Letteratura scientifica selezionata sul tema "Ductile fracture simulations"
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Articoli di riviste sul tema "Ductile fracture simulations"
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Liu, HS, and MW Fu. "Prediction and analysis of ductile fracture in sheet metal forming—Part I: A modified Ayada criterion." International Journal of Damage Mechanics 23, no. 8 (2014): 1189–210. http://dx.doi.org/10.1177/1056789514541559.
Testo completoAbstract (sommario):
A modified ductile fracture criterion is proposed based on the traditional Ayada criterion and coded into the finite element simulation platform of VUMAT/ABAQUS for prediction and analysis of ductile fracture in metal plastic strain processes. In this modified ductile fracture criterion, stress triaxiality is taken into account, and more importantly, the exponential effect of the equivalent plastic strain on the damage behavior, which is generally ignored in other ductile fracture criteria, is also considered. The material related constants in the modified ductile fracture criterion are determined by tensile tests together with finite element simulations. The applicability and reliability of the ductile fracture criterion in ductile fracture prediction in two types of classic stress states, viz. shear stress, tensile stress in sheet metal forming, are investigated based on the deformation behavior and fracture occurrence in two case studies with two typical types of materials, i.e. Al 6061 and T10A. The materials have a wide range of plasticity. The simulation and experimental results verify the applicability and reliability of the developed ductile fracture criterion in prediction of the ductile fracture with and without necking in different stress states of plastic strain.
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Azizi, Muhammad Azim, Mohd Faiz Mohd Ridhuan, Mohd Zakiyuddin Mohd Zahari, Sharafiz Abdul Rahim, and Muhammad Amin Azman. "Peridynamic Model for Tensile Elongation and Fracture Simulations of Polymethyl Methacrylate Notched Specimens." Applied Mechanics and Materials 909 (September 28, 2022): 11–28. http://dx.doi.org/10.4028/p-2z0841.
Testo completoAbstract (sommario):
This paper presents the peridynamic (PD) numerical model for simulating a tensile test until total fracture for a brittle polymeric material namely polymethyl methacrylate (PMMA). U-notched and V-notched specimens were used to investigate the effect of the notches on the elongation and fracture of PMMA. The tensile elongation of PMMA exhibits nonlinearity with respect to the applied load, while the fracture occurs when the material stress has reached the ultimate tensile stress of the material. Similar elongation and fracture properties were applied on PD simulations. Two types of elongation equation are used namely brittle and ductile equations to form PD-brittle and PD-ductile models. The published experimental data of tensile fracture test on notched PMMA specimens are used as reference to validate the simulations of the PD models. The PD numerical force-extension curves have good quantitative similarity for V-notched specimen but adequate quantitative similarity for U-notched specimen. As for the quality of the fractured specimen shape, the PD simulations have good similarity for the V-notched specimen but adequate similarity for the U-notched specimen. The plot of the internal force distribution from the simulations of PD shows good qualitative similarity to the plot of the stress distribution from the published data of FEM in terms of stress concentration. From the PD results, it is observed that the PD-ductile model has better capability in producing accurate simulation of the notched specimens than the PD-brittle model.
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Dzioba, Ihor, and Sebastian Lipiec. "Fracture Mechanisms of S355 Steel—Experimental Research, FEM Simulation and SEM Observation." Materials 12, no. 23 (2019): 3959. http://dx.doi.org/10.3390/ma12233959.
Testo completoAbstract (sommario):
In this study, the fracture mechanisms of S355 ferritic steel were analyzed. In order to obtain different mechanisms of fracture (completely brittle, mixed brittle and ductile or completely ductile), tests were carried out over a temperature range of −120 to +20 °C. Our experimental research was supplemented with scanning electron microscopy (SEM) observations of the specimens’ fracture surfaces. Modeling and load simulations of specimens were performed using the finite element method (FEM) in the ABAQUS program, and accurate calibration of the true stress–strain material dependence was made. In addition, the development of mechanical fields before the crack tip of the cracking process in the steel was analyzed. The distributions of stresses and strains in the local area before the crack front were determined for specimens fractured according to different mechanisms. Finally, the conditions and characteristic values of stresses and strains which caused different mechanisms of fracture—fully brittle, mixed brittle and ductile or fully ductile—were determined.
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Banabic, Dorel, and Abdolvahed Kami. "Applications of the Gurson’s model in sheet metal forming." MATEC Web of Conferences 190 (2018): 01002. http://dx.doi.org/10.1051/matecconf/201819001002.
Testo completoAbstract (sommario):
Recent advances in the modelling of metals encompass modelling of metals structural inhomogeneity, damage, porosity, twinning/untwining and non-local and second order effects. This presentation is focused on modelling the void growth in ductile fractures. The growth and coalescence of microscopic voids are the main mechanisms in ductile fracture of bulk metallic parts. In sheet metals, ductile fracture is preceded by necking during which existing voids do not have significant growth. However, necking is highly sensitive to plastic flow direction which in turn is sensitive to the presence of voids. Also, under biaxial strain loading, the final fracture in the necking region is still controlled by void growth; hence an accurate fracture prediction is crucial for crash simulations. Finally, in super-plastic sheet forming, void growth and coalescence may precede or accompany necking. Therefore, there is as increasing interest in modelling of voids in the sheet metals. As an application, we show how the predictions of some forming limit curves (FLCs) can be affected by accurate simulation of voids growth.
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Watanabe, Atsuo, Kunio Hayakawa, and Shinichiro Fujikawa. "An Anisotropic Damage Model for Prediction of Ductile Fracture during Cold-Forging." Metals 12, no. 11 (2022): 1823. http://dx.doi.org/10.3390/met12111823.
Testo completoAbstract (sommario):
Researchers have formulated equations of ductile fracture to simulate and predict defects in cold-forged parts, e.g., the Cockcroft–Latham criterion. However, these equations are not applicable to certain cases of fracture in forged products. This study formulates a new equation for predicting ductile fractures with better prediction accuracy than the convention by which the cost for trial-and-error design can be reduced. The equation is expressed as a second-rank symmetric tensor, which is the inner product of the stress and strain-increment tensors. The theoretical efficacy of the equation in predicting ductile fractures is verified via a uniaxial tensile test. The practicability of the equation is confirmed by applying it to the simulations of two real cold-forged components: a cold-forged hollow shaft and a flanged shaft. For the hollow shaft, the equation predicts the position where the ductile fracture would initiate, which—to the best of the authors’ knowledge—is unique to this study. For the flanged shaft, the equation predicts the occurrence of diagonal cracks due to different lubrication conditions.
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Simkins, D. C., and S. Li. "Meshfree simulations of thermo-mechanical ductile fracture." Computational Mechanics 38, no. 3 (2005): 235–49. http://dx.doi.org/10.1007/s00466-005-0744-8.
Testo completo
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Tong, Ying. "The Evaluation of Ductile Fracture Criteria (DFC) of 6061-T6 Aluminum Alloy." Applied Mechanics and Materials 44-47 (December 2010): 2837–41. http://dx.doi.org/10.4028/www.scientific.net/amm.44-47.2837.
Testo completoAbstract (sommario):
As one of the principal failures, ductile fracturing restricts metal forming process. Cockcroft-Latham fracture criterion is suited for tenacity fracture in bulk metal-forming simulation. An innovative approach involving physical compression experiments, numerical simulations and mathematic computations provides mutual support to evaluate ductile damage cumulating process and ductile fracture criteria (DFC). The results show that the maximum cumulated damage decreases with strain rate rising, and the incremental ratios, that is damage sensitive rate, vary uniformly during the upsetting processes at different strain rates. The damage sensitive rate decreases rapidly, then it becomes stability in a constant 0.11 after true strain -0.85. The true strain -0.85 was assumed as the fracture strain, and the DFC of 6061-T6 aluminum alloy is almost a constant 0.2. According to DFC, the exact fracture moment and position during various forming processes will be predicted conveniently.
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Sun, Dong Zhi, Michael Krawiec, and Hariaokto Hooputra. "Characterization and Modelling of the Damage Behavior of Extruded Aluminum Profiles for Crash Simulations." Materials Science Forum 877 (November 2016): 674–79. http://dx.doi.org/10.4028/www.scientific.net/msf.877.674.
Testo completoAbstract (sommario):
The damage behavior of aluminum profiles depends strongly on the stress state. Many investigations have shown that both ductile and shear fracture have to be taken into account in damage analysis. Since fracture strains of aluminum profiles are relatively low, damage modelling has to be included in component simulations. However, it is an open question, which kind of damage model can be used for crash simulations and which tests should be performed in order to calibrate the model. An extruded aluminum profile with double chambers of AA6060-T79 was characterized under different stress triaxialities and shear ratios. The damage criteria IDS (Instability, Ductile and Shear fracture) in ABAQUS/Explicit were used for the simulations. An explicit relationship between triaxiality and shear ratio was derived for plane stress state. The influence of the model parameter on the overlapping of both criteria (ductile and shear fracture) was systematically studied for shell element applications. The applied damage model was validated by comparing experimental and calculated results of component tests.
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Kacem, Ahmed, Hervé Laurent, and Sandrine Thuillier. "Prediction of forming limit curve for AA6061-T6 at room and elevated temperatures." IOP Conference Series: Materials Science and Engineering 1238, no. 1 (2022): 012044. http://dx.doi.org/10.1088/1757-899x/1238/1/012044.
Testo completoAbstract (sommario):
Abstract Forming Limit Curve (FLC) has been widely adopted as a practical criterion for evaluating the formability of sheet metals. Predicting a reliable FLC by a virtual methodology could lead to robust process optimization before expensive tool manufacturing. In order to increase the predictive capabilities of the virtual forming tools, an accurate modeling of the forming limit curve should be considered at room and elevated temperatures. In this work, the isothermal forming limit curves of 6000 series aluminum alloy sheet metal are predicted by performing numerical simulations of Nakajima test. A stress triaxiality and Lode angle based ductile fracture criterion is used to determine the forming limit curve. Also, the ductile fracture criterion is extended to add the impact of temperature on ductile fracture prediction. The hybrid experimental-numerical approach is used to calibrate the ductile fracture criterion. The forming limit curve of AA6061-T6 sheet metal, with a thickness of 1 mm, is predicted using the calibrated ductile fracture criterion at room and elevated temperatures. Numerical simulations are performed in 3D with the finite element code Abaqus. The limit strains are determined for specimens undergoing deformation under different strain paths. Influence of temperature on the predicted forming limit curve is discussed.
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Yuan, Huang, Guoyu Lin, and Alfred Cornec. "Verification of a Cohesive Zone Model for Ductile Fracture." Journal of Engineering Materials and Technology 118, no. 2 (1996): 192–200. http://dx.doi.org/10.1115/1.2804886.
Testo completoAbstract (sommario):
In the present paper, ductile crack growth in an aluminium alloy is numerically simulated using a cohesive zone model under both plane stress and plane strain conditions for two different fracture types, shear and normal modes. The cohesive law for ductile fracture consists of two parts—a specific material’s separation traction and energy. Both are assumed to be constant during ductile fracture (stable crack growth). In order to verify the assumed cohesive law to be suitable for ductile fracture processes, experimental records are used as control curves for the numerical simulations. For a constant separation traction, determined experimentally from tension test data, the corresponding cohesive energy was determined by finite element calculations. It is confirmed that the cohesive zone model can be used to characterize a single ductile fracture mode and is roughly independent of stable crack extention. Both the cohesive traction and the cohesive fracture energy should be material specific parameters. The extension of the cohesive zone is restricted to a very small region near the crack tip and is in the order of the physical fracture process. Based on the present observations, the cohesive zone model is a promising criterion to characterize ductile fracture.
Tesi sul tema "Ductile fracture simulations"
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Xenos, Sokratis. "Porous materials : constitutive modeling and computational issues." Electronic Thesis or Diss., Institut polytechnique de Paris, 2024. http://www.theses.fr/2024IPPAX040.
Testo completoAbstract (sommario):
Ce travail porte sur le développement, la calibration et l'implémentation numérique d'un nouveau modèle élastoplastique entièrement explicite, isotrope et indépendant du taux de déformation pour les matériaux métalliques poreux. La microstructure est supposée être constituée d'une distribution aléatoire de vides sphéroïdaux de même forme, orientés de manière aléatoire et avec une probabilité uniforme. Le modèle proposé est basé sur des estimations d'homogénéisation antérieures qui utilisent une théorie de comparaison composite linéaire (LCC). Pour évaluer l'exactitude du modèle analytique, nous réalisons des simulations éléments finis tridimensionnelles à grandes déformationsd'éléments de volume représentatifs (RVE) avec les microstructures correspondantes. Une calibration appropriée des paramètres du modèle conduit à un accord assez précis des prédictions analytiques avec les contraintes moyennes éléments finis et l'évolution de la porosité. Nous montrons, à la fois analytiquement et numériquement, que le rapport d'aspect initial des vides a un effet significatif sur la réponse effective homogénéisée du matériau poreux, entraînant des réponses extrêmement souples pour les vides très oblates, surtout à des triaxialités de contraintes élevées.Ensuite, nous examinons les problèmes computationnels liés à l'implémentation numérique de modèles constitutifs indépendants du taux de déformation qui conduisent à un comportement d'adoucissement. Il est démontré analytiquement que les modèles élastoplastiques basés sur des formulations continues "locales'' peuvent entraîner une perte d'ellipticité des équations aux dérivées partielles (EDP) et des solutions numériques dépendantes du maillage. Pour remédier les problèmes numériques associés, nous proposons une version implicite non locale du nouveau modèle poreux, basée sur l'introduction d'une variable de porosité non locale déterminée à partir de la solution d'une EDP supplémentaire. Nous montrons à la fois analytiquement et numériquement que la version régularisée du modèle permet de préserver les propriétés elliptiques des équations du problème, produisant des solutions convergentes indépendantes du maillage dans le régime post-bifurcation. Le point de bifurcation s'avère être fortement dépendant de la forme des micro-vides, avec des vides très plats (par exemple,un rapport d'aspect inférieur à 0,3) entraînant des déformations à la localisation plus faibles. Il est constaté que la longueur matérielle introduite par la formulation non locale a un effet minimal sur le point de bifurcation prédit, affectant uniquement le gradient post-bifurcation de la courbe contrainte-déformation macroscopique et la taille de lazone fortement déformée dans la structure. Dans la dernière partie de cette étude, les versions locale et non locale du modèle sont efficacement implémentées dans un code commercial d'éléments finis (ABAQUS) et utilisés pour la solution numérique de problèmes de valeurs limites liés aux processus de formage et de rupture ductile. En particulier, les problèmes de test d'expansion de trou (TET) et de test d'impact Charpy (essai Charpy), le phénomène de rupture "cup-and-cone'' ainsi que la rupture ductile d'un spécimen à géométrie complexe et la comparaison avec les résultats expérimentaux correspondants sont analysés en détail. Les prédictions numériques indiquent que la ductilité est une fonction croissante du paramètre de forme des vides, et les matériaux composés de vides oblates de faible rapport d'aspect présentent une initiation et une propagation macroscopiques de fissures prématurées par rapport aux matériaux avec des vides sphériques ou presquesphériques. Enfin, la capacité du modèle à reproduire les résultats expérimentaux avec une précision suffisante suggère qu'il peut être utilisé pour fournir des prédictions avec seulement un petit nombre de paramètres qui peuvent être calibrés à partir de calculs micromécaniques ou de données expérimentales<br>This work is concerned with the development, calibration, and numerical implementation of a novel fully explicit isotropic, rate-independent, elasto-plastic model for porous metallic materials. The microstructure is assumed to consist of a random, with uniform probability, distribution of randomly oriented spheroidal voids of the same shape. The proposed model is based on earlier homogenization estimates that use a Linear Comparison Composite (LCC) theory. The resulting expressions exhibit the simplicity of the well known Gurson model and, thus, its numerical implementation in a finite element code is straightforward. To assess the accuracy of the analytical model, we carry out detailed finite-strain, three-dimensional finite element (FE) simulations ofrepresentative volume elements (RVEs) with the corresponding microstructures. Properparameter calibration of the model leads to fairly accurate agreement of the analytical predictions with the corresponding FE average stresses and porosity evolution. We show, both analytically and numerically, that the initial aspect ratio of the voids has a significant effect on the homogenized effective response of the porous material leading to extremely soft responses for flat oblate voids (e.g., aspect ratio less than 0.5) especially at high stress triaxialities.Next, we examine the computational issues related to the numerical implementation of rate-independent constitutive models that lead to softening behavior. It is shown analytically that elastic-plastic models based on ``local'' continuum formulations that do not incorporate a characteristic length scale may lead to loss of ellipticity of the governing partial differential equations (PDEs) and mesh-dependent numerical solutions. To remedy the associated numerical problems, we propose an implicit non-local version of the porous model developed in this work which is based on the introductionof a non-local porosity variable determined from the solution of an additional PDE. We show both analytically and numerically that the regularized version of the model allows for preservation of the elliptic properties of the governing equations yielding mesh-independent, converged solutions in the post-bifurcation regime. The bifurcation point (i.e., strain-to-localization) is found to be highly dependent on the micro-void's shape, with very flat voids (e.g., aspect ratio less than 0.3) leading to lower localization strains. The material length introduced by the non-local formulation is found tohave minimal effect on the predicted bifurcation point, only affecting the post-bifurcation gradient of the macroscopic stress-strain curve and the size of the highly strained zone in the structure.In the last part of this study, both the local and the non-local versions of the model are efficiently implemented in a commercial finite element code (ABAQUS). The models are used for the numerical solution of boundary value problems (BVPs) related to forming and ductile fracture processes under both quasi-static and dynamic conditions. In particular, the industrially relevant problems of Hole expansion (HET) and Charpy impact (CVN) test, the cup-and-cone fracture phenomenon as well as ductile fracture of a specimen with complex geometry and comparison with corresponding experimentalresults are analyzed in detail. Numerical predictions in all cases indicate that ductility is an increasing function of the void shape parameter and materials comprising flat oblate voids of low aspect ratio exhibit early macroscopic crack initiation and propagation compared to materials with spherical/almost spherical voids. Finally, the model's capability to reproduce experimental results with sufficient accuracy suggests that it can be utilized to provide predictions with only a small amount of parameters that may be calibrated from either micromechanics calculations or experimental data
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Davaze, Valentin. "Modélisation numérique de l'amorçage et la propagation des fissures dans les tôles métalliques ductiles pour les simulations de crash." Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEM060.
Testo completoAbstract (sommario):
Lors d’un crash automobile, les pièces faites de tôles métalliques sont sujettes à rupture. La rupture des matériauxductiles n’est actuellement pas prédite de manière fiable dans un contexte industriel, entraînant des coûts et délaissupplémentaires sur la conception. Cette problématique est alors abordée dans cette thèse CIFRE du Groupe PSAmenée en collaboration avec l’Onera et le Centre des Matériaux. L’objectif de ces travaux est de développer et d’implanterune stratégie numérique fiable de prédiction de fissure par la méthode des Éléments Finis (EF) dans les calculs de crashautomobile. Une première partie de ce travail consiste en la caractérisation puis la modélisation du comportementjusqu’à l’amorçage d’un matériau ductile représentatif: les tôles d’acier DP450. Pour ce faire, des essais sont réaliséssur une large gamme de vitesses de chargement, de triaxialités, et à différentes températures. À partir des résultatsobtenus, un modèle numérique de comportement est établi en tenant compte des différents phénomènes observésinfluençant la fissuration: la plasticité, les effets de vitesse et l’endommagement. Le modèle ainsi défini permet de tenircompte de la plupart des phénomènes observés. Cependant, le recours aux modèles adoucissants pour la modélisationde l’endommagement et des effets thermiques à haute vitesse entraîne une dépendance pathologique des résultatsau maillage utilisé (taille, orientation). Ce problème est résolu par l’implantation d’une méthode de régularisation non-localeadaptée aux calculs en dynamique rapide. Une variable non-locale est alors calculée à travers l’enrichissementd’éléments finis (solides et coques). Celle-ci est traitée comme un nouveau degré de liberté, facilitant ainsi l’échange del’information entre les éléments tout en conservant la parallélisation du code. Cette variable est ensuite introduite dansles équations constitutives permettant par la suite d’obtenir l’indépendance des résultats au maillage. La validation del’approche proposée est finalement réalisée grâce à la confrontation avec des résultats expérimentaux<br>In the event of a car crash, parts made of metal sheets are subjected to failure. Failure of ductile materials is currentlynot reliably predicted in an industrial context, involving additional costs and delays in the design process. This issue isthen addressed in this Ph.D thesis work of the PSA Group carried out in collaboration with Onera and the Centre des Matériaux. The aim of this work is to develop and implement a reliable numerical strategy for crack prediction using the Finite Element Method (FE) in automotive crash simulations. A first part of this work consists in characterizing and then modelling the plastic and fracture behavior of a representative ductile material: the DP450 steel sheets. To do so, tests are performed over a wide range of loading rates, stress triaxialities, and at different temperatures. From the obtained results,a numerical constitutive model is built by taking into account the different observed phenomena influencing crack initiationand propagation: plasticity, strain-rate effects and damage. The constitutive model thus enables to take into account mostof the observed phenomena. However, the use of softening models for modelling damage and thermal effects at highloading rate leads to a pathological dependence of the results on the mesh size and the mesh orientation. This problem issolved by the implementation of a non-local regularization method adapted to dynamic explicit computations. A non-localvariable is then computed through the enrichment of finite elements (continuum and shell). It is therefore treated as a new degree of freedom, which facilitates the exchange of data between the elements while preserving the parallelizationof the code. This variable is then introduced into the constitutive equations, allowing to obtain mesh independent results.The validation of the proposed approach is finally realized through the simulation of experimental results
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Ren, Sicong. "Mesures de champs et simulations par élément finis de l'interaction entre vieillissement dynamique et endommagement dans les alliages métalliques." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM001/document.
Testo completoAbstract (sommario):
Récemment, les observations in-situ par laminographie aux rayons X (au synchrotron) montrent que les multiples bandes de localisation sont les précurseurs de l'endommagement et éventuellement de la rupture en biseau. Ces bandes peuvent être liées aux phénomènes de vieillissement par la déformation (type effet de L"uders ou Portevin-Le Chatelier (PLC)) dont l'influence sur la rupture est encore mal compris. Ces effets sont pourtant observés dans de nombreux alliages industriels comme les aluminiums de la série 2000 ou 5000, ou par exemple, dans le cas des aciers C-Mn pour lesquels un creux de ductilité est observé dans la gamme de température o'u ces effets sont les plus marqués.L'objectif de la thèse consiste à caractériser l'effet PLC et évaluer son influence sur le développement de l'endommagement et donc sur la rupture finale. D'abord, l'effet de vieillissement sur l'écrouissage a été introduit dans un modèle basé sur la densité de dislocations en utilisant les résultats dans la littérature. Ensuite, certains alliages d'aluminium de la série 2000 et un acier C-Mn ont été étudiés par essais mécaniques avec corrélation d'images.Le déclenchement prématuré de localisation a été observé pendant les essais de relaxation, de déchargement et de changement de vitesse pour certains alliages d'aluminium.Les bandes autour de l'entaille dans l'éprouvette d'acier C-Mn ont été observées à haute température. Deux modes de rupture différents ont été observés dans les deux températures. Ces résultats sont comparés avec ceux du modèle KEMC. Enfin, un modèle de comportement couplant les effets de vieillissement (type KEMC) et d'endommagement (type Rousselier) a été développé pour tenter d'expliquer les interactions observées expérimentalement entre ces deux phénomènes<br>Recently, in-situ observations by X-ray laminography (at synchrotron) show that the multiple localization bands are the precursors of damage and possibly the slant fracture. These bands can be related to the strain ageing effect (L"uders or Portevin-Le Chatelier (PLC)) whose influence on the fracture is still poorly understood. These effects are observed in many industrial alloys such as 2000 or 5000 series aluminium alloys, or, for example, in the C-Mn steels for which a ductility drop is observed in the temperature range where these effects are most pronounced.The aim of the thesis is to characterize the PLC effect and to evaluate its influence on the development of ductile damage and therefore on the final fracture. Firstly, the influence of strain ageing on strain hardening was introduced in a model based on the dislocation density using results from the literature. Secondly, several 2000 series aluminium alloys and a C-Mn steel were investigated by mechanical tests combined with Digital Image Correlation. The premature triggering of localization bands was observed in tensile tests involving relaxation, unloading and strain rate jump for certain aluminium alloys. The bands around the notch in the specimens of C-Mn steel were observed at high temperature. Two different modes of fracture were observed at the two temperatures. These results are compared with those produced with the KEMC model. Thirdly, a constitutive model combining the strain ageing (type KEMC) and damage (type Rousselier) was developed in order to explain the experimentally observed interactions between these two phenomena
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Mbarek, Imen Asma. "Étude dynamique pour définition d'aciers de blindage innovants contre les explosions." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0189.
Testo completoAbstract (sommario):
Le travail de thèse de doctorat porte sur une étude complète du comportement dynamique de trois aciers de blindage soumis à des impacts balistiques. Dans un premier temps, afin de comprendre les phénomènes mis en jeu pendant la perforation de cibles fines, des essais de caractérisation du comportement thermo-viscoplastique et de rupture ont été réalisés. Les paramètres des lois de comportement et des critères de rupture ont été identifiés pour alimenter un modèle numérique simulant l'essai de perforation. La réponse des cibles impactées par des projectiles coniques a ensuite été évaluée à l'aide d'essais de perforation. Grâce à cette étude, il est possible de valider l'implémentation des lois et des critères réalisée dans des codes de calcul. Un dispositif de mesure des efforts d'impact et de perforation a donc été développé au cours de la thèse. Il fût montré que la mesure des efforts ainsi obtenue n'est pas intrinsèque au matériau impacté mais qu'elle dépend de la réponse globale du dispositif support-cible. Les résultats numériques issus de l’analyse par la méthode des éléments finis (MEF) ont été comparés aux résultats expérimentaux. Il a été observé un bon accord en terme de courbes balistiques, de modes de rupture, d’efforts dynamiques et de bilan énergétique. La modélisation numérique montre que seule une description précise du comportement mécanique des matériaux et de la rupture permet d'avoir une bonne représentation des performances balistiques des aciers étudiés. Une attention toute particulière a été portée sur l’influence de la tri-axialité des contraintes locales initiée par la forme de l’impactant, de la vitesse de déformation et de la température sur le seuil de déformation à la rupture. En perspective, les résultats issus de cette étude pourront servir dans l'analyse de la réponse des aciers de blindage sous chargements par explosif<br>The main aim of this PhD thesis is to develop a comprehensive study of the dynamic behavior of three armor steels subjected to ballistic impact. In order to have better understanding of the phenomena which take place during the thin targets perforation process, characterization experiments allowing to describe of the thermo-viscoplastic behavior and fracture were carried out. The identification of the constitutive relations and the failure criteria parameters allow to establish a numerical model simulating the perforation test. The ballistic response of armor steels subjected to the impact of conical projectiles was then assessed using perforation testing. This experimental investigation aims at endorsing the implementation of the behavior and fracture models in the calculation software. An experimental set-up for perforation forces measurements was specially developed during the thesis. It has been found that this dynamic force measurement is not intrinsic to the target material. It is rather dependent on the structural response of the used set-up support-target during impact and perforation. The numerical results from the Finite Elements Analysis (FEA) were compared to the experimental data and good agreement was found in terms of ballistic curves, failure patterns, impact forces and energy balance. Numerical investigations show that only an accurate description of the mechanical behavior and the fracture allows a good prediction of the ballistic performances of armor steels. Close attention was paid to the influence of local stress triaxiality induced by the projectile nose shape, strain rate and temperature on the strain to fracture threshold. In the future, these investigations can be used in the behavior analysis of armor steels subjected to blast loading
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Bude, Jérémie. "Ductile fracture simulation using the strong discontinuity method." Thesis, Compiègne, 2015. http://www.theses.fr/2015COMP2243/document.
Testo completoAbstract (sommario):
Dans un contexte d’évaluation de la criticité des chargements, les travaux de thèse ont les objectifs suivants : prendre en compte les phénomènes sous-jacents à le rupture ductile : les phénomènes de dissipation volumique (plasticité et endommagement) et surfaciques (fissuration). On s'intéresse également à régulariser la solution vis-à-vis du maillage, à prédire le phénomène de transition de mode de rupture plan vers un mode de propagation oblique observé pour certains essais. La méthode utilisée est basée sur la méthode des discontinuités fortes. Un des enjeux majeurs de ces travaux est d’étendre son champ d'application au cadre de la modélisation de la rupture ductile, notamment en présence de plasticité et d'endommagement dans le volume. Une première partie des travaux est consacré à l'établissement d'un modèle en hypothèse de petites déformations, avec un modèle matériau de plasticité et d'endommagement couplé de Lemaitre pour le volume et un modèle cohésif endommageable pour le comportement surfacique. Les deux modes de rupture I et II ont été considérés dans les essais numériques. Des résultats montrant les capacités de régularisation de la méthode employée ont été présentés pour divers essais. Une seconde partie des travaux a été consacré à la formulation d'un modèle en hypothèse de grandes transformations, avec également des résultats probants en termes de régularisation de la dépendance à la taille de maille. Les deux éléments présentés ont été implémentés en formulation implicite et explicite, dans FEAP (Finite Element Analysis Program), logiciel académique développé à UC Berkeley par Taylor, et plus récemment dans le logiciel de calcul Eléments Finis Abaqus<br>In the context of loadings criticality analysis, the thesis work have the following objectives : to take into account the underlying phenomena to ductile fracture : the volumetrie (plasticity and damage) and surfacic (fracture) dissipativ mechanisms. We also aim at regularizing the solution with regards to meshing, predicting the transition from a straigh crack propagation to a slant fracture mode observed for certain tests. The chosen method relies on the stron discontinuity method. One of the major challenges of this work is to extend its framework to the ductile fractur modeling framework, by accounting for plasticity and damage in the bulk. The first part of this work is dedicated to th establ'ishment of a model in small strain hypothesis, with a material model that takes into account coupied plasticity an damage in the QUik and a damageable model for the cohesive surfacic behavior. Both modes 1 and Il have been taken int) account in thnumerical examples. Results attesting the regularizing capabilities of the method are presented fo different tests. The second part of this work is dedicated to the formulation of a finite strain mode!, and results showin the good regularizing capabilities of the method are also shown. Both elements have been implemented in FEAP (Finit Element Analysis Program), an academie software developed at UC Berkeley by Taylor, and more recently in the finit element software Abaqus
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Emerson, Tonya Lynn. "Ductile fracture mechanics : modeling, experiments, and computational simulation /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2002. http://uclibs.org/PID/11984.
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Wang, Li. "Ductile fracture simulation of structural steel using the local approach method." Thesis, University of the West of England, Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271053.
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Myers, Andrew T. "Testing and probabilistic simulation of ductile fracture initiation in structural steel components and weldments /." May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Hůlka, Jiří. "Aplikace modelů tvárného porušování při výpočtové simulaci technologických operací." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-227954.
Testo completoAbstract (sommario):
This diploma thesis is an introduction to the ductile fracture under large plastic deformations and is focused to numerical simulation of this type of problems. Explicit finite element method (FEM) is discussed in theoretical introduction as the most powerful tool for numerical calculations in this area. Actual state of research and possibilities of ductile fracture simulations are presented. Applicable fracture criteria are collected in a summary sheet and the most important ones are selected and commented in detail. The problem of implementation of selected criteria into commercial FEM packages is discussed, too. Main part of the work is presented in chapters 7÷9 where two ductile fracture criteria (Equivalent Fracture Strain and Johnson-Cook) are applied to numerical simulation of material cutting. All results were obtained with ABAQUS/Explicit 6.5.1 and their verification was realized by experimental measurement.
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Hütter, Geralf. "Multi-scale simulation of crack propagation in the ductile-brittle transition region." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-121281.
Testo completoAbstract (sommario):
In the present thesis the crack propagation in the ductile-brittle transition region is studied on two scales with deterministic models. In the macroscopic model the ductile failure is described by a non-local Gurson-model whereas the discrete void microstructure is resolved around the crack tip in the microscopic model. The failure by cleavage is not evaluated by means of a post-processing criterion but is modeled equivalently using a cohesive zone model on both scales. Thus, cleavage is not a priori identified with unstable crack propagation but the transition between stable and unstable mode of propagation is a result of the simulation. The problem of handling completely failed material within the framework of non-local damage models is pointed out. A method to overcome this problem is proposed and successfully applied. The case of contained plastic yielding at the crack tip is addressed with a modified-boundary layer model. The macroscopic simulations reproduce many features which are known from experiments like the formation of stretch zones, cleavage after initial ductile tearing, pop-ins with crack arrest, among others. The microscopic simulations substantiate the understanding of the macroscopically observed behavior. Systematic parameter studies are performed. Starting with considerations on the limit cases like pure ductile failure or the lower-ductile brittle transition region allows to separate the effects of the different constitutive parameters. Based on these results, a methodology is proposed to extract the macroscopic material parameters from experiments. This scheme is successfully applied to experimental data from literature. The results show that the behavior of a low-constraint specimen can be reliably predicted with the parameters extracted from a high-constraint specimen<br>In der vorliegenden Arbeit wird die Rissausbreitung im spröd-duktilen Übergangsbereich auf zwei Skalen mittels deterministischer Modelle untersucht. Das duktile Versagen wird im makroskopischen Modell durch ein nichtlokales Gurson-Modell beschrieben, während im mikroskopischen Modell die Porenmikrostruktur im Bereich um die Rissspitze diskret aufgelöst wird. Das mögliche Versagen durch Spaltbruch wird nicht, wie üblich, nachträglich durch ein spannungsbasiertes Kriterium bewertet. Stattdessen wird der Spaltbruch auf beiden Skalen durch ein Kohäsivzonenmodell abgebildet. Somit wird die Spaltbruchinitiierung nicht a priori mit instabiler Rissausbreitung gleichgesetzt. Vielmehr ist die Stabilität der Rissausbreitung ein Ergebnis der Simulationen. Außerdem wird das Problem der der Handhabung vollständig ausgefallenen Materials im Rahmen nichtlokaler Schädigungsmodelle herausgestellt. Es wird eine Methode vorgestellt, dieses Problem zu behandeln und erfolgreich angewendet. In den Simulationen wird der Fall vollständig eingebetteten, plastischen Fließens untersucht. Die Simulationen mit dem makroskopischen Modell geben viele Effekte wieder, die aus Experimenten bekannt sind. Dazu zählen die Ausbildung von Stretchzonen, die Spaltbruchinitiierung nach anfänglichem, duktilem Reißen oder lokale Instabilitäten mit Rissarrest. Die mikroskopischen Simulationen tragen zum Verständnis des makroskopisch beobachteten Verhaltens bei. In der vorliegenden Arbeit werden systematische Parameterstudien durchgeführt. Zunächst werden Grenzfälle wie das rein duktile Versagens oder der Spaltbruch in Abwesenheit der Mikroporen untersucht, um die Einflüsse der einzelnen Materialparameter abzugrenzen. Ausgehend von diesen Ergebnissen wird eine Prozedur vorgeschlagen, die Materialparameter des makroskopischen Modells Schritt für Schritt aus Experimenten zu bestimmen. Diese Prozedur wird erfolgreich auf experimentelle Daten aus der Literatur angewendet. Die Ergebnisse zeigen, dass es das entwickelte Modell erlaubt, das Verhalten einer Bruchmechanikprobe mit geringer Dehnungsbehinderung an der Rissspitze mit denjenigen Materialparametern vorherzusagen, die an Proben mit einer hohen Dehnungsbehinderung ermittelt wurden
Libri sul tema "Ductile fracture simulations"
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Komori, Kazutake. Ductile Fracture in Metal Forming: Modelling and Simulation. Elsevier Science & Technology, 2019.
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Komori, Kazutake. Ductile Fracture in Metal Forming: Modeling and Simulation. Elsevier Science & Technology Books, 2019.
Cerca il testo completoCapitoli di libri sul tema "Ductile fracture simulations"
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Gerke, S., M. Schmidt, M. Dirian, and M. Brünig. "Damage and Fracture of Ductile Sheet Metals: Experiments and Numerical Simulations with New Biaxial Specimens." In Advanced Structured Materials. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-70563-7_5.
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Yoon, D. H., and J. Choung. "Collision simulations between a floating offshore wind turbine and a tanker considering ductile fracture and hydrodynamics of FOWT." In Advances in the Collision and Grounding of Ships and Offshore Structures. CRC Press, 2023. http://dx.doi.org/10.1201/9781003462170-56.
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Spaniel, M. "Numerical Simulation of Ductile Fracture." In The Latest Methods of Construction Design. Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-22762-7_41.
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Kikuchi, Masanori. "Numerical Simulation of Ductile Fracture Process Including Shear-Lip Fracture." In The Mechanical Behavior of Materials X. Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-440-5.839.
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Hello, Gaëtan, Hocine Kebir, and Laurent Chambon. "Numerical Simulation of the Ductile Fracture Growth Using the Boundary Element Method." In Damage and Fracture Mechanics. Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-90-481-2669-9_48.
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Bora, Dipankar, Manoj Kumar, and Sachin S. Gautam. "Continuum Damage Mechanics Based Simulation of Ductile Fracture of Cylindrical Tubes." In Lecture Notes in Mechanical Engineering. Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-6469-3_6.
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Arfaoui, Latifa, Amel Samet, and Amna Znaidi. "Ductile Fracture Characterization of an IF Steel Tensile Test by Numerical Simulation." In Lecture Notes in Mechanical Engineering. Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-27146-6_34.
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Mu, Lei, Zhe Jia, Ben Guan, and Yong Zang. "Finite Element Simulation of Edge Fracture by Mapping the Shear-Induced Ductile Damage into Hole-Expansion Simulation." In Forming the Future. Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-75381-8_137.
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Urata, Shingo, and Shaofan Li. "Simulation of Ductile Fracture in Amorphous and Polycrystalline Materials by Multiscale Cohesive Zone Model." In Mathematical Analysis of Continuum Mechanics and Industrial Applications II. Springer Singapore, 2017. http://dx.doi.org/10.1007/978-981-10-6283-4_4.
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Alves, José, Hazem Eldahshan, Ugo Ripert, Richard Ducloux, Daniel Pino Munoz, and Pierre-Olivier Bouchard. "Advancements in the Simulation of 3D Ductile Damage Transition to Fracture with FORGE®." In Lecture Notes in Mechanical Engineering. Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-42093-1_27.
Testo completoAtti di convegni sul tema "Ductile fracture simulations"
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Li, J. "Meshless Analysis of Ductile Failure." In ASME 2011 Pressure Vessels and Piping Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/pvp2011-57134.
Testo completoAbstract (sommario):
We study ductile fracture using Reproducing Kernel Particle Interpolation and the Gurson-Tvergaard-Needleman (GTN) model. The meshless simulations are compared with the available experimental results and previous finite element simulations for crack propagation. The results agree well with experimental results, and it is confirmed that the proposed method provides a convenient and yet accurate means for simulation of ductile fracture.
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Deng, Xiaomin, and Michael A. Sutton. "Experiments, Analysis and Simulation of Mixed Mode Ductile Fracture." In ASME 2005 Pressure Vessels and Piping Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/pvp2005-71384.
Testo completoAbstract (sommario):
This paper provides a review of findings of a comprehensive research effort by the authors and collaborators in the area of experiments, analysis and simulation of mixed-mode ductile fracture. Topics include mixed-mode Arcan stable tearing tests, the mixed-mode CTOD fracture criterion and its basis, normalization of ductile crack tip fields, ductile failure envelope, crack tunneling and slanting, effects of stress constraint, custom 2D and 3D mixed-mode crack growth simulation codes, and simulations of mixed-mode stable tearing crack growth tests.
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Ding, Huafeng, Caichao Zhu, Zhong Zhou, and Dong Qian. "Ductile Failure in Processed Thin Sheet Metals." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-65584.
Testo completoAbstract (sommario):
Ductile fracture in thin sheet metals is a common failure mechanism that governs many important industrial applications. A variety of simulation methods, ranging from the atomistic to continuum scales, have been proposed and demonstrated. To assess the capabilities of the existing simulation tools, a group of researchers presented their modeling predictions on the so-called Sandia Fracture Challenge problem at the 2012 ASME IMECE conference. The discrepancies between the simulation and experimental results, and among the experimental results themselves led to consensus that more needs to be done to improve the understanding of this complex phenomenon. Following the participation of the Sandia Fracture challenge, further simulations are performed to study the ductile failure in thin sheet metals with conditions that are commonly used for processing. It is shown that failure pattern and load are significantly influenced by the processing conditions.
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Nonn, Aida, Marcelo Paredes, Vincent Keim, and Tomasz Wierzbicki. "Comparison of Fracture Models to Quantify the Effects of Material Plasticity on the Ductile Fracture Propagation in Pipelines." In 2018 12th International Pipeline Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/ipc2018-78366.
Testo completoAbstract (sommario):
Various numerical approaches have been developed in the last years aimed to simulate the ductile fracture propagation in pipelines transporting CO2 or natural gas. However, a reliable quantification of the influence of material plasticity on the fracture resistance is still missing. Therefore, more accurate description of the material plasticity on the ductile fracture propagation is required based on a suitable numerical methodology. In this study, different plasticity and fracture models are compared regarding the ductile fracture propagation in X100 pipeline steel with the objective to quantify the influence of plasticity parameters on the fracture resistance. The plastic behavior of the investigated material is considered by the quadratic yield surface in conjunction with a non-associated quadratic plastic flow potential. The strain hardening can be appropriately described by the mixed Swift-Voce law. The simulations of ductile fracture are conducted by an uncoupled, modified Mohr-Coulomb (MMC) and the micromechanically based Gurson-Tvergaard-Needleman (GTN) models. In contract to the original GTN model, the MMC model is capable of describing ductile failure over wide range of stress states. Thus, ductile fracture resistance can be estimated for various load and fracture scenarios. Both models are used for the simulation of fracture propagation in DWTT and 3D pressurized pipe sections. The results from the present work can serve as a basis for establishing the correlation between plasticity parameters and ductile fracture propagation.
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Fonzo, Andrea, Andrea Meleddu, Giuseppe Demofonti, Michele Tavassi, and Brian Rothwell. "Ductile Fracture Control for High Strength Steel Pipelines." In 2006 International Pipeline Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/ipc2006-10331.
Testo completoAbstract (sommario):
The determination of the toughness values required for arresting ductile fracture propagation has been historically based on the use of models whose resulting predictions can be very unreliable when applied to new high strength linepipe materials (≥X100) and/or different operating conditions. In addition, for the modern high strength steels a methodology for determining the material fracture resistance for arresting running shear fracture starting from laboratory data is still lacking. The work here presented (developed within a PRCI sponsored project) deals with the use of CSM’s proprietary PICPRO® Finite Element code to develop methodologies for ductile fracture propagation control in high grade steel pipes. The relationships providing the maximum crack driving force which can be experienced in a pipe operated at known conditions have been determined, for different types of gas. On the other side, an empirical relationship has been found to correlate the critical Crack Tip Opening Angle (CTOA) determined by laboratory testing, to the critical CTOA on pipe (which represents the material fracture propagation resistance) with the aid of devoted simulations of past full-scale burst tests. By comparing Driving Force and Resistance Force, ductile fracture control for high strength steel pipelines can be achieved.
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Kane, Alexandre, Sigmund Ås, and Erling Østby. "3D Fracture Simulations of SENT Specimens Including Welding Residual Stresses." In ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-84057.
Testo completoAbstract (sommario):
In pipe-laying and reeling operations, high levels of plastic deformation may occur in the pipe wall. The effect of plastic deformation should be investigated and quantified in order to qualify a steel material for a given pipe-laying process. This paper presents a numerical modeling approach for realistic simulation of ductile fracture, including results from FE welding simulations. A 3D model of a SENT specimen is adopted, where crack propagation is modelled using a Gurson model. An elastic-plastic hardening model is used to capture the global deformation of the specimen. Results compare well with experiments. This work is part of an effort to develop an experimental and numerical framework where the influence of welding (HAZ properties, residual stresses and hardening) in fracture assessment. Preliminary results show that there is no influence of residual stresses on fracture strength of an X65 ductile steel.
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Suga, Kazuhiro, Katsumasa Miyazaki, Ryotaro Senda, and Masanori Kikuchi. "Interaction Effect Evaluation of Plural Surface Cracks in Ductile Fracture Process." In ASME 2012 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/pvp2012-78132.
Testo completoAbstract (sommario):
Effect of surface flaw on ductile fracture behavior of non-aligned multiple flaws in plate is studied numerically using Gurson’s constitutive equation. Based on experiments, two parallel non-aligned crack problems are simulated. From experimental and simulation data, crack coalescence, interaction between two cracks and crack penetration was observed. In all cases, ductile fracture processes are obtained and results are compared with experimental ones. Fracture patterns agree well with experimental results. Close qualitative match was obtained by comparing each load displacement curves that are normalized by maximum load. It shows that the mechanism of ductile fracture process is properly captured. By selecting one normalized experimental data as a base setup, maximum load from related simulation results can be predicted. Aligned rules are checked based on these simulations, and H / a criteria verified it’s availability when average crack depth is used as crack depth.
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Miyajima, Yuuki, Masanori Kikuchi, and Akiyuki Takahashi. "Ductile Fracture Simulation of a Pipe of Steam Generator in PWR." In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97582.
Testo completoAbstract (sommario):
Ductile fracture of steam generator pipes may occur due to inner pressure. The final fracture process by inner pressure occurs as a burst of a pipe, and ductile high speed crack growth occurs with large deformation of the structure. For the simulation of such fracture process, Gurson’s yield function is used as a constitutive equation, and large deformation theory is employed. As the simulation is conducted by load control condition, it is difficult to simulate burst phenomenon. Final fracture condition is discussed and finally crack opening displacement is chosen as burst fracture criterion. Fracture simulations of a pipe with multiple through cracks are conducted by changing distances between two crack tips. Burst loads are evaluated, and they are compared with estimated values by Maintenance rules. Surface crack problems are also simulated. Burst loads are also compared with results by limit load analysis method. Conservativeness of conventional evaluation methods are studied and discussed.
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Ryu, Ho-Wan, Hune-Tae Kim, Jae-Jun Han, et al. "Effects of Side Groove on Fracture Toughness." In ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45731.
Testo completoAbstract (sommario):
This paper describes ductile tearing simulation for compact tension (C(T)) specimens using FE damage analysis based on the stress-modified fracture strain model. The side groove effect on J-resistance curve was estimated by experimental and analytical ways. In this paper, SA508 Grade 1A low alloy steel pipe material was considered. Tensile and C(T) specimens are simulated to determine the failure criteria with finite element method. Then, different shapes of C(T) specimens are analysed and the results from simulations are compared with test data for verification of proposed method. Overall, the predicted simulation results show good agreement with test data.
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Dybwad, Jacob, Rikard To¨rnqvist, Erling O̸stby, and Christian Thaulow. "Simulations of Ductile Tearing at Large Strains of Biaxially Loaded Pipes." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79631.
Testo completoAbstract (sommario):
The purpose of the present paper is to present results from analyses of ductile tearing of biaxially loaded pipes subjected to large scale yielding. The paper deals with three dimensional finite element modelling of pipes with a circumferentially orientated surface crack, where the analyses aim to reproduce the crack propagation behaviour of six full scale bend tests of x-65 seamless pipes with different levels of internal overpressure. The tests were performed as a part of the joint industry project Fracture Control - Offshore Pipelines. Ductile tearing is taken into account by using the Gurson-Tvergaard-Needleman formulation, where calibration of the material model parameters is done by reproducing the fracture toughness test of a SENT-specimen of the same material with finite element modelling. The following simulations of the pipes show a good correspondence with the full scale test results, where both the global response and the ductile tearing from the crack are captured. One important result of the study is that the Gurson-Tvergaard-Needleman parameters that were calibrated against the SENT-specimen could successfully be used for the ductile tearing simulation of the full scale pipes.
Rapporti di organizzazioni sul tema "Ductile fracture simulations"
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Kanninen, M. F. L51718 Development and Validation of a Ductile Fracture Analysis Model. Pipeline Research Council International, Inc. (PRCI), 1994. http://dx.doi.org/10.55274/r0010321.
Testo completoAbstract (sommario):
In close cooperation with the Centro Sviluppo Materiali (CSM) and SNAM of Italy, with several years of support from the PRCI NG-18 committee, the Southwest Research Institute (SwRI) has developed and validated a "first principles" predictive model for ductile fracture in a gas transmission pipeline. In particular, the coordinated SwRI and CSM projects for the PRC -supplemented by work contributed by SNAM - has established a theoretically valid methodology and an accompanying line pipe material characterization procedure for gas industry use. This progress provides a theoretically sound framework for designing and operating gas transmission pipelines to be without risk of a large-scale ductile fracture event. However, there remained two important aspects of this technology that needed to be addressed before practical use of the methodology could be made by gas transmission companies. First, because the preceding projects concentrated on pipes with natural gas, to cover the full range of gas transmission pipeline service, the approach needed to be extended to include the effects of gases rich in hydrocarbons. Second, as the number of full-scale pipe fracture experiments that were included in the developmental phase of the research were limited, other data for validation of the model needed to be identified and employed. These two aspects of the ductile fracture methodology development process were conducted concurrently, and have now been completed. The progress that has been provided in detail in this report. The work is culminated by a relation through which the methodology can be applied by pipeline engineers to assess the possibility of a ductile fracture propagation. This report describes the development of a predictive model for ductile fracture in a gas transmission pipeline, thus providing a theoretically sound framework for designing and operating gas pipelines to be without risk of a large-scale ductile fracture event. The model represents an improvement on a number of empirical relations used in designing natural gas pipelines in that this model has been generalized to consider a wide-range of hydrocarbon contents and validated through both additional full-scale instrumented tests carried out by Centro Sviluppo Materiali of Italy and computer simulations conducted at Southwest Research Institute. Application of the model in pipeline design is based on determination of the maximum driving force for fracture, as described in the report, and contrasting this value with measured material resistance that provides a basis for assessing the likelihood of ductile fracture occurring. For existing pipelines the procedure can be used to obtain the maximum operating line pressure that will not put the pipeline at risk of ductile fracture.