Готові списки джерел за темами / Elastoplastic behavior

Добірка наукової літератури з теми "Elastoplastic behavior"

Автор: Grafiati

Опубліковано: 31 січня 2023

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Статті в журналах з теми "Elastoplastic behavior":

Sumarac, Dragoslav, Bojan Medjo, and Natasa Trisovic. "Hysteretic behavior modeling of elastoplastic materials." Theoretical and Applied Mechanics 35, no. 1-3 (2008): 287–304. http://dx.doi.org/10.2298/tam0803287s.

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In the present paper the Preisach model of hysteresis is applied to model cyclic behavior of elasto-plastic material. Rate of loading and viscous effects will not be considered. The problem of axial loading of rectangular cross section and cyclic bending of rectangular tube (box) will be studied in details. Hysteretic stress-strain loop for prescribed history of stress change is plotted for material modeled by series connection of three unite element. Also moment-curvature hysteretic loop is obtained for a prescribed curvature change of rectangular tube (box). One chapter of the paper is devoted to results obtained by FEM using Finite Element Code ABAQUS. All obtained results clearly show advantages of the Preisach model for describing cyclic behavior of elasto-plastic material.

Gilat, Rivka, and Jacob Aboudi. "Behavior of Elastoplastic Auxetic Microstructural Arrays." Materials 6, no. 3 (February 28, 2013): 726–37. http://dx.doi.org/10.3390/ma6030726.

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Jiang, Xin, and Xiao Hang Liu. "Thermal Elastoplastic Behavior of Dispersion Nuclear Fuel Elements." Advanced Materials Research 339 (September 2011): 353–57. http://dx.doi.org/10.4028/www.scientific.net/amr.339.353.

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A representative volume element is chosen to act as the research object to analyze the thermal elastoplastic behavior of the dispersion fuel elements. The large strain elastoplastic analysis is carried out for the mechanicalbehaviors using FEM. The results indicate that with the volume fraction of the fuel particles increasing, the Mises stress and the equivalent plastic strain in the matrix increases, and the first principal stress and the equivalent plastic strain in the cladding increases markedly.

Haghgoo, M., R. Ansari, MK Hassanzadeh-Aghdam, and A. Darvizeh. "Elastoplastic behavior of the metal matrix nanocomposites containing carbon nanotubes: A micromechanics-based analysis." Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 233, no. 4 (May 7, 2017): 676–86. http://dx.doi.org/10.1177/1464420717700927.

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The elastoplastic behavior of aluminum (Al) nanocomposites reinforced with aligned carbon nanotubes (CNTs) is characterized using a unit cell micromechanical model. The interphase zone caused by the chemical reaction between CNT and Al matrix is included in the analysis. To attain the elastoplastic stress–strain curve of the nanocomposites, the successive approximation method together with the von Mises yield criterion is employed. The effects of several important factors including the volume fraction and diameter of CNT, material properties, and size of interphase on the elastoplastic stress–strain curve of the nanocomposites during uniaxial tension are studied. The results indicate that the interphase characteristics significantly affect the elastoplastic behavior of the CNT-reinforced Al nanocomposites. It is also found that the yield stress of the nanocomposites rises with increasing CNT volume fraction or decreasing CNT diameter. Besides, the elastoplastic stress–strain curve of the CNT-reinforced Al nanocomposites is presented for multiaxial tension. The initial yield envelopes of the nanocomposites under longitudinal–transverse biaxial tension are provided too. Comparison between the elastic results of the present model with those of other available micromechanical analyses shows a very good agreement.

Nelson, Richard B., and Alois Dorfmann. "Parallel Elastoplastic Models of Inelastic Material Behavior." Journal of Engineering Mechanics 121, no. 10 (October 1995): 1089–97. http://dx.doi.org/10.1061/(asce)0733-9399(1995)121:10(1089).

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Gamonpilas, Chaiwut, and Esteban P. Busso. "Characterization of Elastoplastic Properties Based on Inverse Analysis and Finite Element Modeling of Two Separate Indenters." Journal of Engineering Materials and Technology 129, no. 4 (December 15, 2006): 603–8. http://dx.doi.org/10.1115/1.2744428.

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A method that can determine uniquely the elastoplastic properties from indentation loading and unloading curves has been developed. It is based on finite element modeling and inverse analysis of two separate indenters. The approach was validated by numerical experiments using a fictitious material. It was demonstrated that the proposed method can uniquely recover the elastoplastic properties using only indentation load-displacement curves of two indenters. Although the proposed procedure has been used to predict elastoplastic strain hardening behavior, it is also applicable to estimate other mechanical properties where there are more than two unknown parameters, such as rate-dependent behavior.

Overaker, D. W., A. M. Cuitin˜o, and N. A. Langrana. "Elastoplastic Micromechanical Modeling of Two-Dimensional Irregular Convex and Nonconvex (Re-entrant) Hexagonal Foams." Journal of Applied Mechanics 65, no. 3 (September 1, 1998): 748–57. http://dx.doi.org/10.1115/1.2789119.

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A nonlinear micromechanical model for two-dimensional irregular hexagonal foams has been developed that allows for anisotropy in morphology and/or material. Based upon the orientation, cross section, length, and material properties of each strut, the resulting microlevel beam behavior within the unit cell determines its structural properties. Nonlinearity is introduced as coupled elastoplastic beam behavior, where the elastoplastic behavior of each beam is considered. The analytical. formulation for the stiffness matrix of the general elastoplastic unit cell is. found by considering compatibility and equilibrium of the unit cell. The structural properties of the elastoplastic unit cell are embedded in a continuum finite element model as material properties, thus capturing the microstructure of the foam in an accurate and efficient model. Structural nonlinearity is therefore directly linked to localized plasticity and its evolution at the microlevel. Elastic analyses investigated the degree of anisotropy in structural properties that was induced by various morphological changes. The differences in stress and deformation behavior between a regular hexagonal foam and a re-entrant foam were also demonstrated. Plastic analyses showed how structural nonlinearity could be explained by localized microstructural behavior. The advantage of this micromechanical model is that it allows a study of the effects of morphology and/or material anisotropies on the overall foam behavior.

Wu, Y., and JW Ju. "Elastoplastic damage micromechanics for continuous fiber-reinforced ductile matrix composites with progressive fiber breakage." International Journal of Damage Mechanics 26, no. 1 (July 28, 2016): 4–28. http://dx.doi.org/10.1177/1056789516655671.

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An elastoplastic damage micromechanical framework considering evolutionary fiber breakage is proposed to predict the overall material behaviors of continuous fiber-reinforced composites with ductile matrix under external loading. In the present work, we assume that the overall nonlinear behavior of a composite is primarily attributed to the plastic deformation in the matrix as well as the damage evolution due to fiber breakage. The effective elastoplastic deformations are governed by means of the effective yield surface derived from a representative microstructure with elastic fibers embedded in an elastoplastic matrix material. The matrix behaves elastically or plastically depending on the local stress, and the effective elastoplastic deformation obeys the associative plastic flow rule and isotropic hardening law. In addition, taking advantage of the eigenstrain due to fiber breakage together with a Weibull statistic model, the evolutionary fiber breakage mechanism is effectively predicted. Finally, the overall elastoplastic stress–strain responses are reached under the framework of micromechanics and damage mechanics. Comparisons between the proposed theoretical predictions and experimental data are performed to illustrate the capability of the proposed framework. In particular, the proposed model is employed to investigate the overall uniaxial and axisymmetric elastoplastic stress–strain responses of the continuous fiber-reinforced metal matrix composites. Studies of the initial yield surfaces at various damage levels are conducted as well.

Shen, Min, Wen Liang Wang, Rui Xu, Jing Wei Tong, and Hong Xia Li. "Prediction of Orthotropic Mechanical Behaviors of Hot-Pressing Weft-Knitted Flax/PP Composites." Advanced Materials Research 287-290 (July 2011): 326–29. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.326.

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The orthotropic mechanical behaviors of weft-knitted flax fiber fabric reinforced polypropylene (PP) composites, which were produced by hot pressing of knit layers composed of a commingled yarn with a flax fiber content of 50vol.%, are investigated in both meso- and macro-scales. In meso-scale, the repeating unit cell (RUC) finite element (FE) model is developed, in which impregnated yarns are assumed to be isotropic elastic while the matrix is modeled as an elastoplastic, isotropic solid. Then, stress-strain curves of the RUC are simulated for its elastoplastic orthotropic parameters. Finally, in macro-scale of its specimen, the tensile behavior of the composite laminates with six parallel plies is simulated by means of 3D elastoplastic FE method. The applicability and limitation of this model have been discussed.

Ju, J. W., and Tsung-Muh Chen. "Micromechanics and Effective Elastoplastic Behavior of Two-Phase Metal Matrix Composites." Journal of Engineering Materials and Technology 116, no. 3 (July 1, 1994): 310–18. http://dx.doi.org/10.1115/1.2904293.

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A micromechanical framework is presented to predict effective (overall) elasto-(visco-)plastic behavior of two-phase particle-reinforced metal matrix composites (PRMMC). In particular, the inclusion phase (particle) is assumed to be elastic and the matrix material is elasto-(visco-)plastic. Emanating from Ju and Chen’s (1994a,b) work on effective elastic properties of composites containing many randomly dispersed inhomogeneities, effective elastoplastic deformations and responses of PRMMC are estimated by means of the “effective yield criterion” derived micromechanically by considering effects due to elastic particles embedded in the elastoplastic matrix. The matrix material is elastic or plastic, depending on local stress and deformation, and obeys general plastic flow rule and hardening law. Arbitrary (general) loadings and unloadings are permitted in our framework through the elastic predictor-plastic corrector two-step operator splitting methodology. The proposed combined micromechanical and computational approach allows us to estimate overall elastoplastic responses of PRMMCs by accounting for the microstructural information (such as the spatial distribution and micro-geometry of particles), elastic properties of constituent phases, and the plastic behavior of the matrix-only materials. Comparison between our theoretical predictions and experimental data on uniaxial elastoplastic tests for PRMMCs is also presented to illustrate the capability of the proposed framework. A straightforward extension to accommodate viscoplastic matrix material is also presented to further enhance the applicability of the proposed method.

Більше джерел

Дисертації з теми "Elastoplastic behavior":

Lee, Haeng-Ki. "Three-dimensional micromechanical damage models for effective elastic and elastoplastic behavior of composite materials with inhomogeneities or microcracks." Restricted to subscribing institutions, 1998. http://proquest.umi.com/pqdweb?did=1562125051&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.

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Alves, Denis Pires Rodrigues. "Modelagem do comportamento termomecânico de treliças espaciais em regime de grandes deslocamentos e deformações." Universidade Federal de Juiz de Fora (UFJF), 2016. https://repositorio.ufjf.br/jspui/handle/ufjf/3598.

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As treliças espaciais são estruturas compostas de barras usualmente metálicas (aço ou alumínio) que são utilizadas para diversas finalidades, mas principalmente para sustentar a cobertura de grandes vãos presentes em galpões e pavilhões. O presente trabalho tem como objetivo a modelagem computacional do comportamento termo-elastoplástico de treliças espaciais em regime de grandes deslocamentos e deformações, utilizando o modelo da equação de transferência de calor e um modelo constitutivo elastoplástico modificado para incluir a influência térmica. Simulações computacionais do modelo resultante podem ser usadas para o desenvolvimento de projetos de estruturas submetidas a grandes variações de temperatura, como as que ocorrem em um incêndio. O método dos elementos finitos (MEF) foi utilizado para determinar o campo de temperaturas na seção transversal das barras, enquanto que para encontrar os deslocamentos e as deformações nas barras em função da variação térmica e do carregamento foi utilizado o método da rigidez direta. Para resolver as equações de equilíbrio não-lineares resultantes do modelo constitutivo termomecânico foi utilizado o método de Newton-Raphson. O código desenvolvido foi inicialmente validado através de simulações computacionais em estruturas simples onde variações de temperatura alteram o módulo de elasticidade, o módulo plástico e a tensão de escoamento do material e podem causar a plastificação e até a ruptura das barras. Posteriormente são apresentados e discutidos os resultados obtidos a partir de treliças mais complexas, com geometria similar às usualmente utilizadas em aplicações de engenharia, submetido a uma situação simplificada de incêndio-padrão. A alta temperatura causa a diminuição da resistência e da rigidez das barras e informações importantes como o tempo de incêndio suportado pela estrutura e o número de barras plastificadas são extraídas das simulações e podem servir como uma medida de segurança para evitar danos maiores em locais com grandes aglomerados de pessoas.
Space trusses are structures usually composed of metalic rods (steel or aluminum) that are used for several purposes, but mainly to sustain the roof of large spans present in sheds and pavilions. The present work has the aim of computationally model the coupled thermo-elastoplastic behavior of space trusses under large displacements and large strains, using the heat transfer equation model and an elastoplastic constitutive model modified to include the thermal influence. Computer simulations of the resulting mathematical model can be used for the development of structural projects under large variations of temperature, as occurs in fire situations. The finite element method (FEM) was used to determine the temperature field in transversal section of rods. In order to find the displacements and strains due to thermal variation and loadings, it was used the direct stiffness method. The Newton-Raphson method was used to solve the resulting non-linear equilibrium equations of the thermomecanic constitutive model. The developed code was initially validated through computational simulations of simple structures where thermal variations affect the Young modulus, the plastic modulus and the yield stress of the material. The results of more complex trusses, with a geometry similar to the ones usually adopted in engineering applications, under a simplified standard fire situation are also presented. The high temperature causes a decrease in the rods' resistance and stiffness and important informations such as the fire time supported by the structure and the number of plastified rods are achieved from the simulations and can be used as a security measure to avoid greater damage in places with large crowds of people.

Nain, Vaibhav. "Efficient thermomechanical modeling of large parts fabricated by Directed Energy Deposition Additive Manufacturing processes." Thesis, Lorient, 2022. http://www.theses.fr/2022LORIS630.

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Les procédés de fabrication additive laser par dépôt de poudre offrent une opportunité unique pour la fabrication de grandes pièces à géométrie complexe. Cependant, les déformations mécaniques induites par ces procédés entrainent des défauts pouvant conduire à des pièces rebutées. Au cours de cette thèse, différents modèles ont donc été développés pour mieux comprendre l’apparition de ces déformations en fonction des paramètres opératoires. Un premier modèle thermomécanique prédit le comportement élastoplastique lors de la construction d’un mur en acier inoxydable 316L. L’apport de chaleur est modélisé par une source double ellipsoïdale mobile et la construction des couches se fait à l’aide d’une méthode hybride « Quiet/Active élément ». Un écrouissage isotrope non linéaire est considéré, avec prise en compte de la restauration d’écrouissage à hautes températures. Afin de réduire drastiquement les temps de calcul, une nouvelle source de chaleur est proposée utilisant une source ellipsoïdale allongée qui moyenne l’énergie sur un intervalle d’espace et de temps. Cependant, un intervalle d’espace trop grand diminue la précision du modèle. De nouveaux paramètres sont alors introduits afin d’identifier le meilleur compromis entre temps de calcul et précision. L’ensemble des modèles proposés est confronté avec succès avec des données expérimentales en termes de température et déplacement et ce pour différents paramètres opératoires. Enfin, des modèles multi-échelles basés l’activation par couche ou les méthodes de déformations inhérentes sont étudiés en vue de réduire les temps de calcul
Directed Energy Deposition (DED) Additive Manufacturing technology offers a unique possibility of fabricating large-scale complex-shape parts. However, process-induced deformation in the fabricated part is still a big obstacle in successfully fabricating large-scale parts. Therefore, multiple numerical models have been developed to understand the accumulation of induced deformation in the fabricated part. The first model predicts the thermo-elastoplastic behaviour that captures the laser movement. The laser-material interaction and metal deposition are modeled by employing a double ellipsoid heat source and the Quiet/Active material activation method respectively. The model considers isotropic non-linear material hardening to represent actual metal behaviour. It also employs an instantaneous stress relaxation model to simulate the effects of physical phenomena like annealing, solid-state phase transformation, and melting. Using this model as a reference case, an efficient model is developed with an objective to reduce the computation time and make it feasible to simulate large-part. The model employs an Elongated Ellipsoid heat source that averages the heat source over the laser path which reduces the computational burden drastically. However, averaging over large laser path results in inaccurate results. Therefore, new parameters are developed that identify the best compromise between computation time reduction and accuracy. Both models are validated with experimental data obtained from several experiments with different process parameters. Finally, other Multi- scale methods such as the Layer-by-layer method and Inherent Strain-based methods are implemented and explored

Blanchard, Samuel. "Caractérisation du comportement non-linéaire des matériaux à partir d'essais statistiquement indéterminés et de champs de déformation fortement hétérogènes." Valenciennes, 2009. http://ged.univ-valenciennes.fr/nuxeo/site/esupversions/1fd10ba0-61f0-4cc4-9e45-d5ed99090a91.

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Cette étude consiste à développer des outils permettant de mieux caractériser le comportement de matériaux ayant subi des transformations lors du procédé de fabrication d’une structure (mise en forme, assemblage). Pour cela, la démarche mise en place s’organise autour de quatre chapitres. Dans le premier, une étude bibliographique permet de faire l’état de l’art des différentes méthodes d’identification de loi de comportement non linéaires. A la suite de cette étude, la Méthode des Champs Virtuels, couplée à des mesures par stéréo corrélation d’images, est mise en œuvre pour identifier les paramètres d’une loi de comportement (élastoplastique) à partir de champs de déformation fortement hétérogènes. Le but de cette étude est de mieux comprendre quels sont les facteurs expérimentaux et numériques pouvant corrompre les résultats de l’identification. Le second chapitre est consacré au développement et à la validation des outils numériques qui seront utilisés pour caractériser le comportement du matériau. Le troisième porte sur l’étude des conséquences de l’utilisation de données expérimentales (imparfaites) sur le calcul de l’équation d’équilibre à la base de la procédure d’identification. Enfin, dans le dernier chapitre, les paramètres du modèle de comportement matériau sont identifiés à partir d’essais fortement hétérogènes (essais Arcan 0°, 45° et 90°). Les résultats obtenus mettent en évidence l’importance des hypothèses utilisées pour modéliser le comportement du matériau ainsi que le fort potentiel de la Méthode des Champs Virtuels pour caractériser le comportement de matériau. Fort potentiel qui peut d’ailleurs être un inconvénient si le problème est mal défini
In this study, tools are developed in order to characterise materials behaviour which are transformed during the structure manufacturing process (forming, assembly). For this goal, four chapters organise the approach. In the first chapter, the literature survey allows to present all methods used to characterise material non linear behaviour. After this survey, the Virtual Fields Method coupled with digitals images correlation measures, is developed to characterise material behaviour from strongly heterogeneous strain fields. The aim of this study is to better understand experimental and numerical factors which have bad impacts on identified results. The second chapter is dedicated to the development and the validation of numerical tools to characterise material behaviour. The third chapter highlights consequences caused by the used of experimental data to compute the equilibrium equation which is the base of identification method. To finish, in the last chapter, behaviour parameters are identified from strongly heterogeneous tests (0°, 45° and 90° Arcan tests). Results obtained highlight importance of hypothesis used to model the material behaviour and all advantages of the Virtuals Fields Method to characterise transformed material. However, these advantages can become disadvantages if the problem is not defined carefully

Caisso, Camille. "Caractérisation et modélisation de la rupture dans le domaine de la transition ductile-fragile de matériaux tubulaires utilisés dans la fabrication de générateurs de gaz pour airbags." Thesis, Brest, École nationale supérieure de techniques avancées Bretagne, 2021. http://www.theses.fr/2021ENTA0014.

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Ce travail porte sur la caractérisation des mécanismes de rupture, ductile et fragile, de matériaux tubulaires utilisés pour la fabrication de générateurs de gaz pour airbag. Lors d’un accident, le coussin d’un airbag est gonflé en quelques millisecondes par un générateur de gaz. En cas de défaillance de ce dernier, un mode de rupture ductile doit être assuré jusqu’à des températures de -60°C. Un essai Charpy sur éprouvette anneau a été proposé pour quantifier le risque de rupture fragile des matériaux des générateurs de gaz. Cependant, cette modification de l’essai Charpy soulève deux problématiques : dans quelle mesure cet essai permet de caractériser la transition ductile-fragile et comment déduire le risque de rupture fragile d’un générateur de gaz en fonctionnement à partir des résultats des essais Charpy ? Pour répondre à ces questions, une approche combinant essais et simulations numériques a été mise en place. Différents essais ont été développés afin de caractériser le comportement et l’endommagement ductile du matériau de l’étude. Une approche locale de la rupture ductile a été adoptée pour la modélisation. Ensuite, une campagne d’essais Charpy sur anneau effectuée pour des températures comprises entre -160°C et 23°C a permis de caractériser la transition ductile-fragile. Une étude numérique de cet essai a été menée puis couplées aux essais Charpy, cela a permis de mettre en place une modélisation de la rupture fragile. Le risque de rupture fragile des éléments structuraux de générateurs de gaz est enfin évalué. L’influence du procédé de fabrication sur le risque de rupture fragile a aussi été étudiée
This work deals with the characterization of the ductile and brittle failure mechanisms of tubular materials used for the manufacture of airbag gas generators. During a crash, airbag cushion is inflated in a few milliseconds by a gas generator. In case of gas generator failure, a ductile failure mode must be ensured up to temperatures of -60°C. A Charpy ring test has been proposed to quantify the risk of brittle failure of gas generator materials. However, this modification of the Charpy test raises two issues: to what extent does this test allow to characterize the ductile-fragile transition and how can the risk of brittle failure of an operating gas generator be deduced from the results of the Charpy test? To answer these questions, an approach combining experiments and numerical simulations was implemented. Various experimental configurations were developed in order to characterize material behavior and ductile damage. The ductile failure is modeled with a local approach. Then, ductile to brittle transition was characterized by a Charpy ring test campaign performed for temperatures between -160°C and 23°C. A numerical study of this test was carried out. Coupled with the Charpy tests, it allowed to set up a model of the brittle failure. The risk of gas generators brittle failure is finally evaluated. The influence of the manufacturing process on the risk of brittle failure was also studied

Manivannan, Ganeshalingam Aerospace Civil &amp Mechanical Engineering Australian Defence Force Academy UNSW. "Viscoplastic modelling of embankments on soft soils." Awarded by:University of New South Wales - Australian Defence Force Academy. School of Aerospace, Civil and Mechanical Engineering, 2005. http://handle.unsw.edu.au/1959.4/38743.

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A major instrumented geosynthetic reinforced approach embankment was constructed to 5.5 m elevation above ground, with prefabricated vertical drains, over a soft compressible clay deposit at Leneghan, Newcastle, Australia in May 1995. The field monitoring of settlements for over six years shows that the embankment manifests significant creep. The instrumentation, field performance and the finite element analyses for predicting the long-term performance of this embankment are described in this thesis. The maximum settlement of 1.1 m was observed one year after the completion of construction. However, the embankment continued to settle at a rate of 0.4 mm/day for the next 5 years. The horizontal displacements of 0.09-0.14 m at various locations and the maximum reinforcement strains of 0.67% were recorded. A numerical model was developed to perform a fully coupled large deformation elasto-viscoplastic finite element analysis for this performance prediction based on creep model proposed by Kutter and Sathialingam (1992). The foundation soil was modelled with creep material behaviour using six noded linear strain triangular elements. A well-documented case history ??? Sackville embankment, New Brunswick, Canada was analysed using this model as a benchmark problem and the model was found to predict all the behaviour characteristics reasonably well. The results obtained from finite element analysis using this model are shown to be in reasonable agreement with the observed performance of Leneghans embankment in terms of settlements, horizontal displacements, excess pore pressures and geosynthetic strains. But, the prediction of settlements was less than satisfactory beyond April 1999. Finite element analyses were performed to study the sensitivity of this embankment behaviour on the variation of hydraulic conductivity values and geosynthetic reinforcement properties. This sensitivity study indicated that the kv variation, the kh/kv ratio and the nominal values of geosynthetic properties adopted in the benchmark analysis are reasonable enough for the long-term behaviour prediction.

Arairo, Wahib. "Influence des cycles hydriques de la dessiccation et de l’humidification sur le comportement hydromécanique des géomatériaux non saturés." Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0028/document.

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Ce travail de recherche porte sur le comportement des milieux poreux (triphasiques), plus particulièrement les sols non saturés sous sollicitations hydro-mécaniques. Un modèle constitutif élastoplastique couplé est développé. Ce modèle original est formulé selon les principes suivants: une loi constitutive est développée pour décrire le comportement de chaque phase (squelette solide, liquide, et gaz). Ensuite, des relations de couplage sont ajoutées entre chacune des phases. Pour le comportement du squelette solide, une loi élastoplastique non associée est adoptée, avec deux surfaces de charges, en cisaillement et en compression. La partie hydrique est décrite par une formulation qui permet de prendre en compte l’effet d’hystérésis. Ce modèle a été enrichi par une relation de couplage hydromécanique qui permet d’exprimer la pression d’entrée d’air en fonction de la porosité. Ensuite, le couplage complet se fait avec la contrainte effective de Bishop en utilisant une nouvelle définition du paramètre de succion χ grâce à laquelle, les différents phénomènes présents dans la réponse des milieux poreux sous différentes sollicitations peuvent être reproduits. Ce modèle est validé par une confrontation à des données expérimentales issues de la littérature sur différents types de sol (sable, limon,…). Le modèle est implanté dans le code aux éléments finis Cast3M. L’analyse de problèmes particuliers, tels que la mise en œuvre d’un cas test d’un sol d’assise soumis à un cycle pluvial, ainsi que l’étude de la stabilité d’une pente, permette de montrer la capacité du modèle à reproduire le comportement des milieux poreux non saturés
This work focuses on the behaviour of porous triphasic media, particularly on unsaturated soils subjected to hydromechanical loading. A coupled elastoplastic constitutive model has been developed. This original model is formulated according to the following principles: (1) a constitutive law describing the behaviour of different phases (solid skeleton, liquid and gas). (2) coupling relationships between each phase. For the behaviour of the solid skeleton, a non associated elastoplastic constitutive law is adopted, with two loading surfaces: shear surface and compression cap surface. The hydric part is discribed using a formulation which allows to take into account the hysteresis effect. This model has been extended using a hydromechanical coupling relation between the air entry value and the porosity. Then the coupling is completed with the Bishop effective stress, using a new definition for the suction parameter χ. Using this formulation, the various phenomena present in the porous media behaviour under different loading can be reproduced. The developed model has been validated through a comparison with experimental data on different types of soil (sand, silt,…). This model is implemented in the french finite element code Cast3M. The analysis of specific problems, such as (1) the study of shallow foundation subjected to cyclic rain event, as well as (2) the study of slope stability, show the model capacity to reproduce the behaviour of unsaturated porous media

Bardel, Didier. "Rôle de la microstructure d'un alliage à durcissement structural sur son comportement et sa tenue mécanique sous sollicitations cycliques après un transitoire thermique." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0045/document.

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Pour fabriquer le caisson-coeur du futur réacteur expérimental Jules Horowitz (RJH), un assemblage de viroles est effectué à l'aide d'un procédé haute énergie : le soudage par faisceau d'électrons (FE). L'aluminium 6061-T6 qui a été choisi pour la fabrication de ces viroles est un alliage à durcissement structural, ce qui signifie que ses propriétés mécaniques sont très fortement dépendantes de son état de précipitation. Lors du soudage des viroles, l'état microstructural du matériau est affecté : on assiste notamment à une dégradation de l'état fin de précipitation (T6). Les conséquences de cette dégradation microstructurale sont diverses. Notamment, l'évolution de l'état de précipitation au cours du soudage engendre une variation du comportement mécanique et impactera donc la distribution des contraintes résiduelles. De plus, les propriétés mécaniques en service à proximité du joint soudé seront grandement modifiées, on assiste par exemple à une chute de la limite d'élasticité. Dans ce travail, des essais cycliques ont été effectués après des chargements thermiques représentatifs d'une opération de soudage mais aussi pendant des essais isothermes. L'analyse de ces résultats et la confrontation à des mesures de Diffusion de Neutrons aux Petits Angles (DNPA) et de Microscopie Electronique en Transmission (MET) permettent de comprendre les effets de la précipitation sur la loi de comportement de l'alliage. Afin de prédire les évolutions microstructurales et mécaniques dans l'alliage 6061, un logiciel de précipitation a été implémenté et couplé à un modèle élastoplastique à base physique. Les résultats obtenus permettent de représenter la grande variété de comportement observé lors de la campagne expérimentale. Un couplage entre simulation éléments finis thermique et précipitation a été effectué et permet d'ouvrir des perspectives de simulations plus physiques pour ce type d'alliage
In order to assemble the pressure vessel of experimental Reactor Jules Horowitz (RJH) of France in the future, the electron beam welding process will be used. Several ferrules in a 6061-T6 age hardening aluminum alloy are used for manufacturing this vessel. The fine precipitation state (T6) is affected significantly by the electron beam welding process. Consequently, this microstructural degradation leads to an evolution of the mechanical behaviour and thus will affect the distribution of residual stresses. Moreover, the mechanical properties of the weld joint at ambiant temperature can be modified, such as the yield stress that may drop from 280 MPa to 55 MPa. In this work, cyclic tensile tests have been performed after anisothermal histories representative of welding and during isothermal treatments. The analysis of these results is compared with Small Angles Neutrons Scattering (SANS) and Transmission Electron Microscopy (TEM) characterizations that allow to understand the effect of the precipitation on the material behaviour. To predict the microstructural evolutions in the 6061 structure, a precipitation model has been developped. The precipitation software "PreciSo" coupled with a Finite Element thermal simulations and elastoplastic models allows to open new prospectives in the physical-based simulations domain

Gaspar, Miguel Gonçalves. "Development of a model of elastoplastic behavior through artificial intelligence." Master's thesis, 2018. http://hdl.handle.net/10773/26912.

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In the past few years, there has been tremendous advances in the accuracy and predictive capabilities of tools for the simulation of materials. Predictive modeling has now become a powerful tool that can also deliver real value through application and innovation to the global industry. Simulation of forming operations, particularly using the nite element method, is clearly dependent on the accuracy of the constitutive models. In the last years, several methodologies were developed to improve the accuracy of constitutive models through parameter identi cation and calibration methodologies. However, independently of the e cacy of the calibration methods, the accuracy of a constitutive model is always constrained to its prede ned mathematical formulation. Additionally, using known elastoplastic formulations, it is impossible to reproduce the material phenomena if these phenomena are not formulated mathematically. In the past several years, arti cial intelligence (AI) techniques have become more robust and complex. This eld has set the ambitious goal of making machines either seemingly or genuinely intelligent. The sub- eld of arti cial intelligence known as machine learning attempts to make computers learn from observations. Machine-learning algorithms are general tools that can be tted to a vast number of problems, including predicting the stress-strain relationship of the material. This work proposes to model the behavior of a metal material using machinelearning (ML) techniques and use this ML in forming simulations. Initially, the ML model is designed and trained using a known plane stress elastoviscoplasticity model to evaluate its competence to replace classical models. Di erent ML topologies and optimization techniques are used to train the model. Then, the AI model is introduced into a nite element analysis (FEA) code, as a user subroutine, and its attainment in forming simulations is evaluated. The replacement of classical formulations by AI techniques for the material behavior de nition is analysed and discussed.
Nos últimos anos, tem havido enormes avanços na precisão e capacidades preditivas de ferramentas para a simulação de materiais. A modelação preditiva tornou-se numa ferramenta poderosa que também pode agregar um grande valor por meio de aplicações e inovações para a indústria global. A simulação das operações de conformação, particularmente usando o método dos elementos finitos, é claramente dependente da precisão dos modelos constitutivos. Nos últimos anos, várias metodologias foram desenvolvidas para melhorar a precisão de modelos constitutivos através de metodologias de identificação e calibração de parâmetros. No entanto, independentemente da eficácia dos métodos de calibração, a precisão de um modelo constitutivo é sempre restrita a sua formulação matemática predefinida. Adicionalmente, usando formulações elastoplasticas conhecidas, e impossível reproduzir os fenomenos do comportamento de materiais se estes comportamentos não forem eficazmente formulados matematicamente. Recentemente, as tecnicas de inteligencia artificial (IA) tornaram-se mais robustas e complexas. Este campo estabeleceu o objetivo ambicioso de tornar as maquinas aparentemente ou genuinamente inteligentes. O sub-campo da inteligencia artificial conhecido como aprendizagem computacional tenta fazer com que os computadores aprendam com as observações. Os algoritmos de aprendizagem computacional são ferramentas gerais que podem ser adaptadas a um grande numero de problemas, incluindo a previsão da relação tensao-deformação do material. Este trabalho propõe modelar o comportamento de um material metalico utilizando tecnicas de aprendizagem computacional (ML) e utilizar este ML na modelação de simulações. Inicialmente, o modelo ML e projetado e treinado usando um modelo de elastoviscoplasticidade em estado plano de tensão de forma a avaliar a sua eficacia na substituição de modelos classicos. Diferentes topologias ML e tecnicas de otimização são usadas para treinar o modelo. Em seguida, o modelo IA e introduzido num codigo de analise de elementos finitos (FEA), como user subroutine, e a sua concretização em simulações de conformação e avaliada. A substituição de formulações classicas por tecnicas de IA para a definiçao do comportamento do material e analisada e discutida.
Mestrado em Engenharia Mecânica

Wang, Chung Chih, and 王中志. "Finite Difference Analysis and Experiment on Buckling Behavior of Elastoplastic Spherical Shells." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/21874794260532507329.

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Книги з теми "Elastoplastic behavior":

Zheng, Maosheng, Zhifu Yin, Haipeng Teng, Jiaojiao Liu, and Yi Wang. Elastoplastic Behavior of Highly Ductile Materials. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-15-0906-3.

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Wang, Yi, Maosheng Zheng, Zhifu Yin, Haipeng Teng, and Jiaojiao Liu. Elastoplastic Behavior of Highly Ductile Materials. Springer, 2019.

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Wang, Yi, Maosheng Zheng, Zhifu Yin, Haipeng Teng, and Jiaojiao Liu. Elastoplastic Behavior of Highly Ductile Materials. Springer Singapore Pte. Limited, 2020.

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Частини книг з теми "Elastoplastic behavior":

Zheng, Maosheng, Zhifu Yin, Haipeng Teng, Jiaojiao Liu, and Yi Wang. "Physical Relationship in Elastoplastic Mechanics." In Elastoplastic Behavior of Highly Ductile Materials, 23–37. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-15-0906-3_2.

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Zheng, Maosheng, Zhifu Yin, Haipeng Teng, Jiaojiao Liu, and Yi Wang. "Fatigue Behavior of Highly Ductile Materials." In Elastoplastic Behavior of Highly Ductile Materials, 137–54. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-15-0906-3_9.

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Zheng, Maosheng, Zhifu Yin, Haipeng Teng, Jiaojiao Liu, and Yi Wang. "Effect of Defects on Pipe Bending Behavior." In Elastoplastic Behavior of Highly Ductile Materials, 107–17. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-15-0906-3_7.

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Zheng, Maosheng, Zhifu Yin, Haipeng Teng, Jiaojiao Liu, and Yi Wang. "Introduction." In Elastoplastic Behavior of Highly Ductile Materials, 1–22. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-15-0906-3_1.

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Zheng, Maosheng, Zhifu Yin, Haipeng Teng, Jiaojiao Liu, and Yi Wang. "Energy Absorption of Highly Ductile Materials." In Elastoplastic Behavior of Highly Ductile Materials, 155–73. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-15-0906-3_10.

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Zheng, Maosheng, Zhifu Yin, Haipeng Teng, Jiaojiao Liu, and Yi Wang. "Solutions to the Typical Problem of Elastoplasticity." In Elastoplastic Behavior of Highly Ductile Materials, 39–63. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-15-0906-3_3.

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Zheng, Maosheng, Zhifu Yin, Haipeng Teng, Jiaojiao Liu, and Yi Wang. "Transfer and Mitigation of Stress Concentration at the Root of a Notch for Highly Ductile Materials." In Elastoplastic Behavior of Highly Ductile Materials, 65–74. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-15-0906-3_4.

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Zheng, Maosheng, Zhifu Yin, Haipeng Teng, Jiaojiao Liu, and Yi Wang. "Elastoplastic Problems in the Manufacturing Process of Bimetallic Composite Tubes." In Elastoplastic Behavior of Highly Ductile Materials, 75–86. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-15-0906-3_5.

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Zheng, Maosheng, Zhifu Yin, Haipeng Teng, Jiaojiao Liu, and Yi Wang. "Plastic Bending and Failure of Highly Ductile Tubes." In Elastoplastic Behavior of Highly Ductile Materials, 87–106. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-15-0906-3_6.

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Zheng, Maosheng, Zhifu Yin, Haipeng Teng, Jiaojiao Liu, and Yi Wang. "Thermal Stress Problems." In Elastoplastic Behavior of Highly Ductile Materials, 119–35. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-15-0906-3_8.

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Тези доповідей конференцій з теми "Elastoplastic behavior":

Baumgarner, Julia, and Davide Piovesan. "Elastoplastic Behavior of SLA Resins in Compression." In ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-73046.

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Abstract Additive manufacturing is a growing field. One of the most common types of 3d printing methods is stereolithography. While the tensile properties of many stereolithographic resins are known, the compressive properties are not publicly available. In this paper, four types of resins that from Formlabs® are tested under compression to estimate their mechanical properties. Testing was performed on Clear, Tough, Durable and High Temperature resins with and without post processing. Post processing was performed in a customized curing oven following direction from the resin manufacturer. After testing, it was found that the Tough and Durable resins performed similarly when green, but the curing process stiffened the Tough Resin. Clear and High Temperature resins performed similarly after curing, whereas the High Temperature resin behaves more like an elastomer when green. We estimated the tangent modulus of the stress-strain curve using a Polynomial fitting and were able to separate the elastic modulus from the viscous modulus. We found that the viscous modulus is non linear and depends upon the velocity of the test. The test presented here are the first comparison of different types of Formalab resins under compression and can shed some light on the anisotropic behavior of many of these resins.

Skolnik, D. A., H. T. Liu, L. Z. Sun, and H. C. Wu. "Anisotropic Elastoplastic Behavior of SiCp/Al Composite Sheets." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-60635.

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Experimental research was performed to study the anisotropic elastoplastic responses of SiCp/Al composite sheets. To investigate the effects of the composite processing, two sets of specimens cut from the heat-treated and as-rolled composite sheets are tested using a universal material-testing machine. The dependence of the strength, plastic flow, and strain ratios on the rolling angles are discussed in detail. To model the phenomena observed in the experiments, a micromechanics based damage framework is developed. The interfacial debonding and the rolling angle’s effects are integrated into this model. Good consistence between the experimental results and the analytical predications shows the validity of the theoretical model.

Schwarz, Stefan, Kurt Maute, and Ekkehard Ramm. "Topology and shape optimization including elastoplastic material behavior." In 7th AIAA/USAF/NASA/ISSMO Symposium on Multidisciplinary Analysis and Optimization. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1998. http://dx.doi.org/10.2514/6.1998-4954.

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Nieto, E. J., B. Hortigón, F. Fernández, and O. Hernández. "New parametric formulation of elastoplastic behavior in ductile metals." In THE 4TH MANUFACTURING ENGINEERING SOCIETY INTERNATIONAL CONFERENCE (MESIC 2011). AIP, 2012. http://dx.doi.org/10.1063/1.4707557.

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Iwatani, Masayoshi, and Ryo Kikuuwe. "An elastoplastic friction compensator with improved static friction behavior." In 2016 55th Annual Conference of the Society of Instrument and Control Engineers of Japan (SICE). IEEE, 2016. http://dx.doi.org/10.1109/sice.2016.7749226.

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Boix Salazar, Julio A., Dirk F. de Lange, Alberto Torres Cruz, Hugo I. Medellín Castillo, and Gilberto Mejía Rodríguez. "Elastoplastic Analysis of a Cantilever Beam Under Combined Compressive and Bending Load." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-65396.

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In this study the elastoplastic behavior of cantilever beams under a combined compressive axial load and an imposed lateral bending deflection are analyzed. Eventhough the particular condition of elastoplastic buckling has been studied before, the developed theories are limited to the prediction of the initial failure of the beam. In the current study the elastoplastic behavior of cantilever beams under compressive load at levels below the critical buckling load are studied in order to determine the remaining load bearing capacity of the beam under combined bending and axial loads, including the behavior at progressive levels of plastic deformation. The elastoplastic bending process is analyzed using the finite element method. In particular, the analysis is focused on the evaluation of the limiting bending force necessary to increase or reduce the curvature of the beam in the plastic zone. The bending force depends on the compressive axial load, the geometrical dimensions of the beam, material coefficients, such as Young’s modulus and yield stress, and the hardening model. The large number of variables involved, is reduced by introducing two dimensionless load parameters. The results of the analysis are presented and discussed for a wide range of dimensionless loads. Also the influence of work hardening on the obtained bending force is analyzed, comparing between an ideal plastic behavior and a bilinear plasticity model with a linear hardening behavior.

Iijima, Kazuhiro, Megumi Sakai, Masahiko Fujikubo, and Akira Tatsumi. "Hydro-Elastoplastic Analysis for Predicting Collapse Behavior of VLFS Under Large Waves." In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-54890.

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This paper addresses collapse behavior of Very Large Floating Structure (VLFS) under large wave loads, as part of risk analysis. In predicting the consequence of collapse, the deformation of VLFS consisting of elastic and plastic ones under the large load event must be addressed. The deformation interacts with the fluid around it. Therefore, hydro-elastoplastic analysis needs to be developed. The whole VLFS structure is modeled as two elastic beams with an elasto-plastic hinge embedded at the connection. The deformation behavior is formulated by using finite element method (FEM). The hydrodynamic behavior is modeled by using Rankine source panel method based on two-dimensional and time-domain potential theory. The two domains are coupled. A series of simulation and tank test results for the basic collapse behavior of VLFS is presented.

Farhat, F., J. F. Shao, and W. Shen. "Micromechanical Modeling of Elastoplastic Behavior of a Shale Gas Reservoir." In Sixth Biot Conference on Poromechanics. Reston, VA: American Society of Civil Engineers, 2017. http://dx.doi.org/10.1061/9780784480779.162.

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Kwon, Y. W., C. Kim, and G. Y. Yang. "A Unified Micromodel for Constitutive Behavior of Metal Matrix Composites Undergoing Plastic Deformation." In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0656.

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Abstract The objective of this study is to develop a unified, three-dimensional micromodel which can describe the nonlinear elastoplastic constitutive behavior of MMC’s with continuous fibers, particles, or aligned short fibers as the reinforcement. In the micromodel, both the reinforcement and the matrix may have elastic and/or elastoplastic deformation(s), respectively. However, as in most cases, the development is shown for elastic reinforcement in an elastoplastic matrix. The micromodel uses a repeating unit-cell model with eight subcells. For a particulate or an aligned short fiber composite, one center subcell represents the particle or the short fiber while the rest of the subcells represent the matrix. On the other hand, two aligned subcells indicate the fiber for a fibrous composite. The micromodel yields the overall effective constitutive equation for an MMC with elastoplastic deformation in the matrix material. The effective stress-strain plots of various MMC’s are predicted using the micromodel for a wide variation of the reinforcement volume fraction. These results are compared to those obtained from the finite element analysis, and the two results agree very well.

Ju, J. W., H. N. Ruan, and Y. F. Ko. "Micromechanical Evolutionary Elastoplastic Damage Model for Fiber-Reinforced Metal Matrix Composites With Fiber Debonding." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59487.

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A micromechanical evolutionary damage model is proposed to predict the overall elastoplastic behavior and interfacial damage evolution of fiber-reinforced metal matrix composites. Progressive debonded fibers are replaced by equivalent voids. The effective elastic moduli of three-phase composites, composed of a ductile matrix, randomly located yet unidirectionally aligned circular fibers, and voids, are derived by using a rigorous micromechanical formulation. In order to characterize the overall elastoplastic behavior, an effective yield criterion is derived based on the ensemble-area averaging process and the first-order effects of eigenstrains.

Звіти організацій з теми "Elastoplastic behavior":

Yasui, Hajime, Yuji Yamamoto, Yasufumi Asada, and Kazunari Takenaka. In-Situ Observation of Elastoplastic Fatigue Fracture Behavior for Aluminum Cylinder Block Using Thermoelastic IR Thermograph. Warrendale, PA: SAE International, September 2005. http://dx.doi.org/10.4271/2005-08-0599.

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Snyder, Victor A., Dani Or, Amos Hadas, and S. Assouline. Characterization of Post-Tillage Soil Fragmentation and Rejoining Affecting Soil Pore Space Evolution and Transport Properties. United States Department of Agriculture, April 2002. http://dx.doi.org/10.32747/2002.7580670.bard.

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Tillage modifies soil structure, altering conditions for plant growth and transport processes through the soil. However, the resulting loose structure is unstable and susceptible to collapse due to aggregate fragmentation during wetting and drying cycles, and coalescense of moist aggregates by internal capillary forces and external compactive stresses. Presently, limited understanding of these complex processes often leads to consideration of the soil plow layer as a static porous medium. With the purpose of filling some of this knowledge gap, the objectives of this Project were to: 1) Identify and quantify the major factors causing breakdown of primary soil fragments produced by tillage into smaller secondary fragments; 2) Identify and quantify the. physical processes involved in the coalescence of primary and secondary fragments and surfaces of weakness; 3) Measure temporal changes in pore-size distributions and hydraulic properties of reconstructed aggregate beds as a function of specified initial conditions and wetting/drying events; and 4) Construct a process-based model of post-tillage changes in soil structural and hydraulic properties of the plow layer and validate it against field experiments. A dynamic theory of capillary-driven plastic deformation of adjoining aggregates was developed, where instantaneous rate of change in geometry of aggregates and inter-aggregate pores was related to current geometry of the solid-gas-liquid system and measured soil rheological functions. The theory and supporting data showed that consolidation of aggregate beds is largely an event-driven process, restricted to a fairly narrow range of soil water contents where capillary suction is great enough to generate coalescence but where soil mechanical strength is still low enough to allow plastic deforn1ation of aggregates. The theory was also used to explain effects of transient external loading on compaction of aggregate beds. A stochastic forInalism was developed for modeling soil pore space evolution, based on the Fokker Planck equation (FPE). Analytical solutions for the FPE were developed, with parameters which can be measured empirically or related to the mechanistic aggregate deformation model. Pre-existing results from field experiments were used to illustrate how the FPE formalism can be applied to field data. Fragmentation of soil clods after tillage was observed to be an event-driven (as opposed to continuous) process that occurred only during wetting, and only as clods approached the saturation point. The major mechanism of fragmentation of large aggregates seemed to be differential soil swelling behind the wetting front. Aggregate "explosion" due to air entrapment seemed limited to small aggregates wetted simultaneously over their entire surface. Breakdown of large aggregates from 11 clay soils during successive wetting and drying cycles produced fragment size distributions which differed primarily by a scale factor l (essentially equivalent to the Van Bavel mean weight diameter), so that evolution of fragment size distributions could be modeled in terms of changes in l. For a given number of wetting and drying cycles, l decreased systematically with increasing plasticity index. When air-dry soil clods were slightly weakened by a single wetting event, and then allowed to "age" for six weeks at constant high water content, drop-shatter resistance in aged relative to non-aged clods was found to increase in proportion to plasticity index. This seemed consistent with the rheological model, which predicts faster plastic coalescence around small voids and sharp cracks (with resulting soil strengthening) in soils with low resistance to plastic yield and flow. A new theory of crack growth in "idealized" elastoplastic materials was formulated, with potential application to soil fracture phenomena. The theory was preliminarily (and successfully) tested using carbon steel, a ductile material which closely approximates ideal elastoplastic behavior, and for which the necessary fracture data existed in the literature.

Oliynyk, Kateryna, and 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, December 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.