Academic literature on the topic 'Propagation des fissures'
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Journal articles on the topic "Propagation des fissures"
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Fan, Pingyang, Jianxin Liu, Wengui Zuo, Min Wang, and Daoyong Zhang. "Experimental Study of Rock-like Materials with Two Unequal Parallel Preexisting Fissures under Uniaxial Compression." Applied Sciences 12, no. 20 (October 15, 2022): 10404. http://dx.doi.org/10.3390/app122010404.
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Fissures substantially impact the engineering stability of rock masses, making research on rock masses with preexisting fissures essential for engineering activities. The development of specimens with different preexisting fissure types was examined in this study. Three different types of specimens with preexisting fissures can be broadly categorized: specimens with few preexisting fissures, specimens with multiple preexisting fissures, and specimens with preexisting fissures and other flaws. Uniaxial compression tests of specimens with preexisting fissures of two unequal lengths were conducted, and the influence of preexisting fissure angle, the distance between the two fissures and fissure length on the peak strength and coalescence mode of specimens were analyzed. A large preexisting fissure length significantly influenced the peak strength and coalescence, and the uniaxial compressive strength (UCS) values of the rock-like materials decreased. In contrast, increasing the long preexisting fissure length influenced the crack propagation and coalescence more extensively in the case of a long preexisting fissure. The preexisting fissure angle and two preexisting fissure distances had a negligible effect on the UCS values of the rock-like materials. However, with increasing long preexisting fissure length, the short preexisting fissure was subject to crack propagation and coalescence.
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Chen, Wei, Wen Wan, Yanlin Zhao, and Wenqing Peng. "Experimental Study of the Crack Predominance of Rock-Like Material Containing Parallel Double Fissures under Uniaxial Compression." Sustainability 12, no. 12 (June 25, 2020): 5188. http://dx.doi.org/10.3390/su12125188.
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Fractured rock mass is a relatively complex medium in nature. It plays a key role in various projects, such as geotechnical engineering, mining engineering and tunnel engineering. Especially, the interaction between fissures has a practical function in the guidance of safe production. This paper takes its research object as rock-like material which contains prefabricated parallel double fissures. It studies how the fissures’ length difference and spacing influence the failure of specimens under uniaxial compression, and analyzes them with fracture mechanics theory. The results include two aspects. Firstly, no matter how the length difference and spacing change, the upper fissure always generates new cracks. Secondly, the length difference and spacing produce three effects on the lower fissure. (1) The fissure propagates less obviously as the length difference increases. With the increase to 40mm, the propagation does not occur at all. (2) The decrease of spacing weakens the propagation. As it is reduced to 5 mm, the propagation stops. (3) The crack propagation is more sensitive to length difference than spacing. Regardless of spacing changes, if a length difference is large enough (40 mm or more), the new crack does not expand, while if it is small enough (10 mm or less), propagation always appears.
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Liu, Cong, Li Wei Chen, Yan Qiu Leng, and Jian Wei Qiao. "Numerical Simulation Analysis of Buried Ground Fissures’ Propagation in Xi’an." Applied Mechanics and Materials 170-173 (May 2012): 1218–25. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.1218.
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Ground fissure disasters are main environmental geological hazards in Xi’an. Therefore, carrying out researches on causes of cracks and mechanisms of hazard-formative, as well as setting economical and effectively countermeasures are major geological disaster puzzles to be solved.According to the key issues existing in the ground fissure researches, we use numerical simulation analysis method to solve them. Numerical simulation analysis shows that, it is reasonable that we use elastic breaking theory to describe its rupture propagation process. This paper introduces smeared crack model and explains the fracture morphology and process of sample which has microcracks inside it. Results show that such sample’s tensile strength is greatly weakened and its tensile failure is brittle fracture. Differential subsidence movement on both sides of the buried ground fissure (fault) not only leads to upwards propagation of existing cracks, whose tendency are opposite to the existing ones, but also leads to the development of nearly vertical crack belt, which is located on the uplift block and develop from top to down. Because of width of buried ground fissures’ affected zone depends on many factors, there are still lots of work to be done on the division of buried ground fissure’s deformation zone.
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Chen, Miao, Shengqi Yang, Ranjith Pathegama Gamage, Wendong Yang, Pengfei Yin, Yuanchao Zhang, and Qiangyong Zhang. "Fracture Processes of Rock-Like Specimens Containing Nonpersistent Fissures under Uniaxial Compression." Energies 12, no. 1 (December 28, 2018): 79. http://dx.doi.org/10.3390/en12010079.
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Many rock engineering accidents have proven that the coalescence of discontinuities in surrounding rock can have a major impact on the security and stable operation of energy infrastructure. To give an insight into the understanding of the crack propagation and coalescence in fissured rock masses, a series of uniaxial compression experiments were conducted on rock-like specimens containing nonpersistent fissures. The digital speckle correlation method (DSCM) and the acoustic emission (AE) monitoring system were adopted to capture the real-time strain field on the specimens’ surfaces and microfracturing events within specimens, respectively. The experimental results indicated that the strength and deformation modulus of specimens were significantly affected by fissure inclination. The damage process showed obvious progressive stain localization failure characteristics. The clear and intuitive full-field strain field development was successfully monitored by the DSCM technique. The real-time strain accumulation, crack initiation, propagation, and coalescence were also analyzed. Each time, the saltation of the strain field was usually accompanied by the fluctuation of the stress curve and obvious AE events. Crack coalescence modes between fissures changed from tension coalescence mode to mixed tension-shear coalescence mode, then to shear coalescence mode with an increase in fissure inclination. Five basic failure modes were identified from the experimental results: Tensile failure across the fissure planes, rotation failure of newly generated blocks, mixed failure mode, shear failure, and splitting failure. An investigation of the fracture processes of rock-like specimens containing nonpersistent fissures using these methods can enhance understanding of the fracture behavior of jointed rocks.
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Rashidi, Ahmad, Mohammad Mahdi Khatib, and Reza Derakhshani. "Structural Characteristics and Formation Mechanism of the Earth Fissures as a Geohazard in Birjand, Iran." Applied Sciences 12, no. 9 (April 20, 2022): 4144. http://dx.doi.org/10.3390/app12094144.
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Earth fissure structures are a common type of geohazard associated with geotechnical surface ruptures that can occur almost anywhere on the ground surface due to a variety of different mechanisms, and in most cases, these hazardous cracks have resulted in severe damage to infrastructure. Investigation of the structural characteristics of fissures in an active tectonic area (such as Birjand in eastern Iran) can improve our understanding of connections between the fissures and structural geology. The first reported earth fissures in NW Birjand are distributed along the North Birjand fault. Field observations and analysis of the detailed topography cross-sections using the real-time kinematic (RTK) technique have been used to infer the fissure development. Morphometric analysis of faults and fissures shows that the long axis of most fissure structures is distributed perpendicular to the strike of the North Birjand fault. The average volume strain in the study area was calculated to be 14.68 percent based on fissure geometry studies, with the maximum volume strain corresponding to the location of the North Birjand fault’s youngest splay. This splay formed fault-propagation folds with exposed fissure structures. This study shows that the fault-propagation folds in this system are subjected to the activity and evolution of the ground fissure as a result of the expansion of tensile stress.
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Zhang, Jie, Yifeng He, Tao Yang, Wenyong Bai, Shoushi Gao, and Yihui Yan. "Study on the Co-Evolution Mechanism of Key Strata and Mining Fissure in Shallow Coal Seam Mining." Applied Sciences 13, no. 14 (July 10, 2023): 8036. http://dx.doi.org/10.3390/app13148036.
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Shallow coal seam mining makes the evolution form of mining fissures in rock and soil layers diversified, which leads to the easy penetration of mining fissures as the main channel of water, sand inrush, and air leakage. In order to reveal the co-evolution mechanism of broken rock beam structure and mining fissures in key strata, taking Hanjiawan Coal Mine as the research background, the relationship between mining fissures and rock beam structure, fissure activation period, propagation characteristics, and connectivity of working face was studied by means of field observation, physical similarity simulation, and theoretical derivation. The research shows that the fracture structure of key strata in shallow coal seam mining mainly includes hinged rock beam and step rock beam structures. Through the analysis of the rock beam structure, we found that the types of mining fissures in the overlying strata of key strata were up and down I-I and I-II mining fissures, and the heights of fissure development were 44.38 m and 98.35 m, respectively. The key block rotation made the mining fissures undergo five dynamic activation processes. The calculation formula of the fissure activation cycle was established, and the rock breaking angle, mining fracture lag distance, and fissure penetration discriminant were obtained and verified by field measurement results.
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Rhazi, Jamal, and Gérard Ballivy. "Suivi de l'injection au moyen de l'émission acoustique." Canadian Geotechnical Journal 30, no. 6 (December 1, 1993): 965–73. http://dx.doi.org/10.1139/t93-094.
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The injection of grout in the microfissures of concrete dams in operation is very tricky because of the high pressures required to penetrate the slightly opened fissures. These conditions of grouting may result in the propagation of the fissures and contribute to the loss of stability of the mass. The technique using acoustical emission to follow the injection in real time has been evaluated. Water injection tests have been carried out on large dimensions (2.64 m × 1.42 m × 0.40 m) fissured concrete slabs instrumented with pressure, load, and displacement transducers. According to a study comparing two types of acoustical emission transducers, the low-frequency transducers would be more appropriate for this type of application. Moreover, the detected acoustical signals are not due to a constant pressure flow, but to the accelerations and decelerations of the grout, and to the mechanisms resulting from the variations of pressure and flow of the fluid (opening and closure of the fissure). Thus these observations confirm that the acoustical emission may be an interesting means to control the injections and, in particular, to determine the process of grout flow. Key words : concrete, fissure, injection, water test, pressure, acoustical emission. [Journal translation]
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Gou, Hong, Peng Shi, Zhijun Wan, Luchang Xiong, Bowen Fan, and Zheng Zhen. "Numerical Analysis of Perforated Symmetric Fissures on Mechanical Properties of Hole-Containing Sandstone." Applied Sciences 13, no. 15 (July 29, 2023): 8780. http://dx.doi.org/10.3390/app13158780.
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The symmetrical fissures located within the surrounding rock of the roadway (borehole) in tunnel engineering activities can easily induce damage and instability of the surrounding rock. Therefore, studying the impact of perforated symmetrical fissures on the mechanical properties of rock with a hole has significant practical significance. Based on indoor experimental results, conventional triaxial compression simulations were performed on symmetrical fissure-hole sandstone using PFC2D. The impact of the dip angle and length of symmetric fissures on the mechanical properties of the hole-containing sandstone was analyzed. Furthermore, the relationship between crack propagation and the macroscopic mechanical properties of the specimen was discussed. The results show that: (1) The deterioration effect of symmetric fissures on hole-containing sandstone can be controlled by increasing the fissure dip angle, suppressing the stress drop phenomenon. However, increasing the fissure length exacerbates the deterioration effect. (2) The effect of symmetrical fissure dip angle on the displacement field near the hole decreases with increasing dip angle while increasing fissure length exacerbates the effect of fissures on the displacement field. (3) As the angle between the fissure and the vertical principal stress increases, the degree of tensile failure weakens while the degree of shear failure increases. (4) During the crack development phase, the extension of the stress concentration zone drives rapid crack growth. It exhibits a stress drop in the macroscopic mechanical properties, followed by the evolution of the stress field with loading, allowing rapid expansion of the microcracks and eventually leading to rock destabilization damage.
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Wang, Z., Y. Zhang, J. Wu, J. Yu, and X. Gong. "Numerical simulation of earth fissures due to groundwater withdrawal." Proceedings of the International Association of Hydrological Sciences 372 (November 12, 2015): 395–98. http://dx.doi.org/10.5194/piahs-372-395-2015.
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Abstract. Excessive groundwater withdrawal can cause land subsidence and earth fissures. The initiation and propagation of earth fissures are related to tensile failure and crack propagation in soils. Based on fracture mechanics, the crack band model (CBM), one of the smear crack models which is relatively easy to construct and convenient to be integrated into standard finite element codes is used in this paper. The calculated results of CBM are less dependent on the sizes of finite elements. The model was applied to simulate the formation and propagation of earth fissures in the hydrostratigraphic units with a bedrock ridge. The simulated positions and patterns of earth fissures coincide with field observations, suggesting that the modeling approach is adept to simulate the initiation and propagation of earth fissures due to groundwater withdrawal.
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Xu, Nai-Zhong, Chang-Qing Liu, You-Jian Wang, and Hong-Bin Dang. "Biaxial Shear Crack Propagation Modes of Rock-Like Specimens with Prefabricated Fissures and Their Strength Characteristics." Shock and Vibration 2021 (August 2, 2021): 1–12. http://dx.doi.org/10.1155/2021/7248926.
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A biaxial shear test is performed on prefabricated, single-fissure type, cubic rock-like specimens by using the TZW-500 rock direct shear apparatus to study the shear strength characteristics, crack coalescence, and propagation modes of the specimens with different geometric parameters. Results show that the crack coalescence and propagation modes of the rock-like specimens with prefabricated fissures can be divided into four types, namely, single main shear crack coalescence mode, main shear crack coalescence and secondary tensile-shear crack propagation mode, main shear crack coalescence and secondary shear crack propagation mode, and main shear crack coalescence and secondary tensile crack propagation mode. All modes are affected by the dip angle α and length l of the prefabricated fissure. When the dip angle of the prefabricated fissure is α∈[0°, 20°) or (70°, 90°], the cracks center on shear failure, and most shear cracks propagate along one end of the prefabricated fissure. At α∈(30°, 50°), the cracks bear the tensile-shear combined action, and the shear cracks propagate along the two ends of the prefabricated fissure. The peak shear strength of the rock-like specimens with prefabricated fissures is also closely related to the dip angle α and length l of the fissure. With the increase in dip angle α of the prefabricated fissure, the peak shear strength of each rock-like specimen decreases initially then increases, and the peak shear strength curve presents a similar “U” shape. At α∈[30°, 60°], the peak shear strength is within the peak-valley interval. When the length l of the prefabricated fissure is increased, the peak shear strength experiences a gradual reduction. When l > 20 mm, the peak shear strength is greatly influenced by l, but the influence is minimal when l ≥ 20 mm. At the same dip angle α and fissure length of l ≥ 20 mm, the correlation between peak shear strength and fissure width b is low.
Dissertations / Theses on the topic "Propagation des fissures"
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Amestoy, Michel. "Propagation de fissures en elasticite plane." Paris 6, 1987. http://www.theses.fr/1987PA066238.
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Ce travail est consacre a une analyse theorique en vue de modeliser le phenomene de propagation de fissures dans un milieu suppose elastique, lineaire, homogene, isotrope (sans forces de masse), en etat de deformation plane. Dans ce cadre d'hypotheses, la situation la plus generale est envisagee (arbitraire sur la geometrie initiale du corps et de la fissure; arbitraire sur le chargement). Une telle entreprise necessite la formulation du critere de propagation, appele a porter sur des quantites convenablement identifiees et l'on peut anticiper que ces quantites representatives seront les facteurs d'intensite de contraintes k::(1)(s), k::(2)(s) a l'extremite de la fissure, au cours de sa propagation (s : abscisse curviligne le long de la courbe propagee). Dans ces conditions, nous nous sommes proposes d'etablir les expressions k::(1)(s), k::(2)(s), plus precisement sous forme d'un developpement vis-a-vis de la variable s, puis de justifier que le critere s'exprime effectivement a l'aide de ces quantites. En particulier, l'equation k::(2)(s) = 0 regit l'evolution geometrique de la fissure en cours de propagation et permet d'envisager une description numerique de cette propagation
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Amestoy, Michel. "Propagation de fissures en élasticité plane." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37602291j.
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Bignonnet, André. "Sur la propagation des fissures de fatigue." Paris, ENSAM, 1991. http://www.theses.fr/1991ENAM0021.
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Le sujet traite consiste d'une part a degager un outil permettant une description raisonnable de la loi de propagation et du seul du non propagation, d'une part a prendre en compte le chargements d'amplitude variable pour la prediction de la propagation. La premiere partie concerne l'influence des principaux parametres de fatigue: rapport r, environnement, longueur de la fissure et leur influence sur la fermeture des fissures. Nous avons montre qu'en regle generale le facteur d'intensite de contrainte de l'ouverture, u, qui permet de calculer la facteur d'intensite de contrainte efficace et la valeur du seuil. La deuxieme partie traite de la propagation sous chargement 'amplitude variable. Une etude parametrique a permis de detaller l'influence de la largeur de bande du spectre et des methodes de comptage mises en uvre. A l'aide de methodes de comptage appropriees nous avons valide l'approche dite du chargement equivalent defini par le moment statistique d'ordre m de la distribution des amplitudes de contraintes, m etant la pente de la loi de paris en amplitude constante, dans le cas d'historiques de contraintes stationnaires de type gaussien
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Zeghloul, Abderrahim. "Comparaison de la propagation en fatigue des fissures courtes et des fissures longues." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37619253w.
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Carlioz, Thomas. "Nucléation et propagation de fissures en conditions anisotropes." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1247/document.
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En partant d'une problématique industrielle correspondant à la naissance de fissures lors de l'excavation d'un tunnel dans un matériau argileux, nous proposons de nous intéresser à un sujet plus large qui est celui de la nucléation d'une fissure de dimension macroscopique. Ainsi, des résultats généraux et théoriques sont établis tout au long de ce mémoire. Ces derniers sont toutefois utilisés pour proposer une interprétation aux faciès de fissuration observés lors de l'excavation de galeries de stockage à grandeur profondeur. Dans un premier temps, un modèle géométrique idéalisé pour des fissures est justifié. Cette étude préalable permet à la fois d'acter la nature fermée des fissures susceptibles de nucléer ainsi que d'utiliser le critère mixte en statuant sur le bienfondé d'une étude bidimensionnelle équivalente. En précisant la notion de longueur de nucléation stable et en s'inspirant des outils classiques de la mécanique linéaire de la rupture, nous établissons dans un second temps notre propre critère de nucléation. Pour ce faire, nous proposons, grâce à des modélisations micromécaniques, de revisiter l'approche thermodynamique usuelle dans un cadre adiabatique afin d'être davantage en accord avec la brutalité du phénomène étudié. Par la suite, nous mettons aux points différentes méthodes permettant d'utiliser le critère suggéré. Enfin, le critère est mis en œuvre dans le cadre de la problématique industrielle initiale pour essayer de donner une justification à l'anisotropie des géométries des fissures observées, et ce, en prenant en compte les différentes directions de forage de l'ouvrage. Dans un deuxième temps, nous proposons de nous intéresser, de manière plus prospective, aux problématiques liées aux modèles locaux d'endommagement. Une attention particulière est accordée à la notion de stabilité des états d'équilibre. Ainsi, une adaptation du critère de Hill est proposée et des différences quantitatives sont soulignées lorsqu'un cadre adiabatique, nous paraissant plus justifié, est pris en compte. Enfin, le problème de la localisation de l'endommagement dans un problème unidimensionnel est abordéStarting from an industrial issue that is cracks onset when excavating a tunnel, this work aims at giving new insights into a more general problematic which is the initiation of macroscopic cracks. Thus, general and theoretical results are established. Nevertheless, they are applied in order to give some explanations to the excavation-induced fractures observed around the deep geological repository. To begin with, an idealised geometrical model is detailed and justified. Thanks to this preliminary work, we establish that the cracks that should be taken into account are closed ones. In addition we show that it's possible for small cracks length to work on an equivalent bidimensionnal problem. This last result allows us to apply the mixed criteria. After giving the definition of a stable crack initiation length we define our own criteria to predict cracks onset. In order to do so and in order to be more in adequacy with the caracter brutal of a crack initiation, we offer through a micromecanic modelisation to deploy the usual thermodynamic approach in an adiabatic context. Different methods to compute the key quantity which is the incremental energy released rate are then built. Finally, the criteria is applied to give some justifications to the anisotropic geometry of the excavation-induced fractures. In a second part of this work, we focuse on the problematics tied to the local damage models. For instance, the notion of stability for an equilibrium state is discussed. Hill's stability critera is adapted to damage problems. Once again, it seems that an adiabatic context is more suited and the differences implied are emphasized. To conclude, we offer to investigate the localisation issue in one dimensionnal problems
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Jung, Olivier. "Influence du grenaillage sur la propagation des fissures." Poitiers, 1997. http://www.theses.fr/1997POIT2315.
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L'objectif de la these est de developper un modele de propagation de fissure par elements finis dans une structure tridimensionnelle en presence de contraintes residuelles. La nature du travail est essentiellement numerique. La premiere partie presente un modele de relaxation de contraintes residuelles sous chargement cyclique, base sur une simulation complete du phenomene, grace a un calcul viscoplastique cyclique par elements finis. Le champ de contraintes residuelles ainsi obtenu peut alors etre introduit dans le calcul de propagation en tant que parametre de chargement supplementaire. En se placant dans le cadre de la mecanique lineaire de la rupture, une comparaison des methodes, numeriques et analytiques, permettant d'evaluer un fic en presence ou non de contraintes residuelles, est effectuee. Un modele general de propagation de fissure par elements finis est alors propose. Les applications de ce modele sont aussi presentees : propagation de fissure sous chargement periodique avec ou sans contraintes residuelles, propagation sous chargement complexe. Dans tous les cas, les previsions du modele sont corrects d'un point de vue qualitatif. Dans le cas de la propagation sous grenaillage, le modele est en bon accord avec l'experience.
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Grégoire, David. "Initiation, propagation, arrêt et redémarrage de fissures sous impact." Phd thesis, INSA de Lyon, 2008. http://tel.archives-ouvertes.fr/tel-00418626.
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Les risques liés à la propagation de fissures sous impact sont encore très difficiles à estimer. La détermination de critères de rupture dynamique uniquement à partir de résultats expérimentaux reste délicate. Ainsi la première étape pour valider des lois de propagation de fissures sous impact passe par le développement d'outils de simulation numérique. Depuis les années 1970, de nombreux codes de calcul mécanique ont été dédiés à l'étude de la propagation de fissures, notamment dans le cas du phénomène de fatigue. La principale difficulté consiste dans la nécessité de suivre la géométrie de la fissure au cours du temps. Ces dernières années, des méthodes alternatives basées sur la partition de l'unité ont permis une description implicite des discontinuités mobiles. C'est le cas de la méthode des éléments finis étendue (X-FEM) qui paraît particulièrement adaptée à la simulation de la propagation dynamique de fissures sous chargement mixte où les trajets de fissures ne sont pas connus a priori. Si ces outils numériques permettent maintenant de représenter l'avancée dynamique d'une fissure, les résultats numériques doivent être comparés à des résultats expérimentaux pour s'assurer que les lois introduites sont physiquement fondées. Notre objectif est donc de développer conjointement des techniques expérimentales fiables et un outil de simulation numérique robuste pour l'étude des phénomènes hautement transitoires que sont l'initiation, la propagation, l'arrêt et le redémarrage de fissures sous impact.Des expériences de rupture dynamique ont donc été réalisées sur du Polyméthacrylate de méthyle (PMMA) durant lesquelles la mixité du chargement varie et des arrêts et redémarrages de fissures se produisent. Deux bancs d'essais différents ont été utilisé, le premier basé sur la technique des barres de Hopkinson (ou barres de Kolsky), le second mettant en jeu un vérin rapide. Le PMMA étant transparent, la position de la fissure au cours de l'essai a été acquise grâce à des caméras rapides mais aussi en utilisant un extensomètre optique (Zimmer), habituellement dédié à la mesure de déplacements macroscopiques d'un contraste noir/blanc. L'utilisation de cet extensomètre pour suivre la fissure au cours de l'essai a permis d'obtenir une localisation très précise de la pointe de la fissure en continu, permettant ainsi l'étude des phases transitoires de propagation. Afin d'étudier le même phénomène dans des matériaux opaques comme les aluminiums aéronautiques (Al 7075), des techniques de corrélation d'images numériques ont été employées en mouchetant les éprouvettes impactées. De nouveaux algorithmes ont été développés afin de traiter les images issues d'une caméra ultra-rapide (jusqu'à 400 000 images par seconde).
Plusieurs géométries ont été envisagées afin d'étudier différents cas de propagation dynamique : initiation en mode I pur, initiation en mode mixte, propagation, arrêt, redémarrage, interaction entre deux fissures, influence d'un trou sur le trajet d'une fissure, branchement dynamique de fissures. Ces expériences ont ensuite été reproduites numériquement afin de valider les algorithmes et les critères de rupture choisis.
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Lesne, Pierre-Marie. "Amorçage et propagation de fissures sous gradients thermiques cycliques." Lille 1, 1985. http://www.theses.fr/1985LIL10111.
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Méthodes de prévision de durée de vie. Étude microstructurale du superalliage IN 100. Étude expérimentale d'une plaque sous gradients thermiques cycliques. Application de la méthode de durée de vie à cette plaque.
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Greciet, Florine. "Régression polynomiale par morceaux pour la propagation de fissures." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0004.
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Un moteur d'avion est constitué de plusieurs familles de matériaux qui subissent de multiples mécanismes de dégradation dès leur fabrication mais également pendant leur cycle de vol (décollage, atterrissage, pressurisation, manœuvre du pilote,...), où encore lors de son repos au sol. Un de ces mécanismes est lié au phénomène de fatigue, qui représente la dégradation subie par une pièce du fait de sollicitations cycliques répétées. Cette dégradation se traduit par l'amorçage d'une fissure et sa propagation jusqu'à rupture de la pièce. La prédiction de la durée de vie en propagation des pièces est donc un point très sensible puisqu'elle impacte à la fois le dimensionnement (étape préalable à la conception des pièces) et les procédures de maintenance (réparation ou changement de la pièce). Les calculs de durées de vie en propagation sont en partie réalisés à partir des lois d'évolutions phénoménologiques décrivant la vitesse d'avancée de la fissure dans un matériau en fonction de la contrainte appliquée. Dans l'objectif d'étudier ces données, qui sont susceptibles d'être modélisées de façon continue et qui laissent observer plusieurs régimes de propagation, nous proposons un modèle de régression polynomiale à plusieurs régimes, soumis à des hypothèses de régularité (continuité et/ou dérivabilité). Suite à cela, nous avons développé des méthodes d'inférence permettant d'estimer le nombre de régimes, les instants de transition et les paramètres de chaque régime. Ces résultats ne seront exploitables par le bureau d'études que s'ils sont obtenus en des temps de calculs raisonnables c'est-à-dire de l'ordre de quelques minutes. Chaque nouvelle méthode a donc été conçue dans l'objectif de réduire les temps de calculs nécessaires à l'estimation des paramètres du modèle. De plus, comme le nombre de régimes présents dans les données n'est pas connu a priori, les deux dernières méthodes que nous proposons n'utilisent aucun a priori sur ce nombre pour estimer les paramètres du modèle. Le travail présenté dans ce mémoire fait l'objet d'une collaboration entre l'équipe de Probabilités et Statistique de l'Institut Elie Cartan de l'université de Lorraine, l’équipe BIGS du centre Inria Nancy Grand Est et la société Safran Aircraft EnginesAn aircraft engine is made up of several families of materials that undergo multiple degradation mechanisms from their manufacture but also during their flight cycle (take-off, landing, pressurization, pilot manoeuvring,...) or during its rest on the ground. One of these mechanisms is related to the phenomenon of fatigue which represents the degradation of a piece due to repeated cyclic stresses. This degradation results in the initiation of a crack and its propagation until the piece ruptures. The prediction of the propagation lifetime of parts is therefore a very sensitive point since it impacts both the dimensioning (step prior to the design of the pieces) and the maintenance procedures (repair or change of the piece). Propagation lifetime calculations are partly based on the laws of phenomenological evolution describing the rate of progress of the crack in a material as a function of the stress applied. In order to study these data, which are likely to be modelled continuously and which allow several propagation regimes to be observed, we propose a polynomial regression model with several regimes, subject to regularity assumptions (continuity and/or differentiability). Following this, we developed inference methods to estimate the number of regimes, transition times and parameters of each regime. These results will only be usable by the engineering office if they are obtained within reasonable calculation times, i.e. in the order of a few minutes. Each new method has therefore been designed to reduce the computation time required to estimate the model parameters. Moreover, since the number of regimes present in the data is not known a priori, the last two methods we propose do not use any a priori on this number to estimate the model parameters. The work presented in this thesis is the subject of a collaboration between the Probability and Statistics team of the Institut Elie Cartan of the University of Lorraine, the BIGS team of Inria Nancy Grand Est and Safran Aircraft Engines
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Lefrancois, André. "Propagation par fatigue de fissures bi et tridimensionnelles dans deux alliages d'aluminium : effets de petite fissure et de chargements aleatoires." Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0089.
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Comparaison du comportement des fissures courtes (inferieures a 0,3-0,4mm) et longues dans deux alliages d'aluminium 2124 et 7475 soumis a deux types de chargement : sollicitations d'amplitude constante, sollicitations incluant des surcharges uniques ou repetees periodiquement
Book chapters on the topic "Propagation des fissures"
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Beskos, D. E., and I. Vgenopoulou. "Wave propagation in saturated, fissured, poroelastic rocks." In Structural Dynamics, 267–72. London: Routledge, 2022. http://dx.doi.org/10.1201/9780203738085-39.
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Li, Sheng, and Chen Yang. "Study on the Fissure Propagation of Jointed Rock Slope Under Unloading Condition." In Lecture Notes in Civil Engineering, 876–83. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-5217-3_88.
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Wang, Y. L., D. S. Liu, K. Li, D. Chen, and X. M. Hu. "Mechanical Characteristics and Failure Modes of Low-Strength Rock Samples with Dissimilar Fissure Numbers." In Advances in Transdisciplinary Engineering. IOS Press, 2021. http://dx.doi.org/10.3233/atde210317.
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The mechanical characteristics and failure modes of low-strength rock sample with various crack dip angles and numbers were investigated by conventional uniaxial compression test and three-dimensional (3D) crack reconstruction. The results indicated that compared with high-strength rock masses, cracks had different influences on the low-strength rock mass mechanical deformation features. Thereinto, the number of fissures can cause post-peak failure stage of stress-strain curve change from swift decline to multi-step down and horizontally extended decline, respectively, showing obvious ductility and ductile-flow deformation and failure characteristics. Due to the structural effect, only under the condition of fissure α < 90°, the modulus of peak strength and elastic modulus lowered with the enhancement of fissure number and had a negative correlation. As the number of fissures increased, the axial peak strain increased first and then decreased, demonstrating a reversed V-shaped change trend. Fissure number can fully affect the crack propagation law only in the case of vertical fissures. The above research findings can complement and improve the study of fissured rock masses.
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MOËS, Nicolas. "Méthodes des éléments finis étendus (XFEM) et des level sets épaisses (TLS)." In Modélisation numérique en mécanique fortement non linéaire, 275–307. ISTE Group, 2023. http://dx.doi.org/10.51926/iste.9081.ch6.
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La méthode des éléments finis étendus (XFEM) permet de gérer la propagation de fissures sans remaillage par l'insertion de sauts de déplacement. Le chemin de la fissure peut être calculé soit par une approche énergétique (facteurs d'intensité de contrainte) soit via la méthode des level sets épaisses qui a l'avantage de gérer la naissance de fissure ainsi que des chemins complexes de fissuration.
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FAVIER, Véronique, André GALTIER, Rémi MUNIER, and Bastien WEBER. "Compromis entre résistance mécanique et tenue en fatigue." In Le développement des aciers à très haute résistance, 109–36. ISTE Group, 2022. http://dx.doi.org/10.51926/iste.9122.ch4.
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Ce chapitre rappelle les principales caractéristiques de la tenue en fatigue, essentielle pour la plupart des pièces de structure en acier. Il aborde ensuite l’influence des nouvelles microstructures sur l’amorçage et la propagation des fissures, ainsi que les moyens d’améliorer la tenue en fatigue par des traitements thermiques et mécaniques adaptés à ces nouvelles nuances d’acier.
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"Crack propagation and threshold strength of fissured clays subjected to cyclic loading." In Advances in Unsaturated Soils, 415–22. CRC Press, 2013. http://dx.doi.org/10.1201/b14393-58.
Full textConference papers on the topic "Propagation des fissures"
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Hénaff, G., and F. Menan. "Influence de l'environnement sur la propagation des fissures de fatigue." In PlastOx 2007 - Mécanismes et Mécanique des Interactions Plasticité - Environnement. Les Ulis, France: EDP Sciences, 2009. http://dx.doi.org/10.1051/ptox/2009017.
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Schroeder, Y., S. Sivan, W. Wilson, J. M. Huyghe, A. Maroudas, and F. P. T. Baaijens. "Intra- and Extrafibrillar Fluid Exchange in the Disc." In ASME 2007 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2007. http://dx.doi.org/10.1115/sbc2007-176329.
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The mechanical properties of the intervertebral disc are regulated by its biochemical composition. With ageing and degeneration the water content of the disc decreases which highly influences the mechanical properties. The disc is subjected to a combination of elastic, viscous and osmotic forces. Osmotic forces are shown to have a major impact on crack opening and propagation [1] and on cellular responses [2]. In particular, osmosis provides an understanding on why fissures in the degenerating disc are so poorly related to external mechanical load [3].
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Davis, Bradley J., Guillaume Michal, Cheng Lu, and Valerie Linton. "Separation Characteristics of an X65 Linepipe Steel From Laboratory-Scale to Full-Scale Fracture Tests." In 2020 13th International Pipeline Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/ipc2020-9545.
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Abstract Separations are small fissures that form along the rolling-plane of some steels when sufficient stresses are created to open planes of weakness in the material. In the pipeline industry, separations have been observed on the fracture surfaces of tensile, Charpy, and drop-weight tear tests — the key tests for determining the fracture arrest capabilities of line pipe steels. When compared, the separation appearance between lab-scale tests and full-scale fracture test are noticeably dissimilar. Therefore, the influence separations have on the fracture behaviour may not clearly scale between lab-scale and full-scale tests. In this study, the separation severity of Charpy, DWTT, and full-fracture propagation test fracture surfaces was measured and compared. Two full-scale burst tests were carried out with pipes containing a CO2/N2 mixture. Fracture surfaces were observed along the length of the pipe and captured when the separation appearance changed. For each pipe section, the corresponding lab-scale test surfaces were compared. With the separations measured across all fracture faces, the separation appearance of the full-scale test surfaces did not provide the same values as the lab-scale tests. However, the lab-scale tests did capture the trend in separation severity for each pipe section. Only the lab-scale test surfaces showed a correlation in separation severity.
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Lu, Y. Michael, Vasanti M. Gharpuray, and William C. Hutton. "The Effect of Posture, Loading Rate, and Diurnal Fluid Changes on the Propensity to Disc Prolapse." In ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-1159.
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Abstract Sudden disc prolapse usually occurs due to a traumatic event when a high compressive force is suddenly applied to the spine in an unfavorable condition. Previous experimental studies have shown that disc prolapse is more likely to occur in normal or slightly degenerated discs, and that for prolapse to occur, the applied load must be a combination of forces (e.g., forward bending and axial compression) (Adams et al. 1982, 1985; Gordon et al. 1991). By definition, for a disc to prolapse it must have a fissure or channel for the passage of nuclear material (Brinckmann et al. 1994). Although this seems a statement of the obvious, it is still not clear how or where the fissure initiates and then propagates to create the channel. Therefore, the purpose of the study was to use a three dimensional viscoelastic finite element (FE) model of a lumbar motion segment to simulate the successive steps required to create a radial fissure in the anulus, and to study the effect of posture, fluid changes and loading rates on propagation of the fissure.
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Hamidov, Elmir, Evren Ozbayoglu, and Silvio Baldino. "Experimental Study on Wellbore Strengthening with Fine Particles." In 57th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2023. http://dx.doi.org/10.56952/arma-2023-0381.
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ABSTRACT One of the most serious issues that arises during drilling operations is lost circulation. Significant study into wellbore strengthening has been conducted over several years in the attempt to improve the fracture gradient and reduce losses. Three ways to wellbore strengthening have been presented in general: 1) Increased fracture plug/hoop stress or "stress cage," 2) particle "screen-out," and 3) fracture propagation resistance. All these options are designed to prevent the spread of the fracture once it has begun. Filter-cake has been identified as having a significant role in wellbore strengthening. Mud cake has been shown to considerably strengthen wellbores, even to the extent of preventing fracture formation. Specifically, fine particles (e.g. ultrafine barite) have been tested to measure strengthening. A true triaxial cell was employed in this study to explore the influence of mud cake on wellbore strengthening for a variety of fluids and operating conditions. The effects of external and internal cakes, as well as the absence of mudcake, have been studied. API filter tests have also been carried out using various mud formulations. INTRODUCTION Drilling under partial or total lost circulation is extremely challenging. Cavernous and vugular structures, natural or induced fissures, unconsolidated sand, very porous tight sands, and tight sands with high sulfide levels are all examples of formations that can cause lost circulation. Even though it is common to use techniques like bridging, gelling, and cementing to remediate to this issue, the results vary depending on the method used. Trying to fix circulation problems can take long time and have a significant cost, especially when this results in considerable nonproductive time (NPT) (Benaissa et al, 2005). When drilling through depleted sands, there is a risk of losing circulation. This is made worse by the sands’ low fracture gradient and the high mud weight needed to avoid shear failure in nearby shales, which both add to the problem. When it comes to depleted sands, the best way to stop circulation problems is to be pro-active rather than re-active (e.g., prevent lost circulation to happen in the first place). This can be done by using techniques from both geomechanics and drilling fluid design. Numerous procedures may be used to prevent or treat lost circulation. The first consideration should be to improve drilling operations. For instance, sophisticated geomechanical models may be used to predict the probability of a hole collapsing or losing circulation. Additionally, expandable casing, managed pressure drilling, and casing while drilling are used. (Majidi et al, 2011) Another option is to select drilling fluids with the proper rheological characteristics, which entails implementing drilling fluid with the proper rheological properties and/or additives to minimize or eliminate lost circulation. The third method of preventing fracture propagation is to use wellbore strengthening techniques, which are composed of specially formulated and sized particulate materials that are introduced into a fracture (natural or induced) and stop the fracture from propagating by isolating it from the wellbore. This can be caused by a high leaked-off fluid depositing solids inside the fracture and creating hard particles within short fractures. (Majidi et al, 2011) This can also be caused by smearing or plastering mudcake on the wellbore wall, which deposits solids within the fractures’ mouth (Marbun et al., 2014; Baldino et al., 2019).
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Shin, Ho-Sang, Jin-Ki Hong, Koo-Kab Chung, Hae-Dong Chung, Gwang-Yil Kim, and Sung-Woo Cho. "Effects of Delta - Ferrite Content on the Integrity of Reactor Vessel Cladding." In ASME 2010 Pressure Vessels and Piping Division/K-PVP Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/pvp2010-25434.
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As the design life of new nuclear power plant increases, the austenitic stainless cladding integrity of reactor vessel becomes one of the new concerns. Since 1970’s, there have been some specific recommendations on delta ferrite content of austenitic cladding of reactor vessels and welds. It has been known that the delta ferrite is beneficial for reducing micro-fissure in welds, though the high delta ferrite content increases the probability of embrittlment of welds. In this study, the mechanical and microstructural properties of austenitic weld metals with the limit values of the recommended range (5 ∼ 18 FN) of the delta ferrite control on low alloy steels were characterized by using bending test and scanning electron microscopy. The base metal was ASME Code Sec. II specification SA 508 Gr. 3 Cl. 1 plate and weld materials were EQ308L and EQ309L strips. Four kinds of cladding were deposited with submerged arc welding process on SA508 cl.3 plates. The bending tests were performed through ASME code Sec. IX and the microstructure of fractured surfaces was analyzed by scanning electron microscopy (SEM). In bending tests, there were no fractures except the highest delta ferrite content specimens (28FN). From the SEM observation of fractured surfaces, cracks initiated from the interface between austenite and ferrites phases in the cladding layer and propagated through the continuous interfaces between two phases. For specimens without continuous interfaces of two phases, though the cracks were observed in the interface of phases, the propagation of cracks was not observed. From the test results, continuous interfaces between austenite matrix and ferrite phase provide the path for crack propagation. And the delta ferrite content affects the integrity of cladding of reactor vessel.
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French, S. M. "Failure Analysis of a Ruptured Final Reheat Tube." In ASME 2007 Pressure Vessels and Piping Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/pvp2007-26360.
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Two damaged final reheat tubes from a 30 year old supercritical unit were submitted to the laboratory for evaluation following the discovering of a failure of one of the tubes after deslagging operations; a third, dented tube was left in service. The 304H stainless steel tubes were installed in 1990 when the reheater was replaced. The bulk microstructure of both tubes shows evidence of sensitization, which is not unusual given this application (reheater). The failed tube appears to be an intergranular separation that started either subsurface or at the ID, propagating to the OD surface. The sensitization of the steel apparently made the material susceptible to corrosion as well as significantly reduced the impact strength of the material to 10–15% of its estimated original level (verified by Charpy impact test). Examination of the dented tube (#101A) showed a subsurface plane of damage some 30 mils from the ID surface, running parallel to the surface. The damage consisted of intergranular separation, caused by the impact loading event, and referred to in the literature as an “attached spalling failure”. Spalling failures occur when the shock wave is reflected from the back surface (the ID surface of the tube), interacting with the incident shock wave as a stress wave. When the magnitude of this tensile stress exceeds the inherent strength of the material, failure occurs. The overall area of the attached spalling failure is being investigated; the concern there is if it is exceptionally large, it may provide a thermal barrier to heat transfer from the OD to the ID and result in a local overheating failure. Within the metallographic sample, however, the damage area was quite small and therefore did not appear to be an immediate issue. The long-term suitability of tube 105A, which remains in service with a dent induced by the same deslagging process that damaged tubes 101A and 103A, is doubtful and should be addressed during the Fall 2006 boiler overhaul. For the shortterm, the assumption was made that cracking due to the deslagging impact would be oriented similar to non-failed tube and extension of these fissures to failure between Spring 2006 and the Fall outage is not expected.