Academic literature on the topic 'Localised failure'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Localised failure.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Localised failure"
1
Mann, A. C. "Localised autonomic failure due to botulinum toxin injection." Journal of Neurology, Neurosurgery & Psychiatry 57, no. 11 (November 1, 1994): 1320. http://dx.doi.org/10.1136/jnnp.57.11.1320.
Full text
2
Bushara, K. O. "Localised autonomic failure due to botulinum toxin injection." Journal of Neurology, Neurosurgery & Psychiatry 59, no. 1 (July 1, 1995): 105. http://dx.doi.org/10.1136/jnnp.59.1.105.
Full text
3
Yahya, N. A., M. Dhanasekar, and H. Abd Hamid. "Localised failure mechanism of concrete pedestals under bridge bearing." Australian Journal of Civil Engineering 18, no. 2 (April 22, 2020): 164–75. http://dx.doi.org/10.1080/14488353.2020.1752094.
Full text
4
Gutiérrez, M. A., and R. De Borst. "Stochastic aspects of localised failure: material and boundary imperfections." International Journal of Solids and Structures 37, no. 48-50 (November 2000): 7145–59. http://dx.doi.org/10.1016/s0020-7683(00)00193-1.
Full text
5
Kwame, J. S., E. Yakushina, and P. Blackwell. "Examining Failure Behaviour of Commercially Pure Titanium During Tensile Deformation and Hole Expansion Test." Journal of Materials and Applications 9, no. 1 (May 15, 2020): 32–37. http://dx.doi.org/10.32732/jma.2020.9.1.32.
Full textAbstract:
Hole expansion ratio is a material parameter which defines the extent to which sheet metals are formed. Research has shown that, the stress state observed at the hole edge after hole expansion test is similar to those observed during conventional uniaxial tensile test. However, conventional tensile test methods are not efficient in evaluating material edge formability. This work utilised optical non-contact measuring techniques to examine failure behaviour during tensile test and hole expansion test of commercially pure titanium sheet, fabricated with either abrasive water jet cutting or electric discharge machining. The work found that, the deformation mode in conventional tensile testing are governed by localised necking and subsequently diffused necking prior to failure. Deformation mode observed in hole expansion test is characterised by localised necking with no visible occurrence of diffused necking prior to failure. The highest strains are concentrated at the hole edge during hole expansion test due to their sensitivity to the hole preparation method with accompanying multiple localised necking sites resulting in non-uniform deformation. Strains become concentrated in the bulk material microstructure rather than the machined edge during tensile testing resulting in single localised deformation site and a more homogenous deformation.
6
Blythe, Ashley, Bronwyn Fox, Mostafa Nikzad, Boris Eisenbart, Boon Xian Chai, Patrick Blanchard, and Jeffrey Dahl. "Evaluation of the Failure Mechanism in Polyamide Nanofibre Veil Toughened Hybrid Carbon/Glass Fibre Composites." Materials 15, no. 24 (December 12, 2022): 8877. http://dx.doi.org/10.3390/ma15248877.
Full textAbstract:
The interface of hybrid carbon/E-glass fibres composite is interlayered with Xantu.layr® polyamide 6,6 nanofibre veil to localise cracking to promote a gradual failure. The pseudo-ductile response of these novel stacking sequences examined under quasi-static three-point bending show a change to the failure mechanism. The change in failure mechanism due to the interfacial toughening is examined via SEM micrographs. The incorporation of veil toughening led to a change in the dominant failure mechanism, resulting in fibre yielding by localised kinking and reduced instances of buckling failure. In alternated carbon and glass fibre samples with glass fibre undertaking compression, a pseudo-ductile response with veil interlayering was observed. The localisation of the fibre failure, due to the inclusion of the veil, resulted in kink band formations which were found to be predictable in previous micro buckling models. The localisation of failure by the veil interlayer resulted in a pseudo-ductile response increasing the strain before failure by 24% compared with control samples.
7
Nguyen, Giang D. "An enriched constitutive modelling framework for localised failure of geomaterials." Obras y proyectos, no. 15 (2014): 33–39. http://dx.doi.org/10.4067/s0718-28132014000100003.
Full text
8
Nguyen, Giang D., Chi T. Nguyen, Vinh P. Nguyen, Ha H. Bui, and Luming Shen. "A size-dependent constitutive modelling framework for localised failure analysis." Computational Mechanics 58, no. 2 (April 21, 2016): 257–80. http://dx.doi.org/10.1007/s00466-016-1293-z.
Full text
9
Bhattacharya, Chittatosh. "Investigation of repeated economiser tube failures of a 135 tph cold cyclone CFB boiler – a case study." Indian Journal of Power and River Valley Development 71, no. 5&6 (July 2, 2021): 73. http://dx.doi.org/10.18311/ijprvd/2021/28066.
Full textAbstract:
There were quick and successive failures of economiser tubes in a four years old cold cyclone circulating fluidised bed 135 tph boiler in a short span of three months. Advance inspection and failure analysis, change in operational practices were used to get the boiler running at full load at the earliest possible time. This paper presents details of the process of inspection, maintenance, operation and failure investigation carried out for the economiser tubes of the boiler. The failure of the economiser tubes was due to external corrosion of the tubes furnace fire side due to presence of sulphur in coal, accompanied by localised erosion by high levels of alpha-quartz in coal ash.
10
Shen, Zhengxiang, Hu Chen, Du Wang, Shuqiang Yuan, Dingyue Cheng, and Guorong Zhu. "Failure Behaviours of Steel Projectiles with Localised Melting Against Armour Plates." Defence Science Journal 69, no. 5 (September 17, 2019): 489–94. http://dx.doi.org/10.14429/dsj.69.13338.
Full textAbstract:
The surface remelting technology of high energy beam can locally weaken the case for controlled fragmentation, which may affect the survivability of the impacting projectiles. Failure behaviours of steel projectiles with melted layers grid normally perforating armour plates was investigated. The results reveal that shear fracture mainly occurs in the nose region of projectiles due to high loading, and the melting zone of projectiles can keep integrity with no damage, which means the survivability of projectile can be assured. Furthermore, an analytical model was proposed to the structural analysis of projectile, which is in accordance with the test results.
Dissertations / Theses on the topic "Localised failure"
1
Yahya, Norrul Azmi. "Strategies for mitigation of the failure of concrete pedestals supporting bridge girder bearings." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/105498/1/Norrul%20Azmi_Yahya_Thesis.pdf.
Full textAbstract:
This thesis explains on the numerical study of localized damage mechanism in concrete pedestals supporting bridge girder bearings. It examined the structural response of concrete pedestals dealing with complex contact interaction behaviour between steel bearing plate and concrete. Three dimensional nonlinear explicit finite element micro models of concrete pedestals were analyzed with various pedestal heights, edge clearance distances, loading geometries, confinement reinforcements and loading eccentricities. Also included are few mitigation strategies had been proposed to minimize the effect of localized failure and therefore which can then improve the structural performance of concrete pedestals.
2
Sivapathasundaram, Mayooran. "Localised pull-through failures of thin steel roof battens subject to wind uplift loads." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/204638/1/Mayooran_Sivapathasundaram_Thesis.pdf.
Full textAbstract:
High wind events such as tropical cyclones, severe storms and tornadoes are more likely to impact the Australian coastal regions due to possible climate changes. Such events can be extremely destructive to building structures, in particular, low-rise buildings with lightweight roofing systems that are commonly made of thin steel roof sheeting and battens. Large wind suction loads that act on the roofs during high wind events cause premature failures of roof connections (fixings), leading to complete roof failures.
Past wind damage investigations showed that the roof sheeting to batten connection failed frequently during high wind events. These local connection failures have been extensively investigated by many researchers and suitable recommendations to eliminate such failures have been proposed. However, this meant the weakest point has now shifted to the batten to truss/rafter connection. These connections are predominantly subjected to localised pull-through failures in which the screw fastener head pulls through the bottom flanges of thin steel roof battens. However, these failures have not been investigated adequately despite the many roof batten pull-through failures and eventual losses of both roof sheeting and battens observed after recent high wind events. Currently available design rules for the pull-through capacity of cold-formed steel screw fastener connections do not address the specific pull-through failures in thin steel roof battens under wind uplift loading. Current design practice of roof battens is based on using the design wind uplift capacity tables published by their manufacturers. However, it is unclear whether these design capacity tables developed for specific roof battens adequately included the effects of pull-through failures.
As for the roof sheeting to batten connections, batten to rafter/truss connections are also subjected to both static and fatigue failures due to static and cyclic wind uplift loads, respectively. Although some experimental studies were conducted in the past using simulated static and cyclic wind loading, they were incomplete and no design rules were developed. Since the climate predictions indicate the likelihood of severe storm events with increased intensity in the future, they are more likely to cause static pull-through failures of roof battens. In addition, a thorough understanding of the static behaviour is first needed to evaluate the fatigue behaviour in depth. Hence this research was aimed at investigating the localised pull-through failures of thin steel roof battens under simulated static wind uplift loads, using laboratory experiments and finite element modelling.
A preliminary and detailed experimental study was first conducted using industrial roof battens and full scale air-box tests and three small scale tests such as two-span batten tests, cantilever batten tests and short batten tests. Suitable small scale test methods were identified to accurately simulate the localised pull-through failures of roof battens. The applicability of the proposed small scale test methods for other roof battens was verified using two-span and short batten tests undertaken using roof battens made at the university workshop. Based on the test results, a suitable modification factor was recommended for use with the pull-through capacity equation presented in the current Australian (AS/NZS 4600: 2005) and American (AISI S100: 2012) cold-formed steel standards to accurately determine the pullthrough failure loads of roof battens.
The main and extensive experimental study was then undertaken using two-span and short batten tests to examine the pull-through failures of roof battens. The tests were conducted to investigate the effects of many critical parameters such as screw fastener tightening, batten height, web angle, steel grade, batten thickness, screw fastener head size, screw fastener location, batten bottom flange width, underside and edge details of the screw fastener head, and screw fastener types on the roof batten pull-through failure behaviour and capacity. Since the test results showed that the pull-through failure behaviour of high strength and low strength steel roof battens significantly differed from each other due to the differences in ductility, two new design rules and relevant capacity reduction factors were developed to accurately determine the design pull-through capacities of roof battens.
The finite element models of both two-span batten and short batten test specimens were modelled and analysed using ABAQUS software. A suitable failure criterion was developed based on constitutive model inputs and employed in the finite element analyses to accurately predict the initiation of pull-through failures of thin steel roof battens associated with the tearing fracture of bottom flange around the screw fastener head edge. The finite element models were validated using the test results, and additional parametric studies were conducted to investigate the parameters which were not considered in the experimental study due to their lower importance on pullthrough failure behaviour and capacity of roof battens. A large pull-through capacity data base was developed using the pull-through failure loads obtained from the tests and finite element analyses. Suitable design rules were then developed using them and finally recommended with suitable capacity reduction factors for the accurate determination of the design pull-through capacities of thin-walled steel roof battens.
This study also investigated the strengthening methods recommended by the roof batten manufacturers and builders and showed that they are inadequate to provide a significant improvement based on the governing pull-through failures of roof battens.
A reliable strengthening method using overlapping short battens as brackets at the supports was recommended and a series of roof batten tests was conducted using two-span batten tests and two types of industrial roof battens. The test results confirmed the adequacy of the proposed strengthening method.
Suitable fragility curves were developed using detailed probabilistic analyses and Monte Carlo simulations based on the governing pull-through failures of thin steel roof battens to predict the likely level of roof damages to a large community for a given wind speed. The pull-through failure behaviour of roof battens was examined by defining eight different cases that are likely to occur during high wind events (for example, with and without dominant openings) and developing relevant fragility curves. The effects of using different batten span and spacing were also investigated using fragility curves. Fragility curves were also used to evaluate the enhancement level that could be achieved with the proposed strengthening method.
In summary, this research study has developed suitable test, design and strengthening methods and fragility curves for thin steel roof battens subject to localised pullthrough failures under high wind uplift loads.
3
Petras, Achilles. "Design of sandwich structures." Thesis, University of Cambridge, 1999. https://www.repository.cam.ac.uk/handle/1810/236995.
Full textAbstract:
Failure modes for sandwich beams of GFRP laminate skins and Nomex honeycomb core are investigated. Theoretical models using honeycomb mechanics and classical beam theory are described. A failure mode map for loading under 3-point bending, is constructed, showing the dependence of failure mode and load on the ratio of skin thickness to span length and honeycomb relative density. Beam specimens are tested in 3-point bending. The effect of honeycomb direction is also examined. The experimental data agree satisfactorily with the theoretical predictions. The results reveal the important role of core shear in a sandwich beam's bending behaviour and the need for a better understanding of indentation failure mechanism. High order sandwich beam theory (HOSBT) is implemented to extract useful information about the way that sandwich beams respond to localised loads under 3-point bending. 'High-order' or localised effects relate to the non-linear patterns of the in-plane and vertical displacements fields of the core through its height resulting from the unequal deformations in the loaded and unloaded skins. The localised effects are examined experimentally by Surface Displacement Analysis of video images recorded during 3-point bending tests. A new parameter based on the intrinsic material and geometric properties of a sandwich beam is introduced to characterise its susceptibility to localised effects. Skin flexural rigidity is shown to play a key role in determining the way that the top skin allows the external load to pass over the core. Furthermore, the contact stress distribution in the interface between the central roller and the top skin, and its importance to an indentation stress analysis, are investigated. To better model the failure in the core under the vicinity of localised loads, an Arcan- type test rig is used to test honeycomb cores under simultaneous compression and shear loading. The experimental measurements show a linear relationship between the out-of-plane compression and shear in honeycomb cores. This is used to derive a failure criterion for applied shear and compression, which is combined with the high order sandwich beam theory to predict failure caused by localised loads in sandwich beams made of GFRP laminate skins and Nomex honeycomb under 3-point bending loading. Short beam tests with three different indenter's size are performed on appropriately prepared specimens. Experiments validate the theoretical approach and reveal the nature of pre- and post-failure behaviour of these sandwich beams. HOSBT is used as a compact computational tool to reconstruct failure mode maps for sandwich panels. Superposition of weight and stiffness contours on these failure maps provide carpet plots for design optimisation procedures.
4
Nikolic, Mijo. "Rock mechanics, failure phenomena with pre-existing cracks and internal fluid flow through cracks." Thesis, Cachan, Ecole normale supérieure, 2015. http://www.theses.fr/2015DENS0043/document.
Full textAbstract:
Cette thèse aborde le problème de la rupture localisée dans les roches, qui caractérise un grand nombre d'applications dans le domaine du génie civil, tels que la rupture du barrage, effondrement des fondations, la stabilité des excavations ou les tunnels, les glissements de terrain et les éboulements. Le risque de rupture localisée devrait être mieux appréhendé pour mieux l'éviter. La rupture localisée dans les roches est généralement caractérisée par une une rupture soudaine et quasi-fragile sans avertissement sous forme de grandes déformations et visibles avant la rupture elle-même. Cela se produit également sous l'influence des hétérogénéités matériels, des fissures existantes et d'autres défauts initiaux.Les trois nouveaux modèles numériques, intégrant les mécanismes de ruptures localisées, l'hétérogénéité de la roche et des fissures existantes et d'autres défauts, sont présentés dans cette thèse. Le premier modèle propose une représentation en 2D de roche composite à deux phases, où la phase solide représente la roche intacte et la faible phase indique les défauts initiaux. Le deuxième modèle représente l'extension du modèle précédent vers un espace 3D, où est considéré un ensemble complet de mécanismes de ruptures en 3D. Les propriétés hétérogènes sont considérées ici par une distribution aléatoire en accord avec la variation statistique de Gausse. Ce modèle est également utilisé pour l'analyse de la roche intacte par spécimens possédant des écarts de formes géométriques qui influencent la résistance à la compression uni-axiale. Le troisième modèle est un modèle en 2D, traitant l’interaction volumétrique entre un fluide et la structure sous l’influence de l’écoulement du fluide à travers le milieu de la roche poreuse.L'approche des lattices discrètes est choisie pour construire un cadre général pour les trois modèles, où les cellules de Voronoï représentent les grains de roche tenus ensemble par les poutres de Timoshenko comme des liens de cohésion. La cinématique améliorée est caractérisée par l'approche intégrée des discontinuités comme un supplément à la cinématique standard de liens cohérents. Cela sert pour la propagation de la macro fissure dans tous les modes de ruptures et de leurs combinaisons, entre les grains de la roche. La formation de la zone du processus de rupture suivie par des microfissures coalescentes, précédant la rupture localisée, est aussi considérée dans les modèles. L’écoulement du fluide est régi par la loi de Darcy, tandis que les conditions de couplage obéissent à la théorie de poroélasticité de Biot.Les résultats des modèles numériques ont été vérifiés par des exemples de la littérature dans le cas des modèles en 2D. Le modèle en 3D a été validé suite aux résultats expérimentaux effectués sur 90 échantillons de roches, où sont considérées de légères déviations géométriques des spécimens.La présentation de ces modèles, ainsi que leurs aspects de mise en œuvre sont présentés en détail. L’approche avec une discontinuité intrinsèque et le caractère local des améliorations nécessaires à la simulation des discontinuités de déplacement orientent vers la condensation statique des degrés de liberté améliorés sont efficacement intégrés dans l’architecture des éléments finisThis thesis deals with the problem of localized failure in rocks, which occurs often in civil engineering practice like in dam failure, foundation collapse, stability of excavaations, slopes and tunnels, landslides and rock falls. The risk of localized failure should be better understood in order to be prevented. The localized failure in rocks is usually characterized by a sudden and brittle failure without warning in a sense of larger and visible deformations prior to failure. This happens also under the strong influence of material heterogeneities, preexisting cracks and other defects.The three novel numerical models, incorporating the localized failure mechanisms, heterogeneity of rock and preexisting cracks and other defects, are presented in this thesis. First model deals with 2D plane strain two-phase rock composite, where stronger phase represents the intact rock and weaker phase initial defects. Second model represents the extension of the previous model towards the 3D space, where full set of 3D failure mechanisms is considered. Heterogeneous properties are taken here through the random distribution and Gauss statistical variation of material properties. The latter model is also used for the analysis of intact rock core specimens geometrical shape deviations influencing the uni-axial compressive strength. Third model is a 2D, dealing with volumetric fluid-structure interaction and localized failure under the influence of fluid flow throughthe porous rock medium.The discrete beam lattice approach is chosen for general framework for three models, where Voronoi cells represent the rock grains kept together by Timoshenko beams as cohesive links. The enhanced kinematics characterized for embedded discontinuity approach is added upon standard kinematics of cohesive links. This serves for the macro crack propagation in all failure modes and their combinations, between the rock grains. The fracture process zone formation followed by micro-cracks coalescence, preceding the localized failure, is considered as well. Fluid flow is governed by a Darcy law, while coupling conditions obey Biot's theory of poroplasticity. The results of the numerical models were verified by the benchmarks available from literature in 2D case. The 3D model was validated against the experimental results conducted on 90 rock specimens, where even slight geometrical deviations of specimens are considered.Presentation of these models, as well as their implementation aspects are given in full detail. Embedded discontinuity concept and the local nature of enhancements required to capture the displacement discontinuities leads to the very efficient approach with static condensation of enhanced degrees of freedom and technique that can be efficiently incorporated into finite element code architecture
5
Do, Xuan Nam. "Localized failure in dynamics for brittle and ductile materials." Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2356.
Full textAbstract:
La défaillance des matériaux et structures d'ingénierie peut être considéré comme le résultat d'une interaction complexe entre différents phénomènes physiques tels que la nucléation des cavités, les microfissures, les microvides et d'autres processus irréversibles. Ces micro-défauts se fondent éventuellement en une ou plusieurs macro-fissures conduisant à une diminution de la capacité portante et finalement à une défaillance de la structure considérée. La prévention des défaillances des structures et des composants structurels a toujours été un sujet important et une préoccupation majeure en ingénierie. Cette thèse vise à représenter une défaillance localisée dans des matériaux non linéaires sans dépendance de maillage. Un intérêt particulier sera le cas de l’adoucissement dynamique des déformations. Les phénomènes localisés sont pris en compte en utilisant l'approche des discontinuités embarquées fortes dans laquelle le champ de déplacement est amélioré pour capturer la discontinuité. Sur la base de cette approche, on a d'abord développé un modèle unidimensionnel de barres élasto-plastique capable de représenter une défaillance pour des matériaux ductiles avec un durcissement combiné dans une zone de processus de fracture FPZ et un adoucissement avec des discontinuités fortes encastrées. Les résultats comparant le modèle unidimensionnel proposé aux travaux (semi-) analytiques sont présentés. Il a été démontré que la stratégie proposée offre des solutions indépendantes de maillage. La déformation augmente dans le domaine de l’adoucissement avec une diminution simultanée de la contrainte. Le problème se décharge élastiquement à l'extérieur de la zone d’adoucissement de déformation. L'énergie dissipée se trouve à disparaître. Le modèle a également été comparé à un modèle de dommage unidimensionnel capable de représenter la fracture dynamique de la barre d'endommagementélasto-endommagée dans la zone de traitement de fracture - FPZ et de adoucissement avec de discontinuités fortes encastrées pour trouver un bon accord entre deux modèles. Un modèle d'éléments finis bidimensionnel a été développé, capable de décrire à la fois le mécanisme de dommage diffus accompagné d'un durcissement initial et d'une réponse d’adoucissement ultérieure de la structure. On a analysé les résultats de plusieurs simulations numériques effectuées sur des essais mécaniques classiques sous des charges progressivement croissantes telles que le test Brésilien ou le test de flexion en trois points. Le cadre de dynamique proposé est montré pour augmenter la robustesse de calcul. On a constaté que la direction finale des macro-fissures est assez bien prédite et que l'influence des effets d'inertie sur les solutions obtenues est assez modeste notamment en comparaison entre différentes mailles. Ce modèle bidimensionnel a été étendu plus loin dans le modèle bidimensionnel de discontinuité intégrée en viscodamage pour aider à explorer brièvement la mise en œuvre du schéma de point intermédiaire de second ordre qui peut fournir des résultats améliorés sous limitation de la régularisation visqueuse du modèle de dégâts localisésFailure of engineering materials and structures can be considered as a result of a complex interplay between different physical phenomena such as nucleation of cavities, microcracks,microvoids and other irreversible processes. These micro-defects eventually coalesce into one or more macro-cracks leading to a decrease in the load-bearing capability and finally, to failure of the structure under consideration. Prevention of failure of structures and structural parts has always been a critical subject and a major concern in engineering. This thesis aims to represent localized failure in non linear materials without mesh dependency. Of special interest will be the case of dynamic strain-softening. Localized phenomena are taken into account by using the embedded strong discontinuities approach in which the displacement field is enhanced to capture the discontinuity. Based upon this approach, a one-dimensional model for elasto-plastic bar capable of representing failure for ductile materials with combined hardening in FPZ-fracture process zone and softening with embedded strong discontinuities was first developed. Results comparing the proposed one-dimensional model to (semi-) analytical works are presented. It was shown that the proposed strategy provides mesh independent solutions. Strain increases in the softening domain with a simultaneous decrease of stress. The problem unloads elastically outside the strain softening region. The strain energy is found to vanish. The model was also compared with a one dimensional damage model capable of representing the dynamic fracture for elasto-damage bar with combined hardening in fracture process zone - FPZ and softening with strong embedded discontinuities to find a good agreement between two models. A two-dimensional finite element model was developed, capable of describing both the diffuse damage mechanism accompanied by initial strain hardening and subsequent softening response of the structure. The results of several numerical simulations, performed on classical mechanical tests under slowly increasing loads such as Brazilian test or three-point bending test were analyzed. The proposed dynamics framework is shown to increase computational robustness. It was found that the final direction of macro-cracks is predicted quite well and that influence of inertia effects on the obtained solutions is fairly modest especially in comparison among different meshes. This two-dimensional model was expanded further into the two dimensional continuum viscodamage-embedded discontinuity model to help briefly explore the implementation of the second order mid-point scheme that can provide improved results under limitation of viscous regularization of localized failure damage model
6
Tano, Robert. "Modelling of localized failure with emphasis on band paths /." Luleå, 2001. http://epubl.luth.se/1402-1544/2001/08/index.html.
Full text
7
Burger, B. B. "A study of localized failure modes in brittle materials." Master's thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/17652.
Full textAbstract:
Localization studies arise from the need to accurately model the behaviour of materials which exhibit instabilities due to strain softening or geometric effects. Localization in finite element modelling of brittle materials such as concrete and rock is a relatively unexplored area in computational mechanics, and this work applies current concepts to an isotropic damage model. The onset of localization is characterised by a bifurcation, where spatially uniform deformation is replaced by highly localized bands of large strain. Simple bifurcation analysis techniques are used, and are shown to extend the present predictive capability of the damage model and to indicate the direction of further refinement. Numerical studies of localization in concrete and norite are presented, together with boundary value problems of importance in mining applications. It is shown that qualitative agreement is obtained with experimental results.
8
Jukic, Miha. "Finite elements for modeling of localized failure in reinforced concrete." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2013. http://tel.archives-ouvertes.fr/tel-00997197.
Full textAbstract:
In this work, several beam finite element formulations are proposed for failure analysis of planar reinforced concrete beams and frames under monotonic static loading. The localized failure of material is modeled by the embedded strong discontinuity concept, which enhances standard interpolation of displacement (or rotation) with a discontinuous function, associated with an additional kinematic parameter representing jump in displacement (or rotation). The new parameters are local and are condensed on the element level. One stress resultant and two multi-layer beam finite elements are derived. The stress resultant Euler-Bernoulli beam element has embedded discontinuity in rotation. Bending response of the bulk of the element is described by elasto-plastic stress resultant material model. The cohesive relation between the moment and the rotational jump at the softening hinge is described by rigid-plastic model. Axial response is elastic. In the multi-layer beam finite elements, each layer is treated as a bar, made of either concrete or steel. Regular axial strain in a layer is computed according to Euler-Bernoulli or Timoshenko beam theory. Additional axial strain is produced by embedded discontinuity in axial displacement, introduced individually in each layer. Behavior of concrete bars is described by elastodamage model, while elasto-plasticity model is used for steel bars. The cohesive relation between the stress at the discontinuity and the axial displacement jump is described by rigid-damage softening model in concrete bars and by rigid-plastic softening model in steel bars. Shear response in the Timoshenko element is elastic. Finally, the multi-layer Timoshenko beam finite element is upgraded by including viscosity in the softening model. Computer code implementation is presented in detail for the derived elements. An operator split computational procedure is presented for each formulation. The expressions, required for the local computation of inelastic internal variables and for the global computation of the degrees of freedom, are provided. Performance of the derived elements is illustrated on a set of numerical examples, which show that the multi-layer Euler-Bernoulli beam finite element is not reliable, while the stress-resultant Euler-Bernoulli beam and the multi-layer Timoshenko beam finite elements deliver satisfying results.
9
Ngo, Van Minh. "Localized failure for coupled thermo-mechanics problems : applications to steel, concrete and reinforced concrete." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2013. http://tel.archives-ouvertes.fr/tel-00978452.
Full textAbstract:
During the last decades, the localized failure of massive structures under thermo-mechanical loads becomes the main interest in civil engineering due to a number of construction damaged and collapsed due to fire accident. Two central questions were carried out concerning the theoretical aspect and the solution aspect of the problem. In the theoretical aspect, the central problem is to introduce a thermo-mechanical model capable of modeling the interaction between these two physical effects, especially in localized failure. Particularly, we have to find the answer to the question: how mechanical loading affect the temperature of the material and inversely, how thermal loading result in the mechanical response of the structure. This question becomes more difficult when considering the localized failure zone, where the classical continuum mechanics theory can not be applied due to the discontinuity in the displacement field and, as will be proved in this thesis, in the heat flow. In terms of solution aspect, as this multi-physical problem is mathematical represented by a differential system, it can not be solved by an 'exact' analytical solution and therefore, numerical approximation solution should be carried out. This thesis contributes in both two aspects. Particularly, thermomechanical models for both steel and concrete (the two most important materials in civil engineering), which capable of controling the hardening behavior due to plasticity and/or damage and also the softening behavior due to the localized failure, are carried out and discussed. Then, the thermomechanical problems are solved by 'adiabatic' operator split procedure, which 'separates' the multi-physical process into the 'mechanical' part and the 'thermal' part. Each part is solved individually by another operator split procedure in the frame-work of embbed-discontinuity finite element method. In which, the 'local' discontinuities of the displacement field and the heat flow is solved in the element level, for each element where localized failure is detected. Then, these discontinuities are brought into the 'static condensation' form of the overall equilibrium equation, which is used to solved the displacement field and the temperature field of the structure at the global level. The thesis also contributes to determine the ultimate response of a reinforced concrete frame submitted to fire loading. In which, we take into account not only the degradation of material properties due to temperature but also the thermal effect in identifying the total response of the structure. Moreover, in the proposed method, the shear failure is also considered along with the bending failure in forming the overal failure of the reinforced structure. The thesis can also be extended and completed to solve the behavior of reinforced concrete in 2D or 3D case considering the behavior bond interface or to take into account other type of failures in material such as fatigue or buckling. The proposed models can also be improved to determine the dynamic response of the structure when subjected to earthquake and/or impact.
10
Dujc, Jaka. "Finite element analysis of limit load and localized failure of structures." Cachan, Ecole normale supérieure, 2008. http://tel.archives-ouvertes.fr/tel-00505153/fr/.
Full textAbstract:
Ce travail a pour objet l’analyse limite des structures par la méthode des éléments finis. Lorsqu’une structure atteint sa charge limite, certaines de ses composantes sont dans la phase inélastique de leur comportement, alors que dans les parties les plus critiques, du fait de la localisation des déformations inélastiques, se produit la rupture du matériau. Les effets de localisation sont, dans les matériaux fragiles liés à l’apparition et au développement de macro fissures alors qu’ils sont, dans les matériaux ductiles, gouvernés par les bandes de cisaillement localisées. L’étude de la charge limite est ainsi reliée à la modélisation du comportement inélastique standard du matériau mais également à la modélisation des effets localisés correspondant au comportement adoucissant des matériaux. Le comportement inélastique standard du matériau est, dans ce travail, décrit par des modèles élastoplastiques, élastoviscoplastiques ou élastiques non linéaires. Tous les modèles de comportement sont définis en termes d’efforts généralisés. Un certain nombre d’approches mathématiques et d’algorithmes numériques sont disponibles mais sont bien souvent inefficaces et manquent de précision. Ainsi, nous utilisons une approche développée plus récemment s’appuyant sur une méthode d’éléments finis enrichis de discontinuités. Nous avons développé de nouvelles formulations d’éléments standards prenant en compte des cinématiques et des descriptions des champs de déplacements discontinus complexes. Plusieurs formulations d’éléments finis ont été développées pour l’analyse de différents composants structurels. Nous présentons, dans un premier temps, un élément fini dédié à l’analyse limite des plaques en béton armé. La formulation d’un élément de plaque élastoplastique et élastoviscoplastique écrite en efforts généralisés associée à une procédure commune d’intégration sont présentées ensuite. Un élément de coque non linéaire, faisant intervenir une fonction seuil à deux surfaces incluant à la fois un écrouissage isotrope et un écrouissage cinématique est ensuite présenté. Les deux derniers éléments finis développés dans ce travail sont dédiés à la modélisation de la rupture localisée dans les poutres planes et les solides bidimensionnels. L’élément de poutre d’Euler-Bernouilli est enrichi par une discontinuité en rotation. Une stratégie s’appuyant sur l’analyse préalable, par un modèle raffiné, d’une partie de la structure est proposée afin d’obtenir les paramètres du modèle constitutif de la poutre. Enfin, nous présentons la formulation d’un élément quadrangulaire à discontinuité forte dont la cinématique permet de prendre en compte des sauts de déplacements linéaires dans les deux directions normale et tangentielle le long de la surface de discontinuité. Des résultats numériques montrent que les éléments développés ainsi que les algorithmes associés constituent un outil efficace et robuste d’analyse de la charge limite et de la rupture des structures. Parmi les exemples, nous présentons la simulation de la propagation d’une fissure dans un matériau fragile ainsi que le développement d’une bande de cisaillement dans un matériau ductile. Les codes numériques associés aux formulations présentées dans ce travail ont été générés par l’outil de programmation symbolique et d’optimisation de code AceGen. Les performances des éléments sont présentés à travers un grand nombre d’exemples numériques réalisés à partir du code AceFemThe dissertation deals with limit load and limit ductility analysis of structures by the finite element method. When structure is at its limit load, several structural components behave inelastically, while in the critical parts of the structure, due to localization of inelastic strains, failure of material appears. Localized effects in brittle materials are related to appearance and formation of a large (macro) crack, while failure in ductile materials is governed by localized shear bands. The study of limit load is thus related to modeling both standard inelastic material effects, as well as modeling of localized failure of material, often reffered to as material softening. Standard inelastic material effects are in this work described with elastoplastic, elastoviscoplastic and nonlinear elastic material models. All the material models are defined at the level of stress-resultants. Several mathematical approaches and numerical algorithms for modeling localized effects are at hand, but they are often inefficient or inaccurate. Therefor, we use an up-to-date approach, based on a finite element method with embedded discontinuity. We derive new finite element formulations with a quite complex kinematics of the basic elements, as well as rather complex description of discontinuous displacement fields. We derived several finite element formulations for analysis of different structural components. First we present a finite element for limit load analysis of reinforced concrete plates. Stress-resultant elastoplastic and elastoviscoplastic plate finite element formulation along with a unified computational procedure that covers both formulations are presented next. Further, a nonlinear shell finite element, based on a two-surface yield function, that includes both isotropic and kinematic material hardening is presented. The last two finite elements derived in this work are intended to model the localized failure in planar beams and 2D solids. The embedded discontinuity in rotations was built into elastoplastic Euler-Bernoulli beam finite element, and a procedure, based on a precomputed analysis of a part of a structure, by using a refined numerical model, is proposed to obtain the beam constitutive model parameters. Finally, we derive an elastoplastic quadrilateral two-dimensional finite element formulation with embedded strong discontinuity, whose kinematics can model linear jumps in both normal and tangential displacements along the discontinuity line. Numerical simulations show, that the derived finite elements, along with the accompanied numerical algorithms, are an efficient and a rather robust tool for limit load and failure analysis of structures. Among other examples, we present a simulation of crack growth in brittle material and a simulation of shear band failure in ductile material. All the computer codes of the finite element formulations presented in this work have been generated through the symbolic programming of the finite element computer code and the expression optimization in AceGen computer program. The performance of these elements has been presented in numerous numerical examples, all performed by the AceFem computer program
Books on the topic "Localised failure"
1
Ali, Christopher. The Policies of Localism. University of Illinois Press, 2017. http://dx.doi.org/10.5406/illinois/9780252040726.003.0003.
Full textAbstract:
Chapters 2 through 5 house the case studies for the book. Each chapter is sub-divided by country to give the reader a detailed understanding of the dynamics at play. Chapter 2 assesses the structural regulation of local television by focusing on a key issue in the debate over local television. It thus considers the FCC’s quadrennial ownership reviews in the United States, the fee-for-carriage debate in Canada, and Ofcom’s reviews of public service broadcasting in the United Kingdom. This chapter also introduces two key terms: public good and market failure. The chapter demonstrates how the local is bound so tightly to commercial markets, broadcasting technologies and the status quo that alternatives views are effective erased.
2
Lachmann, Helen J., and Giampaolo Merlini. The patient with amyloidosis. Edited by Giuseppe Remuzzi. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780199592548.003.0152.
Full textAbstract:
Amyloidosis is a disorder of protein folding in which normally soluble plasma proteins are deposited in the extracellular space in an abnormal insoluble fibrillar form. The process of amyloid formation and deposition causes cytotoxicity and progressive organ dysfunction. Amyloid is remarkably diverse and can be hereditary or acquired, localized or systemic, and lethal or merely an incidental finding. The most important numerically are AL amyloidosis, in which the fibrils are composed of monoclonal immunoglobulin light chains, and AA amyloidosis, in which the acute phase reactant Serum Amyloid A component forms the fibrils.The kidney is involved in 75% of patients with systemic amyloidosis. Heavy proteinuria or nephrotic syndrome is characteristic of most amyloid variants.Without treatment, systemic disease is usually fatal but measures that reduce the supply of amyloid fibril precursor proteins can result in regression of amyloid deposits, prevention of organ failure, and improved quality of life and survival. Early diagnosis, before irreversible organ damage has occurred, is the key to effective treatment. Recent advances in diagnosis and therapy have much improved the outlook of patients with AL amyloidosis, but agents with broader promise are under investigation.
3
Hickey, Sam, and Naomi Hossain, eds. The Politics of Education in Developing Countries. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198835684.001.0001.
Full textAbstract:
This book examines the politics of the learning crisis in the global South, where learning outcomes have stagnated or worsened, despite progress towards Universal Primary Education since the 1990s. Comparative analysis of education reform in Bangladesh, Cambodia, Ghana, Rwanda, South Africa, and Uganda highlights systemic failure on the frontline of education service delivery, driven by deeper crises of policymaking and implementation: few governments try to raise educational standards with any conviction, and education bureaucracies are unable to deliver even those learning reforms that get through the policy process. Introductory chapters develop a theoretical framework within which to examine the critical features of the politics of education. Case study chapters demonstrate that political settlements, or the balance of power between contending social groups, shape the extent to which elites commit to adopting and implementing reforms aimed at improving learning outcomes, and the nature this influence takes. Informal politics and power relations can generate incentives that undermine rather than support elite commitment to development, politicizing the provision of education. Tracing reform processes from their policy origins down to the frontline, it seems that successful schools emerged as localized solutions to specific solutions, often against the grain of dysfunctional sectoral arrangements and the national-level political settlement, but with local political backing. The book concludes with discussion of the need for more politically attuned approaches that focus on building coalitions for change and supporting ‘best-fit’ types of problem-solving fixes, rather than calling for systemic change.
4
Toprani, Anand. Oil and the Great Powers. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198834601.001.0001.
Full textAbstract:
During the first half of the twentieth century, a lack of oil constrained Britain and Germany from exerting their economic and military power independently. Having fought World War I with oil imported from the United States, Britain was determined to avoid relying upon another great power for its energy needs ever again. Even before the war had ended, Whitehall began implementing a strategy of developing alternative sources of oil under British control. Britain’s key supplier would be the Middle East—already a region of vital importance to the British Empire, but one whose oil potential was still unproven. There turned out to be plenty of oil in the Middle East, but Italian hostility after 1935 threatened British transit through the Mediterranean. As war loomed in 1939, Britain’s quest for independence from the United States was a failure. Germany was in an even worse position than Britain. The Third Reich went to war dependent on petroleum synthesized from coal, meager domestic crude oil production, and overland imports—primarily from Romania. German leaders were confident, however, that they had sufficient oil to fight a series of short, localized campaigns that would deliver to them the mastery of Europe. Their plan derailed following Germany’s swift victory over France, when Britain refused to make peace. This left Germany responsible for satisfying Europe’s oil requirements while cut off from world markets. A looming energy crisis in Axis Europe, an absence of strategic alternatives, and ideological imperatives all compelled Germany to invade the Soviet Union in 1941—a decision that ultimately sealed its fate.
Book chapters on the topic "Localised failure"
1
Johannes, Martin, and Ole Thybo Thomsen. "Localised Effects in Sandwich Structures with Internal Core Junctions:Modelling and Experimental Characterisation of Load Response, Failure and Fatigue." In Major Accomplishments in Composite Materials and Sandwich Structures, 229–77. Dordrecht: Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-90-481-3141-9_10.
Full text
2
Rudnicki, J. W. "Localized Failure in Brittle Rock." In Thermo-Hydromechanical and Chemical Coupling in Geomaterials and Applications, 25–40. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118623565.ch2.
Full text
3
Ouzzane, Adil, Pierre Colin, Nacim Betrouni, and Arnauld Villers. "Failure or Recurrence Management." In Technical Aspects of Focal Therapy in Localized Prostate Cancer, 209–14. Paris: Springer Paris, 2014. http://dx.doi.org/10.1007/978-2-8178-0484-2_18.
Full text
4
Atienza, F., J. Almendral, A. Arenal, E. G. Torrecilla, J. Jiménez, and M. Ortiz. "Impact of Localisa on Ablation Management." In New Advances in Heart Failure and Atrial Fibrillation, 201–4. Milano: Springer Milan, 2003. http://dx.doi.org/10.1007/978-88-470-2087-0_27.
Full text
5
Monsky, Paul. "Tight Closure’s Failure to Localize - a Self-Contained Exposition." In Commutative Algebra, 593–607. New York, NY: Springer New York, 2012. http://dx.doi.org/10.1007/978-1-4614-5292-8_19.
Full text
6
Gu, Xiaoqiang, Maosong Huang, and Jiangu Qian. "Micromechanics-Based Constitutive Modeling and DEM Simulation of Localized Failure in Soil." In Springer Series in Geomechanics and Geoengineering, 229–35. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-13506-9_33.
Full text
7
Perez, C. A., and M. A. Lockett. "Localized Carcinoma of the Prostate: Patterns of Failure with External Beam Radiation Therapy." In Carcinoma of the Prostate, 225–41. Berlin, Heidelberg: Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-642-60956-5_16.
Full text
8
Ibrahimbegovic, A. "Computations, testing, uncertainty propagation and size effect in localized failure of massive composite structures." In Insights and Innovations in Structural Engineering, Mechanics and Computation, 38–43. Taylor & Francis Group, 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742: CRC Press, 2016. http://dx.doi.org/10.1201/9781315641645-7.
Full text
9
Thomsen, Ole Thybo. "Characterisation and Assessment of Failure and Fatigue Phenomena in Sandwich Structures Induced by Localized Effects." In Experimental Analysis of Nano and Engineering Materials and Structures, 31–32. Dordrecht: Springer Netherlands, 2007. http://dx.doi.org/10.1007/978-1-4020-6239-1_15.
Full text
10
Bachmann, Ivana, and Javier Bustos-Jiménez. "Using Localized Attacks with Probabilistic Failures to Model Seismic Events over Physical-Logical Interdependent Networks." In Network Science, 1–14. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-97240-0_1.
Full textConference papers on the topic "Localised failure"
1
McCallum, Marcus, Chas Jandu, and Andrew Francis. "Probabilistic and Deterministic Approach to the Setting of In-Line Inspection Intervals." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-50350.
Full textAbstract:
All pipelines are susceptible to the possibility of corrosion damage. Corrosion is a time dependent process that leads to localised gradual thinning of the pipeline wall and if allowed to continue will eventually cause failure of the pipewall. Due to the progressive nature of corrosion the likelihood of failure increases with time. One means of mitigating the likelihood of such failures is to perform an in-line inspection using a metal loss detection tool. The frequency of inspection is an important parameter to operators since if it is too high, excessive costs will be incurred and if it is too low, failure involving loss of supply, threats to safety and the environment may follow. Operators therefore seek the optimum frequency. This paper describes a robust method for optimizing inspection intervals based on the use of structural reliability analysis.
2
Poon, Chun Ting, Connor Mullins, Lukas Radziunas, Enda O’Connell, Aengus Connolly, and Sean Leen. "Finite Element Design Study of Dynamics in Submarine Power Cables for Offshore Renewable Wind Energy." In ASME 2022 4th International Offshore Wind Technical Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/iowtc2022-98245.
Full textAbstract:
Abstract The future of energy in Ireland will include significant emphasis on offshore renewable energy due to the country’s excellent marine resources, with a potential 70 GW of ocean energy available within 100 km of the Irish coastline [1]. A key challenge to improving uptake of offshore wind energy is the reliability of power transmission via submarine power cables (SPCs). Dynamic cables associated with floating offshore wind turbines are critical infrastructure that consist of a complex arrangement of sub-components with different functions, including strength, insulation and corrosion resistance. Fretting, wear, and fatigue have been demonstrated as key contributing factors to damage and failure of cable conductors within laboratory testing of SPCs [2]. This paper presents a finite element design study for dynamic power cables based on a systematic model development relating an offshore submarine cable with a representative laboratory test arrangement. Initially a global finite element model is developed to replicate a floating wind turbine with attached dynamic cable via Flexcom [3] and OpenFAST [4] (without fretting fatigue damage) operating in an offshore marine environment. Simplified SPC and multi-strand wire models are developed using Abaqus [5] to understand the localised fretting conditions between individual wires. The results of these models are implemented into a localised and highly detailed frictional contact model, constructed to represent a crossed-cylinder laboratory fretting test arrangement, using results from the global assessment as boundary conditions. The localised finite element analysis (FEA) is used to predict potential fretting fatigue damage. This research aims to develop a systematic methodology for fretting fatigue in SPC copper conductors, helping to identify suitable design aspects (e.g., lay angle, lay direction, wire diameter, and number of layers) for reduction of fretting fatigue damage and extension of cable service life.
3
Newton, Christopher D., Jonathan P. Jones, Adam L. Chamberlain, and Martin R. Bache. "Inhomogeneous Strain Distribution in SiCf/SiC Coupons Under Tensile Loading." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63045.
Full textAbstract:
The complex structural architecture and inherent processing artefacts within ceramic matrix composites combine to induce inhomogeneous deformation and damage prior to ultimate failure. Bulk measurements of strain via extensometry or even localised strain gauging will fail to characterise such inhomogeneity when performing conventional mechanical testing on laboratory scaled coupons. The current research project has, therefore, applied digital image correlation (DIC) techniques to the room temperature axial assessment of a SiCf/SiC composite under static and ratchetted loading. As processed SiCf/SiC panels were subjected to detailed X-ray computed tomography (XCT) inspection prior to specimen extraction and subsequent mechanical testing. In situ DIC strain measurements were taken throughout the period of room temperature monotonic and ratchet style tensile tests. Contemporary acoustic emission (AE) signals were also recorded to indicate significant damage events and the onset of ultimate failure. Data from these separate monitoring techniques were correlated to indicate the sensitivity or otherwise to pre-existing artefacts within the as received CMC panels.
4
De Souza, Valdir, Eugenia Marinou, Andrew Legge, and Vicky Nwafor. "Failure Investigation of a Corrosion Leak in a C77 Block and Tubing Bonnet in a Chemical Injection System – A Case History." In SPE International Oilfield Corrosion Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/205054-ms.
Full textAbstract:
Abstract This paper presents a case history outlining the investigation performed to evaluate the causes of failure between a C77 block and tubing bonnet line, used for delivering scale inhibitor to a production well. The data review indicated that the failure occurred as a result of synergistic corrosion effects, including incompatibility between the scale inhibitor chemical and the metallurgies of the block (13Cr SS) and tubing (carbon steel). The analysis showed that while each of the relevant corrosion mechanisms (oxygen corrosion, galvanic and localised corrosion) may not be the root cause for the failure individually, in combination they proved detrimental to system integrity. The study also highlighted that while chemical inhibitor compatibility testing with appropriate flow-wetted metallurgies is common practice, the environment and configuration used for testing is not always representative of the field conditions or specific process operations (e.g., oxygen ingress due to unblanketed tanks, presence of dissimilar materials). In the present case, for example, the most significant oxygen sources were found to be the dissolved oxygen in the tap water used to mix the scale inhibitor to make up the final formulation; and the glycol blended into the product to give it ‘winterised’ properties. Lastly, the paper summarises the recommendations that were put forth to address the issue, such as evaluation of different metallurgies, a more suitable scale inhibitor and implementation of process monitoring, especially of oxygen levels.
5
Sharples, J. K., M. A. Wilkes, S. F. Yellowlees, D. W. Beardsmore, G. T. Melvin, R. Hurlston, and C. T. Watson. "Analysis of Multiple Co-Planar Surface Breaking Flaws Loaded in Tension Under Cleavage Failure Conditions." In ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/pvp2006-icpvt-11-93562.
Full textAbstract:
In procedures such as R6 and BS 7910 for assessing the structural integrity of structures, complex multiple flaws located in close proximity to each other are generally characterised as one, larger, single flaw. Recent studies have shown that the current characterisation rules may be non-conservative under some circumstances. Concurrent experimental and analytical programmes are being undertaken in order to further investigate this potential non-conservatism for situations where the possibility of cleavage failure has to be taken into account when assessing structures or components containing multiple flaws. The analytical work has involved inelastic finite element modelling in conjunction with numerical analysis based on the weakest link methodology for cleavage initiation to determine the probability of cleavage failure. This has allowed the probability of failure for the situation of multiple adjacent flaws to be compared with that for the single characterised flaw to determine whether the characterisation rules are conservative. Initial results from the cases studied so far indicate that: • For flaws that do not touch, the probability of cleavage failure for the single characterised flaw is higher than the original flaws, confirming that the characterisation process is conservative in this case (perhaps significantly so). • For low aspect ratio (depth/length ≪ 1.0) flaws in contact, the probability of cleavage failure for the single characterised is higher than the original flaws, confirming that the characterisation process is conservative in this case. • However, for high aspect ratio (depth/length ∼ 1.0) flaws in contact, the probability of cleavage failure for the single characterised flaw is lower than the original flaws, indicating that the characterisation process may be non-conservative in this case. This paper covers the initial stages of a much larger programme. The analyses presented in this paper are in the process of being extended to allow for crack-tip constraint effects. Early results from these further analyses indicate that the loss of constraint between interacting flaws may be a significant factor and could eliminate at least some of the perceived non-conservatism for the high aspect ratio flaw. Further work is also underway to examine the effect of any localised coalescence of defects (a re-entrant region); the current analyses consider defects that are only just in contact. Further papers are therefore expected.
6
Cosham, Andrew, Phil Hopkins, David G. Jones, and Julian Barnett. "Warm Pre-Stressing and Leaks in Pipelines." In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-24085.
Full textAbstract:
Line pipe steel is a carbon manganese steel. The toughness of line pipe steel undergoes a transition from high toughness (on the upper shelf) to low toughness (on the lower shelf) as the temperature decreases. A fluid will cool significantly as it expands through a leak in a pipeline. This has led to the suggestion that localised cooling of the material surrounding the leak might be sufficient to cool the material down to below the ductile to brittle transition temperature and cause a brittle fracture. Warm pre-stressing occurs when a load is applied to a structure containing a defect and then the temperature of the structure is reduced. Warm pre-stressing causes the defect in the structure to fail at a higher load at the lower temperature than if it had not experienced this prior loading at the previously higher temperature. A programme of single edge notch bend tests has been conducted on behalf of National Grid Carbon to demonstrate the beneficial effect of warm pre-stressing in a line pipe steel. The material tested was a sample of 914.4 mm outside diameter, 19.1 mm wall thickness, Grade API 5L X60 line pipe. Single edge notch bend specimens were subject to the ‘load-cool-fail’ cycle and the ‘load-unload-cool-fail’ cycle. The effect of different levels of stable ductile crack growth during the pre-load was also investigated. Warm pre-stressing is shown to have a beneficial effect. The load at failure in the specimens that had been subject to warm pre-stressing was higher than those that had not been subject to warm pre-stressing, and, in most cases, it was higher than the pre-load. The fracture toughness (in terms of the stress intensity factor) of the specimens that had been subject to warm pre-stressing was 1.4 to 1.7 times higher than that of those that had not been subject to warm pre-stressing. The results of the tests were conservatively predicted using the theoretical models. Also, the results are consistent with previous tests on structural steels. Therefore, localised cooling of the material around a leak in a pipeline is not predicted to result in a failure.
7
Motarjemi, Afshin. "Assessment of a Corrosion Under Insulation (CUI) Using DNV RP-F101 Procedure." In ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-78016.
Full textAbstract:
Corrosion under insulation is a typical type of localised corrosion in oil and gas industry especially when water penetrates into a damaged thermal insulation/coating. An area of corrosion under insulation (CUI) was observed on the external surface of a pipe on topside of an offshore platform after removing the insulation. Surveys of depth measurements of the corroded area in both longitudinal and circumferential directions (with respect to the pipe axial direction) using a depth micrometer tool were performed and then converted to a river-bottom profile following the procedure of DNV RP-F101 Part A. A best estimate of the failure pressure safe working pressure (maximum operating pressure) of the pipe were calculated. The former was then compared against the finite element analysis (FEA) results which showed good agreement when axial stresses were excluded. The effect of assumptions such as confidence level and inspection sizing accuracy are also discussed.
8
Gowda, Kumar K., S. L. Ajit Prasad, and Vinayaka Nagarajaiah. "Design Optimization of T-Root Geometry of a Gas Engine HP Compressor Rotor Blade for Lifing the Blade Against Fretting Failure." In ASME 2016 Power Conference collocated with the ASME 2016 10th International Conference on Energy Sustainability and the ASME 2016 14th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/power2016-59331.
Full textAbstract:
Stress Concentration Factor (SCF) is significant in machine elements as it gives rise to localised stresses which lead to peak stresses introducing cracks which propagate further and hence the component fails before the desired design life. Turbine blades are subjected to high centrifugal stresses and vibratory stresses in a Gas Engine HP Rotor. The vibratory stresses arise due to air wake flow excitations called Nozzle Passing Frequency (NPF). Hence, Turbomachinery industry calls for an optimum structurally rigid blade root geometry. An optimum blade root was defined, as a root with practical geometry, which when loaded returns the minimum fillet SCF. In the present work an approach has been done for design optimization of fillet stresses at sharp edges of T-root blade, optimization of platform dimensions, shank dimensions, root land dimensions and to ensure that stress distribution is uniformly spread along the filleted width of the root land on both sides of the blade, which otherwise will lead to crack initiation, propagation and hence, fretting failure at blade root lands. This may further lead to blade lift and effect on stage and overall gas engine failure over a period of cycles. Hence, a special attention is made on SCF of the T root -blade which fails and to guarantee for safe and reliable operation under all possible service conditions. Finite Element Analysis (FEA) is used to determine the fillet stresses and Peterson’s SCF chart is effectively utilized to modify the blade root. The root is modified due to the difficulty in manufacturing the butting surface of the tang which grips the blade to the disk crowns having small contact area. The blade height is suitably designed using Campbell diagram by ensuring the working frequency is well within 6e excitations for the specified operating speeds. Hence, increasing the life of the HP compressor blade.
9
Newton, Christopher D., J. Paul Jones, Louise Gale, and Martin R. Bache. "Detection of Strain and Damage Distribution in SiCf/SiC Mechanical Test Coupons." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75791.
Full textAbstract:
The complex structural architecture and inherent processing artefacts within ceramic matrix composites combine to induce inhomogeneous deformation and damage prior to ultimate failure. Sophisticated mechanical characterisation is vital in support of a fundamental understanding of deformation in ceramic matrix composites. On the component scale, “damage tolerant” design and lifing philosophies depend upon laboratory assessments of macro-scale specimens, incorporating typical fibre architectures and matrix under representative stress-strain states. Bulk measurements of strain via extensometry or even localised strain gauging will fail to characterise such inhomogeneity when performing conventional mechanical testing on laboratory scaled coupons. The current research project has, therefore, applied digital image correlation (DIC), electrical resistance monitoring and acoustic emission techniques to the room and high temperature assessment of a SiCf/SiC composite under axial fatigue loading. Data from these separate monitoring techniques plus ancillary use of X-Ray computed tomography and optical inspection were correlated to monitor the onset and progression of damage during cyclic loading.
10
Bunsell, A. R., S. Blassiau, Y. Mezie`re, Y. Favry, and J. Ch Teissedre. "NDE of Carbon Fiber Composite Pressure Vessels." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33481.
Full textAbstract:
The use of advanced composites in pressure vessels requires means of periodically evaluating residual minimum lifetimes in order for them to remain in service. Tests based on the prediction of crack propagation are not applicable for composite vessels as, in the absence of stress raisers or localised damage, the failure processes are diffuse and particularly damaging if the reinforcing fibers fail. Acoustic emission has been used to detect this type of damage. At a constant pressure it has been shown that even unidirectional carbon fiber reinforced resin continues to emit which reveals a continuing failure process involving the failure of fibers. The rate of emission under a constant pressure has been shown to obey a simple law which allows the damage accumulation to be calculated as a function of time. A maximum damage threshold can be determined experimentally so that master curves corresponding to the damage accumulated by a pressure vessel under constant pressure over the lifetime required can be calculated. A comparison between these master curves and the rate of damage accumulation of any other pressure vessel of the same type reveals if it will fail before or after the desired lifetime. The effects of pressure variations during service have been seen to be minor but even if this is not the case a comparison with the master curves still allows minimum lifetimes to be predicted. The technique does not require the vessels to be removed from the vehicle which is immobilised for a minimum of time.
Reports on the topic "Localised failure"
1
Scrymgeour, David, Andrew N. Fisher, Calvin Chan, Jason M. Meeks, Daniel Robert Ward, and Craig Y. Nakakura. Localized Electromagnetic Probing for Failure Analysis in Noisy Environments. Office of Scientific and Technical Information (OSTI), September 2019. http://dx.doi.org/10.2172/1569344.
Full text
2
Bano, Masooda. Curricula that Respond to Local Needs: Analysing Community Support for Islamic and Quranic Schools in Northern Nigeria. Research on Improving Systems of Education (RISE), August 2022. http://dx.doi.org/10.35489/bsg-rise-wp_2022/103.
Full textAbstract:
Involving local communities in school management is seen to be crucial to improving the quality of education in state schools in developing countries; yet school-based management committees remain dormant in most such contexts. Drawing on ethnographic fieldwork with a rich network of community-supported Islamic and Quranic schools in the state of Kano in northern Nigeria—a sub-Saharan African region with very low education indicators, low economic growth, and political and social instability—this paper shows how making school curricula responsive to local value systems and economic opportunities is key to building a strong sense of community ownership of schools. Under community-based school management committees, control over more substantive educational issues—such as the content of school curricula and the nature of aspirations and concepts of a good life that it promotes among the students—remains firmly in the hands of the government education authorities, who on occasion also draw on examples from other countries and expertise offered by international development agencies when considering what should be covered. The paper shows that, as in the case of the urban areas, rural communities or those in less-developed urban centres lose trust in state schools when the low quality of education provided results in a failure to secure formal-sector employment. But the problem is compounded in these communities, because while state schools fail to deliver on the promise of formal-sector employment, the curriculum does promote a concept of a good life that is strongly associated with formal-sector employment and urban living, which remains out of reach for most; it also promotes liberal values, which in the local communities' perception are associated with Western societies and challenge traditional values and authority structures. The outcomes of such state schooling, in the experience of rural communities, are frustrated young people, unhappy with the prospect of taking up traditional jobs, and disrespectful of parents and of traditional authority structures. The case of community support for Islamic and Quranic schools in northern Nigeria thus highlights the need to consider the production of localised curricula and to adjust concepts of a good life to local contexts and economic opportunities, as opposed to adopting a standardised national curriculum which promotes aspirations that are out of reach.
3
Bano, Masooda. Curricula that Respond to Local Needs: Analysing Community Support for Islamic and Quranic Schools in Northern Nigeria. Research on Improving Systems of Education (RISE), August 2022. http://dx.doi.org/10.35489/bsg-rise-wp_2022/103.
Full textAbstract:
Involving local communities in school management is seen to be crucial to improving the quality of education in state schools in developing countries; yet school-based management committees remain dormant in most such contexts. Drawing on ethnographic fieldwork with a rich network of community-supported Islamic and Quranic schools in the state of Kano in northern Nigeria—a sub-Saharan African region with very low education indicators, low economic growth, and political and social instability—this paper shows how making school curricula responsive to local value systems and economic opportunities is key to building a strong sense of community ownership of schools. Under community-based school management committees, control over more substantive educational issues—such as the content of school curricula and the nature of aspirations and concepts of a good life that it promotes among the students—remains firmly in the hands of the government education authorities, who on occasion also draw on examples from other countries and expertise offered by international development agencies when considering what should be covered. The paper shows that, as in the case of the urban areas, rural communities or those in less-developed urban centres lose trust in state schools when the low quality of education provided results in a failure to secure formal-sector employment. But the problem is compounded in these communities, because while state schools fail to deliver on the promise of formal-sector employment, the curriculum does promote a concept of a good life that is strongly associated with formal-sector employment and urban living, which remains out of reach for most; it also promotes liberal values, which in the local communities' perception are associated with Western societies and challenge traditional values and authority structures. The outcomes of such state schooling, in the experience of rural communities, are frustrated young people, unhappy with the prospect of taking up traditional jobs, and disrespectful of parents and of traditional authority structures. The case of community support for Islamic and Quranic schools in northern Nigeria thus highlights the need to consider the production of localised curricula and to adjust concepts of a good life to local contexts and economic opportunities, as opposed to adopting a standardised national curriculum which promotes aspirations that are out of reach.
4
Trim, M., Matthew Murray, and C. Crane. Modernization and structural evaluation of the improved Overhead Cable System. Engineer Research and Development Center (U.S.), March 2021. http://dx.doi.org/10.21079/11681/40025.
Full textAbstract:
A modernized Overhead Cable System prototype for a 689 ft (210 m) Improved Ribbon Bridge crossing was designed, assembled, and structurally tested. Two independent structural tests were executed, i.e., a component-level compression test of the BSS tower was performed to determine its load capacity and failure mode; and a system-level ‘dry’ test of the improved OCS prototype was conducted to determine the limit state and failure mode of the entire OCS. In the component-level compression test of the BSS tower, the compressive capacity was determined to be 102 kips, and the failure mode was localized buckling in the legs of the tower section. During system-level testing, the prototype performed well up to 40.5 kips of simulated drag load, which corresponds to a uniformly distributed current velocity of 10.7 ft/s. If a more realistic, less conservative parabolic velocity distribution is assumed instead, the drag load for an 11 ft/s current is 21.1 kips. Under this assumption, the improved OCS prototype has a factor of safety of 1.9, based on a 689-ft crossing and 11-ft/s current. The OCS failed when one of the tower guy wires pulled out of the ground, causing the tower to overturn.
5
Rahmani, Mehran, and Manan Naik. Structural Identification and Damage Detection in Bridges using Wave Method and Uniform Shear Beam Models: A Feasibility Study. Mineta Transportation Institute, February 2021. http://dx.doi.org/10.31979/mti.2021.1934.
Full textAbstract:
This report presents a wave method to be used for the structural identification and damage detection of structural components in bridges, e.g., bridge piers. This method has proven to be promising when applied to real structures and large amplitude responses in buildings (e.g., mid-rise and high-rise buildings). This study is the first application of the method to damaged bridge structures. The bridge identification was performed using wave propagation in a simple uniform shear beam model. The method identifies a wave velocity for the structure by fitting an equivalent uniform shear beam model to the impulse response functions of the recorded earthquake response. The structural damage is detected by measuring changes in the identified velocities from one damaging event to another. The method uses the acceleration response recorded in the structure to detect damage. In this study, the acceleration response from a shake-table four-span bridge tested to failure was used. Pairs of sensors were identified to represent a specific wave passage in the bridge. Wave velocities were identified for several sensor pairs and various shaking intensities are reported; further, actual observed damage in the bridge was compared with the detected reductions in the identified velocities. The results show that the identified shear wave velocities presented a decreasing trend as the shaking intensity was increased, and the average percentage reduction in the velocities was consistent with the overall observed damage in the bridge. However, there was no clear correlation between a specific wave passage and the observed reduction in the velocities. This indicates that the uniform shear beam model was too simple to localize the damage in the bridge. Instead, it provides a proxy for the overall extent of change in the response due to damage.
6
S. Abdellatif, Omar. Localizing Human Rights SDGs: Ghana in context. Raisina House, June 2021. http://dx.doi.org/10.52008/gh2021sdg.
Full textAbstract:
In September 2015, Ghana along all UN member states endorsed the Agenda 2030 Sustainable Development Goals (SDGs) as the cardinal agenda towards achieving a prosperous global future. The SDGs are strongly interdependent, making progress in all goals essential for a country’s achievement of sustainable development. While Ghana and other West African nations have exhibited significant economic and democratic development post-independence. The judiciary system and related legal frameworks, as well as the lack of rule law and political will for safeguarding the human rights of its citizens, falls short of considering violations against minorities. Will Ghana be able to localize human rights related SDGs, given that West African governments historically tended to promote internal security and stability at the expense of universal human rights? This paper focuses on evaluating the commitments made by Ghana towards achieving Agenda 2030, with a particular focus on the SDGs 10 and 16 relating to the promotion of reduced inequalities, peace, justice and accountable institutions. Moreover, this paper also analyzes legal instruments and state laws put in place post Ghana’s democratization in 1992 for the purpose of preventing discrimination and human rights violations in the nation. The article aims to highlight how Ghana’s post-independence political experience, the lack of rule of law, flaws in the judiciary system, and the weak public access to justice are obstacles to its effective localization of human rights SGDs. Those obstacles to Ghana’s compliance with SDGs 10 and 16 are outlined in this paper through a consideration of human rights violations faced by the Ghanaian Muslim and HIV minorities, poor prison conditions, limited public access to justice and the country’s failure to commit to international treaties on human rights. Keywords: Ghana, human rights, rule of law, security, Agenda 2030
7
Habib, Ayman, Darcy M. Bullock, Yi-Chun Lin, and Raja Manish. Road Ditch Line Mapping with Mobile LiDAR. Purdue University, 2021. http://dx.doi.org/10.5703/1288284317354.
Full textAbstract:
Maintenance of roadside ditches is important to avoid localized flooding and premature failure of pavements. Scheduling effective preventative maintenance requires mapping of the ditch profile to identify areas requiring excavation of long-term sediment accumulation. High-resolution, high-quality point clouds collected by mobile LiDAR mapping systems (MLMS) provide an opportunity for effective monitoring of roadside ditches and performing hydrological analyses. This study evaluated the applicability of mobile LiDAR for mapping roadside ditches for slope and drainage analyses. The performance of alternative MLMS units was performed. These MLMS included an unmanned ground vehicle, an unmanned aerial vehicle, a portable backpack system along with its vehicle-mounted version, a medium-grade wheel-based system, and a high-grade wheel-based system. Point cloud from all the MLMS units were in agreement in the vertical direction within the ±3 cm range for solid surfaces, such as paved roads, and ±7 cm range for surfaces with vegetation. The portable backpack system that could be carried by a surveyor or mounted on a vehicle and was the most flexible MLMS. The report concludes that due to flexibility and cost effectiveness of the portable backpack system, it is the preferred platform for mapping roadside ditches, followed by the medium-grade wheel-based system. Furthermore, a framework for ditch line characterization is proposed and tested using datasets acquired by the medium-grade wheel-based and vehicle-mounted portable systems over a state highway. An existing ground filtering approach is modified to handle variations in point density of mobile LiDAR data. Hydrological analyses, including flow direction and flow accumulation, are applied to extract the drainage network from the digital terrain model (DTM). Cross-sectional/longitudinal profiles of the ditch are automatically extracted from LiDAR data and visualized in 3D point clouds and 2D images. The slope derived from the LiDAR data was found to be very close to highway cross slope design standards of 2% on driving lanes, 4% on shoulders, as well as 6-by-1 slope for ditch lines. Potential flooded regions are identified by detecting areas with no LiDAR return and a recall score of 54% and 92% was achieved by the medium-grade wheel-based and vehicle-mounted portable systems, respectively. Furthermore, a framework for ditch line characterization is proposed and tested using datasets acquired by the medium-grade wheel-based and vehicle-mounted portable systems over a state highway. An existing ground filtering approach is modified to handle variations in point density of mobile LiDAR data. Hydrological analyses, including flow direction and flow accumulation, are applied to extract the drainage network from the digital terrain model (DTM). Cross-sectional/longitudinal profiles of the ditch are automatically extracted from LiDAR data, and visualized in 3D point clouds and 2D images. The slope derived from the LiDAR data was found to be very close to highway cross slope design standards of 2% on driving lanes, 4% on shoulder, as well as 6-by-1 slope for ditch lines. Potential flooded regions are identified by detecting areas with no LiDAR return and a recall score of 54% and 92% was achieved by the medium-grade wheel-based and vehicle-mounted portable systems, respectively.