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Artigos de revistas sobre o assunto "Behaviour isotropy"
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Kim, J., e R. A. Antonia. "Isotropy of the small scales of turbulence at low Reynolds number". Journal of Fluid Mechanics 251 (junho de 1993): 219–38. http://dx.doi.org/10.1017/s0022112093003398.
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Spectral local isotropy tests are applied to direct numerical simulation data, mainly at the centreline of a fully developed turbulent channel flow. Despite the small Reynolds number of the simulation, the high-wavenumber behaviour of velocity and vorticity spectra is consistent with local isotropy. This consistency is verified by the relationship between streamwise wavenumber spectra and spanwise wavenumber spectra. The high-wavenumber behaviour of the pressure spectrum is also consistent with local isotropy and compares favourably with the calculation of Batchelor (1951), which assumes isotropy and joint normality of the velocity field at two points in space. The latter assumption is validated by the shape but not the magnitude of the quadruple correlation of the streamwise velocity fluctuation at small separations. There is only partial support for local spectral isotropy away from the centreline as the magnitude of the mean strain rate increases.
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SHAFI, H. S., e R. A. ANTONIA. "Small-scale characteristics of a turbulent boundary layer over a rough wall". Journal of Fluid Mechanics 342 (10 de julho de 1997): 263–93. http://dx.doi.org/10.1017/s0022112097005612.
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Measurements of the spanwise and wall-normal components of vorticity and their constituent velocity derivative fluctuations have been made in a turbulent boundary layer over a mesh-screen rough wall using a four-hot-wire vorticity probe. The measured spectra and variances of vorticity and velocity derivatives have been corrected for the effect of spatial resolution. The high-wavenumber behaviour of the spectra conforms closely with isotropy. Over most of the outer layer, the normalized magnitudes of the velocity derivative variances differ significantly from those over a smooth wall layer. The differences are such that the variances are much more nearly isotropic over the rough wall than on the smooth wall. This behaviour is consistent with earlier observations that the large-scale structure in this rough wall layer is more isotropic than that in a smooth wall layer. Isotropy-based approximations for the mean energy dissipation rate and mean enstrophy are consequently more reliable in this rough wall layer than in a smooth wall layer. In the outer layer, the vorticity variances are slightly larger than those over a smooth wall; reflecting structural differences between the two flows.
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Gautam, Rajeeb, e Ron CK Wong. "Transversely isotropic stiffness parameters and their measurement in Colorado shale". Canadian Geotechnical Journal 43, n.º 12 (1 de dezembro de 2006): 1290–305. http://dx.doi.org/10.1139/t06-083.
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Drained stress path triaxial tests and confined torsion tests were conducted on Colorado shale core samples to investigate transversely isotropic stiffness parameters at small strain deformation. Nonlinear plastic behaviour occurred along the primary loading path even at strains less than 0.01%. Nonlinear, hysteric behaviour was only observed during the loading–unloading path. However, the shale material displayed transverse isotropy in deformation, and very small or nondetectable Poisson's ratios in vertical and horizontal directions. This special response alludes to the postulate that the Colorado shale could be approximated by a transversely isotropic elasticity model at small strain levels with negligible yielding.Key words: anisotropy, elasticity, stiffness, triaxial test, torsion test, shale.
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CHOI, KWING-SO, e JOHN L. LUMLEY. "The return to isotropy of homogeneous turbulence". Journal of Fluid Mechanics 436 (10 de junho de 2001): 59–84. http://dx.doi.org/10.1017/s002211200100386x.
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Three types of homogeneous anisotropic turbulence were produced by the plane distortion, axisymmetric expansion and axisymmetric contraction of grid-generated turbulence, and their behaviour in returning to isotropy was experimentally studied using hot-wire anemometry. It was found that the turbulence trajectory after the plane distortion was highly nonlinear, and did not follow Rotta's linear model in returning to isotropy. The turbulence wanted to become axisymmetric even more than it wanted to return to isotropy. In order to show the rate of return to isotropy of homogeneous turbulence, a map of the ratio of the characteristic time scale for the decay of turbulent kinetic energy to that of the return to isotropy was constructed. This demonstrated that the rate of return to isotropy was much lower for turbulence with a greater third invariant of the anisotropy tensor. The invariant technique was then applied to the experimental results to develop a new turbulence model for the return-to-isotropy term in the Reynolds stress equation which satisfied the realizability conditions. The effect of the Reynolds number on the rate of return to isotropy was also investigated and the results incorporated in the proposed model.
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ANTONIA, R. A., T. ZHOU e Y. ZHU. "Three-component vorticity measurements in a turbulent grid flow". Journal of Fluid Mechanics 374 (10 de novembro de 1998): 29–57. http://dx.doi.org/10.1017/s0022112098002547.
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All components of the fluctuating vorticity vector have been measured in decaying grid turbulence using a vorticity probe of relatively simple geometry (four X-probes, i.e. a total of eight hot wires). The data indicate that local isotropy is more closely satisfied than global isotropy, the r.m.s. vorticities being more nearly equal than the r.m.s. velocities. Two checks indicate that the performance of the probe is satisfactory. Firstly, the fully measured mean energy dissipation rate 〈ε〉 is in good agreement with the value inferred from the rate of decay of the mean turbulent energy 〈q2〉 in the quasi-homogeneous region; the isotropic mean energy dissipation rate 〈εiso〉 agrees closely with this value even though individual elements of 〈ε〉 indicate departures from isotropy. Secondly, the measured decay rate of the mean-square vorticity 〈ω2〉 is consistent with that of 〈q2〉 and in reasonable agreement with the isotropic form of the transport equation for 〈ω2〉. Although 〈ε〉≃〈εiso〉, there are discernible differences between the statistics of ε and εiso; in particular, εiso is poorly correlated with either ε or ω2. The behaviour of velocity increments has been examined over a narrow range of separations for which the third-order longitudinal velocity structure function is approximately linear. In this range, transverse velocity increments show larger departures than longitudinal increments from predictions of Kolmogorov (1941). The data indicate that this discrepancy is only partly associated with differences between statistics of locally averaged ε and ω2, the latter remaining more intermittent than the former across this range. It is more likely caused by a departure from isotropy due to the small value of Rλ, the Taylor microscale Reynolds number, in this experiment.
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Svendsen, Bob, e Kolumban Hutter. "A continuum approach for modelling induced anisotropy in glaciers and ice sheets". Annals of Glaciology 23 (1996): 262–69. http://dx.doi.org/10.3189/s0260305500013525.
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This paper presents a formulation of a continuum model for so-called (stress or deformation) induced anisotropy in natural ice which, unlike computer-based Taylor-type models, can be incorporated in numerical simulations of large ice masses to account for the effects of this process on the flow of these bodies in a physical fashion. To do this, we treat natural ice as a rigid-elastic, non-linear inelastic material which can develop transverse isotropic behaviour (accounting for the simplest kind of induced anisotropy in natural ice masses), where the degree of such anisotropy at each point is controlled by the distribution of crystal glide-plane orientations there. This distribution is described by a so-called orientation-distribution function, for which an evolution relation can be derived. The central constitutive assumption of this formulation relates this distribution to the “structure” tensor representing the transverse isotropy of the material. On the basis of this relation, the model predicts in particular isotropic (e.g. classical Glen’s flow-law type) behaviour at a given point when the distribution of crystal glide-plane orientations is uniform there.
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KANG, HYUNG SUK, e CHARLES MENEVEAU. "Passive scalar anisotropy in a heated turbulent wake: new observations and implications for large-eddy simulations". Journal of Fluid Mechanics 442 (24 de agosto de 2001): 161–70. http://dx.doi.org/10.1017/s0022112001005225.
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The effects of passive scalar anisotropy on subgrid-scale (SGS) physics and modelling for large-eddy simulations are studied experimentally. Measurements are performed across a moderate Reynolds number wake flow generated by a heated cylinder, using an array of four X-wire and four cold-wire probes. By varying the separation distance among probes in the array, we obtain filtered and subgrid quantities at three different filter sizes. We compute several terms that comprise the subgrid dissipation tensor of kinetic energy and scalar variance and test for isotropic behaviour, as a function of filter scale. We find that whereas the kinetic energy dissipation tensor tends towards isotropy at small scales, the SGS scalar-variance dissipation remains anisotropic independent of filter scale. The eddy-diffusion model predicts isotropic behaviour, whereas the nonlinear (or tensor eddy diffusivity) model reproduces the correct trends, but overestimates the level of scalar dissipation anisotropy. These results provide some support for so-called mixed models but raise new questions about the causes of the observed anisotropy.
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Svendsen, Bob, e Kolumban Hutter. "A continuum approach for modelling induced anisotropy in glaciers and ice sheets". Annals of Glaciology 23 (1996): 262–69. http://dx.doi.org/10.1017/s0260305500013525.
Texto completo da fonteResumo:
This paper presents a formulation of a continuum model for so-called (stress or deformation) induced anisotropy in natural ice which, unlike computer-based Taylor-type models, can be incorporated in numerical simulations of large ice masses to account for the effects of this process on the flow of these bodies in a physical fashion. To do this, we treat natural ice as a rigid-elastic, non-linear inelastic material which can develop transverse isotropic behaviour (accounting for the simplest kind of induced anisotropy in natural ice masses), where the degree of such anisotropy at each point is controlled by the distribution of crystal glide-plane orientations there. This distribution is described by a so-called orientation-distribution function, for which an evolution relation can be derived. The central constitutive assumption of this formulation relates this distribution to the “structure” tensor representing the transverse isotropy of the material. On the basis of this relation, the model predicts in particular isotropic (e.g. classical Glen’s flow-law type) behaviour at a given point when the distribution of crystal glide-plane orientations is uniform there.
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Jiménez-Morales, F., e J. J. Luque. "Collective behaviour in a cellular automaton and isotropy of the neighbourhood". Physica A: Statistical Mechanics and its Applications 212, n.º 1-2 (dezembro de 1994): 118–22. http://dx.doi.org/10.1016/0378-4371(94)90141-4.
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Wandrol, Ivo, Karel Frydrýšek e Daniel Čepica. "Analysis of the Influence of Thermal Loading on the Behaviour of the Earth’s Crust". Applied Sciences 13, n.º 7 (29 de março de 2023): 4367. http://dx.doi.org/10.3390/app13074367.
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The article focuses on the deformation and strain-stress analysis of the Earth’s crust under external thermal loading. More specifically, the influence of cyclic changes in the surface temperature field on the stress and displacement inside the crust over a two-year time span is investigated. The finite element program MSC.Marc Mentat was used to calculate the stresses and displacements. For practical analysis reasons, the Earth’s crust is simplified as a planar, piecewise homogeneous, isotropic model (plane strain), and time-varying temperature functions of illumination (thermal radiation) from the Sun are considered in the local isotropy sections of the model. Interaction between the Earth’s crust and mantle is defined by the Winkler elastic foundation. By applying a probabilistic approach (Monte Carlo Method), a new stochastic model of displacements and stresses and new information on crustal displacements relative to the Earth’s mantle were obtained. The results proved the heating influence of the Sun on the Earth’s crust and plate tectonics.
Teses / dissertações sobre o assunto "Behaviour isotropy"
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Hosseinian, Armin. "Numerical simulations of fluid flow through a single rough walled fracture". Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/1764.
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The morphological properties of rock fractures may have a significant influence on their hydromechanical behaviour. Fracture surface roughness could change the fluid flow regime from laminar to turbulent, while it causes the flow properties to deviate from cubic law for smooth channels due to a change in fracture equivalent hydraulic aperture. Different empirical (including the well known Joint Roughness Coefficient, JRC) and statistical methods have been proposed for surface roughness characterisation in an attempt to link them to the hydromechanical behaviour of fractures.This thesis aims to investigate the potential for assessment of fluid behaviour by studying its surface geometrical properties. D[subscript]R[subscript]1 and D[subscript]R[subscript]2, the 2D and 3D roughness parameters developed recently using Riemannian geometry, were used to correlate fracture geometry to its flow behaviour. Also, the 2D Riemannian isotropy parameter (I[subscript]R[subscript]2) was used to correlate surface roughness anisotropy with directionality in fluid flow behaviour along different directions.Numerical simulations in both 2D and 3D were performed assuming the laminar flow regime using FLUENT software. This assumption is, to a large extent, acceptable for situations where the height to length ratios of a fracture is very small. 2D analysis of synthetic profiles with different geometries demonstrated how a change in profile roughness can affect flow response, for example, the pressure drop. JRC flow channels developed in this work as combinations of pairs of JRC profiles were simulated numerically. The analysis results indicated that channels with a similar JRC average for the upper and lower walls but a different JRC profile number responded differently when they were subjected to fluid flow. Therefore, assuming special fluid properties, correlations developed using the pressure drop of a fracture can be estimated by its analogy to JRC flow channels.3D simulations of a corrugated plane were performed assuming different asperity height distributions, for fluid travelling along different directions with respect to surface geometry and at different shear displacements. No asperity contact and failure is assumed in the analysis performed in this work. D[subscript]R[subscript]2 analysis results of the corrugated plane indicated how fluid flow could be related to surface geometry. For instance, it was observed that the pressure drop was maximised along the direction of maximum roughness and reduced to its minimum along a perpendicular direction which shows anisotropy in fluid flow behaviour. Significant changes in pressure drop due to shear offset indicated the importance of fracture wall displacements with respect to each other. A detailed analysis of one synthetically generated surface, and also five surfaces with identical statistical parameters except their correlation distances being different, further confirmed the above concepts. This was followed by analysing a real rock like fracture which was studied elsewhere for fracture shear tests in the lab. Simulation of this surface was performed with particular interest in identifying the locations where the velocity magnitude reduced to nearly zero after the fracture was subjected to a shear offset corresponding to maximum shear stress. These areas were found to be very similar to the locations of asperity degradations as observed through lab experiments. The roughness analysis of the surface was in agreement with the correlation found between the mechanical and hydraulic behaviour of the surface.The results of this research demonstrate how detailed analysis of surface geometry could provide valuable information with respect to surface flow behaviour. Detailed discussions and interpretations of the results will be presented and various conclusions will be made.
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Pistenon, Nicolas. "Découvrir la loi de comportement de matériaux viscoélastiques non linéaires par réseaux de neurones à base physique et données expérimentales". Electronic Thesis or Diss., Université Paris sciences et lettres, 2024. http://www.theses.fr/2024UPSLM044.
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Les méthodes d'apprentissage automatique basées sur les réseaux de neurones offrent de nouvelles perspectives pour la modélisation du comportement mécanique des matériaux. Grâce à leur capacité à servir d'interpolateurs universels de fonctions, ces réseaux sont capables de capturer une grande variété de comportements complexes. Cependant, leur mise en œuvre requiert des ensembles de données volumineux, souvent difficilement accessibles par des moyens expérimentaux. Afin de pallier cette limitation, ce manuscrit introduit différents biais physiques permettant de modéliser le comportement mécanique de matériau, et plus spécifiquement le comportement viscoélastique non linéaire, à partir de données expérimentales restreintes.Les deux principes fondamentaux de la thermodynamique constituent un cadre contraignant pour la formulation de lois de comportement. Il permet de réduire le nombre de données nécessaires à l'entraînement des modèles, tout en renforçant leur robustesse face aux erreurs de mesure.Les réseaux de neurones récurrents, quant à eux, sont particulièrement bien adaptés pour modéliser des comportements dépendant de l'histoire du chargement. Leurs mémoires cachées offrent une analogie intéressante avec les variables internes introduites par le principe de l'état local en mécanique. Cependant, ces réseaux posent des défis en matière d'entraînement et de généralisation. Pour surmonter ces difficultés, un modèle de réseau de neurones à encodage mécanique est proposé. Ce modèle tire parti des variables internes d'un modèle de viscoélasticité linéaire pour encoder l'histoire du matériau, ce qui s'avère suffisant pour modéliser le comportement mécanique non linéaire du matériau.Un des défis majeurs de la modélisation en trois dimensions à partir de données expérimentales réside dans la prise en compte des symétries matérielles pour éviter des essais redondants. Dans le cas des matériaux isotropes, une méthode d'augmentation de données par rotation aléatoire des essais, combinée à un apprentissage par transfert latéral, permet de développer une loi de comportement 3D en utilisant seulement deux types d'essais uniaxiaux. Une formulation thermodynamique respectant intrinsèquement l'isotropie du matériau est proposée, bien que des défis d'entraînement restent à surmonter pour optimiser cette approcheThe application of machine learning techniques based on neural networks provides novel insights into the modelling of the mechanical behaviour of materials. These networks are capable of capturing a wide variety of complex behaviours due to their ability to act as universal function approximators. However, the deployment of these techniques requires large datasets, which are often difficult to obtain experimentally. This manuscript introduces various physical biases that enable the modelling of mechanical behaviour, specifically non-linear viscoelastic behaviour, using limited experimental data, thereby addressing this limitation.The two fundamental principles of thermodynamics provide a robust framework for constraining the formulation of constitutive laws. This approach reduces the quantity of data required for model training, while simultaneously improving the models' resilience to measurement errors.Recurrent neural networks, on the other hand, are particularly well-suited for modelling behaviour that depends on the loading history. Their hidden memories mirror the internal variables introduced in mechanics by the local state principle. However, these networks present challenges in terms of training and generalisation. To overcome these difficulties, a neural network model with mechanical encoding is proposed. This model employs the internal variables of a linear viscoelasticity model to encode the material's history, which proves to be sufficient for modelling its non-linear mechanical behaviour.One of the most significant challenges in three-dimensional modelling from experimental data is the incorporation of material symmetries in order to avoid the need for superfluous testing. For isotropic materials, a method of increasing the data set by randomly rotating the tests, combined with lateral transfer learning, enables the development of a three-dimensional constitutive law using only two types of uniaxial test. A thermodynamically consistent formulation that inherently preserves the material's isotropy is proposed; however, challenges related to training remain to be addressed in order to optimise this approach
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Marinho, Fernando Antonio Medeiros. "Shrinkage behaviour of some plastic soils". Thesis, Imperial College London, 1994. http://hdl.handle.net/10044/1/11381.
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Bonner, Mark James. "The creep behaviour of oriented and isotropic polyethylene". Thesis, University of Leeds, 1995. http://etheses.whiterose.ac.uk/11285/.
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The long term plastic deformation, (creep), behaviour in tension of both oriented and isotropic polyethylene has been studied using a variety of relatively simple experimental techniques, primarily dead loading creep tests. In an attempt to gain an understanding of the mechanisms controlling creep two different viscoelastic models have been applied to the data. The first of these was a two process model, involving two activated Eyring processes in parallel. The second was a Fotheringham and Cherry type model, with a co-operative jump based on a single activated process. In the oriented state the two process model has been successful in describing the behaviour of the material. The Fotheringham and Cherry type model was not successful in describing the behaviour of this material. A complete expression of the two process model has been shown to fully describe the behaviour of one grade at one draw ratio, and an approximation of the model for the other draw ratios and grades has indicated that creep of oriented polyethylene is controlled by a c-shear mechanism. Because of time constraints it was only possible to analyse the behaviour of one grade of the isotropic material with the Fotheringham and Cherry model. Whilst this was successful the activated parameters obtained from it seem very low and would seem to indicate a chain rotation mechanism. Whilst it appears that the two process model should also describe this data, it has not been possible to produce a conclusive fit. It is considered that this is due to limitations in the computing software used for fitting. Hence an approximation of the model was used to produce approximate activation parameters. In addition to the investigation into the rate controlling mechanism of creep the data obtained for the oriented state has been shown to be consistent with the existence of a unique relationship between three important mechanical properties, (strain, strain rate and stress). This relationship holds provided that the initial morphology of the material is equivalent prior to orientation taking place. It has also been shown that the creep data obtained for the isotropic state are consistent with the existence of double yield points in polyethylene. Finally the creep data have been used in a computer model of craze deformation in order to investigate the rate controlling mechanism of slow crack growth. This has shown that craze failure, and hence crack lifetime is controlled by tensile creep to failure of fibrils at the base of the craze.
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Benamar, Rhali. "Nonlinear dynamic behaviour of fully clamped beams and rectangular isotropic and laminated plates". Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280910.
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Khan, Kamran-Ahmed. "A time integration scheme for stress - temperature dependent viscoelastic behaviors of isotropic materials". [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1146.
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Al-Shehri, Abdulhadi S. "Tensile and fracture behaviour of isotropic and die-drawn polypropylene-clay nanocomposites : compounding, processing, characterization and mechanical properties of isotropic and die-drawn polypropylene/clay/polypropylene maleic anhydride composites". Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/5223.
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As a preliminary starting point for the present study, physical and mechanical properties of polypropylene nanocomposites (PPNCs) for samples received from Queen's University Belfast have been evaluated. Subsequently, polymer/clay nanocomposite material has been produced at Bradford. Mixing and processing routes have been explored, and mechanical properties for the different compounded samples have been studied. Clay intercalation structure has received particular attention to support the ultimate objective of optimising tensile and fracture behaviour of isotropic and die-drawn PPNCs. Solid-state molecular orientation has been introduced to PPNCs by the die-drawing process. Tensile stress-strain measurements with video-extensometry and tensile fracture of double edge-notched tensile specimens have been used to evaluate the Young's modulus at three different strain rates and the total work of fracture toughness at three different notch lengths. The polymer composite was analyzed by differential scanning calorimetry, thermogravimetric analysis, polarizing optical microscopy, wide angle x-ray diffraction, and transmission electron microscopy. 3% and 5% clay systems at various compatibilizer (PPMA) loadings were prepared by three different mixing routes for the isotropic sheets, produced by compression moulding, and tensile bars, produced by injection moulding process. Die-drawn oriented tensile bars were drawn to draw ratio of 2, 3 and 4. The results from the Queen's University Belfast samples showed a decrement in tensile strength at yield. This might be explained by poor bonding, which refers to poor dispersion. Voids that can be supported by intercalated PP/clay phases might be responsible for improvement of elongation at break. The use of PPMA and an intensive mixing regime with a two-step master batch process overcame the compatibility issue and achieved around 40% and 50% increase in modulus for 3% and 5% clay systems respectively. This improvement of the two systems was reduced after drawing to around 15% and 25% compared with drawn PP. The work of fracture is increased either by adding nanoclay or by drawing to low draw ratio, or both. At moderate and high draw ratios, PPNCs may undergo either an increase in the size of microvoids at low clay loading or coalescence of microvoids at high clay loading, eventually leading to an earlier failure than with neat PP. The adoption of PPMA loading using an appropriate mixing route and clay loading can create a balance between the PPMA stiffness effect and the degree of bonding between clay particles and isotropic or oriented polymer molecules. Spherulites size, d-spacing of silicate layers, and nanoparticles distribution of intercalated microtactoids with possible semi-exfoliated particles have been suggested to optimize the final PPNCs property.
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Vure, Narayana Rao S. "Effect of cooling rate and stacking sequence on the fatigue behavior of notched quasi-isotropic APC-2 laminates". Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-03042009-040905/.
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Pontiroli, Christophe. "Comportement au souffle des structures en béton armé : analyse expérimentale et modélisation". Cachan, Ecole normale supérieure, 1995. http://www.theses.fr/1995DENS0005.
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Pour déterminer la vulnérabilité et la ruine des structures en béton armé soumises à une onde de choc engendrée par une explosion, le centre d'études de Gramat (c. E. G. ) a développé un nouveau modèle de comportement pour le béton. Ce modèle isotrope, base sur la théorie de l'endommagement utilise deux variables scalaires d'endommagement afin de prendre en compte divers phénomènes tels que: la dissymétrie en tension et compression, le caractère unilatéral (ouverture-fermeture de fissures), l'existence de déformations anélastiques, les effets des vitesses de déformation et les effets de frottement. Couplé à une méthode de régularisation de la localisation, ce modèle permet d'assurer une indépendance des résultats vis à vis du maillage. La formulation explicite, sans processus itératif, de cette loi de comportement permet également d'obtenir une certaine rapidité (temps de calcul) et robustesse (instabilités lors de la rupture du béton) lors des simulations numériques. Afin de valider ce modèle de comportement du béton en dynamique, des essais de souffle sur des dalles circulaires en béton arme ont été réalises au c. E. G. A l'aide d'un tube a choc. Des comparaisons calculs/expériences montrent les capacités et possibilités de cette nouvelle formulation
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Abdi, Hadj. "Mechanical and Hydromechanical Behavior of Host Sedimentary Rocks for Deep Geological Repository for Nuclear Wastes". Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30924.
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Sedimentary rocks are characterized with very low permeability (in the order of 10-22 m2), low diffusivity, a possible self-healing of fractures, and a good capacity to retard radionuclide transport. In recent years, sedimentary rocks are investigated by many research groups for their suitability for the disposal of radioactive waste. Development of deep geologic repositories (DGRs) for the storage of radioactive waste within these formations causes progressive modification to the state of stress, to the groundwater regime, and to the chemistry of the rock mass. Thermal effects due to the ongoing nuclear activity can cause additional disturbances to the system. All these changes in the system are coupled and time-dependent processes. These coupled processes can result in the development of an excavation damaged zone (EDZ) around excavations. More permeable than the undisturbed rock, the EDZ is likely to be a preferential pathway for water and gas flow. Consequently, the EDZ could be a potential exit pathway for the radioactive waste to biosphere. An investigation of the Hydraulic-Mechanical (HM) and Thermal-Hydraulic-Mechanical-Chemical (THMC) behaviour of sedimentary rock formations is essential for the development of DGRs within such formations.
This research work consists of (1) an experimental investigation of the mechanical behaviour of the anisotropic Tournemire argillite, (2) modeling of the mechanical behaviour of the Tournemire argillite, and (3) numerical simulations of the mechanical and hydromechanical behavior of two host sedimentary rocks, the Tournemire argillite and Cobourg limestone, for deep geological repository for nuclear wastes.
The experimental program includes the measurements of the physical properties of the Tournemire argillite and its mechanical response to loading during uniaxial compression tests, triaxial compression tests with different confining pressures, unconfined and confined cyclic compression tests, Brazilian tests, and creep tests. Also, acoustic emission events are recorded to detect the initiation and propagation of microcracks within the rock during the uniaxial testing.
The approach for modeling the mechanical behaviour of the Tournemire argillite consists of four components: elastic properties of the argillite, a damage model, the proposed concept of mobilized strength parameters, and the classical theory of elastoplasticity. The combination of the four components results in an elastoplastic-damage model for describing the mechanical behaviour of the Tournemire argillite. The capabilities of the model are evaluated by simulating laboratory experiments.
Numerical simulations consist of: (1) a numerical simulation of a mine-by-test experiment at the Tournemire site (France), and (2) numerical simulations of the mechanical and hydromechanical behaviour of the Cobourg limestone within the EDZ (Canada). The parameters influencing the initiation and evolution of EDZ over time in sedimentary rocks are discussed.
Livros sobre o assunto "Behaviour isotropy"
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Vinson, Jack R. The Behavior of Shells Composed of Isotropic and Composite Materials. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-015-8141-7.
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Vinson, Jack R. The behavior of shells composed of isotropic and composite materials. Dordrecht: Kluwer Academic Publishers, 1993.
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Center, Langley Research, ed. Buckling and postbuckling behavior of compression-loaded isotropic plates with cutouts. Washington, D.C: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1990.
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Illg, Walter. Effect of partial interlaminar bonding on impact resistance and loaded-hole behavior of graphite/epoxy quasi-isotropic laminates. Hampton, Va: Langley Research Center, 1986.
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Illg, Walter. Effects of partial interlaminar bonding on impact resistance and loaded hole behavior of graphite/epoxy quasi-isotropic laminates. [Washington, DC]: National Aeronautics and Space Administration, Scientific and Technical Information Branch, 1986.
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Behavior of Sandwich Structures of Isotropic and Composite Materials. CRC Press LLC, 2018.
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Behavior of Sandwich Structures of Isotropic and Composite Materials. CRC Press LLC, 2018.
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Vinson, JackR. Behavior of Sandwich Structures of Isotropic and Composite Materials. CRC Press LLC, 2018.
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Vinson, JackR. Behavior of Sandwich Structures of Isotropic and Composite Materials. CRC Press LLC, 2018.
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Vinson, Jack R. Behavior of Shells Composed of Isotropic and Composite Materials. Springer, 2013.
Encontre o texto completo da fonteCapítulos de livros sobre o assunto "Behaviour isotropy"
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Puzrin, Alexander M. "Isotropic Elastic Behaviour". In Constitutive Modelling in Geomechanics, 117–29. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-27395-7_10.
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Odé, H. "Wavefronts in Transversely Isotropic Media". In Mechanical Behavior of Crustal Rocks, 299–310. Washington, D. C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm024p0299.
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Vinson, Jack R. "Vibration of Isotropic Shells". In The Behavior of Shells Composed of Isotropic and Composite Materials, 221–37. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-015-8141-7_12.
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Yahya, M. F., S. A. Ghani e J. Salleh. "Modeling Plain Woven Composite Model with Isotropic Behavior". In Proceedings of the International Colloquium in Textile Engineering, Fashion, Apparel and Design 2014 (ICTEFAD 2014), 19–24. Singapore: Springer Singapore, 2014. http://dx.doi.org/10.1007/978-981-287-011-7_4.
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Altenbach, H. "On the Extension of Creep-Damage Theories for Isotropic Materials to the Case of Anisotropic Materials". In Anisotropic Behaviour of Damaged Materials, 261–93. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-540-36418-4_8.
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Vinson, Jack R. "Curvilinear Coordinate Systems". In The Behavior of Shells Composed of Isotropic and Composite Materials, 1–14. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-015-8141-7_1.
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Vinson, Jack R. "Energy Methods for Shells". In The Behavior of Shells Composed of Isotropic and Composite Materials, 183–206. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-015-8141-7_10.
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Vinson, Jack R. "Elastic Stability of Shells". In The Behavior of Shells Composed of Isotropic and Composite Materials, 207–20. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-015-8141-7_11.
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Vinson, Jack R. "Very Thick Walled Cylindrical Shells". In The Behavior of Shells Composed of Isotropic and Composite Materials, 238–85. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-015-8141-7_13.
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Vinson, Jack R. "Anisotropic Elasticity and Laminate Theory". In The Behavior of Shells Composed of Isotropic and Composite Materials, 286–324. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-015-8141-7_14.
Texto completo da fonteTrabalhos de conferências sobre o assunto "Behaviour isotropy"
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Kriz, A., e W. Müllner. "Frequency-Selective Analysis of the Isotropic Behaviour and Measurement Uncertainty of the Field Strength Measurement System Field Nose". In 2004_EMC-Europe_Eindhoven, 1–4. IEEE, 2004. https://doi.org/10.23919/emc.2004.10806000.
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Amarnath, C., e K. N. Umesh. "Studies on Isotropy of Planar 5-Bar Linkages". In ASME 2004 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/detc2004-57103.
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The ability to move at reasonable ease in all directions is an important requirement in the design of manipulators. The degree of ease of mobility varies from point to point in the workspace of the manipulator’s end effector. Maximum ease of mobility is obtained at an isotropic point, and the minimum occurs at singularities. An attempt has been made here to use a geometric approach for determining the isotropic points in the workspace of planar 5-bar linkages. The geometrical approach leads to interesting observations on the location of isotropic points in the workspace. The procedure also yields a technique for the synthesis of 5-bar linkages and associated coupler points exhibiting isotropic behaviour. Additionally it has been shown that coupler points exhibiting isotropic mobility occur in pairs.
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Ciambella, Jacopo, e David C. Stanier. "Orientation Effects in Short Fibre-Reinforced Elastomers". In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-40430.
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The large strain behaviour of a short fibre-reinforced composite is studied through numerical simulations. The reinforcing fibres yield the macroscopic response transversely isotropic which is indeed the case of many reinforcements currently used in composites: short carbon fibres, cellulose whiskers, carbon nanotubes. As a result of the analysis, it is shown that the reorientation of the fibres that takes place at large strain has a significant effect on the overall material response by changing the axis of isotropy. This behaviour can be adequately described by using a transversely isotropic model whose strain energy function depends on three invariants: two isotropic and one representing the stretch along the direction of the fibres. To assess its capabilities, the model is compared to the results of experiments carried out by the authors on nickel-coated chopped carbon fibres in a vulcanised natural rubber matrix for which the fibre orientation is achieved by controlling an external magnetic field prior to curing. Possible applications include micro-sized propulsion devices and actuators.
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Peravali, S., T. H. Hyde, K. A. Cliffe e S. B. Leen. "An Anisotropic Creep Damage Model for Anisotropic Weld Metal". In ASME 2007 Pressure Vessels and Piping Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/creep2007-26262.
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Past studies from creep tests on uniaxial specimens and Bridgman notch specimens, for a P91 weld metal, showed that anisotropic behaviour (more specifically transverse isotropy) occurs in the weld metal, both in terms of creep (steady-state) strain rate behaviour and rupture times (viz. damage evolution). This paper describes the development of a finite element (FE) continuum damage mechanics methodology to deal with anisotropic creep and anisotropic damage for weld metal. The method employs a second order damage tensor following the work of Murakami and Ohno [1] along with a novel rupture stress approach to define the evolution of this tensor, taking advantage of the transverse isotropic nature of the weld metal, to achieve a reduction in the number of material constants required from test data (and hence tests) to define the damage evolution. Hill’s anisotropy potential theory is employed to model the secondary creep. The theoretical model is implemented in a material behaviour subroutine within the general-purpose, non-linear FE code ABAQUS [2]. The validation of the implementation against established isotropic continuum damage mechanics solutions for the isotropic case is described. A procedure for calibrating the multiaxial damage constants from notched bar test data is described for multiaxial implementations. Also described is a study on the effect of uniaxial specimen orientation on anisotropic damage evolution.
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Accardi, Mario Alberto, e Daniele Dini. "Modelling of the Mechanical Behaviour of Human Joints Cartilage". In STLE/ASME 2008 International Joint Tribology Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/ijtc2008-71308.
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A significant component of our understanding of cartilage mechanical behaviour is the ability to model its response to various types of mechanical loading, for which we require detailed knowledge of cartilage material properties. The Finite Element Analysis software ABAQUS is renowned for the ability to model poroelastic materials using the soil consolidation theory. In this research, ABAQUS has been used to model and investigate the mechanical behaviour of articular cartilage, mainly using indentation and unconfined compression techniques. A biphasic model of articular cartilage was first created and subsequently modified to incorporate more detailed material descriptions. Various material constitutive laws (and mechanical properties), accounting for the strain dependent permeability of the porous matrix, solid viscoelasticity and transverse isotropy, have been adopted to produce increasingly sophisticated models. The presence of collagen fibril networks embedded in the solid has been also considered and Fibril Reinforced Elastic and Viscoelastic models produced. A salient feature of these models is their ability to simulate fibril stiffening by replicating the nonlinear fibrillar response. In this paper, we provide an overview of the state-of-art modelling techniques adopted to simulate cartilage behaviour. The comparative study performed by the authors provides a critical assessment of the effectiveness of such techniques.
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Wunderwald, Dirk, e Leonhard Fottner. "Experimental Investigation of Boundary Layer Transition and Turbulence Structures on a Highly Loaded Compressor Cascade". In ASME 1995 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/95-gt-129.
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Detailed measurements have been performed on a compressor cascade in order to obtain information about the overall performance, the state of the boundary layer, and the topology of turbulent boundary layers. The analysis of profile pressure distributions and wake traverse measurements across the midspan section of the cascade blade provide information on the loss behaviour. Using surface-mounted hot-film gauges on the suction side of the measuring blade different transition phenomena have been investigated under the influence of various inlet flow conditions representative of engine operation. Extensive measurements with 3D-hot-sensor anemometry have been evaluated to show essential features of the turbulent boundary layer. The results point out the dependence of turbulence characteristics, e.g. turbulent kinetic energy distribution and Reynolds stresses, on the inlet flow conditions and the upstream boundary layer development. The influence of free-stream turbulence intensity is discussed and the non-isotropy of the Reynolds normal stresses is presented.
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Wunderwald, Dirk, e Leonhard Fottner. "Experimental Investigation of Turbulence Structures in the Boundary Layer of a Highly Loaded Turbine Cascade". In ASME 1996 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-gt-249.
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An experimental study has been performed on a turbine cascade in order to obtain detailed information about the overall performance, the state of the boundary layer, and the topology of turbulent boundary layers. The analysis of profile pressure distributions and wake traverse measurements across the midspan section of the cascade blade provide information on the loss behaviour. Using surface-mounted hol-film gauges on the suction side of the measuring blade, transition modes have been investigated under the influence of various inlet flow conditions representative of engine operation. Extensive measurements with 3D-hot-sensor anemometry have been evaluated to show essential features of the turbulent suction side boundary layer. The paper describes the dependence of turbulence characteristics, e.g. integral length scales and turbulent kinetic energy distribution, on the inlet flow conditions and the upstream boundary layer development. The influence of free-stream turbulence intensity and streamline curvature is discussed and the non-isotropy of the Reynolds normal stresses is presented. The evaluation of Reynolds stresses as well as triple order correlations should provide a further insight into the structure of turbulence and lead to a more realistic turbulence modelling.
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de la Rosa, A. Breña, G. Wang e W. D. Bachalo. "The Effect of Swirl on the Velocity and Turbulence Fields of a Liquid Spray". In ASME 1990 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1990. http://dx.doi.org/10.1115/90-gt-032.
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This work reports an experimental study of the effect of swirl on the structure of a liquid spray, i.e., on the behaviour of drops and their interaction with the gaseous phase, and on the velocity and turbulence fields of the spray in the swirling flow. Three vane type swirlers having low, medium, and high swirl numbers were used in the tests. The swirlers were placed on the liquid supply tube of a pressure atomizer and tested in the wind tunnel under specified conditions. Properties of the dispersed phase such as velocity and size distributions, particle number density, and volume flux were measured at several locations within the swirling flow field. In addition, mean velocity and turbulence properties were obtained for the gas phase. The results show that flow reversal of the drops is present at the high swirl number within the recirculation region. The spatial distribution of drops reveals a widening of the spray with increasing swirl strength while the concentration of large drops is shown to increase near the core of the swirling field with increasing swirl number. Plots of the turbulence kinetic energy, normal Reynolds stresses, and Reynolds shear stresses show double-peak radial distributions which indicate regions in the flow where high energy content, mean velocity gradients, and large shear forces are present. The decay of turbulence velocities in the axial direction was observed to be very fast, an indication of high diffusion and dissipation rates of the kinetic energy of turbulence. The significance of the turbulence measurements is that these double peak profiles indicate a deviation of the swirling spray from isotropy. This information should be relevant to researchers modelling these complex flows.
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Calise, Gian J., e Anil Saigal. "Mechanical Behavior of Octahedral and Octet Structures Produced From CLIP Technology". In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-88192.
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This research concerns the production of mechanical metamaterials by a new means of additive manufacturing (AM). Mechanical metamaterials are man-made materials in which the mechanical properties are defined mainly by their structures rather than the properties of each material component. They are typically cellular lattice structures consisting of various arrangements of interconnected webs and struts. These metamaterials have a wide range of applications, but due to a recent breakthrough technology in the field of AM developed by Carbon, called Continuous Liquid Interface Production (CLIP), they can now be produced with ease at substantially higher speeds on a large scale. Using the CLIP process, Adidas is now utilizing these metamaterials in the midsoles of their new athletic shoes. More information about the mechanical response of parts produced by CLIP was needed to assess their relevance in this application. The goal of this research was to quantitatively determine the isotropy of octahedral and octet lattice structures produced from CLIP technology. Carbon claims that CLIP technology, unlike most other AM processes, produces parts that are isotropic. This means parts will have the same mechanical properties regardless of the direction of applied load. This claim has yet to be proven on lattice structures like the octahedral and octet structures. Those particular lattice structures are popular in the field of mechanical metamaterials because they are more structurally efficient than foams that are made of the same material with similar densities. The degree of isotropy of samples was measured by comparing values of various mechanical properties. These properties include Young’s modulus, a common measure of elasticity, and peak stress, a common measure of strength. Results indicated relatively isotropic behavior because mechanical properties varied based on the axis of compression by 6.5%, on average. The physical responses and failure mechanisms were also consistent.
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Martinez, Michae¨l, e George Brown. "Evolution of Pipe Properties During Reel-Lay Process: Experimental Characterisation and Finite Element Modelling". In ASME 2005 24th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2005. http://dx.doi.org/10.1115/omae2005-67074.
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The development of finite element analysis, in terms of simulation power and theoretical model accuracy, enables one to understand and simulate industrial processes more precisely, especially those involving non linear behaviour and analysis. Reeled pipe technology is one of these, and has a lot to gain from this increasing efficiency. In the reel-lay process the pipe is first reeled onto a drum on a vessel for transportation. During offshore installation the pipe is unreeled, straightened and deployed into the sea. During the process, the pipe is fully and cyclically plastified. Plastification modifies the pipe properties, which is not by itself detrimental but should be understood by the designer. Pipe properties are affected in three ways: geometrical shape – reeling and straightening induce some residual ovalisation; mechanical properties – yield stress, hardening slope, isotropy are modified; and fatigue properties. Technip and IFP have studied these property evolutions for many years, both from an experimental and a numerical point of view. The present paper discusses the first two points. A wide experimental programme has been performed. Full scale pipes were reeled and straightened on a bending rig device especially built for that purpose. Pipe ovalisation was monitored through the whole process. Pipe mechanical properties were also fully characterised in the pipe axial, hoop and thickness directions, both in tension and compression, before and after reeling process. Extruded and UOE pipes were tested and characterised. Pipe initial properties are dependent on the manufacturing process but they are modified by the reeling process. Reeling induces some anisotropy that cannot be properly accounted for by usual plasticity models. Finite element simulations with Abaqus software, using the material behaviour of unreeled pipe, underestimate stiffness evolution in the hoop direction and overestimate ovalisation induced by the reeling process. Anisotropy has indeed a great effect on ovalisation that results from an interaction between axial and hoop loading. Hardening is also a key parameter. A new plasticity model has been written in an Abaqus User Material Model, known as UMAT. The new model is based on an anisotropic Hill criterion and special attention is paid to the hardening. This new model reduces by more than two the error on ovality estimation, and gives a realistic prediction of material anisotropy evolution through the process. Although, the tuning of the model coefficients is more complex than for usual models, its use is quite straightforward and does not increase computation time.
Relatórios de organizações sobre o assunto "Behaviour isotropy"
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Speranza, Vito, e Roberto Pantani. Investigation of isotactic polypropylene crystallization in processing conditions. Universidad de los Andes, dezembro de 2024. https://doi.org/10.51573/andes.pps39.gs.msd.1.
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Flow and pressure applied during polymer transformation processes of semi-crystalline polymers can significantly affect the kinetics of crystallization, final morphology, and properties of the part. In commonly used polymer transformation processes, the molten polymer is subjected to high pressure and thermal stress, as well as intense shear and elongational flow fields. The effect of pressure on crystallization kinetics is significant from both scientific and technological perspectives since the polymer solidifies under high pressure in important industrial processing techniques. On the other hand, the high shear rates experienced during the polymer processing can lead to the development of a highly non-uniform morphology that is typically very different from what is observed for quiescent crystallization of the same polymer. One example is injection molding, where the high shear rates experienced by a polymer melt close to the cold walls of the cavity can lead to a highly oriented layer (“skin” layer), whereas the low flow field close to sample mid-plane can lead to an isotropic layer (“core” layer) developing the so-called “skin-core” morphology. Thus, an understanding of polymer crystallization behavior with respect to the processing conditions is required to enable the rational design of materials and to optimize the final properties of the parts. This work explored the effects of the pressure and flow field on the kinetics of crystallization of isotactic polypropylene (i.e., iPP). The study of the effect of pressure on the crystallization kinetics of iPP was conducted using a dilatometer in the pressure range from 10 MPa to 100 MPa. Several isothermal flow experiments were carried out using two different devices: the Linkam shear cell and the Multi-Pass Rheometer (MPR). To describe the evolution into isotropic structures and fibrillar structures, a Kolmogoroff–Avrami–Evans model was adopted.
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Oliynyk, Kateryna, e Matteo Ciantia. Application of a finite deformation multiplicative plasticity model with non-local hardening to the simulation of CPTu tests in a structured soil. University of Dundee, dezembro de 2021. http://dx.doi.org/10.20933/100001230.
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In this paper an isotropic hardening elastoplastic constitutive model for structured soils is applied to the simulation of a standard CPTu test in a saturated soft structured clay. To allow for the extreme deformations experienced by the soil during the penetration process, the model is formulated in a fully geometric non-linear setting, based on: i) the multiplicative decomposition of the deformation gradient into an elastic and a plastic part; and, ii) on the existence of a free energy function to define the elastic behaviour of the soil. The model is equipped with two bonding-related internal variables which provide a macroscopic description of the effects of clay structure. Suitable hardening laws are employed to describe the structure degradation associated to plastic deformations. The strain-softening associated to bond degradation usually leads to strain localization and consequent formation of shear bands, whose thickness is dependent on the characteristics of the microstructure (e.g, the average grain size). Standard local constitutive models are incapable of correctly capturing this phenomenon due to the lack of an internal length scale. To overcome this limitation, the model is framed using a non-local approach by adopting volume averaged values for the internal state variables. The size of the neighbourhood over which the averaging is performed (characteristic length) is a material constant related to the microstructure which controls the shear band thickness. This extension of the model has proven effective in regularizing the pathological mesh dependence of classical finite element solutions in the post-localization regime. The results of numerical simulations, conducted for different soil permeabilities and bond strengths, show that the model captures the development of plastic deformations induced by the advancement of the cone tip; the destructuration of the clay associated with such plastic deformations; the space and time evolution of pore water pressure as the cone tip advances. The possibility of modelling the CPTu tests in a rational and computationally efficient way opens a promising new perspective for their interpretation in geotechnical site investigations.
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A REEXAMINATION ON CALIBRATION OF CYCLIC CONSTITUTIVE MODEL FOR STRUCTURAL STEELS. The Hong Kong Institute of Steel Construction, agosto de 2022. http://dx.doi.org/10.18057/icass2020.p.267.
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Exquisite calibration of model parameter is crucial for simulation accuracy of cyclic constitutive model. This paper is aiming to clarify the influence of different calibration factors on the calibration results and simulation performances of Chaboche combined isotropic/kinematic hardening constitutive model. The influencing calibration factors include the definition of proof strength point on unloading-reloading path, the definition of unloading elastic modulus, the relative proportion of initial back stress and saturation back stress. Based upon different influencing factors, the Chaboche model parameters of LYP225 steel and Q460 steel are calibrated. Accordingly, the main cyclic behavior curves, including the hysteretic stress-strain curves, the evolutionary curves of stress amplitude and plastic work are simulated. Through analyzing the errors between experimental and simulated results, rational suggestions for the valuation of each influencing factor are provided. By taking these suggestions, the calibration of model parameters are able to yield favorable simulation performances and promising convenience for subsequent comparative studies.