toujours le stade ii. Cette analyse permet d'etablir des modeles de prevision de duree de vie

La fatigue représente la deuxième cause d’endommagement des structures métalliques anciennes après la corrosion. Celle-ci se manifeste par l’apparition de fissures, dans les zones fortement sollicitées présentant des concentrations de contraintes importantes, et peut mener à terme à la ruine de l’ouvrage. Dans le cas des structures métalliques anciennes, les fissures de fatigue s’amorcent généralement au droit des trous de rivets rendant difficile leur détection par les techniques de contrôle non destructif conventionnelles. De même, les matériaux métalliques anciens de la construction, et notamment le fer puddlé, limitent l’utilisation de certaines techniques. Dans le cadre de ce travail de thèse, l’objectif principal est d’étudier l’efficacité d’un renforcement par composites collés dans le cas de fissures de fatigue émanant de trous de rivets. Pour cela, des éprouvettes de petites dimensions, présentant un perçage central et une unique fissure de fatigue en bord de perçage, ont été considérées. De même, deux matériaux métalliques, acier doux et fer puddlé, ainsi que deux procédés de renforcement PRFC (polymères renforcés de fibres de carbone), à Module Normal et à Ultra Haut Module, sont étudiés. Pour chaque procédé de renforcement, différentes configurations de renforcement ont été testées et notamment la mise en précontrainte du plat composite MN avant collage. Cela a permis de mettre en évidence l’efficacité de la technique de collage de plats PRFC pour un renforcement à la fatigue de matériaux métalliques anciens. Par ailleurs, les expressions analytiques simples proposées pour le facteur d’intensité de contraintes pourront par la suite être utilisés pour une application aux structures rivetées en tenant compte de la présence du rivet ainsi que celle des plaques assemblées<br>After corrosion, fatigue phenomenon is the main cause of damage in old metallic structures. Fatigue cracks appear in stress concentration area subject to high stresses, and can lead to the ruin of the bridge. In old metallic structures, fatigue cracks mainly occur at the edge of the rivet hole and are thus difficult to detect with the common non-destructive inspection technique (NDI). Moreover, due to the poor quality of the old metallic materials, particularly puddled iron, some of the NDI techniques cannot be used. The main objective of the present work is to study the effectiveness of carbon fibre reinforced polymer (CFRP) laminates in reinforcing fatigue crack emanating from the rivet hole. Thus, investigations on small-scale specimens were done. These specimens consist of metallic plates with center hole from which one single crack emanates. Two metallic materials, puddled iron and mild steel, and two reinforcement processes were used. These reinforcement processes consist of Normal Modulus (NM) and Ultra High Modulus (HHM) CFRP laminates. Furthermore, symmetrical and un-symmetrical reinforcement configurations are considered as well as pre-stressing NM laminates before application. The experimental results showed firstly the efficiency of the different studied reinforcement configurations in slowing down crack propagation. In conclusion of this work, the achieved results, particularly those in terms of Stress Intensity Factor, could be used for reinforcement of riveted structures by CFRP bonding, taking into account the presence of rivets as well as the presence of the others elements of the assembly

L'etude proposee a pour vocation une meilleure comprehension du comportement endommageable de stratifies composites a fibres longues de carbone et a matrice organique sous cyclage thermique. Deux approches, experimentale et analytique, sont utilisees, s'appuyant sur les connaissances deja acquises en fatigue mecanique. Des stratifies croises, sollicites en fatigue mecanique et en cyclage thermique, ont montre des similitudes de comportement de la fissuration matricielle. Ces analogies ont permis d'identifier une analyse du type diffusion du cisaillement ou shear lag en cyclage thermique, prealablement validee pour la seule sollicitation de fatigue mecanique. Bien que les cinetiques beaucoup plus rapides en cyclage thermique ne puissent etre correctement estimees par le modele identifie en fatigue mecanique, les previsions concernant l'amorcage et les valeurs de densite a saturation sont en tres bon accord avec les resultats experimentaux.

La maîtrise des mécanismes de rupture dans les problèmes de fretting requiert une analyse pluridisciplinaire des différents phénomènes physiques couplés pour prendre en compte les effets globaux et locaux, les sollicitations multiaxiales non proportionnelles et les conditions de contact interfacial avec frottement. Un modèle tridimensionnel éléments finis étendus mufti-échelles dédié au contact avec frottement entre les faces de la fissure est proposé. Une formulation faible mixte à trois champs permet une définition intrinsèque de la fissure avec sa propre discrétisation indépendante du maillage de la structure. Un solveur stabilisé adapté de la méthode LATIN est implémenté. Les propriétés de stabilité et les performances du modèle sont illustrées dans plusieurs exemples bidimensionnels et tridimensionnels. Le modèle est validé par comparaison avec un code éléments finis industriel. Une stratégie mufti-modèles globale basée sur l'analyse expérimentale et la simulation numérique de la propagation des fissures est développée afin de prédire la durée de vie de composants en frelling fatigue. Des essais de fretting fatigue sont réalisés afin d'analyser l'amorçage et la propagation de fissures. Les sollicilatrons tribologiques au cours du cycle sont déterminées par la résolution du contact deux-corps. La prédiction du risque d'amorçage des fissures est conduite. Ces résultats sont utilisés comme données d'entrée pour la modélisation X-FEM des essais de frettlng bidimensionnels et tridimensionnels. La simulation de la propagation des fissures est réalisée à l'aide de critères de propagation multiaxiale non proportionnels et d'une loi de propagation expérimentale<br>Fretting fatigue crack modelling in a predictive approach requires a multi-physical analysis of the numerous global and local affects such as the mufti-axial non proportional loading and the frictional contact conditions between the crack faces. A 30 multi-scale extended finite element model dedicated to frictional crack growth is developed. The use of a three-field weak formulation allows an intrinsic definition of the crack interface with its own discretization independent from the structure mesh. A stabilized solver based on the LATIN method is proposed. Two- dimensional and three-dimensional examples illustrate the stability and the performances of the model. It is validated using comparisons with an industrial finite element code. A global mufti-model strategy based on experimental and numerical crack analysis is proposed to predict fife time of components subjected to fretting fatigue. Fretting tests are performed ta analyse crack initiation and crack growth. The two-body contact loading is computed. Crack risk prediction is conducted. These results are used as input data for 20 and 30 numerical X-FEM modelling of the fretting test. Crack growth simulation is performed using mufti-axial fatigue criteria and experimental crack growth law

Ce manuscrit est une contribution à l’étude de la propagation de fissure en fatigue à très grand nombre de cycles. Nous développons un outil numérique permettant de modéliser cette propagation de fissure en mode I et d’étudier la formation de l’œil de poisson, caractéristique de ce type de rupture. Premièrement, une procédure numérique itérative basée sur la méthode des éléments finis en 3D est développée pour étudier l’évolution de la forme de fissure au cours de la propagation et calculer le nombre de cycles de propagation lorsqu’un calcul analytique n’est pas possible. La méthode de fermeture virtuelle de fissure est utilisée pour calculer le facteur d’intensité de contraintes en chaque étape de propagation de la fissure. Deuxièmement, un modèle de couplage thermomécanique basé sur la méthode des éléments finis en 3D est proposé pour estimer l’évolution du champ température au cours de la propagation de fissure. Ce modèle consiste à tout d’abord calculer l’énergie de déformation plastique par cycle venant de la zone plastique cyclique au front de la fissure et utiliser ensuite une partie de cette énergie comme une source de chaleur mobile afin de calculer l’évolution de température. L’énergie de déformation plastique par cycle est déterminée par deux méthodes. L’une est basée sur un calcul élastoplastique en 3D avec un comportement élastique plastique parfait. L’autre s’appuie sur une relation empirique entre l’énergie de déformation plastique par cycle par unité de longueur de fissure et la variation du facteur d’intensité de contraintes. Les résultats numériques sont en bon accord avec des mesures expérimentales<br>This manuscript is a contribution to the study of the crack propagation in very high cycle fatigue domain. We develop a numerical tool which allows to model this crack propagation in mode I and to study the formation of fish eye crack, a characteristic of this failure. Firstly, an iterative numerical procedure based on three dimensional finite element method is developed to study the evolution of crack form during the crack propagation and to calculate the number of cycles to failure when it is not possible to find an analytical solution. The virtual crack closure technique is used to calculate the stress intensity factor in each step of crack growth process. Secondly, a coupled thermomecanical finite element model in 3D is proposed to estimate the evolution of the temperature field during the crack propagation. The problem is solved into 2 steps. In the first step, we calculate the plastic energy per cycle from the cyclic plastic zone at the crack front. In the second step, we use a fraction of this energy as a mobile heat source to estimate the temperature field evolution. The plastic energy per cycle is calculated by two methods. The first one is based on an elastic-plastic finite element analysis with a perfectly elastic-plastic constitutive law. The second one is based on an empirical relation between the energy plastic per cycle per unit of crack length and the range of stress intensity factor. Numerical results obtained agree fairly well with experimental results

Le but de cette etude est de caracteriser, par la methode de diffraction des rayons x, le niveau des contraintes residuelles et de l'ecrouissage sur les pieces rompues par propagation de fissure en fatigue sur un alliage d'aluminium 7175 t7351. Dans une partie preliminaire, une calibration entre la deformation plastique imposee et la largeur de pic de diffraction a ete effectuee et l'influence de la rugosite de surface sur la determination de contrainte par drx a ete mise en evidence par experimentation, sur la surface de rupture, les effets des conditions de charge cyclique, de la rugosite de surface de rupture et la fermeture de fissure sur les distributions de contrainte residuelle et de l'ecrouissage ont ete mis en evidence. Dans les sous-couches de rupture, les trois stades d'evolution de contraintes residuelles en fonction de la profondeur ont ete discutes en tenant compte des effets des conditions de charge cyclique, de la rugosite de surface de piece rompue et de la fermeture de fissure. Les deformations plastiques equivalentes ont ete estimees par l'intermediaire de la largeur de pic de diffraction des rayons x. Les valeurs de taille de zone plastique monotone trouvees a partir des evolutions de contrainte residuelle et de la largeur de pic correspondent bien a celles evaluees par le modele de levy

Abstract This chapter discusses the structural limits in Section III NB and Section VIII Division 2 as related to specific structural failure modes considered applicable to pressure vessel and piping design. The rules and requirements for Section III NB and Section VIII Division 2 are based on the design-by-analysis philosophy addressing specific structural failure modes of structural collapse, rupture, instability, fatigue, and progressive deformation. The chapter begins with a discussion on the interactions between materials, environments, mechanical, and thermal loads as aided by other disciplines since this is critical for every part of every pressure vessel design. It provides a brief history of development of Code analytic tools and discusses the use of elastic 3D finite element analysis (FEA) results and the application of elastic-plastic (EP)-FEA. The chapter then discusses the intent of the primary stress limits in the Code. Consideration is given to the definitions in the Code and the discussion in the Criteria document. The chapter then addresses why the primary-plus-secondary stress intensity range is necessary and shows how to apply it. Two procedures for calculating stress intensity are presented, and the impact of thermal stresses is discussed for definition and application. The chapter also discusses six areas in which the Code presents fundamental procedures and expands on these fundamentals by presenting guidelines for a singular view of acceptable procedures that are consistent with the original intent for Section III and consistent with the current rules. Finally, it comments on the elastic-plastic FEA methods to protect against plastic collapse, to determine protection against local failure, and to assess fatigue and ratchet limits. History Tom Ahl was the original author of this chapter for the first edition. Marcus N. Bressler updated this chapter for the second and third editions. Chakrapani Basavaraju updated this chapter for the fourth, fifth and sixth editions. The current online edition has been updated by Chakrapani Basavaraju and Jason Lambin.

Abstract Composite materials have drawn considerable consideration from the offshore business, basically because of their high explicit quality. Notwithstanding weight decrease, composites offer extra advantages, for example, fatigue resistance, damping, and thermal (protection) properties, and high erosion resistance. As a part of design procedure there are requirements of mechanical strength based on criteria referring to failure modes, such as rupture by over loading, fatigue failures, buckling or an unstable fracture. Three dimensional nonlinear assessment of riser is carried out in time domain using ABAQUS/Aqua. The response time histories so obtained are used for the study of fatigue safety assessment of riser. It is based on a bi-linear approach to model fatigue crack growth and incorporates a failure limit to describe the interaction between rupture and plastic failure. Using Monte Carlo Simulation, tests of fatigue reliability and fatigue crack size evolution are obtained. It is observed that bilinear S-N curve and crack growth models leads to higher estimate of fatigue life. Sensitivity behavior pertinent to limit state adopted has been thoroughly examined. These outcomes implicate assessment of components of the marine structures to ensure minimization of the surprises due to wide scatter of the fatigue phenomenon in marine environment.

The U. S. Department of Energy’s Advanced Turbine Systems (ATS) program supports the development of high efficiency gas turbines for industrial and power generation applications. As part of this program, CMSX-10K, a third generation single crystal Ni-base superalloy, is being considered for use in turbine blade applications in an ATS engine. In support of the design and casting process development of CMSX-10K, assessment of component tolerance to casting defects was performed. Single crystal specimens with primary axis orientation between 4 and 26 degrees and bicrystal specimens with low angle boundaries (LABs) having between 0 and 18 degrees of misorientation were used. The effects of primary axis misorientation and LABs on critical mechanical properties were evaluated. Primary axis misorientation of greater than 15 degrees reduced tensile and high-cycle fatigue properties. Similarly, stress rupture properties were reduced for primary axis misorientation of greater than 20 degrees. LABs having greater than 10 degrees of misorientation caused significantly reduced stress rupture life. LABs having greater than 12 degrees of misorientation also resulted in reduced tensile and high-cycle fatigue properties.

A continuum damage mechanics (CDM) coupled unified viscoplasticity model has been developed to predict the creep-fatigue life of modified Grade 91 steel. A tertiary creep model termed MPC-Omega codified in Part 10 of API (and also implemented in the ASME BP&amp;V Code for Grade 22V and more recently Grade 91 Steel) is also employed for creep damage evaluation. As MPC-Omega has a direct relationship with Larson-Miller parameter (LMP) coefficients, creep damage coefficients in the unified constitutive model (UCM) are tied with MPC-Omega coefficients in order to utilize WRC and API 579-1 Grade 91 creep rupture database. The model is validated against long-term creep, LCF, creep-fatigue and TMF experimental responses at T = 20–600°C.

The Working Group on Design by Analysis in collaboration with the Working Group on Elevated Temperature Construction has developed a proposal for elevated temperature analysis in the ASME Boiler and Pressure Vessel Code Section VIII Division 2 Part 5, Design by Analysis. Elevated temperature is defined as the temperature where the allowable stress is time-dependent, that is, controlled by creep. The proposal is divided into the potential failure modes: rupture, ratcheting, fatigue, buckling, and service conditions. Linear elastic and inelastic analysis options rely on published approaches. The focus of the presentation will be on the Linear Elastic analysis options which include a fatigue screening, a ratcheting assessment, and an assessment for burst. Multiple conditions are allowed in the analysis. The proposed rules will be presented.

The method of strain range partitioning developed by Manson offers a possibility for treatment of creep-fatigue interactions. It partitions the strain-range of a complex hysteresis loop into four elementary strain range types. Although the method has its merits it is difficult to apply because of lacking experimental data and difficult loop reconstructions. The paper describes an approach which separates the inelastic strain range only into a fatigue portion and a creep portion following both a power law Coffin-Manson relationship. Coefficients and exponents were determined by a simple least square fitting procedure from a set of literature data. The plastic part agreed very well with the experimentally determined fatigue curve. The creep part could, however, only be understood using fatigue-modified stress rupture data accounting for cyclic softening. With this approach it was possible to determine number of cycles to creep failure as a function of the pure creep strain range. This procedure was applied to a set of literature data of grade 91 steel which covered a temperature range of 500°C, 550°C, 600°C with stress controlled and strain controlled hold-times. Life-times were predicted in a range corresponding with the scatter of pure fatigue or creep curves, which means that a very good agreement was obtained. The paper will give a thorough description of the procedure and demonstrate its applicability to design codes.

Depleting oil reserves in shallow water are opening the avenues of new ventures in deep sea conditions. India is no exception; deep sea explorations are highly recommended and exercised. As part of the design process, there are requirements of structural strength based on criteria referring to failure modes, such as rupture by over loading, fatigue failures, buckling or an unstable fracture. 3D Nonlinear dynamic analysis of riser is obtained in the time domain using finite element solver ABAQUS/Aqua. The response histories so obtained are employed for the study of fatigue reliability analysis of riser. It is based on a bi-linear relationship to model fatigue crack growth and incorporates a failure criterion to describe the interaction between fracture and plastic collapse. Uncertainty modeling, especially on fatigue crack growth parameters, is undertaken with the aid of recently published data in support of the bi-linear crack growth relationship. Results pertaining to fatigue reliability and fatigue crack size evolution are presented using Monte Carlo Simulation. The bi-linear S-N curve and crack growth models are found to lead to higher fatigue life estimation. Sensitivity behavior pertinent to limit state adopted has been thoroughly investigated. These findings implicate inspection schemes for components of the marine structures to ensure minimization of the surprises due to wide scatter of the fatigue phenomenon in marine environment.

The stress concentration factor (SCF) for the roots of screw threads in bolted joints under static loadings is analyzed using 3-D elastic FEM taking account the spiral of screw threads. At first, the stress states at the roots of screw threads in initial clamping state in a bolted joint where two hollow cylinders were clamped with a bolt and a nut were analyzed in initial clamping. The elastic FEM result of SCF for the first root was obtained as SCF=3.2. When the bolt was clamped in initial clamping (preload) at the 60 % of bolt yield stress, the plastic deformations were found at the first and the second roots, and non-engaged screw threads. It was found that as the external tensile loads increased, the development in plastic deformation region increased from the first root to the other roots as well as the non-engaged screw threads. It was found that the rupture occurred from the non-engaged screw threaded part while the plastic deformation increased at each root of screw threads. The numerical result was coincided with the experimental result. In the experiments, it was observed that the rupture occurred from the non-engaged screw thread and not from the first root of screw thread. Also, the bolt fatigue was predicted from FEM and it was shown that a fatigue fracture occurred from the first root.

As part of the xLPR (Extremely Low Probability of Rupture) project, the stress intensity factor (SIF) solutions required for crack growth calculations were updated. This involved extension of existing solutions and development of new solutions as well. For surface cracks, the Universal Weight Function Method (UWFM) was implemented to handle complex stress distributions. In addition, a crack transition model was developed to more accurately capture the surface to through-wall crack transition. Finally, solutions for idealized through-wall cracks were extended to various pipe sizes and longer crack lengths. In this paper, the SIF (K) solutions in xLPR Version 2.0 were validated against existing experimental data. The SIF modules in the xLPR code were used to simulate fatigue crack growth of circumferential cracks in pipes under bending up to wall penetration and to through-wall crack transition stage until idealized through-wall cracks were formed. The predicted fatigue crack growth results (mainly crack shape evolution) using the xLPR K-solutions provided good agreement with experimental data.

Marine riser is a major component of offshore drilling and productions systems that are either fixed or floating. Since, a marine riser is intended to remain in station for the productive life of an oil field; it will be exposed to wide variety of hazards, with the potential for environmental damage, structural failure or damage to the material. As part of the design process, there are requirements of structural strength based on criteria referring to failure modes, such as rupture by over loading, fatigue failures, buckling or unstable fracture. 3D Nonlinear dynamic analysis of riser is carried out in the time domain using finite element solver ABAQUS/Aqua. The response histories so obtained are employed for the study of fatigue and fracture reliability analysis of riser under random waves and random waves together-with vessel motion. In the present study application of structural concepts for the evaluation of the fatigue resistance of marine risers, including reliability techniques has been presented. The limit state function has been established for cumulative fatigue damage using S-N curve approach and fracture mechanics approaches considering number of parameters, random in nature. Reliability methods deal with the uncertain nature of loads, resistance etc. and lead to prediction of the failure and a rational measure of the safety coefficient. Response surface method (RSM) in conjunction with First Order Reliability Method (FORM) has been used for reliability estimation. The results are compared with Monte Carlo simulation method. The design point important for the probabilistic design is located on the failure surface. The effects of the uncertainties in various random variables on riser fatigue reliability are highlighted.

Abstract Recently, Barua et. al [ANL-20/03, 2020] developed new design rules for high temperature concentrating solar power metallic components. These rules are to be used in conjunction with the Section III, Division 5 rules of the ASME Boiler &amp; Pressure Vessel Code and include three design by analysis options — i) design by elastic analysis with reduced margin, ii) design by elastic analysis with reduced margin and simplified creep-fatigue evaluation, and iii) design by inelastic analysis. In this paper, we report the corresponding design data for a nickelbased high temperature alloy – Alloy 740H. The current Alloy 740H Code Case includes some basic material properties such as Young’s modulus, Poisson’s ratio, thermal properties, yield strength, tensile strength, and allowable stress So. However, a complete design check for high temperature components — i.e., primary load and buckling checks, ratcheting strain limits, and creep-fatigue evaluation — requires additional material data including allowable stress Sm, relaxation strength, isochronous stress-strain curves, minimum-stress-to-rupture Sr, fatigue diagrams, and creep-fatigue damage envelope. We construct these design data from the available material data in the literature and data generated recently at Idaho National Laboratory as part of a U.S. Department of Energy – Solar Energy Technology Office funded project. We also develop an inelastic constitutive model for use with the design by inelastic analysis method.

Over the past decade, several long-duration subduction earthquakes took place in different locations around the world, e.g., Chile in 2010, Japan in 2011, China in 2008, and Indonesia in 2004. Recent research has revealed that long-duration, large-magnitude earthquakes may occur along the Cascadia subduction zone of the Pacific Northwest Coast of the U.S. The duration of an earthquake often affects the response of structures. Current seismic design specifications mostly use response spectra to identify the hazard and do not consider duration effects. Thus, a comprehensive understanding of the effect of the duration of the ground motion on structural performance and its design implications is an important issue. The goal of this study was to investigate how the duration of an earthquake affects the structural response of special concentric braced frames (SCBFs). A comprehensive experimental program and detailed analytical investigations were conducted to understand and quantify the effect of duration on collapse capacity of SCBFs, with the goal of improving seismic design provisions by incorporating these effects. The experimental program included large-scale shake table tests, and the analytical program consisted of pre-test and post-test phases. The pre-test analysis phase performed a sensitivity analysis that used OpenSees models preliminarily calibrated against previous experimental results for different configuration of SCBFs. A tornado-diagram framework was used to rank the influence of the different modeling parameters, e.g., low-cycle fatigue, on the seismic response of SCBFs under short- and long-duration ground motions. Based on the results obtained from the experimental program, these models were revisited for further calibration and validation in the post-test analysis. The experimental program included three large-scale shake-table tests of identical single-story single-bay SCBF with a chevron-brace configuration tested under different ground motions. Two specimens were tested under a set of spectrally-matched short and long-duration ground motions. The third specimen was tested under another long-duration ground motion. All tests started with a 100% scale of the selected ground motions; testing continued with an ever-increasing ground-motion scale until failure occurred, e.g., until both braces ruptured. The shake table tests showed that the duration of the earthquake may lead to premature seismic failure or lower capacities, supporting the initiative to consider duration effects as part of the seismic design provisions. Identical frames failed at different displacements demands because of the damage accumulation associated with the earthquake duration, with about 40% reduction in the displacement capacity of the two specimens tested under long-duration earthquakes versus the short-duration one. Post-test analysis focused first on calibrating an OpenSees model to capture the experimental behavior of the test specimens. The calibration started by matching the initial stiffness and overall global response. Next, the low-cycle fatigue parameters were fine-tuned to properly capture the experimental local behavior, i.e., brace buckling and rupture. The post-test analysis showed that the input for the low-cycle fatigue models currently available in the literature does not reflect the observed experimental results. New values for the fatigue parameters are suggested herein based on the results of the three shake-table tests. The calibrated model was then used to conduct incremental dynamic analysis (IDA) using 44 pairs of spectrally-matched short- and long-duration ground motions. To compare the effect of the duration of ground motion, this analysis aimed at incorporating ground-motion variability for more generalized observations and developing collapse fragility curves using different intensity measures (IMs). The difference in the median fragility was found to be 45% in the drift capacity at failure and about 10% in the spectral acceleration (Sa). Using regression analysis, the obtained drift capacity from analysis was found to be reduced by about 8% on average for every additional 10 sec in the duration of the ground motion. The last stage of this study extended the calibrated model to SCBF archetype buildings to study the effect of the duration of ground motion on full-sized structures. Two buildings were studied: a three-story and nine-story build that resembled the original SAC buildings but were modified with SCBFs as lateral support system instead of moment resisting frames. Two planer frames were adopted from the two buildings and used for the analysis. The same 44 spectrally-matched pairs previously used in post-test analysis were used to conduct nonlinear time history analysis and study the effect of duration. All the ground motions were scaled to two hazard levels for the deterministic time history analysis: 10% exceedance in 50 years and 2% exceedance in 50 years. All analysis results were interpreted in a comparative way to isolate the effect of duration, which was the main variable in the ground-motion pairs. In general, the results showed that the analyzed SCBFs experienced higher drift values under the long-duration suite of ground motions, and, in turn, a larger percentage of fractured braces under long-duration cases. The archetype SCBFs analysis provided similar conclusions on duration effects as the experimental and numerical results on the single-story single-bay frame.