Готові списки джерел за темами / Mechanical Representative Elementary Volume

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Добірка наукової літератури з теми "Mechanical Representative Elementary Volume"

Автор: Grafiati

Опубліковано: 11 січня 2025

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Статті в журналах з теми "Mechanical Representative Elementary Volume"

Zhang, Ting Ting, E. Chuan Yan, Xian Ming Hu, and Yang Bing Cao. "Fractal Description of Rock Mass Structure Representative Elementary Volume." Advanced Materials Research 594-597 (November 2012): 439–45. http://dx.doi.org/10.4028/www.scientific.net/amr.594-597.439.

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Анотація:

The mechanical parameters of the rock masses are scale dependent because of the existence of the discontinuities. The self-similarity of the discontinuities makes the application of fractal theory in the description of the rock mass structure possible. The novel point in this study is that the structure representative elementary volume (SREV) of rock mass is proposed. Rock mass structures were obtained through the two-dimensional discontinuity network simulation results, from which ten pieces of square rock mass specimens were chosen. The side lengths of the specimens were increased in turn from 1m to 10m. And the fractal dimension of each specimen with different sizes was calculated by the box-counting principal of the fractal geometry. The fractal dimensions of the rack mass structures became larger with their side lengths increasing, and finally stable. And the SREV of the rock mass was determined based on the variation rule of the fractal dimensions. Further, the relation between the structure representative elementary volume (SREV) and mechanical parameter representative elementary volume (REV) was qualitatively analyzed from the strength differences between the discontinuities and intact rock. And the conclusion was inferred that the size of the SREV was the upper limit of mechanical parameter REV. Meanwhile, the conclusion was verified by the results of the finite element method. This study can provided a referring value for the estimation of the mechanical parameter REV in future.

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Gasmi, H., M. Touahmia, A. Torchani, E. Hamdi, and A. Boudjemline. "Determination of Fractured Rock’s Representative Elementary Volume by a Numerical Simulation Method." Engineering, Technology & Applied Science Research 9, no. 4 (August 10, 2019): 4448–51. http://dx.doi.org/10.48084/etasr.2854.

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The present study aims at developing a numerical program called DISSIM which can analyze the homogenization of rock massifs using a new subroutine which calculates Representative Elementary Volume (REV). The DISSIM methodology consists of two steps. The first step involves the modeling of the fractured network in order to provide a surface simulation that represents the real fracture of the examined front. The second step is to numerically model the wave propagation through the simulated fracture network while characterizing the attenuation of vibrations due to the effect of discontinuities. This part allows us to determine in particular the wave propagation velocity through the fractured mass, from which we can determine the homogenized Young's modulus. However, after extensive bibliographic research, it was realized that a third step appeared to be necessary. In fact, it is necessary to look for a representative elementary volume on which we apply the proposed homogenization method. Two types of the representative elementary volume are proposed in this article, the geometric REV and the mechanical REV. The presentation of these two types of REV and the DISSIM methodology are detailed in this paper. Then, this methodology was applied to the study of a real case. The present research provides a method allowing the calculation of both types of REV for fissured rocks. The case study yielded comparable results between the mechanical REV and the geometric REV, which is compatible with previous research studies.

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Perreux, Dominique M., and W. Steven Johnson. "A Model for Prediction of Bone Stiffness Using a Mechanical Approach of Composite Materials." Journal of Biomechanical Engineering 129, no. 4 (January 22, 2007): 494–502. http://dx.doi.org/10.1115/1.2746370.

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A model to predict the bone stiffness is presented in this paper. The objective is to obtain a description of bone stiffness of a representative elementary volume (REV) based on a small set of physical parameters. The main idea is to use measurable information related to the orientation and the density of a basic elementary submicrostructure (ESMS). This ESMS is the first arrangement of the basic components. A simple rule-of-mixtures approach is used to provide the elastic properties for the ESMS. The basic properties are dependent on the volume fraction of the mineralized phase. The orientation and the density of the ESMS is described by a tensor and a scalar, respectively. The model is used to obtain the elastic properties of both the cortical and trabecular bones. Data from femoral bone are used to verify this approach.

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Huang, Xiao, Siyuan Li, Jionghao Jin, and Chong Shi. "Determining Digital Representation and Representative Elementary Volume Size of Broken Rock Mass Using the Discrete Fracture Network–Discrete Element Method Coupling Technique." Applied Sciences 14, no. 2 (January 10, 2024): 606. http://dx.doi.org/10.3390/app14020606.

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Obtaining the digital characterization and representative elementary volume (REV) of broken rock masses is an important foundation for simulating their mechanical properties and behavior. In this study, utilizing the broken surrounding rock of the main powerhouse at the Liyang pumped storage power station as an engineering background, a three-dimensional fracture network generation program is first developed based on the theories of discrete fracture network (DFN) and discrete element method (DEM). The program is then integrated with a distinct element modelling platform to generate equivalent rock mass models for broken rock masses based on the DFN–DEM coupling technique. Numerical compression tests are conducted on cylindrical rock specimens produced using the proposed modelling approach, aiming to determining the REV size of the target rock masses at the Liyang power station. A comparative validation is also performed to examine the REV result obtained from the proposed approach, which adopted a REV measuring scale index (RMSI) to determine the REV size. Results indicate that the organic integration of DFN simulation techniques and DEM platforms can effectively construct numerical models for actual broken rock masses, with structural surface distributions statistically similar to the real ones. The results also show that the REV size of the investigated rock masses determined by the cylindrical rock models is 5 m × 10 m, which aligns with the size determined by the cubic rock models, as the target cubes show the same height as the cylindrical specimens. This study provides a model and parameter basis for the numerical calculation of the mechanical behavior of broken rock mass.

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Li, H., A. Levy, and G. Ben-Dor. "Analytical prediction of regular reflection over rigid porous surfaces in pseudo-steady flows." Journal of Fluid Mechanics 282 (January 10, 1995): 219–32. http://dx.doi.org/10.1017/s0022112095000115.

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An analytical model for solving the flow field associated with regular reflections of straight shock waves over porous layers has been developed. The governing equations of the gas inside the porous material were obtained by simplifying the general macroscopic balance equations which were obtained by an averaging process over a representative elementary volume of the microscopic balance equations as originally done by Bear & Bachmat (1990). The analytical predictions of the proposed model were compared to experimental results of Skews (1992) and Kobayashi, Adachi & Suzuki (1993). Very good to excellent agreement was evident.

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Baek, Y., O. I. Kweon, Y. S. Seo, K. S. Kim, and G. W. K im. "Analysis of elastic behaviour of granite using homogenisation theory." Journal of Nepal Geological Society 34 (October 9, 2006): 25–28. http://dx.doi.org/10.3126/jngs.v34i0.31875.

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We carried out photographic analysis of randomly distributed discrete elements in the lnada granite. The modal analysis of granite was also conducted simultaneously with the above photographic analysis. The results show that quartz and feldspar including mica occupy 99.4% of the total volume of the fine-grained granite. Based on the results of previous studies, an elastic homogenisation method is applied to analyse the macro-level stress distribution in the lnada granite, which is a composite material of rock-forming minerals with micro discontinuities. For proper rock sampling and specimen preparation, the representative elementary volume (REV) should be determined in rock mechanical tests and numerical analyses. We determined the REV of the lnada granite using a stereoscopic microscope and applying a homogenisation numerical analysis.

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Buonsanti, Michele, Fortunato Ceravolo, Giovanni Leonardi, and Francesco Scopelliti. "Interfaces Behavior in Glued Granular Materials." Key Engineering Materials 665 (September 2015): 113–16. http://dx.doi.org/10.4028/www.scientific.net/kem.665.113.

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In this paper a micro-scale model to investigate the structural integrity of a runway surface has been developed. By performing stress analysis on a representative volume element (RVE), our model specification has been focalized on two elementary mixture constituents, two rigid components glued together by asphalt. The analysis is performed under thermo-mechanical actions, as those produced by landing gear impact and variable high surface temperatures. Three different interfaces (rigid to rigid, rigid to soft and soft to soft), three different asphalt density and two different values of surface temperature have been considered in the simulation. Resulting stress and strain fields are compared to define the greater critical conditions and to evaluate the micro-scale structural integrity

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Li, MY, YJ Cao, WQ Shen, and JF Shao. "A damage model of mechanical behavior of porous materials: Application to sandstone." International Journal of Damage Mechanics 27, no. 9 (January 5, 2017): 1325–51. http://dx.doi.org/10.1177/1056789516685379.

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In this work, a multiscale model based on the Fast Fourier Transform (FFT) technique is applied to describe the mechanical behavior of porous materials. The effects of the microstructures (such as pore shape, number, size, distribution and orientation) on the overall strength of the porous medium and its microstress distribution are fully studied. The elastoplastic model is further extended by including a damage process. The influences of microstructure on the damage evolution of the porous medium are discussed and illustrated numerically. Then the proposed multiscale damage model is applied to study the macroscopic behavior of porous sandstone. According to the microstructure of the studied material, a representative elementary volume with randomly distributed spherical pores is considered. The solid phase of the sandstone is assumed to obey the Drucker–Prager criterion. Taking advantage of the FFT-based method, the evolution of generated damage is clearly illustrated during the loading process at the microscopic level. Comparisons between numerical results and experimental data show the efficiency of the proposed numerical model.

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Zhao, Tianyi, Huawei Zhao, Zhengfu Ning, Xiangfang Li, and Qing Wang. "Permeability prediction of numerical reconstructed multiscale tight porous media using the representative elementary volume scale lattice Boltzmann method." International Journal of Heat and Mass Transfer 118 (March 2018): 368–77. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2017.11.004.

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Sadat, Salima, Allel Mokaddem, Bendouma Doumi, Mohamed Berber, and Ahmed Boutaous. "Investigation of the effect of thermal stress on the interface damage of hybrid biocomposite materials." Mechanics and Mechanical Engineering 23, no. 1 (July 10, 2019): 253–58. http://dx.doi.org/10.2478/mme-2019-0034.

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Abstract In this paper, we have studied the effect of thermal stress on the damage of fiber-matrix interface of a hybrid biocomposite composed of two natural fibers, Hemp, Sisal, and Starch matrix. Our genetic modeling used the nonlinear acoustic technique based on Cox’s analytical model, Weibull’s probabilistic model, and Lebrun’s model describing the thermal stress by the two coefficients of expansion. The stress applied to our representative elementary volume is a uni-axial tensile stress. The numerical simulation shows that the Hemp- Sisal/Starch hybrid biocomposite is most resistant to thermal stresses as compared with Hemp/Starch biocomposite. It also shows that hybrid biocomposite materials have a high resistance to applied stresses (mechanical and thermal) compared to traditional materials and biocomposite materials. The results obtained in our study coincide perfectly with the results of Antoine et al., which showed through experimental tests that natural fibers perfectly improve the mechanical properties of biocomposite materials.

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Більше джерел

Дисертації з теми "Mechanical Representative Elementary Volume"

Min, Ki-Bok. "Determination of equivalent hydraulic and mechanical properties of fractured rock masses using the distinct element method." Licentiate thesis, KTH, Land and Water Resources Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1550.

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Анотація:

The equivalent continuum approach uses equivalent propertiesof rock mass as the input data for a continuum analysis. Thisis a common modeling method used in the field of rock mechanicsand hydrogeology. However, there are still unresolvedquestions; how can the equivalent properties be determined andis the equivalent continuum approach suitable for modeling thediscontinuous fractured rock mass.

The purpose of this paper is to establish a methodology todetermine the equivalent hydraulic and mechanical properties offractured rock masses by explicit representations of stochasticfracture systems, to investigate the scale-dependency of theproperties, and to investigate the conditions for theapplication of the equivalent continuum approach for thefractured rock masses. Geological data used for this study arefrom the site characterization of Sellafield, Cumbria, UK. Aprogram for the generation of stochastic Discrete FractureNetwork (DFN) is developed for the realization of fractureinformation and ten parent DFN models are constructed based onthe location, trace length, orientation and density offractures. Square models with the sizes varying from 0.25 m× 0.25 m to 10 m × 10 m are cut from the center ofthe each parent network to be used for the scale dependencyinvestigation. A series of the models in a parent network arerotated in 30 degrees interval to be used for investigation oftensor characteristic. The twodimensional distinct elementprogram, UDEC, was used to calculate the equivalentpermeability and compliance tensors based on generalizedDarcys law and general theory of anisotropic elasticity.Two criteria for the applicability of equivalent continuumapproach were established from the investigation: i) theexistence of properly defined REV (Representative ElementaryVolume) and ii) existence of the tensor in describing theconstitutive equation of fractured rock The equivalentcontinuum assumption cannot be accepted if any one of the abovetwo criteria is not met. Coefficient of variation and meanprediction error is suggested for the measures toquantitatively evaluate the errors involved in scale dependencyand tensor characteristic evaluation.

Equivalent permeability and mechanical properties (includingelastic modulus and Poissons ratios) determined onrealistic fracture network show that the presence of fracturehas a significant effect on the equivalent properties. Theresults of permeability, elastic moduli and Poisson's ratioshow that they narrow down with the increase of scale andmaintain constant range after a certain scales with someacceptable variation. Furthermore, Investigations of thepermeability tensor and compliance tensor in the rotated modelshow that their tensor characteristics are satisfied at acertain scale; this would indicate that the uses of theequivalent continuum approach is justified for the siteconsidered in this study.

The unique feature of the thesis is that it gives asystematic treatment of the homogenization and upscaling issuesfor the hydraulic and mechanical properties of fractured rockswith a unified approach. These developments established a firmfoundation for future application to large-scale performanceassessment of underground nuclear waste repository byequivalent continuum analysis.

Keywords :Equivalent continuum approach, Equivalentproperty, Representative Elementary Volume (REV), DistinctElement Method, Discrete Fracture Network (DFN)

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Grondin, Jérémy. "Apport de la nanoindentation et de la microscopie à force atomique pour la compréhension des propriétés élastiques d’un polymère semi-cristallin aux différentes échelles microstructurales." Electronic Thesis or Diss., Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2024. http://www.theses.fr/2024ESMA0023.

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Cette thèse vise à approfondir la compréhension des relations entre le module d’élasticité d’un polypropylène isotactique (iPP) et sa microstructure à différentes échelles. Une approche expérimentale multi-échelle originale est développée, combinant essais d’indentation et microscopie à force atomique (AFM) pour la caractérisation du module d’élasticité et de la morphologie tridimensionnelle des sphérolites. Le travail s'articule autour de quatre axes : (i) la caractérisation de la morphologie sphérolitique par AFM, (ii) des essais d’indentation à diverses échelles en utilisant différentes techniques (AFM en mode mécanique, nanoindentation, et macro-indentation), (iii) la caractérisation du module d’élasticité au sein des sphérolite à travers des cartographies de module obtenue par nanoindentation et par AFM en mode mécanique, et (iv) l’évaluation d’un volume élémentaire représentatif (VER) mécanique à partir d’essais d’indentation sphérique.Un protocole original a permis de produire des échantillons massifs de iPP avec une surface plane, peu rugueuse et sans attaque chimique, conservant ainsi la microstructure tridimensionnelle de surface. Les résultats révèlent des éléments nouveaux sur la microstructure des sphérolites et la nanostructure lamellaire de la phase α. Outre les observations classiques (formes en gerbe ou rosette), une échelle intermédiaire est identifiée : les branches radiales des sphérolites, de taille micrométrique, constituées de lamelles cristallines orientées orthoradialement. Ces lamelles adoptent une organisation « lath-like » dans les branches et « cross-hatching » dans les zones de fermeture. La longue période (Lp) moyenne est mesurée localement par AFM, et est cohérente avec la littérature (SAXS).Les cartographies par nanoindentation ont montré un gradient décroissant du module du centre vers les bords des sphérolites. Les branches situées sur les axes principaux de croissance affichent les modules les plus élevés, tandis que les zones latérales montrent des valeurs plus faibles. Cette variation est attribuée à la densité, à l'organisation ou à l’orientation des lamelles. À l’échelle lamellaire, les cartographies obtenues par AFM en mode mécanique montrent des hétérogénéités significatives. Certaines branches affichent des modules élevés, probablement liés à la microstructure sous la surface. Une transition est observée, avec des valeurs plus faibles au centre et plus élevées en périphérie, marquant un changement de module avec la croissance radiale. Toutefois, aucune corrélation directe n'a été établie avec des paramètres géométriques comme la longue période Lp ou l'angle d’émergence des lamelles, suggérant que ces paramètres microstructuraux ne suffisent pas à eux seuls à capturer la complexité de la microstructure. Une étude d’indentation sphérique multi-échelle a permis d’explorer les effets d’échelle sur le module d’élasticité du iPP. Les résultats révèlent que les modules mesurés par AFM sont significativement plus élevés que ceux obtenus par nanoindentation et macro-indentation, ces dernières présentant des valeurs assez similaires. Plusieurs hypothèses sont proposées et discutées pour expliquer cette différence, notamment le volume sondé, la vitesse de sollicitation et le cadre d'analyse. L’échelle de transition vers un VER mécanique n’est pas précisément déterminée, mais les résultats suggèrent qu’elle se situe à l’échelle intra-sphérolitique, lorsque plusieurs branches sont sondées. Cette évaluation pourrait varier avec d'autres microstructures. Enfin, l’étude des transitions entre techniques d’indentation a montré que varier la taille des pointes offre un gain limité sur le volume sondé, révélant ainsi les limites des équipements actuels pour explorer pleinement ces transitions d’échelle
The aim of this thesis is to gain a deeper understanding of the relationships between the elastic modulus of isotactic polypropylene (iPP) and its microstructure at different scales. An original multi-scale experimental approach is developed, combining indentation tests and atomic force microscopy (AFM) to characterize the elastic modulus and three-dimensional morphology of spherulites. The work is structured around four axes: (i) characterization of spherulitic morphology by AFM, (ii) indentation tests at various scales using different techniques (AFM in mechanical mode, nanoindentation, and macro-indentation), (iii) characterization of elastic modulus within spherulites through modulus mappings obtained by nanoindentation and AFM in mechanical mode, and (iv) evaluation of a mechanical representative elementary volume (REV) from spherical indentation tests. An original protocol was used to produce bulk iPP samples with a flat, slightly rough surface and without chemical etching, thus preserving the three-dimensional surface microstructure. The results reveal new insights into the microstructure of spherulites and the lamellar nanostructure of the α-phase. In addition to the classic observations (sheaf or rosette shapes), an intermediate scale is identified: the micrometer-sized radial branches of spherulites, made up of orthoradially oriented crystalline lamellae. These lamellae adopt a “lath-like” organization in the branches and “cross-hatching” in the closure zones. The average long period (Lp) is measured locally and is consistent with the literature (SAXS).Nanoindentation mapping showed a decreasing modulus gradient from the center to the edges of the spherulites. Branches located on the main growth axes show the highest moduli, while lateral areas show lower values. This variation is attributed to the density, organization or orientation of the lamellae. At lamellar scale, AFM in mechanical mode mappings show significant heterogeneity. Some branches display high moduli, probably linked to the subsurface microstructure. A transition is observed, with lower values in the center and higher at the periphery, marking a change in modulus with radial growth. However, no direct correlation was established with geometric parameters such as the long period Lp or the lamella emergence angle, suggesting that these microstructural parameters alone are not sufficient to capture the complexity of the microstructure. A multi-scale spherical indentation study explored the effects of scale transition on the elastic modulus of iPP. The results reveal that the moduli measured by AFM are significantly higher than those obtained by nano-indentation and macro-indentation, the latter presenting fairly similar values. Several hypotheses were proposed and discussed to explain this difference, including the volume probed, the strain rate and the analysis framework. The scale transition to a mechanical REV is not precisely determined, but the results suggest that it lies at the intra-spherulitic scale, when several branches are probed. This assessment could vary with other microstructures. Finally, the scale transition study between indentation techniques showed that varying tip size offers limited gain in probed volume, revealing the limitations of current equipment to fully explore these scale transitions

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Baghbanan, Alireza. "Scale and Stress Effects on Hydro-Mechanical Properties of Fractured Rock Masses." Doctoral thesis, KTH, Teknisk geologi och geofysik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4772.

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In this thesis, the effects of size and stress on permeability, deformability and strength of fractured rock masses are investigated. A comparison study was carried out to examine the effects of considering, or not considering, the correlation between distributions of fracture apertures and fracture trace lengths on the hydro-mechanical behavior of fractured rocks. The basic concepts used are the fundamental principles of the general theory of elasticity, Representative Elementary Volume (REV), the tensor of equivalent permeability, and the strength criteria of the fractured rocks. Due to the size and stress dependence of the hydro-mechanical properties of rock fractures, the overall effective (or equivalent) hydro-mechanical properties of the fractured rocks are also size and stress-dependent. However, such dependence cannot be readily investigated in laboratory using small samples, and so numerical modeling becomes a necessary tool for estimating their impacts. In this study, a closed-form relation is established for representing the correlation between a truncated lognormal distribution of fracture apertures and a truncated power law distribution of trace lengths, as obtained from field mapping. Furthermore, a new nonlinear algorithm is developed for predicting the relationship between normal stress and normal displacement of fractures, based on the Bandis model and the correlation between aperture and length. A large number of stochastic Discrete Fracture Network (DFN) models of varying sizes were extracted from some generated large-sized parent realizations based on a realistic fracture system description from a site investigation programme at Sellafield, UK, for calculating the REV of hydro-mechanical properties of fractured rocks. Rotated DFN models were also generated and used for evaluation of the distributions of directional permeabilities, such that tensors of equivalent permeability could be established based on stochastically established REVs. The stress-dependence of the permeability and the stress-displacement behaviour were then investigated using models of REV sizes. The Discrete Element Method (DEM) was used for numerical simulation of the fluid flow, deformability properties and mechanical strength behavior of fractured rocks. The results show significant scale-dependency of rock permeability, deformability and strength, and its variation when the correlation between aperture and trace length of fractures are concerned, with the overall permeability and deformability more controlled by dominating fractures with larger apertures and higher transmissivity and deformability, compared with fracture network models having uniform aperture. As the second moment of aperture distribution increases, a fractured rock mass shows more discrete behavior and an REV is established in smaller value of second moment with much larger model size, compared with the models with uniform fracture aperture. When the fracture aperture pattern is more scattered, the overall permeability, Young’s modulus and mechanical strength change significantly. The effect of stress on permeability and fluid flow patterns in fractured rock is significant and can lead to the existence or non-existence of a permeability tensor. Stress changes the fluid flow patterns and can cause significant channeling and the permeability tensor, and REV may be destroyed or re-established at different applied stress conditions. With an increase in the confining stress on the DEM models, the strength is increased. Compared with the Hoek-Brown criterion, the Mohr-Coulomb strength envelope provides a better fit to the results of numerical biaxial compression tests, with significant changes of the strength characteristic parameters occurring when the second moment of the aperture distribution is increased.
QC 20100702

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Noorian-Bidgoli, Majid. "Strength and deformability of fractured rocks." Doctoral thesis, KTH, Mark- och vattenteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155719.

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Анотація:

This thesis presents a systematic numerical modeling framework to simulate the stress-deformation and coupled stress-deformation-flow processes by performing uniaxial and biaxial compressive tests on fractured rock models with considering the effects of different loading conditions, different loading directions (anisotropy), and coupled hydro-mechanical processes for evaluating strength and deformability behavior of fractured rocks. By using code UDEC of discrete element method (DEM), a series of numerical experiments were conducted on discrete fracture network models (DFN) at an established representative elementary volume (REV), based on realistic geometrical and mechanical data of fracture systems from field mapping at Sellafield, UK. The results were used to estimate the equivalent Young’s modulus and Poisson’s ratio and to fit the Mohr-Coulomb and Hoek-Brown failure criteria, represented by equivalent material properties defining these two criteria. The results demonstrate that strength and deformation parameters of fractured rocks are dependent on confining pressures, loading directions, water pressure, and mechanical and hydraulic boundary conditions. Fractured rocks behave nonlinearly, represented by their elasto-plastic behavior with a strain hardening trend. Fluid flow analysis in fractured rocks under hydro-mechanical loading conditions show an important impact of water pressure on the strength and deformability parameters of fractured rocks, due to the effective stress phenomenon, but the values of stress and strength reduction may or may not equal to the magnitude of water pressure, due to the influence of fracture system complexity. Stochastic analysis indicates that the strength and deformation properties of fractured rocks have ranges of values instead of fixed values, hence such analyses should be considered especially in cases where there is significant scatter in the rock and fracture parameters. These scientific achievements can improve our understanding of fractured rocks’ hydro-mechanical behavior and are useful for the design of large-scale in-situ experiments with large volumes of fractured rocks, considering coupled stress-deformation-flow processes in engineering practice.

QC 20141111

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Hill, Richard Lee Sr. "Development of a representative volume element of lithium-ion batteries for thermo-mechanical integrity." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67781.

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Анотація:

Thesis (Nav. E. and S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 67-69).
The importance of Lithium-ion batteries continues to grow with the introduction of more electronic devices, electric cars, and energy storage. Yet the optimization approach taken by the manufacturers and system designers is one of test and build, an approach that nearly every other industry has long abandoned. A computational model is required to reduce the expensive build-test cycle and allow safer, cheaper batteries to be built. The path to building this computational model will involve many different processes and one of those processes dictates the homogenizing of the interior of the battery casing by treating the interior as a homogenized Representative Volume Element. This study explains this process and outlines a procedure for the development of this particular model for both cylindrical and prismatic / pouch cells. Over twenty different mechanical tests were performed on fully-discharged cylindrical and pouched / prismatic lithium-ion batteries, in casings and without casings under multiple loading conditions. These included lateral indentation by a rod, axial compression, through-thickness compression, in-plane unconfined compression, in-plane confined compression, hemispherical punch indentation and three-point bending. Extensive testing on the battery cell and jelly roll of 18650 lithium ion cylindrical cell, combined with the use of analytical solutions to estimate material properties of the cell, yielded the development of a finite element model. It was found that the suitably calibrated model of high density compressible foam provided a very good prediction of the crash behavior of cylindrical battery cell subjected to high intensity lateral and axial loads. For the prismatic / pouch cell, the measured load-displacement data allowed calculation of the individual compression stress-strain curves for the separator, the active anode and cathode materials. The average stress-volumetric strain relation was derived from averaging the properties of individual layers as well as from direct measurement on the bare cell. This information was then used as an input to the FE model of the cell. The model was composed of shell elements representing the Al and Cu foil and solid elements for the active material with a binder lumped together with the separator. Very good correlation was obtained between LS-Dyna numerical simulation and test results for the through-thickness compression, punch indentation and confined compression. Closed form solutions were also derived for the latter three problems which helped explain the underlying physics and identified important groups of parameters. It was also demonstrated that a thin Mylar pouch enclosure provided considerable reinforcement and in some cases changed the deformation and failure mechanism. This paper reports on the results generated for the Li-ion Battery Consortium at MIT.
by Richard Lee Hill, Sr.
Nav.E.and S.M.

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Zhou, Pin. "The Use of the Continuity Factor as a Tool to Represent Representative Elementary Volume in Rock Engineering Design." Licentiate thesis, KTH, Jord- och bergmekanik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-144591.

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Medikonda, Sandeep. "Micro-Mechanical Models for Impact and Non-Local Averaging in Composites." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1522419945945237.

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McConaha, Matthew. "Graded Lattice Structure Density Optimization for Additive Manufacturing." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1523634949822303.

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Soares, Gilson Francisco Paz. "Homogeneização de um material composto formado por uma matriz polimérica com uma segunda fase particulada." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2010. http://hdl.handle.net/10183/30141.

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O estudo numérico do comportamento estrutural de materiais compostos apresenta-se, desde os últimos anos, como um campo muito fértil de pesquisas, o que justifica o crescimento exponencial de trabalhos científicos nesta área. Atualmente é possível desenhar as propriedades físicas do material adequando-os ao uso que se queira dar a eles. Especificamente quanto às propriedades mecânicas vinculadas a função estrutural que o material em estudo possa ter, estas podem, na atualidade, ser quantificadas, modificadas e otimizadas. No presente trabalho, explora-se um material composto formado por uma matriz polimérica e uma segunda fase particulada com distribuição aleatória. Para realizar esse estudo foi utilizado o método dos elementos discretos e o método dos elementos finitos. No primeiro caso é apresentado um estudo onde se realizam tentativas de determinar o elemento de volume representativo considerando o comportamento do material como não-linear. No segundo caso, aplicando o método dos elementos finitos, realiza-se um estudo considerando a matriz e a fase particulada com comportamento elástico linear, determinando o elemento de volume representativo e comparando os resultados, em termos de constantes elásticas homogeneizadas, com propostas teóricas fornecidas pela micromecânica clássica. Um estudo da convergência da malha e exercícios de otimização foram realizados sobre o composto simulado. Finalmente, realiza-se um estudo não-linear através do método dos elementos finitos, onde a matriz é elástica e a fase particulada hiperelástica, onde se determina o elemento de volume representativo e se faz aplicações para verificação da eficácia dos resultados.
The numerical study of the composite material mechanical behavior has shown lately a fertile field of research, which justifies the exponential growing of scientific works in this area. Nowadays it is possible to design the material properties adapting them to the usage that we want to give them. Specifically, regarding to the mechanical properties, there are methods that allow us to modify them in a rational way to reach different objectives. In the present work, different aspects are analyzed of a composite material built with a polymeric matrix and a second particulate phase with random distribution. The Discrete Element Method (DEM) and the Finite Element Method (FEM) were used to carry out the present work. Firstly, an application of DEM, a study of different alternatives is shown to determine the volume representative element (RVE) considering the non-linear behavior of the studied material. Secondly, an application of FEM, a study considering the matrix and particulate phase, both, with linear elastic behavior. This application consists on computing the RVE and comparing these results with analytical proposals available in the Micromechanics classical bibliography. A mesh convergence study of the FEM models used and simple applications of optimization are also presented. Finally, another application of FEM is presented. In this case a non linear study is shown, where the matrix is considered linear elastic, and the particulate phase is hyperelastic. In this case the RVE was determined and some applications to verify the consistency of the results obtained are presented.

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Farichah, Himatul, and 法麗佳. "Representative Elementary Volume of P32 and Hydraulic Conductivity of Fractured Rock masses." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/u97928.

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碩士
國立中央大學
土木工程學系
105
This study presents the representative elementary volume (REV) of P32 (fracture intensity) and hydraulic conductivity of fractured rock mass. Discrete fracture network (DFN) generated by FracMan is adopted to create rock mass models. A series of parametric studies including dip angle, dip direction, Fisher constant κ, size of rock mass model, shape of rock mass model, specimen volume, fracture diameter, and P32 were investigated to study the REV of P32. Based on the results of the parametric studies, a novel equation to quantify the COV (Coefficient of variance) of P32 in terms of specimen volume, fracture diameter and P32 was established. A precise REV size can be obtained easily by assigning the acceptable COV. Thereafter, some case studies were used to verify the proposed novel equation. Conventional Oda and Oda gold were adopted to estimate the hydraulic conductivity of the fractured rock mass. By using Oda conventional, a series of parametric studies including specimen volume, fracture diameter, P32, transmissivity, and aperture were investigated to study the REV of hydraulic conductivity. Subsequently, that REV of hydraulic conductivity was compared with the REV of P32. In the other hand, by using Oda gold, only P32 was chosen as parametric study. Eventually, a proposed new method was conducted by examining the Monte Carlo simulation for REV of hydraulic conductivity determination.

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Книги з теми "Mechanical Representative Elementary Volume"

Anonyma. Elementary Course in Mechanical Drawing for Manual Training and Technical Schools ...: With Chapters on Machine Sketching and the Blue-Printing Process; Volume 1. Creative Media Partners, LLC, 2023.

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Beowulf. Elementary Course in Mechanical Drawing for Manual Training and Technical Schools ...: With Chapters on Machine Sketching and the Blue-Printing Process; Volume 1. Creative Media Partners, LLC, 2018.

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Частини книг з теми "Mechanical Representative Elementary Volume"

Andreeva, M. V., A. V. Kalyuzhnyuk, V. V. Krutko, N. E. Russkikh, and I. A. Taimanov. "Representative Elementary Volume via Averaged Scalar Minkowski Functionals." In Lecture Notes in Mechanical Engineering, 533–39. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92144-6_40.

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Dal Fabbro, Pierandrea, Mattia Maltauro, Luca Grigolato, Stefano Rosso, Roberto Meneghello, Gianmaria Concheri, and Gianpaolo Savio. "Representative Volume Element Analysis in Material Coextrusion." In Lecture Notes in Mechanical Engineering, 371–79. Cham: Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-58094-9_41.

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Bachmat, Yehuda, and Jacob Bear. "On the Concept and Size of a Representative Elementary Volume (Rev)." In Advances in Transport Phenomena in Porous Media, 3–20. Dordrecht: Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-3625-6_1.

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Vignesh, P., R. Krishna Kumar, and M. Ramu. "Evaluation of Mechanical and Thermal Behaviour of Particle-Reinforced Metal Matrix Composite Using Representative Volume Element Approach." In Lecture Notes in Mechanical Engineering, 415–25. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-13-1780-4_40.

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El Houdaigui, F., S. Forest, A. F. Gourgues, and D. Jeulin. "On the Size of the Representative Volume Element for Isotropic Elastic Polycrystalline Copper." In IUTAM Symposium on Mechanical Behavior and Micro-Mechanics of Nanostructured Materials, 171–80. Dordrecht: Springer Netherlands, 2007. http://dx.doi.org/10.1007/978-1-4020-5624-6_17.

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Brünig, Michael, Sanjeev Koirala, and Steffen Gerke. "Numerical Analysis of Damage and Failure in Anisotropic Sheet Metals During Biaxial Loading." In Lecture Notes in Mechanical Engineering, 283–93. Cham: Springer International Publishing, 2024. http://dx.doi.org/10.1007/978-3-031-58006-2_22.

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AbstractIn the paper, the influence of stress state and loading direction with respect to the principal axes of anisotropy on damage and fracture behavior of the anisotropic aluminum alloy EN AW-2017A is discussed. The focus is on numerical calculations on the micro-level considering void-containing representative volume elements revealing information on damage mechanisms. Using experimental data taken from uniaxial and biaxial tests, material parameters are identified. Based on numerical studies on the micro-scale with differently loaded void-containing cubes, it is shown that the stress state, the load ratio and the loading direction with respect to the principal axes of anisotropy have an influence on evolution of damage processes on the micro-scale and on the corresponding damage strains.

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Skripnyak, Vladimir A., Evgeniya G. Skripnyak, and Vladimir V. Skripnyak. "Failure Mechanisms of Alloys with a Bimodal Graine Size Distribution." In Springer Tracts in Mechanical Engineering, 521–34. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-60124-9_23.

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AbstractA multi-scale computational approach was used for the investigation of a high strain rate deformation and fracture of magnesium and titanium alloys with a bimodal distribution of grain sizes under dynamic loading. The processes of inelastic deformation and damage of titanium alloys were investigated at the mesoscale level by the numerical simulation method. It was shown that localization of plastic deformation under tension at high strain rates depends on grain size distribution. The critical fracture stress of alloys depends on relative volumes of coarse grains in representative volume. Microcracks nucleation at quasi-static and dynamic loading is associated with strain localization in ultra-fine grained partial volumes. Microcracks arise in the vicinity of coarse and ultrafine grains boundaries. It is revealed that the occurrence of a bimodal grain size distributions causes increased ductility, but decreased tensile strength of UFG alloys. The increase in fine precipitation concentration results not only strengthening but also an increase in ductility of UFG alloys with bimodal grain size distribution.

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Guo, Rongjiao, and Renjun Yan. "Prediction of Mechanical Properties and Analysis of Damage Evolution of Fiber Bundles in Carbon Fiber Reinforced Composite Materials." In Lecture Notes in Mechanical Engineering, 633–46. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-1876-4_50.

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AbstractFiber bundles are an important component of woven composite materials, and predicting the mechanical properties of fiber bundles can provide a basis for the study of the mechanical properties of woven composite materials. This paper establishes the micro representative volume element (RVE) model of composite materials, and obtains the equivalent elastic constant of yarn through the model homogenization theory and periodic boundary conditions. Strength prediction is performed through the VUMAT user subroutine of ABAQUS. This paper uses the maximum stress standards and Von Mises standards to predict the damage initiation of TC33 carbon fiber and epoxy resin matrix, respectively. Combined with the constant degradation method, the simulation of the damage behaviors of the micro model is achieved, and the equivalent strength of the fiber bundle is obtained. The effectiveness and correctness of this method are verified by comparing the numerical model results with the Chamis theoretical model results. The accurate prediction of mechanical properties and damage process of fiber bundles provides theoretical support for the analysis of mechanical properties of composites, and has guiding significance for the performance design of composite materials.

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Abendroth, Martin, Stephan Roth, Alexander Malik, Andreas Seupel, Meinhard Kuna, and Bjoern Kiefer. "Modeling and Evaluation of the Thermo-mechanical Behavior of Filter Materials and Filter Structures." In Multifunctional Ceramic Filter Systems for Metal Melt Filtration, 387–425. Cham: Springer International Publishing, 2024. http://dx.doi.org/10.1007/978-3-031-40930-1_16.

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AbstractTo capture and predict the chemo-thermo-mechanical behavior of ceramic foam filters, material models and simulation tools are required. The description of the thermo-mechanical inelastic behavior as well as the in-situ layer formation on reactive filters have been the aims of this subproject. Challenging aspects in the whole progress are the exact geometrical replication of the underlying foam structure of the filter and the lack of experimental data for many relevant loading cases. The software FoamGUI is developed to generate parametrized, periodic three-dimensional representative volume elements (RVE) of foam structures, which are used in continuum and fluid mechanical simulations as well as for 3D-printing. Calculation concepts are formulated to predict the inelastic deformation and failure behavior of ceramic open-cell foams under thermo-mechanical loading. First-order homogenization approaches are used to conclude from the mesoscopic behavior of the foam RVE to the macroscopic response of filter structures. A hybrid approach is developed in the established framework of rate-independent plasticity in combination with neural networks, which replace the plastic flow potential and the evolution equations of internal state variables. Another modeling aspect is motivated by the experimentally observed growth of an in situ layer during the so-called reactive phase of the filtration process. This phenomenon motivates the development of a model to describe diffusion, chemical reactions and phase transition processes of multi-phase/multi-component systems using the phase-field method. This allows the simulation of spatially and temporally resolved microstructure evolution leading to the layer formation.

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Rajendran, Mohan Kumar, Michael Budnitzki, and Meinhard Kuna. "Multi-scale Modeling of Partially Stabilized Zirconia with Applications to TRIP-Matrix Composites." In Austenitic TRIP/TWIP Steels and Steel-Zirconia Composites, 679–721. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-42603-3_21.

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Abstract The understanding of how the microstructure influences the mechanical response is an essential pre-requisite for materials tailored to match specific requirements. The aim of this chapter is to further this understanding in the context of Mg-PSZ-TRIP-steel composites on three different scales using a set of methods ranging from phase-field simulations over micromechanics to continuum constitutive modeling. On the microscale, using a Ginzburg-Landau type phase-field model the effects of cooling- and stress-induced martensitic phase transformation in MgO-PSZ is clearly distinguished. Additionally with this method the role of energy barrier in variant selection and the effect of residual stress contributing to the stability of the tetragonal phase are also investigated. On the mesomechanical scale, an analytical 2D model for the martensitic phase transformation and self-accommodation of inclusions within linear elastic materials has been successfully developed. The influences of particle size and geometry, chemical driving force, temperature and surface energy on the $$t \rightarrow m$$ t → m transformation are investigated in a thermostatic approach. On the continuum scale, a continuum material model for transformation plasticity in partially stabilized zirconia ceramics has been developed. Nonlinear hardening behavior, hysteresis and monoclinic phase fraction during a temperature cycle are analyzed. Finally, The mechanical properties of a TRIP steel matrix reinforced by ZrO$$_2$$ 2 particles are analyzed on representative volume elements. Here the mechanical properties of the composite as function of volume fraction of both constituents and the strength of the interface are studied.

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Тези доповідей конференцій з теми "Mechanical Representative Elementary Volume"

Konovalov, D. A., E. O. Smirnova, and A. S. Smirnov. "Determining AlMg6/10%SiCp representative elementary volume size by kinetic indentation." In MECHANICS, RESOURCE AND DIAGNOSTICS OF MATERIALS AND STRUCTURES (MRDMS-2018): Proceedings of the 12th International Conference on Mechanics, Resource and Diagnostics of Materials and Structures. Author(s), 2018. http://dx.doi.org/10.1063/1.5084483.

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de Lemos, Marcelo J. S., and Nicolau B. Santos. "Turbulent Heat Transfer in Channels With Solid and Porous Baffles." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81505.

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Simulations are presented for turbulent flow in a channel containing baffles made with solid and porous materials. The equations of mass continuity, momentum and energy are written for an elementary representative volume yielding a set of equations valid for the entire computational domain. These equations are discretized using the control volume method and the resulting system of algebraic equations is relaxed with the SIMPLE method. The presented numerical results for the friction factor f and for the Nusselt number Nu were compared with available data. Further simulations comparing the effectiveness of the porous material used showed that no advantages are obtained when using low porosity baffles in the turbulent flow regime.

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de Lemos, Marcelo J. S., and Viviani T. Magro. "Nusselt Number and Temperature Distribution in an Horizontal Cavity Containing a Layer of Porous Material at the Bottom." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-41468.

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Horizontally-layered porous media in enclosures represents an important configuration with many technological applications in mechanical and aerospace engineering. This work presents numerical solutions for flow and heat transfer in square cavities partially obstructed with porous material. The microscopic flow and energy equations are integrated in a representative elementary volume in order to obtain a set of equations valid in both the clear flow region and in the porous matrix. A unique set of equations is discretized with the control volume method and solved with SIMPLE algorithm. Heat transfer enhancement across the porous cavity is calculated as the permeability or the porosity of the porous substrate increase.

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de Lemos, Marcelo J. S., and Luzia A. Tofaneli. "Pressure Drop Characteristics of Parallel-Plate Channel Flow With Porous Obstructions at Both Walls." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-41453.

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In this work, numerical solutions are presented for turbulent flow in a channel containing fins made with porous material. The condition of spatially periodic cell is applied longitudinally along the channel. A macroscopic tow-equation turbulence model is employed in both the porous region and the clear fluid. The equations of momentum, mass continuity and turbulence transport equations are written for an elementary representative volume yielding a set of equations valid for the entire computational domain. These equations are discretized using the control volume method and the resulting systems of algebraic equations is relaxed with the SIMPLE method. Results are presented for the velocity field as a function of Reynolds number, porosity and permeability of the fins.

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Wu, Xuehai, John G. Georgiadis, and Assimina A. Pelegri. "Biphasic Representative Elemental Volumes for 3-D White Matter Elastography." In ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-73372.

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Abstract White matter (WM) characterization is challenging due to its anisotropic and inhomogeneous microstructure that necessitates multiscale and multi-modality measurements. Shear elastography is one such modality that requires the accurate interpretation of 3D shear strain measurements, which hinge on developing appropriate constitutive tissue models. Finite element methods enable the development of such models by simulating the shear response of representative elemental volumes (REV). We have developed triphasic (axon, myelin, glia), 2D REVs to simulate the influence of the intrinsic viscoelastic property and volume fraction of each phase. This work constitutes the extension of 2D- to 3D-REVs, focusing on the effect of the intrinsic material properties and their 3D representation on the viscoelastic response of the tissue. By lumping the axon and myelin phases, a flexible 3D REV generation and analysis routine is then developed to allow for shear homogenization in both the axial and transverse directions. The 2D and 3D models agree on stress distribution and total deformation when 2D cross-sectional snapshots are compared. We also conclude that the ratio of transverse to axial transverse modulus is larger than one when axon fibers are stiffer than the glial phase.

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de Lemos, Marcelo J. S., and Nicolau B. Santos. "Laminar Heat Transfer in a Parallel Plate Channel With Solid and Porous Baffles." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-62362.

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Simulations are presented for laminar flow in a channel containing fins made with solid (impermeable) and porous materials. The equations of mass continuity, momentum and energy are written for an elementary representative volume yielding a set of equations valid for the entire computational domain. These equations are discretized using the control volume method and the resulting system of algebraic equations is relaxed with the SIMPLE method. The presented numerical results for the friction factor f and the Nusselt number Nu were compared with available data indicating that results herein differ by less than 5% in relation to published results. Further simulations comparing the effectiveness of the porous material used showed that no advantages are obtained for using low porosity baffles in the laminar flow regime.

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Zhou, Feng, Nicholas Hansen, and Ivan Catton. "VAT Based Modeling of Heat Exchanger and Obtaining Closure From CFD Solution." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-37519.

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VAT is used to rigorously cast the point-wise conservation of energy, momentum and mass equations into a form that represents the thermal and hydraulic properties of heat exchanger channel morphology. At the lower level, the media is described by a representative elementary volume (REV). Closure terms in the VAT equations are related to a local friction factor and a heat transfer coefficient of the REV. The terms in the closure expressions are complex and relating experimental data to the closure terms resulting from Volume Averaging Theory (VAT) is difficult. In this work we use CFD to obtain detailed solutions to flow through an element of a heat exchanger and use these results to evaluate the closure terms needed for a fast running VAT based code. The VAT based code can then be used to solve the heat transfer characteristics of the higher level heat exchanger. A comparison is then made of the CFD closure and experimental data rescaled by VAT scaling. The objective is to show how heat exchangers can be modeled as porous media based on Volume Averaging Theory and how CFD can be used in place of a detailed, often formidable, experimental effort.

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Goldfarb, Eric J., Ken Ikeda, and Nicola Tisato. "Evaluating samples smaller than the representative elementary volume (REV)." In First International Meeting for Applied Geoscience & Energy. Society of Exploration Geophysicists, 2021. http://dx.doi.org/10.1190/segam2021-3594787.1.

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Al Hattamleh, O., M. Razavi, and B. Muhunthan. "Experimental determination of representative elementary volume of sands using X-ray computed tomography." In MATERIALS CHARACTERISATION 2009. Southampton, UK: WIT Press, 2009. http://dx.doi.org/10.2495/mc090141.

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Keehm, Youngseuk, and Tapan Mukerji. "Permeability and relative permeability from digital rocks: Issues on grid resolution and representative elementary volume." In SEG Technical Program Expanded Abstracts 2004. Society of Exploration Geophysicists, 2004. http://dx.doi.org/10.1190/1.1845147.

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